RU2643023C2 - Solution for chemical conversion treatment and steel sheet subjected to chemical conversion treatment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: solution for chemical treatment of the steel sheet with a plating coating based on zinc contains soluble molybdate, vanadium salt, amine, oxoat of element 4 of the Periodic Table of Chemical Elements group, and a phosphate compound. The molar ratio of molybdenum to vanadium in the solution for the chemical treatment is from 0.4 to 5.5, the mole ratio of amine to vanadium in the solution for the chemical treatment is 0.3 or more, the content of the hydrophilic resin in the solution for the chemical treatment is not more than 100 wt % per the total amount of vanadium and molybdenum in the solution for the chemical treatment. The total content of fluoride due to fluoride ion or metalloprotein ion in the solution for the chemical treatment is not more than 30 wt % per the total amount of vanadium and molybdenum in the solution for the chemical treatment, and the silicon content due to the silanole group, in the solution for the chemical treatment is not more than 50 wt % per the total amount of vanadium and molybdenum in the solution for the chemical treatment. The said steel sheet has a zinc-based cladding layer containing from 0.1 to 22.0 wt % of aluminium and a chemical conversion film disposed thereon. The chemical conversion film includes the first chemical conversion layer placed on the surface of the cladding coating based on zinc and containing vanadium, molybdenum, and phosphor, and the second chemical conversion layer placed on the first chemical conversion layer containing the element oxoat of Group 4 of the Periodic Table of Chemical Elements. The percentage of pentavalent vanadium based on vanadium of mixed valence in the chemical conversion film is 0.7 or more.

EFFECT: production of a steel sheet with improved corrosion resistance and blackening resistance.

5 cl, 3 dwg, 41 tbl, 4 ex

Description

FIELD OF THE INVENTION

[0001] The present invention relates to chemically treated steel sheet and to a solution for chemically treating a zinc plated clad steel sheet.

State of the art

[0002] Zinc-based cladding steel sheets have been widely used in applications such as automobiles, building materials, and home electrical appliances. Typically, the surface of a clad steel sheet is subjected to a chromium-free chemical treatment to give it corrosion resistance without oiling. The chromium-free chemical treatment is conventionally divided into organic processing and inorganic processing. Organic treatments allow the formation of a thick film containing organic resin, while inorganic treatments allow the formation of a thin film (film thickness: 1 μm or less) to obtain spot weldability. Organic treatments can give relatively high corrosion resistance compared to inorganic treatments. Some of the inorganic treatments also exhibit high corrosion resistance to the same extent as organic treatments, using a zinc plated clad steel sheet containing aluminum and magnesium in its clad layer as a starting sheet for chemical treatment.

[0003] For example, inorganic treatments based on titanium, based on zirconium, based on molybdenum, and based on their complexes, depending on various corrosion inhibitors, have been developed. Further, in order to increase the corrosion resistance, inorganic treatments have also been developed in which a silane coupling agent, a silica sol, an organic acid, or the like are further added (for example, see Patent Documents (PTL) 1-3).

[0004] Patent Document (PTL) 1 describes a chemically treated steel sheet obtained by forming a chromium-free chemical conversion film containing valve metal and soluble valve metal fluoride on the surface of a zinc-clad steel sheet. PTL 2 describes a chemically treated steel sheet obtained by forming a chromium-free chemical conversion film containing: a zirconium compound, a vanadyl compound (VO ²⁺ salt), and the like; organic acid; silicon dioxide compound; fluoride; lubricant; or the like, on the surface of a steel sheet with a zinc-based clad coating containing magnesium, aluminum and silicon. PTL 3 describes a chemically treated steel sheet obtained by forming a chromium-free chemical conversion film containing a basic zirconium compound, a vanadyl compound, a phosphate compound, a cobalt compound, an organic acid, or the like, on the surface of a zinc clad coating steel sheet.

[0005] As disclosed in Patent Documents (PTL) 1-3, chromium-free chemical treatments in which corrosion inhibitors are complex compounds, and organic acid, fluoride, a silane coupling agent, or the like, are added to enhance the functionality of the free chrome chemical conversion film, and which can give even higher corrosion resistance of the film than the corrosion resistance of the film obtained by traditional chromate treatments. However, when a chemically treated steel sheet obtained by forming a chromium-free chemical conversion film on the surface of a zinc-clad steel sheet is stored for a long period of time at high temperature and in a humid environment, the chemically-treated steel sheet sometimes has a blackened clad surface layer due to oxidation. Blackening the surface of the cladding layer not only affects the appearance, but also has harmful effects, such as a decrease in weldability by spot welding. This phenomenon is particularly noticeable in a zinc coated clad steel sheet containing aluminum and magnesium in its clad layer.

[0006] As a means of suppressing the blackening of a zinc-clad steel sheet, PTL 4 offers an organic chemical treatment in which the hexavalent molybdenum oxoate and amine are co-present. According to the method according to PTL 4, the amine forms a complex with a molybdenum derivative of an oxoacid to suppress the reaction of molybdenum oxoate with a cladding layer of zinc alloy, and thereby a complex pentavalent or hexavalent molybdenum oxoate is formed in the chemical conversion film (the so-called “molybdenum blue”). Pentavalent molybdenum oxoate in a chemical conversion film becomes hexavalent molybdenum oxoate as a result of reaction with oxygen, which penetrates the film. Thus, pentavalent molybdenum oxoate in the chemical conversion film captures oxygen, which penetrates the film, so that the surface of the clad layer is oxidized, and blackening is also suppressed as a result.

List of references

Patent Literature

[0007]

PTL 1

Japanese Published Patent Application No. 2002-194558

PTL 2

Japanese Published Patent Application No. 2003-055777

PTL 3

WO2007 / 123276

PTL 4

Japanese Published Patent Application No. 2005-146340

SUMMARY OF THE INVENTION

Technical challenge

[0008] In order to impart high corrosion resistance to a chemically treated steel sheet, it is necessary to sufficiently dry the chemical treatment solution applied to the surface of the steel sheet to form an insoluble film. When the drying temperature is low and the drying is insufficient, the corrosion resistance is significantly reduced. Therefore, when a chemically treated steel sheet is manufactured on a continuous production line, it is necessary to dry the chemical treatment solution at a high temperature of the steel sheet, the temperature being from about 50 to 200 ° C., in order to achieve both sufficient drying and productivity.

[0009] Recently, the removal of CO ₂ as a countermeasure against global warming and energy saving as a measure to counter energy shortages have been required. In particular, in order to meet the requirements of Section 3 regarding emissions, products were needed that contribute to the elimination of CO ₂ already at the stage at which raw materials for products are made. Accordingly, also in the case of chromium-free chemical treatment, a decrease in the drying temperature and a reduction in the drying time were required.

[0010] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a chemically treated steel sheet that has excellent corrosion and blackening resistance obtained by using a zinc-clad steel sheet as a starting sheet, and which can be produced even when the applied chemical treatment solution is dried at a low temperature and for a short period of time.

[0011] Another objective of the present invention is the provision of a solution for chemical treatment, capable of forming a chemical conversion film, which increases the corrosion resistance and resistance to blackening, even when dried at low temperature and for a short period of time.

The solution of the problem

[0012] The inventors have conducted chromium-free chemical treatment studies for a zinc-clad steel sheet in terms of the relationship between the processing conditions (such as the composition of the chemical conversion film and the drying temperature) and various qualitative properties. As a result, the inventors of the present invention have found that to increase the corrosion resistance it is important to form a film from an insoluble complex with a small residual amount of soluble salt and solvent. That is, it was found that when excessive amounts of fluoride, organic acid and amine with a high boiling point remain in the chemical conversion film, the corrosion resistance is significantly reduced. In particular, it was found that the composition of the solution for chemical treatment is significantly important, since when the solution for chemical treatment is dried at a low temperature and for a short period of time, the complex salt is less likely to form, and fluoride, organic acid and high boiling amine.

[0013] As a result of a thorough study, taking into account these circumstances, the inventors of the present invention found that the problems described above can be solved by forming a chemical conversion film using a chemical treatment solution containing water-soluble molybdate, a vanadium salt, an amine having a low boiling point, an oxoate of a group element 4 elements of the periodic table of chemical elements (according to the IUPAC nomenclature) and phosphate, and conducted additional studies to complete this grip.

[0014] That is, the present invention relates to the following chemical treatment solution:

[1] A chemical treatment solution for coating a zinc-plated cladding steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% Aluminum, the chemical treatment solution containing water-soluble molybdate, vanadium salt, amine, oxoate of an element of the group of 4 elements of the Periodic table of chemical elements and a phosphate compound in which the molar ratio of molybdenum to vanadium in a solution for chemical treatment is from 0.4 to 5.5, the molar ratio of amine to vanadium in rast The amount for chemical treatment is 0.3 or more, the content of the hydrophilic resin in the solution for chemical treatment is not more than 100 wt.%, calculated on the total amount of vanadium and molybdenum in the solution for chemical treatment, the total fluorine content due to fluorine ion or metal fluoride ion, in the solution for chemical treatment is not more than 30 wt.%, calculated on the total amount of vanadium and molybdenum in the solution for chemical treatment, and the silicon content due to the silanol group in the solution for chemical tion treatment is not more than 50 wt.%, based on the total amount of vanadium and molybdenum in solution to chemical treatment.

[2] The chemical treatment solution according to [1], wherein the amine has a molecular weight of 80 or less.

[0015] Further, the present invention relates to the following chemically treated steel sheet:

[3] A chemically treated steel sheet comprising a zinc-based cladding steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% Aluminum, and a chemical conversion film placed on the cladding-based layer zinc, and the chemical conversion film includes a first chemical conversion layer located on the surface of the zinc-based cladding coating and containing vanadium, molybdenum and phosphorus, and a second chemical conversion layer located on the first chemical conversion layer and comprising oksoat element group 4 elements of the periodic table of chemical elements, and the percentage of pentavalent vanadium, calculated as vanadium mixed valence in the chemical conversion film is 0.7 or more.

[4] A chemically treated steel sheet according to [3], wherein the oxoate of an element of group 4 of the elements of the Periodic Table of Chemical Elements is zirconium oxoate, and the chemical conversion film contains from 1 to 60 parts by weight of molybdenum, from 2 to 20 parts by weight vanadium, and from 10 to 50 parts by weight of phosphorus, based on 100 parts by weight of zirconium.

[5] A chemically treated steel sheet according to [3] or [4], wherein the zinc-coated cladding steel sheet is a hot dip aluminum and magnesium galvanized steel sheet having a hot dip galvanized aluminum and clad aluminum a layer containing from 0.1 to 22.0 wt.% aluminum and from 1.5 to 10.0 wt.% magnesium.

Advantageous Results of the Invention

[0016] According to the present invention, it is possible to produce a chemically treated steel sheet with excellent corrosion and blackening resistance even when the chemical treatment solution applied to the surface of the zinc-clad steel sheet is dried at a low temperature and for a short period of time. .

Brief Description of the Drawings

FIG. 1 is a transmission electron microscope (TEM) image of a cross section of a test sample according to one example of a chemically treated steel sheet according to the present invention, manufactured at a drying temperature of 80 ° C;

FIG. 2 is a diagram showing the distribution of elements in a test sample from its surface in the depth direction; and

FIG. 3 is a diagram showing a chemical binding energy intensity profile corresponding to a vanadium 2p orbital on the interface between the chemical conversion film and the cladding layer at the interface of the test sample of another example of a chemically treated steel sheet according to the present invention.

Description of Embodiments

[0018] A chemically treated steel sheet according to the present invention includes a zinc-based cladding steel sheet (a starting sheet for chemical processing) and a chemical conversion film formed on the surface of the zinc-based cladding steel sheet. Next, each component will be described.

[0019] [Zinc-based cladding steel sheet]

As a starting sheet for chemical treatment, a zinc coated cladding steel sheet having excellent corrosion resistance and appearance is used. As used herein, the term “zinc-based cladding steel sheet” means a clad steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% Aluminum and 50 wt.% Or more zinc. Examples of the zinc-plated cladding steel sheet include hot-dip galvanized steel sheet (GI), hot dip galvanized steel sheet (GA), hot-dip galvanized steel sheet and zinc-coated clad steel, and hot-dip steel sheet with zinc-aluminum-magnesium clad coating. The plating layers of hot dip galvanized steel sheet (GI) and hot dip galvanized steel sheet (GA) also contain 0.1 wt.% Or more aluminum to prevent oxidation. The zinc coated clad steel sheet may be made by hot dip galvanizing, galvanizing, vapor deposition, or the like.

[0020] For example, a hot dip steel sheet with zinc-aluminum-magnesium clad coating can be manufactured by hot dip galvanizing using an alloy cladding bath containing from 1.0 to 22.0 wt.% Aluminum and from 1.5 up to 10.0 wt.% magnesium, with the remainder being essentially zinc. To increase the adhesion strength between the steel substrate and the cladding layer, silicon can be added to the cladding bath, which inhibits the growth of the iron-aluminum alloy layer at the interface between the steel substrate and the cladding layer, in the range from 0.005 to 2.0 wt.%. Further, to prevent the generation and growth of the Zn ₁₁ Mg ₂ phase, which adversely affects its appearance and corrosion resistance, titanium, boron, a boron-titanium alloy, a titanium-containing compound or a boron-containing compound can be added to the clad bath. The added amounts of these compounds are preferably set so that the titanium content ranges from 0.001 to 0.1 wt.%, And the boron content ranges from 0.0005 to 0.045 wt.%.

[0021] The type of steel substrate of the zinc plated cladding steel sheet is not particularly limited. Examples of the steel substrate include ordinary steel, low alloy steel, and stainless steel.

[0022] [Chemical conversion film]

A chemical conversion film is formed on the surface of a zinc-plated cladding steel sheet. Chemical conversion film improves corrosion resistance and blackening resistance of zinc coated clad steel sheet. The chemical conversion film includes a first chemical conversion layer (reaction layer) located on the surface of the zinc-clad steel sheet and mainly composed of vanadium, molybdenum and phosphorus, and a second chemical conversion layer placed on the first chemical conversion layer and in mainly consisting of an oxoate element of a group of 4 elements of the periodic table of chemical elements.

[0023] As used here, the term "corrosion resistance" provides one or both of the corrosion resistance of the flat part and the corrosion resistance of the treated part. “Corrosion resistance of a machined part” is the corrosion resistance of a machined part (machined part), such as bending, in which a chemically treated steel sheet is deformed, and “corrosion resistance of a flat part” means the corrosion resistance of a different part than the machined part in chemically treated steel sheet.

[0024] [Solution for chemical treatment]

A chemical conversion film is formed by applying and drying an alkaline solution for chemical treatment containing 1) water-soluble molybdate, 2) a vanadium salt, 3) an amine having a low boiling point, 4) an oxoate of an element of the group of 4 elements of the Periodic table of chemical elements, and 5) phosphate. By adjusting the pH of the solution for chemical treatment to an alkaline value, it is possible to form a first chemical conversion layer (reaction layer) without using a fluorine derivative or the like even on the aluminum portion of the surface of the clad layer having lower reactivity. When using a chemical treatment solution with such a composition, it becomes possible to form a chemical conversion film that can increase the corrosion resistance and blackening resistance of the zinc-clad steel sheet, even when the chemical treatment solution is dried at low temperature and for a short period of time . It should be noted that vanadium, caused by the vanadium salt, molybdenum, caused by water-soluble molybdate, and phosphorus, due to phosphate, are localized in the first chemical conversion layer. Further, the oxoate of an element of the group of 4 elements of the Periodic table of chemical elements is localized in the second chemical conversion layer. Next, each element contained in the chemical treatment solution will be described.

[0025] 1) Molybdate

Molybdate stabilizes the valency of vanadium in a chemical treatment solution and improves the blackening and corrosion resistance of chemically treated steel sheet. It was concluded that the molybdenum acid ion (hereinafter also referred to as the Mo-acid ion) forms a complex with the pentavalent vanadium ion (hereinafter also referred to as the pentavalent V ion) in an alkaline solution for chemical treatment, thereby stabilizing the valence of vanadium so that it is pentavalent.

[0026] The molar ratio of molybdenum to vanadium in the solution for chemical treatment, that is, the molar ratio of elemental molybdenum due to molybdate to elementary vanadium due to the vanadium salt (Mo / V) in the solution for chemical treatment varies from 0.4 up to 5.5. When the molar ratio of elemental molybdenum to elemental vanadium is less than 0.4, a problem arises such that the valence state of vanadium cannot be maintained as pentavalent. When the molar ratio of elemental molybdenum to elemental vanadium is more than 5.5, the Mo acid ion is more likely to form condensed acid, and the Mo acid ion, which forms a complex with the pentavalent V ion, becomes insufficient, so there is a problem that valency V cannot be stable.

Further, when a chemical conversion film is formed using a chemical treatment solution in which molybdate and amine are simultaneously present, a complex pentavalent or hexavalent molybdenum oxoate is formed in the chemical conversion film.

[0027] When a chemical conversion film is formed under alkaline conditions using a chemical treatment solution in which vanadium salt, molybdate and amine are present together, molybdenum predominantly reacts with the surface of the cladding layer together with the vanadium salt and phosphorus to form the first chemical conversion layer ( reaction layer) on the surface of the clad layer. As a result of this, molybdate forms a homogeneous reaction layer on the surface of the cladding layer together with vanadium acid and phosphorus, and thereby blackening resistance can be improved. Further, due to the combined presence of molybdate and an amine in a chemical conversion film, a complex pentavalent or hexavalent molybdenum oxoate is formed, the pentavalent molybdenum oxoate being oxidized, thereby forming an oxidized film; oxidized film also contributes to corrosion resistance. In addition, when the lattice defect described above occurs, the cladding layer appears to have a gray appearance, and the metallic luster is further suppressed due to greater absorption of light with a wavelength in the visible region of the spectrum.

[0028] The type of molybdate is not particularly limited to the extent that molybdate can perform the above functions. Examples of molybdate include molybdenum acid, ammonium molybdate and an alkali metal salt of molybdenum acid. Among them, from the viewpoint of corrosion resistance, molybdenum acid or ammonium molybdate is particularly preferred. The amount of molybdenum contained in the chemical conversion film preferably ranges from 1 to 60 parts by weight, based on 100 parts by weight of an element of the group of 4 elements of the Periodic Table of the chemical elements (e.g. zirconium). When the amount of molybdenum is less than 1 part by weight, there is a problem in that the blackening resistance cannot be sufficiently increased. When the amount of molybdenum is more than 60 parts by weight, the amount of molybdate that has not reacted with the surface of the cladding layer becomes excessive, so that there is such a problem that the corrosion resistance of the treated part can be reduced.

[0029] 2) Vanadium salt

Vanadium salt not only enhances corrosion resistance, but also improves blackening resistance. When a chemical conversion film is formed under alkaline conditions using a chemical treatment solution in which vanadium salt, molybdate and amine are present together, vanadium mainly reacts with the surface of the cladding layer together with molybdenum acid and phosphorus to form the first chemical conversion layer (reaction layer) on surface cladding layer. In this way, vanadium forms a homogeneous reaction layer on the surface of the cladding layer together with molybdenum acid and an element of the group of 4 elements of the Periodic table of chemical elements, and thereby increase the corrosion resistance and resistance to blackening.

[0030] The type of vanadium salt is not particularly limited insofar as the vanadium salt can fulfill the above functions. Examples of the vanadium salt include ammonium metavanadate, sodium metavanadate, potassium metavanadate, and vanadate obtained by dissolving vanadium pentoxide with an amine. In all these vanadium salts, the valence state of vanadium is pentavalent (hereinafter, vanadium having a valency of 5 is also called “pentavalent V”). Among them, ammonium metavanadate or vanadate obtained by dissolving vanadium pentoxide with an amine are particularly preferred in terms of corrosion resistance.

[0031] Typically, a pentavalent V ion in a chemical treatment solution has low valency stability. Accordingly, if the pentavalent V ion in the chemical treatment solution remains on its own, the concentration of the pentavalent V ion becomes insufficient to achieve a concentration at which the above reaction layer can be formed. Thus, as described above, the combined presence of molybdate under alkaline conditions increases the concentration of pentavalent V ion in the solution for chemical treatment. Further, it is assumed that the pentavalent V ion does not exhibit a higher solubility in the solution for chemical treatment than the vanadium ion in the bivalent to tetravalent state, chelated during reduction with organic acid or the like, and thereby more likely to deposit on the surface of the clad layer, generating a reaction.

[0032] The content of the vanadium salt in the chemical treatment solution is preferably 8 g / L or less, based on the vanadium atom. When this content is more than 8 g / l, the stability of the chemical treatment solution decreases, so that there is the possibility of precipitation when the chemical treatment solution is stored at room temperature for about a month. In this regard, in the case when the solution for chemical treatment is used immediately after its preparation, the aforementioned stability problem does not arise even when the above content is over 8 g / l.

[0033] The amount of vanadium contained in the chemical treatment solution preferably ranges from 2 to 20 parts by weight based on 100 parts by weight of an element of the group of 4 elements of the Periodic Table of the chemical elements (eg, zirconium). When the amount of vanadium is less than 2 parts by weight, there is such a problem that the corrosion resistance and the resistance to blackening cannot be sufficiently increased. When the amount of vanadium is more than 20 parts by weight, there is a risk that the amount of pentavalent vanadium that does not react with the surface of the clad layer may become excessive, causing a decrease in corrosion resistance.

[0034] The percentage of pentavalent vanadium based on mixed valence vanadium in the chemical conversion film is 0.7 or more. When the percentage of pentavalent vanadium based on mixed valence vanadium in the chemical conversion film is less than 0.7, there is such a problem that the blackening resistance cannot be sufficiently increased.

[0035] 3) Amine

Amine dissolves a salt containing pentavalent vanadium (hereinafter also referred to as the “pentavalent vanadium salt”) in a solution for chemical treatment, while maintaining the valence state of vanadium pentavalent (tetravalent when an organic acid is used), and also forms a complex pentavalent or hexavalent molybdenum from molybdate. The amine is preferably an amine having a low boiling point. The low boiling amine is an amine having a molecular weight of 80 or less. An amine having a molecular weight of 80 or less typically has a low boiling point and almost does not remain in the chemical conversion film, even when the chemical treatment solution is dried at a low temperature and for a short period of time, so that the amine can contribute to an increase in corrosion persistence. Examples of the low boiling amine include ammonia (used as aqueous ammonia), ethanolamine, 1-amino-2-propanol and ethylenediamine. When an excess amount of amine remains in the chemical conversion film after drying, the corrosion resistance of the chemically treated steel sheet is undesirably reduced due to leaching of the amine. Therefore, the amount of amine remaining in the chemical conversion film is preferably 10 wt.% Or less based on nitrogen, for reasons of preventing a decrease in the corrosion resistance of the chemically treated steel sheet. When using an amine having a molecular weight of 80 or less, the amount of residual amine can be 10 wt.% Or less based on nitrogen.

[0036] By dissolving pentavalent vanadium in a liquid amine or in an aqueous amine solution, a pentavalent vanadium salt having a low solubility in water can be mixed into a solution for chemical treatment, while maintaining the valence state of pentavalent vanadium. When a pentavalent vanadium salt is dissolved in a liquid amine, adding the resulting solution to an aqueous solution containing molybdate allows a solution to be prepared for chemical treatment. In addition, when a pentavalent vanadium salt is dissolved in an aqueous amine solution, a pentavalent vanadium salt can be added after molybdate and an amine to thereby directly prepare a solution for chemical treatment, or a pentavalent vanadium salt can be dissolved in an aqueous amine solution, and then obtained the solution may be added to the molybdate-containing aqueous solution to prepare a solution for chemical treatment. As a rule, an aqueous solution containing tetravalent vanadium (V ⁴⁺ ) is blue, while an aqueous solution containing pentavalent vanadium (V ⁵⁺ ) is yellow, and thus the valency of vanadium can be judged by the color of the solution for chemical treatment .

[0037] As described above, when vanadate is used as the vanadium salt, vanadium pentoxide is dissolved in the amine to prepare the vanadate. At this time, dissolution of pentavalent vanadium in the amine generates heat. The problem arises that pentavalent vanadium can be reduced to tetravalent vanadium in an environment with a high temperature of 40 ° C or higher. Thus, in order to dissolve the pentavalent vanadium salt in the amine, while maintaining the valence state of pentavalent vanadium, it is necessary to maintain the temperature of the environment surrounding pentavalent vanadium below 40 ° C. The manner in which the ambient temperature is kept below 40 ° C is not particularly limited. For example, by adding vanadium pentoxide to an amine solution (diluting the amine and vanadium pentoxide), the temperature of the medium can be kept below 40 ° C.

[0038] The molar ratio of amine to vanadium in the chemical treatment solution is 0.3 or more. When the molar ratio is less than 0.3, there is such a problem that the valence state of vanadium cannot be maintained at the pentavalent level. The molar ratio of amine to vanadium is preferably 10 or less, from those considerations that, while maintaining the valence of vanadium, to prevent the effect of reaching a plateau, and from the point of view of reducing the cost of the amine.

[0039] 4) Oxoate element of the group of 4 elements of the Periodic table of chemical elements

The oxoate of an element of the group of 4 elements of the Periodic table of chemical elements forms a dense chemical conversion film to increase corrosion resistance. That is, while it is difficult to form a dense chemical conversion film using a chemical treatment solution containing only molybdate and a vanadium salt, it is possible to form a chemical conversion film having high barrier properties by crosslinking molybdenum and vanadium by the addition of an oxoate of an element of the group of 4 elements of the Periodic table chemical elements.

[0040] The type of oxoate of an element of the group of 4 elements of the Periodic Table of the chemical elements is not particularly limited. Examples of an oxoate of an element of a group of 4 elements of the Periodic Table of Chemical Elements include derivatives of titanium, zirconium and hafnium. Examples of the type of oxoate include an oxygenate salt of bromine, an ammonium salt, an alkali metal salt and an alkaline earth metal salt. Among them, ammonium salt is preferred as an oxoate of an element of the group of 4 elements of the Periodic Table of Chemical Elements, and from the viewpoint of corrosion resistance, ammonium zirconium carbonate is particularly preferred.

[0041] 5) Phosphate

In addition, the chemical treatment solution contains phosphate. Phosphate interacts with the oxoate of an element of the group of 4 elements of the Periodic table of chemical elements with the formation of a dense chemical conversion film, thereby increasing corrosion resistance. The type of phosphate is not particularly limited to the extent that phosphate can perform the above functions. Examples of phosphate include alkali metal phosphate and ammonium phosphate. In particular, ammonium hydrogen phosphate or ammonium dihydrogen phosphate is preferred, which can sufficiently increase corrosion resistance even when dried at low temperature and for a short period of time. The amount of phosphorus in the chemical conversion film preferably ranges from 10 to 50 parts by weight based on 100 parts by weight of an element of the group of 4 elements of the Periodic Table of the chemical elements (e.g. zirconium). When the amount of phosphorus is less than 10 parts by weight, a crack is more likely to occur, which will form a defect in the chemical conversion film, so that there is such a problem that corrosion resistance may be reduced. When the amount of phosphorus is more than 50 parts by weight, unreacted phosphate remains in the chemical conversion film, so that there is such a problem that corrosion resistance may be reduced.

[0042] It should be noted that when a specific component used in a conventional chromium-free chemical treatment is added to the above chemical treatment solution, the expected characteristics of the chemically treated steel sheet may not be sufficient. For example, when a certain type of organic resin, silane coupling agent or organic acid is added, the pentavalent V ion is more likely to be reduced to the tetravalent vanadium ion, so that blackening resistance may be reduced. Further, the surface of the cladding coating adsorbs a functional group having a polarity, and thereby the formation of a reaction layer on this part is inhibited, and as a result of this there is such a problem that corrosion resistance is reduced. This phenomenon can also be observed when a film-forming auxiliary agent (a solvent such as butyl cellosolve) is added to form a film from an aqueous solution of an organic resin at low temperature. Thus, with respect to the chemical treatment solution according to the present invention, it is preferred that it does not contain an organic acid, an organic resin, a silane coupling agent and a film-forming auxiliary.

[0043] The above specific component is not substantially contained in the chemical treatment solution. That is, the chemical treatment solution for the most part may not be made up by the above component. As used here, the term "essentially not contained" means that "can be contained in such a range that the above effects of the present invention are achieved," and also means that "it is preferably not contained at all for reasons of achieving the essential effects of the above described invention." Examples of a specific component include a hydrophilic resin, a fluorine derivative due to a fluoride ion or a metal fluoride ion, and silicon due to a silanol group.

[0044] A hydrophilic resin is a resin that dissolves or uniformly disperses in an aqueous medium, and contains a hydrophilic functional group in an amount sufficient to enable the resin to dissolve or uniformly disperse in an aqueous medium. A hydrophilic resin may also be called an aqueous resin. A hydrophilic resin of any one type, or two or many types, may be used. Examples of the hydrophilic resin include a resin that dissolves or uniformly disperses in an aqueous medium to increase the viscosity of the aqueous medium; more specific examples of it include acrylic resin, polyolefin, epoxy resin and polyurethane, which have a hydrophilic functional group as needed as a result of the modification. Examples of the hydrophilic functional group include a hydroxyl group, a carboxyl group and an amino group. A hydrophilic functional group may also be applied of any one type, or two or many types.

[0045] At the same time, a polar group is present on the surface of the zinc-clad coating steel sheet, which typically exists on the surface of the metal, such as a hydroxyl group. It is believed that the aforementioned reaction layer is formed as a result of the specific interaction of the polar group with the component that makes up the reaction layer, such as molybdenum and vanadium in the chemical treatment solution.

[0046] Accordingly, it is believed that when a large amount of hydrophilic resin is present in the chemical treatment solution, the hydrophilic functional group interacts, such as hydrogen bonding or dehydration condensation, with a polar group on the surface of the clad-coated steel sheet based zinc, so that the polar group that must interact with the component in the reaction layer becomes insufficient relative to the component in the reaction layer, and as a result inhibited the formation of the reaction layer, whereby the expected characteristics of chemically-treated steel sheet are insufficient.

[0047] For the aforementioned reasons, the permissible level of hydrophilic resin in the chemical treatment solution is not more than 100 wt.% (That is, 100 wt.% Or less), based on the total amount of vanadium and molybdenum in the chemical treatment solution. When the content of the hydrophilic resin is more than 100 wt.%, The formation of the reaction layer is inhibited, so that the expected functions, such as corrosion resistance and blackening resistance, chemically treated steel sheet may be insufficient. From a position of sufficiently high manifestation of the expected functions in a chemically treated steel sheet, the content of the hydrophilic resin is preferably as low as possible; for example, its content is preferably 50 wt.% or less, more preferably 20 wt.% or less, and most preferably 0 wt.%.

[0048] Fluorine due to a fluoride ion or a metal fluoride ion can exhibit etching on the surface of a zinc-clad coating steel sheet to form a fluoride layer. Examples of fluorine include F ^- and MF ₆ ^2- . As used here, "M" refers to a tetravalent metal element, for example, zirconium, titanium or silicon. Examples of the aforementioned component that serves as a fluorine source include potassium fluoride (KF), titanium ammonium fluoride ((NH ₄ ) ₂ TiF ₆ ), and hydrofluoric acid (H ₂ SiF ₆ ). A fluorine derivative of any one type, or two or many types thereof, can be used.

[0049] It is believed that when a large amount of fluorine is present in the chemical treatment solution, the surface of the zinc clad clad steel sheet is dissolved by the etching action of the fluorine, and the fluorine from the chemical treatment solution is concentrated on the dissolved portion, and on the surface of the steel a zinc-clad coating sheet forms a thin layer of fluoride so that a polar group that is open to the surface of the zinc-clad coating steel sheet for interaction with the component in the reaction layer becomes insufficient relative to the component in the reaction layer, causing inhibition of the formation of the reaction layer, as a result of which the expected characteristics of the chemically treated steel sheet are insufficient. Examples of a component that results from dissolution of the surface of a zinc clad coating steel sheet include Zn ²⁺ , Al ³⁺ and Mg ²⁺ , and examples of fluoride include ZnF ₂ , AlF ₃ and MgF ₂ . It should be noted that the presence of fluoride on a chemically treated steel sheet can be confirmed by X-ray photoelectron spectroscopy (XPS).

[0050] For the above considerations, the total fluorine content due to the fluoride ion or metal fluoride ion in the chemical treatment solution is not more than 30 wt.% (That is, 30 wt.% Or less), based on the total amount of vanadium and molybdenum in solution for chemical treatment. When the content of the fluorine derivative is more than 30 wt.%, The formation of the reaction layer may be inhibited, so that the expected functions of the chemically treated steel sheet, such as corrosion resistance and blackening resistance, may be insufficient. From the standpoint of a sufficiently high manifestation of the expected functions in a chemically treated steel sheet, the fluorine content is preferably as low as possible; for example, its content is preferably 10 wt.% or less, more preferably 5 wt.% or less, and most preferably 0 wt.%.

[0051] Silicon due to the silanol group has a hydroxyl group. Accordingly, it is assumed that when the chemical treatment solution contains silicon, the presence of silicon, the source of which is the silanol group, inhibits the formation of the reaction layer for the same reason as with respect to the hydrophilic resin. That is, it is believed that when a large amount of silicon is present in the solution for chemical treatment, the hydrophilic group in the silanol group interacts, such as the formation of a hydrogen bond or condensation with dehydration, with the polar group on the surface of the zinc-plated steel sheet, so that the polar group that must interact with the component in the reaction layer becomes insufficient relative to the component in the reaction layer, and as a result, the image is inhibited the reaction layer, as a result of which the expected characteristics of the chemically treated steel sheet are insufficient. Examples of a component that serves as a source of silicon include a silane coupling agent; more specific examples of it include 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane and vinylethoxysilane.

[0052] For the above considerations, the content of silicon originating from the silanol group in the chemical treatment solution is not more than 50 wt.% (That is, 50 wt.% Or less), based on the total amount of vanadium and molybdenum in the chemical treatment solution. When the silicon content is more than 50 wt.%, The formation of the reaction layer can be inhibited, so that the expected characteristics, such as corrosion resistance and resistance to blackening, chemically treated steel sheet may be insufficient. From a position of sufficiently high manifestation of the expected characteristics in a chemically treated steel sheet, the silicon content is preferably as low as possible; for example, its content is preferably 20 wt.% or less, more preferably 10 wt.% or less, and most preferably 0 wt.%.

[0053] The presence and content of a hydrophilic resin, fluorine or silicon in a chemical treatment solution can be determined using known analyzers, such as an infrared (IR, IR) spectrometer, a nuclear magnetic resonance spectrometer (NMR, NMR), an emission spectroscopy analyzer Inductively coupled plasma (ICP), and X-ray fluorescence analyzer.

[0054] A method for identifying the structure of a chemical conversion film is not particularly limited. For example, it can be confirmed that a chemical conversion film includes a first chemical conversion layer and a second chemical conversion layer by examining a cross section of a chemically treated steel sheet using a transmission electron microscope (TEM). Further, energy-dispersive X-ray spectroscopy (EDS) measurement can be used to identify the component contained in each chemical conversion layer. Further, glow emitting optical emission spectroscopy (GDS) can be used to identify the distribution of each component. Moreover, X-ray photoelectron spectroscopy (XPS) can be used to identify the percentage of pentavalent vanadium based on mixed valence vanadium in a chemical conversion film.

[0055] [Method of forming a chemical conversion film]

As described above, a chemical conversion film is formed by applying a chemical treatment solution containing each of the above components to the surface of a zinc coated clad steel sheet and drying it.

[0056] The method for applying a solution for chemical treatment is not particularly limited. Examples of a method for applying a solution for chemical treatment include a roller coating method, a centrifugation coating method, and a spray coating method. The amount of precipitated solution for chemical treatment preferably varies within the range from 50 to 1000 mg / m ² . When the amount to be deposited is less than 50 mg / m ² , the corrosion resistance cannot be sufficiently improved. When the deposited amount is more than 1000 mg / m ² , the corrosion resistance becomes undesirably excessive. Further, taking into account spot welding, the deposited amount of the chemical conversion film more preferably ranges from 50 to 500 mg / m ² .

[0057] The drying temperature of the chemical treatment solution (sheet temperature) may be a normal (room) temperature, but is preferably 30 ° C or higher. The chemical treatment solution of the present invention can increase the corrosion and blackening resistance even when it is dried at low temperature and for a long period of time. When the drying temperature exceeds 120 ° C, undesired cracking occurs due to shrinkage with a reduction in the volume of the chemical conversion film as a result of, for example, rapid decomposition of the ammonium components, so that there is a problem that the corrosion resistance of the chemically treated steel sheet may be reduced. Therefore, the drying temperature of the chemical treatment solution is preferably within the range of 30 to 120 ° C, and more preferably 35 to 85 ° C.

[0058] As described above, the chemical treatment solution according to the present invention contains the aforementioned water-soluble molybdate, vanadium salt, amine, oxoate of an element of group 4 of the Periodic Table of the chemical elements, and the phosphate compound and molybdate and amine are contained in the above predetermined salt ratio vanadium. In addition, the chemical treatment solution according to the present invention contains neither the aforementioned hydrophilic resin, nor fluorine due to the fluoride ion or metal fluoride ion, nor silicon due to the silanol group, or, alternatively, contains these elements only to the above specific allowable amount. Since such a solution for chemical treatment is used for production, the chemically treated steel sheet according to the present invention includes a cladding steel sheet based on zinc, vanadium, molybdenum, phosphorus and oxoate of an element of group 4 of the elements of the Periodic table of chemical elements, and includes a two-layer a structure of a first chemical conversion layer and a second chemical conversion layer. Therefore, the chemically treated steel sheet according to the present invention has excellent corrosion resistance and blackening resistance even when the chemical treatment solution is dried at a low temperature and for a short period of time.

[0059] The present invention will now be explained in detail with reference to Examples, which, however, should not be construed as limiting the scope of the invention.

Examples

[0060] [Production of zinc plated clad steel sheet]

A steel strip of ultralow carbon steel with titanium addition having a sheet thickness of 0.5 mm was used as a sheet substrate for hot dip galvanizing of a zinc alloy clad steel sheet having a zinc-based layer containing 6 wt.% Aluminum, 3 wt.% magnesium, 0.020 wt.% silicon, 0.020 wt.% titanium, and 0.0005 wt.% boron (deposited amount of clad coating 90 g / m ² on each side), on a continuous hot dip galvanizing process line, and received plakira A zinc alloy steel sheet was used as a starting sheet for chemical treatment.

[0061] [Example 1]

The water-soluble molybdenum salt, vanadium salt, amine, oxoate of an element of group 4 elements of the Periodic table of chemical elements and phosphate, which are shown in Table 1, were dissolved in water to prepare solutions 1-50 for chemical treatment. The name and symbol of each compound added to the chemical treatment solution are shown in Table 1. The composition and color of each chemical treatment solution are shown in Tables 2-1, 2-2, 3-1, 3-2, 4-1 and 4 -2. It should be noted that the dissolution of the vanadium salt was carried out in an aqueous solution having a liquid temperature of 40 ° C or lower containing an amine to prevent the recovery of vanadium.

[0062] Table 1

Type of Symbol Connection Name Chemical formula Molecular mass Molybdate M1 Ammonium molybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ · 4H ₂ O - Vanadium salt V1 Vanadium Pentaoxide V ₂ O ₅ - V2 Ammonium Metavanadate NH ₄ VO ₃ - V3 Sodium Metavanadate NaVO ₃ - Amine EA Ethanolamine C ₂ H ₇ NO 61 DEA Diethanolamine C ₄ H ₁₁ NO ₂ 105 IPA 1-amino-2-propanol C ₃ H ₉ NO 75 Tmah Tetramethylammonium Hydroxide (CH ₃ ) ₄ N ⁺ OH ^- 91 EDTA Ethylenediaminetetraacetic acid (HOOCCH ₂ ) ₂ NCH ₂ CH ₂ N (CH ₂ COOH) ₂ 292 EN Ethylenediamine NH ₂ CH ₂ CH ₂ NH ₂ 60 NH Water ammonia NH ₄ OH 35 Group 4 oxoate A1 Ammonium Zirconium Carbonate (NH ₄ ) ₂ Zr (OH) ₂ (CO ₃ ) ₂ - Phosphate P1 Ammonium hydrogen phosphate (NH ₄ ) ₂ HPO ₄ - P2 Ammonium dihydrogen phosphate NH ₄ H ₂ PO ₄ - P3 Ammonium Orthophosphate (NH ₄ ) ₃ PO ₄ - P4 Phosphoric acid H ₃ PO ₃ - P5 1-hydroxyethane-1,1-diphosphonic acid C ₂ H ₈ O ₇ P ₂ - Fluorine compound F1 Potassium fluoride Kf - F2 Titanium ammonium fluoride (NH ₄ ) ₂ TiF ₆ - F3 Hydrofluoric Acid H ₂ SiF ₆ - Silicon compound S1 3-aminopropyltrimethoxysilane H ₂ NC ₃ H ₆ Si (OCH ₃ ) ₃ - S2 3-Glycidoxypropyltriethoxysilane (H ₂ CCHO) CH ₂ OC ₃ H ₆ Si (OC ₂ H ₅ ) ₃ - S3 Vinylethoxysilane H ₂ C = CHSi (OC ₂ H ₅ ) ₃ -

[0063] Table 2-1

Category Solution for chemical treatment No. Molybdate Vanadium salt Amine Compound Mo concentration (g / l) Compound The concentration of V (g / l) Compound Concentration
(g / l) Example one M1 0,075 V1 0.10 EA 0,036 Comparative example 2 M1 0.019 V1 0.10 IPA 0,044 Example 3 M1 0,075 V2 0.01 EN 0,035 Example four M1 0,075 V2 0.10 NH 0,021 Comparative example 5 M1 5.00 V3 0.10 EA 0,036 Example 6 M1 1.51 V3 2.00 IPA 0.883 Example 7 M1 0,075 V1 0.10 EN 0,036 Comparative example 8 M1 0,075 V2 0.10 NH 0.007 Example 9 M1 24.0 V3 8.00 EN 15.1 Comparative example 10 M1 1.51 V1 8.00 NH 8.79 Comparative example eleven M1 0.015 V3 8.00 EA 15.3 Example 12 M1 0,075 V3 0.02 NH 0,027 Example 13 M1 24.0 V2 8.00 EA 15.3 Example fourteen M1 45,2 V3 8.00 IPA 18.8 Comparative example fifteen M1 90,4 V1 8.00 EN 15.1 Example 16 M1 24.0 V2 10.00 EA 19,2 Example 17 M1 24.0 V2 8.00 IPA 18.8 Comparative example eighteen M1 24.0 V3 8.00 EN 1.89 Example 19 M1 22.6 V3 8.00 DEA 39.6 Example twenty M1 0.753 V3 0.80 EA 3.07

Table 2-2

Category Solution for chemical treatment No. Group 4 oxoate Phosphate Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Compound Zr concentration (g / l) Compound The concentration of P (g / l) Example one A1 5,0 P1 0.25 0.40 0.30 Yellow Comparative example 2 A1 5,0 P2 0.25 0.10 0.30 Yellowish green Example 3 A1 5,0 P4 0.25 4.00 3.00 Yellow Example four A1 5,0 P5 0.05 0.40 0.30 Yellow Comparative example 5 A1 5,0 P3 0.25 26.55 0.30 Yellowish green Example 6 A1 5,0 P3 0.25 0.40 0.30 Yellow Example 7 A1 5,0 P4 6.00 0.40 0.30 Yellow Comparative example 8 A1 5,0 P2 0.25 0.40 0.10 Yellowish green Example 9 A1 40,0 P1 20,0 1,59 1,60 Yellow Comparative example 10 A1 40,0 P3 20,0 0.10 1,60 Yellowish green Comparative example eleven A1 40,0 P2 20,0 0.00 1,60 Yellowish green Example 12 A1 40,0 P5 20,0 1,59 1,60 Yellow Example 13 A1 40,0 P4 2.00 1,59 1,60 Yellow Example fourteen A1 40,0 P3 20,0 3.00 1,60 Yellow Comparative example fifteen A1 40,0 P2 20,0 6.00 1,60 Yellowish green Example 16 A1 40,0 P1 20,0 1.27 1,60 Yellow Example 17 A1 40,0 P5 60.0 1,59 1,60 Yellow Comparative example eighteen A1 40,0 P3 20,0 1,59 0.20 Yellowish green Example 19 A1 40,0 P1 20,0 1,50 2.40 Yellow Example twenty A1 40,0 P4 20,0 0.50 3.20 Yellow

[0064] Table 3-1 Category Solution for chemical treatment No. Molybdate Vanadium salt Amine Compound Mo concentration (g / l) Compound The concentration of V (g / l) Compound Concentration
(g / l) Example 21 M1 24.0 V2 8.00 NH 8.79 Example 22 M1 24.0 V2 8.00 EN 15.1 Example 23 M1 24.0 V3 8.00 Tmah 22.9 Example 24 M1 14.1 V2 5.00 NH 11.0 Example 25 M1 1.98 V3 0.30 EA 1.15 Example 26 M1 0,075 V1 0.10 EN 0,036 Example 27 M1 24.0 V3 8.00 EDTA 73,4 Example 28 M1 25,4 V2 3.00 NH 1.65 Example 29th M1 0.942 V2 1.00 NH 1.10 Example thirty M1 6.59 V1 1.00 IPA 5.89 Example 31 M1 3,50 V2 2.00 NH 2.20 Example 32 M1 0,075 V1 0.10 EDTA 0.172 Example 33 M1 1.41 V3 0.50 IPA 1.77 Example 34 M1 0,075 V2 0.10 NH 0,021 Example 35 M1 3.77 V3 0.80 IPA 3.77 Example 36 M1 24.0 V2 8.00 NH 8.79 Example 37 M1 3,50 V1 2.00 IPA 4.71 Example 38 M1 0,075 V3 0.10 EA 0,036 Example 39 M1 3.11 V3 0.30 IPA 1.06 Example 40 M1 7.53 V2 8.00 EN 22.6

Table 3-2

Category Solution for chemical treatment No. Group 4 oxoate Phosphate Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Compound Zr concentration (g / l) Compound The concentration of P (g / l) Example 21 A1 40,0 P2 0.50 1,59 1,60 Yellow Example 22 A1 5,0 P4 0.25 1,59 1,60 Yellow Example 23 A1 40,0 P1 20,0 1,59 1,60 Yellow Example 24 A1 33.5 P5 0.60 1,50 3.20 Yellow Example 25 A1 5,0 P3 0.25 3,50 3.20 Yellow Example 26 A1 14.0 P4 6.00 0.40 0.30 Yellow Example 27 A1 40,0 P1 20,0 1,59 1,60 Yellow Example 28 A1 27.0 P2 0.50 4,50 0.80 Yellow Example 29th A1 46.5 P2 0.50 0.50 1,60 Yellow Example thirty A1 5,0 P2 0.25 3,50 4.00 Yellow Example 31 A1 7.5 P2 0.50 0.93 1,60 Yellow Example 32 A1 5,0 P1 0.25 0.40 0.30 Yellow Example 33 A1 40,0 P3 0.50 1,50 2.40 Yellow Example 34 A1 40,0 P2 0.50 0.40 0.30 Yellow Example 35 A1 5,0 P3 0.25 2,50 3.20 Yellow Example 36 A1 33.5 P2 0.50 1,59 16,0 Yellow Example 37 A1 14.0 P2 0.50 0.93 1,60 Yellow Example 38 A1 33.5 P3 0.50 0.40 0.30 Yellow Example 39 A1 40,0 P4 20,0 5.50 2.40 Yellow Example 40 A1 20.5 P4 0.50 0.50 2.40 Yellow

[0065] Table 4-1

Category Solution for chemical treatment No. Molybdate Vanadium salt Amine Compound Mo concentration (g / l) Compound Concentration
V (g / l) Compound Concentration
(g / l) Example 41 M1 24.0 V3 8.00 EN 15.1 Example 42 M1 0,075 V3 0.10 NH 0,021 Example 43 M1 0.471 V1 0.50 DEA 4.12 Example 44 M1 24.0 V2 8.00 NH 8.79 Example 45 M1 23.5 V2 5.00 IPA 29.4 Example 46 M1 24.0 V2 8.00 NH 8.79 Example 47 M1 0,075 V3 0.10 IPA 0,044 Example 48 M1 0,075 V2 0.10 IPA 0,044 Example 49 M1 0,075 V1 0.10 Tmah 0,054 Example fifty M1 14.1 V1 3.00 EN 5.75

Table 4-2 Category Solution for chemical treatment No. Group 4 oxoate Phosphate Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Compound Zr concentration (g / l) Compound The concentration of P (g / l) Example 41 A1 40,0 P5 20,0 1,59 1,60 Yellow Example 42 A1 40,0 P2 20,0 0.40 0.30 Yellow Example 43 A1 5,0 P1 0.25 0.50 4.00 Yellow Example 44 A1 46.5 P2 0.50 1,59 1,60 Yellow Example 45 A1 27.0 P1 7.50 2,50 4.00 Yellow Example 46 A1 5,0 P5 0.25 1,59 1,60 Yellow Example 47 A1 40,0 P3 20,0 0.40 0.30 Yellow Example 48 A1 27.0 P5 7.50 0.40 0.30 Yellow Example 49 A1 5,0 P1 0.25 0.40 0.30 Yellow Example fifty A1 7.5 P4 6.00 2,50 1,60 Yellow

[0066] The surface of the base sheet for chemical treatment was degreased and dried. Then, each of the solutions No. 1-18 for chemical treatment shown in Table 2-1 was applied to the surface of the initial sheet for chemical treatment, and immediately after that it was heated and dried at a low temperature (temperature of a steel strip at 40 or 80 ° С) using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. Thus, chemically treated steel sheets No. 1-36 having a chemical conversion film were made. It should be noted that the deposited amount of the chemical conversion film on all chemically treated steel sheets was found to be 200 mg / m ² .

[0067] [Assessment of chemically treated steel sheet]

For test samples cut from each chemically treated steel sheet, the structure of the chemical conversion film was identified; determined the percentage of pentavalent vanadium based on vanadium mixed valence in the film; the deposited amount of the film was measured; and subjected the test samples to a corrosion test and a blackening test.

[0068] (1) Identification of the structure of the chemical conversion film

The structure of the chemical conversion film was identified using the aforementioned TEM, EDS, and XPS methods.

[0069] For example, FIG. 1 is a TEM cross-sectional view of a test sample of chemically treated steel sheet No. 17. As illustrated in FIG. 1, a chemical conversion film has a two-layer structure including a first chemical conversion layer and a second chemical conversion layer.

FIG. 2 shows the distribution of elements in a test sample of chemically treated steel sheet No. 17, from its surface in the depth direction, measured using the GDS method. The abscissa in FIG. 2 indicates the measurement time (respectively, depth from the surface), and the ordinate indicates the relative intensity. As shown in FIG. 2, in a chemical conversion film of chemically treated steel sheet No. 17, the first chemical conversion layer contains large amounts of molybdenum, vanadium and phosphorus, and the second chemical conversion layer contains zirconium.

[0071] Although not specifically illustrated, another chemically treated steel sheet classified in the Examples also confirmed that the chemical conversion film has a two-layer structure of the same kind as chemically treated steel sheet No. 17 and contains vanadium, molybdenum and phosphorus in the first chemical conversion layer, and the oxoate of an element of the group of 4 elements of the Periodic table of chemical elements in the second chemical conversion layer. The two-layer structure of the chemical conversion film was not confirmed in the chemically treated steel sheets described in the Comparative Examples.

[0072] (2) Measurement of the deposited amount of chemical conversion film

To confirm the amount of deposited amount of coating, the amount of zirconium in the film was measured using an X-ray fluorescence analyzer, and the measurement results were used as an indicator of the deposited amount of coating.

[0073] (3) Measurement of the percentage of pentavalent vanadium based on mixed valence vanadium in a chemical conversion film

The percentage of pentavalent vanadium based on mixed valence vanadium (V ⁵⁺ / V) in the chemical conversion film was determined by analyzing the chemical binding state of vanadium in the chemical conversion film using X-ray photoelectron spectroscopy (XPS). Two points of the surface layer of the chemical conversion film and the interface between the chemical conversion film and the cladding layer were taken as points for analysis for each position from 10 locations arbitrarily selected from the above test samples. An analysis of the interface between the chemical conversion film and the cladding layer was performed after the chemical conversion film was sprayed from the surface layer using an argon beam. The depth to which the chemical conversion film was sprayed was determined by measuring the thickness of the chemical conversion film from a cross-sectional survey using TEM. The percentage of pentavalent vanadium based on mixed valence vanadium was determined by the percentage of the peak area at about 516.5 eV due to V ⁵⁺ (S _V5 ), based on the total sum of the peak area due to V ⁵⁺ and the peak area at 514 eV due to V ⁴⁺ (S _V4 ) (S _V5 + S _V4 )). The average percentage of 10 measurement positions on each test sample was used as the percentage of pentavalent vanadium based on mixed valence vanadium (V ⁵⁺ / V) in the chemically treated steel sheet.

[0074] For example, FIG. 3 represents the intensity profile of the chemical bonding energy corresponding to the vanadium 2p orbital on the film / cladding layer interface in one place from 10 measurement positions in which a test sample of chemically treated steel sheet No. 12 obtained by drying solution No. 4 for chemical treatment at a drying temperature of 80 ° C. The abscissa in FIG. 3 indicates binding energy, and ordinate indicates relative intensity for a short period of time (per second). Next, the solid line Mv in FIG. 3 is a chemical bond energy intensity profile actually measured at a measurement position. The dotted line P _v5 indicates the peak due to pentavalent vanadium, the dotted line P _v4 indicates the peak due to tetravalent vanadium, and the solid line B indicates the baseline.

[0075] From FIG. 3, it was confirmed that the percentage of V ⁵⁺ in the chemical conversion film was 0.7 or more in the aforementioned test sample. It was confirmed that the percentage of V ⁵⁺ in the chemical conversion film was 0.7 or more also in other chemically treated steel sheets, although this is not specifically illustrated.

[0076] (4) Corrosion Test of the Flat Part

The edge surface of the test piece was sealed from each chemically treated steel sheet, and it was tested in salt fog for 120 hours in accordance with JIS Z2371, and then white rust was examined on the surface of the test piece. Each chemically treated steel sheet was evaluated as follows: when the percentage of the area where white rust formed was 5% or less, an “A” rating was given; when the percentage was from more than 5% to 10% or less, a rating of "B" was given; when the percentage was from more than 10% to less than 30%, a rating of "C" was given; and when the percentage was 30% or more, it was rated as “D”.

[0077] (5) Corrosion test of the treated part

An exhaust test was carried out with a roller (roller height: 4 mm, pressure: 1.0 kN) on a test specimen of 30 mm × 250 mm from each chemically treated steel sheet, and the edge surface of the test specimen was sealed and subjected to salt spray testing in within 24 hours in accordance with JIS Z2371; after that, white rust was examined on the sliding surface. Each chemically treated steel sheet was evaluated as follows: when the percentage of the area where white rust formed was 5% or less, an “A” rating was given; when the percentage was from more than 5% to 10% or less, a rating of "B" was given; when the percentage was from more than 10% to less than 30%, a rating of "C" was given; and when the percentage was 30% or more, it was rated as “D”.

[0078] (6) Blacking Test

A test sample from each chemically treated steel sheet was left to stand for a predetermined time in a humid atmosphere (temperature 60 ° C, relative humidity (RH) 90%), and then the gloss of the test sample was compared before and after the test. Gloss (L value) of the test sample was measured using a spectroscopic differential colorimeter (TC-1800; manufactured by Tokyo Denshoku Co., Ltd.). Each chemically treated steel sheet was evaluated as follows: when the difference ΔL in gloss was 3.0 or less, a rating of "A" was given; when the difference ΔL in gloss was from more than 3.0 to 6.0 or less, a rating of "B" was given; when the difference ΔL in gloss was from more than 6.0 to less than 10.0, a rating of "C" was given; and when the difference ΔL in gloss was 10.0 or more, a rating of "D" was given.

[0079] (7) Evaluation Results

The solutions used for chemical treatment, the proportion of each element in the chemical conversion film, the results of the corrosion resistance test and the results of the blacking test for each chemically treated steel sheet are shown in Tables 5-1, 5-2, 6-1 and 6-2 . It should be noted that in the following tables, the proportion of each element in a chemical conversion film is presented in parts by weight of each element per 100 parts by weight of zirconium.

[0080] Table 5-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemical conversion film
(parts by weight) Mo V P Example one one 200 40 1,5 2.0 5,0 Comparative example 2 2 200 40 0.4 2.0 5,0 Example 3 3 200 40 1,5 0.2 5,0 Example four four 200 40 1,5 2.0 1,0 Comparative example 5 5 200 40 100.0 2.0 5,0 Example 6 6 200 40 30.1 40,0 5,0 Example 7 7 200 40 1,5 2.0 120.0 Comparative example 8 8 200 40 1,5 2.0 5,0 Example 9 one 200 80 1,5 2.0 5,0 Comparative example 10 2 200 80 0.4 2.0 5,0 Example eleven 3 200 80 1,5 0.2 5,0 Example 12 four 200 80 1, .5 2.0 1,0 Comparative example 13 5 200 80 100.0 2.0 5,0 Example fourteen 6 200 80 30.1 40,0 5,0 Example fifteen 7 200 80 1,5 2.0 120.0 Comparative example 16 8 200 80 1,5 2.0 5,0

Table 5-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example one one 0.92 A A A Comparative example 2 2 0.40 D D D Example 3 3 0.88 B B B Example four four 0.79 B B A Comparative example 5 5 0.45 C D D Example 6 6 0.95 A B A Example 7 7 0.75 B B A Comparative example 8 8 0.40 C C D Example 9 one 0.95 A A A Comparative example 10 2 0.41 D D D Example eleven 3 0.91 B B B Example 12 four 0.81 B B A Comparative example 13 5 0.46 C D D Example fourteen 6 0.98 A B A Example fifteen 7 0.77 B B A Comparative example 16 8 0.41 C C D

[0081] Table 6-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Tempera drying
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 17 9 200 40 60.0 20,0 50,0 Comparative example eighteen 10 200 40 3.8 20,0 50,0 Comparative example 19 eleven 200 40 0,0 20,0 50,0 Example twenty 12 200 40 0.2 0.1 50,0 Example 21 13 200 40 60.0 20,0 5,0 Example 22 fourteen 200 40 113.0 20,0 50,0 Comparative example 23 fifteen 200 40 226.0 20,0 50,0 Example 24 16 200 40 60.0 25.0 50,0 Example 25 17 200 40 60.0 20,0 150.0 Comparative example 26 eighteen 200 40 60.0 20,0 50,0 Example 27 9 200 80 60.0 20,0 50,0 Comparative example 28 10 200 80 3.8 20,0 50,0 Comparative example 29th eleven 200 80 0,0 20,0 50,0 Example thirty 12 200 80 0.2 0.1 50,0 Example 31 13 200 80 60.0 20,0 5,0 Example 32 fourteen 200 80 113.0 20,0 50,0 Comparative example 33 fifteen 200 80 226.0 20,0 50,0 Example 34 16 200 80 60.0 25.0 50,0 Example 35 17 200 80 60.0 20,0 150.0 Comparative example 36 eighteen 200 80 60.0 20,0 50,0

Table 6-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 17 9 0.92 A A A Comparative example eighteen 10 0.43 C C D Comparative example 19 eleven 0.35 C C D Example twenty 12 0.95 B B B Example 21 13 0.92 B B A Example 22 fourteen 0.86 A B A Comparative example 23 fifteen 0.25 C D D Example 24 16 0.85 A B A Example 25 17 0.90 B B A Comparative example 26 eighteen 0.32 C C D Example 27 9 0.95 A A A Comparative example 28 10 0.44 C C D Comparative example 29th eleven 0.36 C C D Example thirty 12 0.98 B B B Example 31 13 0.95 B B A Example 32 fourteen 0.89 B D B Comparative example 33 fifteen 0.26 C D D Example 34 16 0.88 A B A Example 35 17 0.93 B B A Comparative example 36 eighteen 0.33 C C D

[0082] As is evident from Tables 5-1, 5-2, 6-1 and 6-2, chemically treated steel sheets, each of which has a chemical conversion film, in which the percentage of pentavalent vanadium based on mixed valence vanadium in chemical the conversion film is 0.7 or more, and which includes a first chemical conversion layer containing vanadium, molybdenum and phosphorus, and a second chemical conversion layer located on the first chemical conversion layer and containing an oxoate of an element of the group of 4 elements Periodic a table of chemical elements, the chemical conversion film being placed on the surface of a zinc-plated cladding steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% aluminum, have favorable corrosion and blackening resistance . A chemical conversion film is obtained by applying a chemical treatment solution that contains water-soluble molybdate, a vanadium salt, an amine, an oxoate of an element of group 4 of the Periodic Table of the chemical elements and phosphate, in which the molar ratio of molybdenum to vanadium is from 0.4 to 5.5, and the molar ratio of amine to vanadium is 0.3 or more on a zinc coated clad steel sheet, followed by drying. Favorable corrosion and blackening resistance of chemically treated steel sheets are obtained even when the chemical treatment solution applied to the clad steel sheet is dried at a relatively low drying temperature of 40 ° C or 80 ° C.

[0083] In addition, as is apparent from Tables 5-1, 5-2, 6-1, and 6-2, when the percentage of pentavalent vanadium in the chemical conversion film is 0.7 or less, corrosion resistance and blackening resistance are worse .

[0084] [Example 2]

Then, chemically treated steel sheets No. 37-100 were made in the same way as chemically treated steel sheet No. 1, except that the type and quantity of the applied solutions for chemical treatment were changed, as shown in the following tables, and evaluated in the same way, as chemically treated steel sheets No. 1-36. The results are shown in the following Tables 7-1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1 and 10-2.

[0085] Table 7-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 37 19 200 40 56.5 20,0 50,0 Example 38 twenty 500 40 1.9 2.0 50,0 Example 39 21 500 40 60.0 20,0 1.3 Example 40 22 one hundred 40 480.0 160,0 5,0 Example 41 23 300 40 60.0 20,0 50,0 Example 42 24 1000 40 42,2 14.9 1.8 Example 43 25 500 40 39.6 6.0 5,0 Example 44 26 400 40 0.5 0.7 42.9 Example 45 27 250 40 60.0 20,0 50,0 Example 46 28 one hundred 40 94.2 11.1 1.9 Example 47 29th 150 40 2.0 2.2 1,1 Example 48 thirty fifty 40 131.8 20,0 5,0 Example 49 31 one hundred 40 46.7 26.7 6.7 Example fifty 32 400 40 1,5 2.0 5,0 Example 51 33 250 40 3,5 1.3 1.3 Example 52 34 10,000 40 0.2 0.3 1.3

Table 7-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 37 19 0.87 B B A Example 38 twenty 0.93 A A A Example 39 21 0.96 B B A Example 40 22 0.92 B B A Example 41 23 0.91 B B A Example 42 24 0.89 A B A Example 43 25 0.85 B A A Example 44 26 0.93 B B B Example 45 27 0.76 B B A Example 46 28 0.79 B B A Example 47 29th 0.91 B A A Example 48 thirty 0.86 A B A Example 49 31 0.98 B A A Example fifty 32 0.86 B B A Example 51 33 0.70 A B A Example 52 34 0.95 B A B

[0086] Table 8-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 53 35 1000 40 75.3 16,0 5,0 Example 54 36 300 40 71.6 23.9 1,5 Example 55 37 300 40 25.0 14.3 3.6 Example 56 38 150 40 0.2 0.3 1,5 Example 57 39 1000 40 7.8 0.8 50,0 Example 58 40 500 40 36.7 39.0 2,4 Example 59 41 one hundred 40 60.0 20,0 50,0 Example 60 42 300 40 0.2 0.3 50,0 Example 61 43 150 40 9,4 10.0 5,0 Example 62 44 fifty 40 51.6 17,2 1,1 Example 63 45 200 40 87.2 18.5 27.8 Example 64 46 300 40 480.0 160,0 5,0 Example 65 47 fifty 40 0.2 0.3 50,0 Example 66 48 200 40 0.3 0.4 27.8 Example 67 49 250 40 1,5 2.0 5,0 Example 68 fifty fifty 40 188.3 40,0 80.0

Table 8-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 53 35 0.83 A B A Example 54 36 0.79 A B A Example 55 37 0.75 B A A Example 56 38 0.78 A A B Example 57 39 0.71 B A B Example 58 40 0.93 A B A Example 59 41 0.85 A A A Example 60 42 0.98 B A B Example 61 43 0.85 B B A Example 62 44 0.79 A B A Example 63 45 0.99 A A A Example 64 46 0.97 B B A Example 65 47 0.90 B A B Example 66 48 0.73 B A B Example 67 49 0.86 B B A Example 68 fifty 0.71 B B A

[0087] Table 9-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 69 19 200 80 56.5 20,0 50,0 Example 70 twenty 500 80 1.9 2.0 50,0 Example 71 21 500 80 60.0 20,0 1.3 Example 72 22 one hundred 80 480.0 160,0 5,0 Example 73 23 300 80 60.0 20,0 50,0 Example 74 24 1000 80 42,2 14.9 1.8 Example 75 25 500 80 39.6 6.0 5,0 Example 76 26 400 80 0.5 0.7 42.9 Example 77 27 250 80 60.0 20,0 50,0 Example 78 28 one hundred 80 94.2 11.1 1.9 Example 79 29th 150 80 2.0 2.2 1,1 Example 80 thirty fifty 80 131.8 20,0 5,0 Example 81 31 one hundred 80 46.7 26.7 6.7 Example 82 32 400 80 1,5 2.0 5,0 Example 83 33 250 80 3,5 1.3 1.3 Example 84 34 10,000 80 0.2 0.3 1.3

Table 9-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 69 19 0.87 B B A Example 70 twenty 0.93 A A A Example 71 21 0.73 B B A Example 72 22 0.86 B B A Example 73 23 0.73 B B A Example 74 24 0.73 A B A Example 75 25 0.89 B A A Example 76 26 0.72 B B B Example 77 27 0.75 B B A Example 78 28 0.81 B B A Example 79 29th 0.75 B A A Example 80 thirty 0.84 A B A Example 81 31 0.77 B A A Example 82 32 0.81 B B A Example 83 33 0.92 A B A Example 84 34 0.72 B A B

[0088] Table 10-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film
(parts by weight) Mo V P Example 85 35 1000 80 75.3 16,0 5,0 Example 86 36 300 80 71.6 23.9 1,5 Example 87 37 300 80 25.0 14.3 3.6 Example 88 38 150 80 0.2 0.3 1,5 Example 89 39 1000 80 7.8 0.8 50,0 Example 90 40 500 80 36.7 39.0 2,4 Example 91 41 one hundred 80 60.0 20,0 50,0 Example 92 42 300 80 0.2 0.3 50,0 Example 93 43 150 80 9,4 10.0 5,0 Example 94 44 fifty 80 51.6 17,2 1,1 Example 95 45 200 80 87.2 18.5 27.8 Example 96 46 300 80 480.0 160,0 5,0 Example 97 47 fifty 80 0.2 0.3 50,0 Example 98 48 200 80 0.3 0.4 27.8 Example 99 49 250 80 1,5 2.0 5,0 Example one hundred fifty fifty 80 188.3 40,0 80.0

Table 10-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 85 35 0.90 A B A Example 86 36 0.71 A B A Example 87 37 0.89 B A A Example 88 38 0.97 A A B Example 89 39 0.82 B A B Example 90 40 0.77 A B A Example 91 41 0.90 A A A Example 92 42 0.86 B A B Example 93 43 0.70 B B A Example 94 44 0.98 A B A Example 95 45 0.98 A A A Example 96 46 0.79 B B A Example 97 47 0.95 B A B Example 98 48 0.81 B A B Example 99 49 0.90 B B A Example one hundred fifty 0.79 B B A

[0089] As is evident from Tables 7-1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1 and 10-2, chemically treated steel sheets, each of which has a chemical conversion a film in which the percentage of pentavalent vanadium based on mixed valence vanadium in a chemical conversion film is 0.7 or more, and which includes a first chemical conversion layer containing vanadium, molybdenum and phosphorus, and a second chemical conversion layer located on the first chemical conversion layer and containing an oxoate of an element of a group of 4 elements A periodic table of chemical elements, wherein a chemical conversion film is placed on the surface of a zinc-coated cladding steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% Aluminum, have favorable corrosion and blackening resistance in a wide range of precipitated amounts of chemical conversion film. A chemical conversion film is obtained by applying a chemical treatment solution that contains water-soluble molybdate, a vanadium salt, an amine, an oxoate of an element of group 4 of the Periodic Table of the chemical elements and phosphate, in which the molar ratio of molybdenum to vanadium is from 0.4 to 5.5, and the molar ratio of amine to vanadium is 0.3 or more on a zinc coated clad steel sheet, followed by drying. Favorable corrosion and blackening resistance of chemically treated steel sheets are obtained regardless of the deposited amount of the chemical conversion film, even when the chemical treatment solution deposited on the clad steel sheet is dried at a relatively low drying temperature of 40 or 80 ° C.

[0090] Then, chemically treated steel sheets No. 101-106 were made, which were comparative materials, in the same way as chemically treated steel sheet No. 1, except that the chemical treatment solutions were accordingly changed according to prototypes A-C, and evaluated in the same manner as in Example 1 according to the aforementioned evaluation criteria. The results are shown in the following Tables 11-1 and 11-2.

[0091] [Prototype A]

A commercially available partially reduced treatment chromate solution (ZM-3387; manufactured by Nihon Parkerizing Co., Ltd.) was applied to the surface of a chemical treatment base sheet, and immediately after that it was heated and dried at a low temperature (steel strip temperature) 40 or 80 ° C) using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. It should be noted that the amount of chromium deposited in the chemical conversion film was 200 mg / m ² .

[0092] [Prototype B]

A blue clear chemical treatment solution, to which ammonium zirconium carbonate, vanadyl tartrate, phosphoric acid and citric acid were added, was applied to the surface of the initial sheet for chemical treatment, and immediately after that it was heated and dried at a low temperature (steel strip temperature 40 or 80 ° C) using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. Vanadyl tartrate was obtained by reducing vanadium pentoxide in an aqueous solution of tartaric acid. It should be noted that both the deposited amount of zirconium and the deposited amount of vanadium in the chemical conversion film were 200 mg / m ² .

[0093] [Prototype C]

A colorless transparent solution for chemical treatment, to which a titanium derivative of hydrofluoric acid and phosphoric acid were added, was applied to the surface of the initial sheet for chemical treatment, and immediately after that it was heated and dried at a low temperature (temperature of a steel strip of 40 or 80 ° С) using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. It should be noted that the deposited amount of titanium in the chemical conversion film was 200 mg / m ² .

[0094] Table 11-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Comparative example 101 Prototype A 200 40 - - - Comparative example 102 Prototype A 200 80 - - - Comparative example 103 Prototype B 200 40 - - - Comparative example 104 Prototype B 200 80 - - - Comparative example 105 Prototype C 200 40 - - - Comparative example 106 Prototype C 200 80 - - -

Table 11-2 Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Comparative example 101 Prototype A - C D A Comparative example 102 Prototype A - C D A Comparative example 103 Prototype B - D D D Comparative example 104 Prototype B - C D D Comparative example 105 Prototype C - D D D Comparative example 106 Prototype C - C D D

[0095] Chemically treated steel sheets Nos. 101 and 102 obtained using a commercially available chromate treatment solution were inferior in terms of the corrosion resistance of the flat part and the corrosion resistance of the treated part, since the chemical treatment solution was dried at low temperature. Further, each of the chemically treated steel sheets No. 103-106 obtained using a chemical treatment solution in which vanadium was reduced by the addition of an organic acid, or a chemical treatment solution containing fluoride, had noticeably worse corrosion resistance of the flat part, corrosion resistance the treated part and the resistance to blackening, since the solution for chemical treatment was dried at low temperature.

[0096] As described above, from a comparison between the test results of the prototypes shown in Tables 11-1, 11-2, and the Examples shown in Tables 5-1, 5-2, 6-1, 6-2, 7- 1, 7-2, 8-1, 8-2, 9-1, 9-2, 10-1, 10-2, it can be revealed that the chemically treated steel sheet according to the present invention has favorable corrosion resistance and blackening resistance Compared with those for prototypes. Further, it can be found that a chemically treated steel sheet is obtained by forming a chemical conversion film made from a chemical treatment solution according to the present invention. Further, it can be shown that favorable corrosion resistance and blackening resistance are also obtained by drying the solution for chemical treatment at low temperature.

[0097] [Example 3]

A chemically treated steel sheet was prepared according to the following procedure. As a starting sheet for chemical treatment, a steel strip of ultralow carbon steel with titanium addition having a sheet thickness of 0.5 mm was used as a sheet substrate for hot dip galvanizing a zinc alloy clad steel sheet having a zinc based layer containing 0.018 wt.% Aluminum (deposited amount of cladding is 90 g / m ² on each side), on a continuous hot dip galvanizing production line, and the resulting clad The leaf sheet was used as a starting sheet for chemical treatment.

[0098] The surface of the base sheet for chemical treatment was degreased and dried. Then, each of the chemical treatment solutions No. 19-50 shown in Tables 2-1, 2-2, 3-1, 3-2, 4-1 and 4-2 was applied to the surface of the initial sheet for chemical treatment, and immediately after that, it was heated and dried at a low temperature (temperature of a steel strip of 40 or 80 ° C) using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. Thus, chemically treated steel sheets No. 107-170 were manufactured.

[0099] For test samples cut from each chemically treated steel sheet, the structure of the chemical conversion film was identified; determined the percentage of pentavalent vanadium based on vanadium mixed valence in the film; the deposited amount of the film was measured; and subjected the test samples to a corrosion test and a blackening test. The solutions used for chemical treatment, the proportion of each element in the chemical conversion film, the corrosion test results and the blackening test results for each chemically treated steel sheet are shown in Tables 12-1, 12-2, 13-1, 13-2 , 14-1, 14-2, 15-1, and 15-2. It should be noted that the proportion of each element in a chemical conversion film is presented in parts by weight of each element per 100 parts by weight of zirconium.

[0100] Table 12-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film
(parts by weight) Mo V P Example 107 19 200 40 56.5 20,0 50,0 Example 108 twenty 500 40 1.9 2.0 50,0 Example 109 21 500 40 60.0 20,0 1.3 Example 110 22 one hundred 40 480.0 160,0 5,0 Example 111 23 300 40 60.0 20,0 50,0 Example 112 24 1000 40 42,2 14.9 1.8 Example 113 25 500 40 39.6 6.0 5,0 Example 114 26 400 40 0.5 0.7 42.9 Example 115 27 250 40 60.0 20,0 50,0 Example 116 28 one hundred 40 94.2 11.1 1.9 Example 117 29th 150 40 2.0 2.2 1,1 Example 118 thirty fifty 40 131.8 20,0 5,0 Example 119 31 one hundred 40 46.7 26.7 6.7 Example 120 32 400 40 1,5 2.0 5,0 Example 121 33 250 40 3,5 1.3 1.3 Example 122 34 10,000 40 0.2 0.3 1.3

Table 12-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 107 19 0.91 B B A Example 108 twenty 0.78 A A A Example 109 21 0.87 B B A Example 110 22 0.82 B B A Example 111 23 0.88 B B A Example 112 24 0.77 B B A Example 113 25 0.73 B B A Example 114 26 0.99 B B B Example 115 27 0.73 B B A Example 116 28 0.79 B B A Example 117 29th 0.89 B B A Example 118 thirty 0.91 A B A Example 119 31 0.87 B B A Example 120 32 0.89 B B A Example 121 33 0.74 B B A Example 122 34 0.86 B B B

[0101] Table 13-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 123 35 1000 40 75.3 16,0 5,0 Example 124 36 300 40 71.6 23.9 1,5 Example 125 37 300 40 25.0 14.3 3.6 Example 126 38 150 40 0.2 0.3 1,5 Example 127 39 1000 40 7.8 0.8 50,0 Example 128 40 500 40 36.7 39.0 2,4 Example 129 41 one hundred 40 60.0 20,0 50,0 Example 130 42 300 40 0.2 0.3 50,0 Example 131 43 150 40 9,4 10.0 5,0 Example 132 44 fifty 40 51.6 17,2 1,1 Example 133 45 200 40 87.2 18.5 27.8 Example 134 46 300 40 480.0 160,0 5,0 Example 135 47 fifty 40 0.2 0.3 50,0 Example 136 48 200 40 0.3 0.4 27.8 Example 137 49 250 40 1,5 2.0 5,0 Example 138 fifty fifty 40 188.3 40,0 80.0

Table 13-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 123 35 0.90 A B A Example 124 36 0.82 B B A Example 125 37 0.82 B B A Example 126 38 0.87 A A B Example 127 39 0.90 B B B Example 128 40 0.77 B B A Example 129 41 0.77 A A A Example 130 42 0.77 B B B Example 131 43 0.85 B B A Example 132 44 0.80 B B A Example 133 45 0.77 A A A Example 134 46 0.79 B B A Example 135 47 0.80 B B B Example 136 48 0.74 B B B Example 137 49 0.81 B B A Example 138 fifty 0.93 A A A

[0102] Table 14-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 139 19 200 80 56.5 20,0 50,0 Example 140 twenty 500 80 1.9 2.0 50,0 Example 141 21 500 80 60.0 20,0 1.3 Example 142 22 one hundred 80 480.0 160,0 5,0 Example 143 23 300 80 60.0 20,0 50,0 Example 144 24 1000 80 42,2 14.9 1.8 Example 145 25 500 80 39.6 6.0 5,0 Example 146 26 400 80 0.5 0.7 42.9 Example 147 27 250 80 60.0 20,0 50,0 Example 148 28 one hundred 80 94.2 11.1 1.9 Example 149 29th 150 80 2.0 2.2 1,1 Example 150 thirty fifty 80 131.8 20,0 5,0 Example 151 31 one hundred 80 46.7 26.7 6.7 Example 152 32 400 80 1,5 2.0 5,0 Example 153 33 250 80 3,5 1.3 1.3 Example 154 34 10,000 80 0.2 0.3 1.3

Table 14-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 139 19 0.73 B B A Example 140 twenty 0.78 A A A Example 141 21 0.78 B B A Example 142 22 0.78 B B A Example 143 23 0.86 B B A Example 144 24 0.74 B B A Example 145 25 0.90 B B A Example 146 26 0.85 B B B Example 147 27 0.87 B B A Example 148 28 0.91 B B A Example 149 29th 0.95 B B A Example 150 thirty 0.79 A B A Example 151 31 0.91 B B A Example 152 32 0.78 B B A Example 153 33 0.94 B B A Example 154 34 0.94 B B B

[0103] Table 15-1

Category Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated film amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Mo V P Example 155 35 1000 80 75.3 16,0 5,0 Example 156 36 300 80 71.6 23.9 1,5 Example 157 37 300 80 25.0 14.3 3.6 Example 158 38 150 80 0.2 0.3 1,5 Example 159 39 1000 80 7.8 0.8 50,0 Example 160 40 500 80 36.7 39.0 2,4 Example 161 41 one hundred 80 60.0 20,0 50,0 Example 162 42 300 80 0.2 0.3 50,0 Example 163 43 150 80 9,4 10.0 5,0 Example 164 44 fifty 80 51.6 17,2 1,1 Example 165 45 200 80 87.2 18.5 27.8 Example 166 46 300 80 480.0 160,0 5,0 Example 167 47 fifty 80 0.2 0.3 50,0 Example 168 48 200 80 0.3 0.4 27.8 Example 169 49 250 80 1,5 2.0 5,0 Example 170 fifty fifty 80 188.3 40,0 80.0

Table 15-2

Category Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Percentage V ⁵⁺ Corrosion resistance Resistance to blackening Flat part Machined part Example 155 35 0.91 A B A Example 156 36 0.82 B B A Example 157 37 0.82 B B A Example 158 38 0.86 A A B Example 159 39 0.84 B B B Example 160 40 0.87 B B A Example 161 41 0.78 A A A Example 162 42 0.84 B B B Example 163 43 0.96 B B A Example 164 44 0.82 B B A Example 165 45 0.82 A A A Example 166 46 0.74 B B A Example 167 47 0.68 B B B Example 168 48 0.83 B B B Example 169 49 0.87 B B A Example 170 fifty 0.78 A A A

[0104] As is evident from Tables 12-1, 12-2, 13-1, 13-2, 14-1, 14-2, 15-1 and 15-2, it can be shown that all chemically treated steel sheets, each of which has a chemical conversion film in which the percentage of pentavalent vanadium based on mixed valence vanadium in the chemical conversion film is 0.7 or more, and which includes a first chemical conversion layer containing vanadium, molybdenum and phosphorus, and a second chemical conversion layer located on the first chemical conversion layer and containing approx oat element of the group of 4 elements of the Periodic table of chemical elements, and the chemical conversion film is placed on the surface of the zinc-coated cladding steel sheet having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% aluminum, have favorable corrosion resistance and resistance to blackening. A chemical conversion film is obtained by applying a chemical treatment solution that contains water-soluble molybdate, a vanadium salt, an amine, an oxoate of an element of group 4 elements of the Periodic Table of the chemical elements and phosphate, in which the molar ratio of molybdenum to vanadium is from 0.4 to 5.5, and the molar ratio of amine to vanadium is 0.3 or more on a zinc coated clad steel sheet, followed by drying. Favorable corrosion resistance and blackening resistance of chemically treated steel sheets are obtained over a wide range of deposited amounts of chemical conversion film, even when the chemical treatment solution is dried at a relatively low drying temperature.

[0105] From the above results, it can be shown that the chemically treated steel sheet according to the present invention has excellent corrosion resistance of the treated part and resistance to blackening, even when the chemical treatment solution is dried at a relatively low drying temperature and for a short period of time.

[0106] [Example 4]

[Preparation of solution No. 51 for chemical treatment]

Ammonium molybdate, vanadium pentoxide, ethanolamine, ammonium zirconium carbonate (AZC), ammonium hydrogen phosphate, which are shown in Table 1, and water were mixed so that the concentrations are as shown in Tables 16-1 and 16-2, to obtain a solution No. 51 for chemical processing. The composition and color of each chemical treatment solution are shown in Tables 16-1 and 16-2. In Table 16-2, “Mo / V” refers to the molar ratio of elemental molybdenum to elemental vanadium, and “amine / V” refers to the molar ratio of amine to elemental vanadium.

[0107] [Preparation of solutions No. 52-57 for chemical treatment]

Each of the solutions No. 52-57 for chemical treatment was obtained in the same way as the solution No. 51 for chemical treatment, except that the concentration of molybdenum, the type of vanadium salt and the concentration of vanadium, the type and concentration of amine, the concentration of zirconium, and the type of phosphate and the phosphate concentration was changed as shown in Tables 16-1 and 16-2.

[0108] Table 16-1

Solution for chemical treatment No. M1 Vanadium salt Amine Category Mo concentration
(g / l) Compound V concentration
(g / l) Compound Concentration
(g / l) 51 0,075 V1 0.10 EA 0,036 Example 52 0,075 V2 0.10 NH 0,021 53 24.0 V2 8.00 EA 15.3 54 1.98 V3 0.30 EA 1.15 55 3.11 V3 0.30 IPA 1.06 56 24.0 V2 8.00 NH 8.79 57 14.1 V2 0.30 EN 5.75

Table 16-2 Solution for chemical treatment No. AZC Phosphate Mo / V
(molar ratio) Amine / v
(molar ratio) Color of processing solution Category Zr concentration
(g / l) Compound P concentration
(g / l) 51 5,0 P1 0.25 0.40 0.30 Yellow Example 52 5,0 P5 0.05 0.40 0.30 Yellow 53 40,0 P4 2.00 1,59 1,60 Yellow 54 5,0 P3 0.25 3,50 3.20 Yellow 55 40,0 P4 20,0 5.50 2.40 Yellow 56 46.5 P2 0.50 1,59 1,60 Yellow 57 7.5 P4 6.00 2,50 1,60 Yellow

[0109] [Preparation of solutions No. 58-64 for chemical treatment]

Each of the solutions No. 58-64 for chemical processing was obtained in the same way as the solutions No. 1-57 for chemical treatment, except that the organic resin as a hydrophilic resin was further admixed so that the organic resin has a concentration as shown in Tables 17-1 and 17-2. In Table 17-2 shown, “AR” means acrylic resin, “PO” means polyolefin, “ER” means epoxy, and “PU” means polyurethane. In addition, the amount of organic resin in Table 17-2 represents the amount (wt.%) Of organic resin based on the total amount of vanadium and molybdenum in the chemical treatment solution.

[0110] It should be noted that “Voncoat 40-418EF” manufactured by DIC Corporation (“Voncoat” is a registered trademark of this company) was used as an “acrylic resin”; Zaikthene A type-AC, manufactured by Sumitomo Seika Chemicals Co., Ltd., was used as the “polyolefin”. ("Zaikthene" represents the registered trademark of this company); Adeka Resin EM-0434AN manufactured by Adeka Corporation was used as the “epoxy resin” (Adeka Resin represents the registered trademark of this company); and “Adeka Bontighter HUX-232” manufactured by Adeka Corporation was used as “polyurethane” (“Adeka Bontighter” is a registered trademark of this company).

[0111] [Preparation of solutions No. 65 and 66 for chemical treatment]

Each of solutions No. 65 and 66 for chemical treatment was obtained in the same way as solution No. 51 for chemical treatment, except that the concentration of molybdenum, the type of vanadium salt and the concentration of vanadium, the type and concentration of amine, the concentration of zirconium, the type of phosphate and phosphate concentration, type and concentration of the organic resin were varied as shown in Tables 17-1 and 17-2

[0112] Table 17-1

Solution for chemical treatment No. M1 Vanadium salt Amine AZC Category Mo concentration
(g / l) Compound V concentration
(g / l) Compound Concentration
(g / l) Zr concentration
(g / l)) 58 0,075 V1 0.10 EA 0,036 5,0 Comparative example 59 0,075 V2 0.10 NH 0,021 5,0 Comparative example 60 24.0 V2 8.00 EA 15.3 40,0 Example 61 1.98 V3 0.30 EA 1.15 5,0 Comparative example 62 3.11 V3 0.30 IPA 1.06 40,0 Example 63 24.0 V2 8.00 NH 8.79 46.5 Example 64 14.1 V2 0.30 EN 5.75 7.5 Comparative example 65 1.00 V1 0.30 IPA 2.00 1,0 Comparative example 66 1.00 V1 0.30 IPA 2.00 1,0 Comparative example

Table 17-2

Solution for chemical treatment No. Phosphate Organic resin Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Category Compound P concentration
(g / l) Compound Concentration
(g / l) Amount (wt.%) 58 P1 0.25 AR 50,0 28500 0.40 0.30 Yellow Comparative example 59 P5 0.05 PO 80.0 45600 0.40 0.30 Yellow Comparative example 60 P4 2.00 Er 20,0 63.0 1,59 1,60 Yellow Example 61 P3 0.25 AR 5.00 220 3,50 3.20 Yellow Comparative example 62 P4 20,0 PO 0.50 15.0 5.50 2.40 Yellow Example 63 P2 0.50 Er 20,0 63.0 1,59 1,60 Yellow Example 64 P4 6.00 PU 200 1170 2,50 1,60 Yellow Comparative example 65 - - PU 200 13300 0.53 2.72 Yellow Comparative example 66 P1 1.00 PU 200 13300 0.53 2.72 Yellow Comparative example

[0113] [Preparation of solutions No. 67-73 for chemical treatment]

Each of the solutions No. 67-73 for chemical treatment was obtained in the same way as the solutions No. 51-57 for chemical treatment, except that the fluorine compound that generates the fluoride ion or metal fluoride ion in water is additionally mixed as follows. that the fluorine compound has a concentration as shown in Tables 18-1 and 18-2. The amount of fluorine compound in Table 18-2 is the amount (wt.%) Of elemental fluorine based on the total amount of vanadium and molybdenum in the solution for chemical treatment. Elementary fluorine is caused by a fluoride ion or metal fluoride ion in a solution for chemical treatment.

[0114] Table 18-1

Solution for chemical treatment No. M1 Vanadium salt Amine AZC Category Mo concentration
(g / l) Compound V concentration
(g / l) Compound Concentration
(g / l) Zr concentration
(g / l) 67 0,075 V1 0.10 EA 0,036 5,0 Comparative example 68 0,075 V2 0.10 NH 0,021 5,0 Comparative example 69 24.0 V2 8.00 EA 15.3 40,0 Example 70 1.98 V3 0.30 EA 1.15 5,0 Example 71 3.11 V3 0.30 IPA 1.06 40,0 Comparative example 72 24.0 V2 8.00 NH 8.79 46.5 Comparative example 73 14.1 V2 0.30 EN 5.75 7.5 Comparative example

Table 18-2

Solution for chemical treatment No. Phosphate Fluorine compound Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Category Compound P concentration
(g / l) Compound Concentration
(g / l) Amount (wt.%) 67 P1 0.25 F1 2.00 373 0.40 0.30 Yellow Comparative example 68 P5 0.05 F2 1.00 570 0.40 0.30 Yellow Comparative example 69 P4 2.00 F3 0.50 2.00 1,59 1,60 Yellow Example 70 P3 0.25 F1 0.50 22.0 3,50 3.20 Yellow Example 71 P4 20,0 F2 10.0 293 5.50 2.40 Yellow Comparative example 72 P2 0.50 F3 50,0 156 1,59 1,60 Yellow Comparative example 73 P4 6.00 F1 20,0 117 2,50 1,60 Yellow Comparative example

[0115] [Preparation of solutions No. 74-80 for chemical treatment]

Each of the solutions No. 74-80 for chemical treatment was obtained in the same way as the solutions No. 51-57 for chemical treatment, except that the silicon compound that forms the silanol group in water is further mixed so that the silicon compound has concentration as shown in Tables 19-1 and 19-2. The amount of silicon compound in Table 19-2 is the amount (wt.%) Of elemental silicon calculated on the total amount of vanadium and molybdenum in the solution for chemical treatment. Elemental silicon is due to the silanol group in the solution for chemical treatment.

[0116] Table 19-1

Solution for chemical treatment No. M1 Vanadium salt Amine AZC Category Mo concentration
(g / l) Compound V concentration
(g / l) Compound Concentration
(g / l) Zr concentration
(g / l) 74 0,075 V1 0.10 EA 0,036 5.00 Comparative example 75 0,075 V2 0.10 NH 0,021 5.00 Comparative example 76 24.0 V2 8.00 EA 15,327 40,0 Example 77 1.98 V3 0.30 EA 1,150 5.00 Comparative example 78 3.11 V3 0.30 IPA 1,060 40,0 Comparative example 79 24.0 V2 8.00 NH 8,794 46.5 Example 80 14.1 V2 0.30 EN 5,748 7.50 Comparative example

Table 19-2

Solution for chemical treatment No. Phosphate Silicon compound Mo / V
(molar ratio) Amine / v
(molar ratio) The color of the solution for processing Category Compound P concentration
(g / l) Compound Concentration
(g / l) Amount (wt.%) 74 P1 0.25 S1 2.00 179 0.40 0.30 Yellow Comparative example 75 P5 0.05 S2 5.00 2850 0.40 0.30 Yellow Comparative example 76 P4 2.00 S3 0.20 1.00 1,59 1,60 Yellow Example 77 P3 0.25 S1 5.00 220 3,50 3.20 Yellow Comparative example 78 P4 20,0 S2 8.00 235 5.50 2.40 Yellow Comparative example 79 P2 0.50 S3 10.0 31.0 1,59 1,60 Yellow Example 80 P4 6.00 S1 20,0 117 2,50 1,60 Yellow Comparative example

[0117] It should be noted that in order to prevent the recovery of vanadium in the preparation of a solution for chemical treatment, a vanadium salt was added and dissolved in an aqueous solution having a liquid temperature of 40 ° C or lower containing an amine. As expected, since the color of each chemical treatment solution is yellow, the valence state of the vanadium contained in each chemical treatment solution is pentavalent (V ⁵⁺ ).

[0118] [Obtaining chemically treated steel sheets No. 171-200]

The surface of the initial sheet for chemical treatment was degreased and dried. Then, the chemical treatment solution No. 51, shown in Tables 16-1 and 16-2, was applied to the surface of the initial sheet for chemical treatment in the amount of the deposited amount of the conversion film shown in Table 20-1, and immediately after that it was heated and dried at a temperature drying (steel strip temperature) 40 ° C for 2 seconds using an electric channel drying oven with automated unloading, with the formation of a chemical conversion film. In this way, a chemically treated steel sheet No. 171 was made.

[0119] Further, solutions No. 52-80 for chemical treatment were used instead of solution No. 51 for chemical treatment to obtain chemically treated steel sheets No. 172-200 in the same way as for chemically treated steel sheet No. 51, except that the chemical treatment solutions were applied to the chemical treatment source sheet in the amount of precipitation shown in Table 20-1 or 21-1, and heated and dried at the drying temperature shown in Table 20-1 or 21-1. It should be noted that the drying time is 6 seconds when the drying temperature is 80 ° C.

[0120] [Measurement and evaluation of chemically treated steel sheets]

For test samples cut from each chemically treated steel sheet, the structure of the chemical conversion film was identified, and the test samples were tested for corrosion resistance and the test for resistance to blackening in the same way as in Example 1.

[0121] As a result, it was confirmed on the chemically treated steel sheets listed in the Examples that the two-layer structure (that is, the first and second chemical conversion layers), like the chemically treated steel sheet No. 17, for example, contains vanadium, molybdenum and phosphorus in the first chemical conversion layer, and oxoate of an element of the group of 4 elements of the Periodic table of chemical elements in the second chemical conversion layer. However, the two-layer structure in the chemical conversion film was not confirmed in each chemically treated steel sheet classified in the Comparative Examples.

[0122] The type of solution for chemical treatment, the amount of precipitation, drying temperature, the content of molybdenum, vanadium and phosphorus in the chemical conversion film, the percentage of pentavalent vanadium and the results of various evaluations in each case are shown in Tables 20-1, 20-2, 21- 1 and 21-2. It should be noted that each component ratio of molybdenum, vanadium and phosphorus denotes parts by weight of each element per 100 parts by weight of elemental zirconium.

[0123] Table 20-1

Solution for chemical treatment No. Solution for chemical treatment No. Precipitated Amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Category Mo V P 171 51 200 40 1,5 2.0 5,0 Example 172 52 200 80 1,5 2.0 1,0 Example 173 53 200 40 60.0 20,0 5,0 Example 174 54 500 40 39.6 6.0 5,0 Example 175 55 1000 40 7.8 0.8 50,0 Example 176 56 fifty 40 51.6 17,2 1,1 Example 177 57 fifty 80 188.3 40,0 80.0 Example 178 58 200 40 1,5 2.0 5,0 Comparative example 179 59 200 80 1,5 2.0 1,0 Comparative example 180 60 200 40 60.0 20,0 5,0 Example 181 61 500 40 39.6 6.0 5,0 Comparative example 182 62 1000 40 7.8 0.8 50,0 Example 183 63 300 40 480.0 160,0 5,0 Example 184 64 fifty 80 188.3 40,0 80.0 Comparative example 185 65 200 80 100.0 50,0 0,0 Comparative example 186 66 200 80 100.0 50,0 100.0 Comparative example

Table 20-2 Solution for chemical treatment No. Solution for chemical treatment No. Evaluation results Category V ⁵⁺ / V Corrosion resistance of the flat part Corrosion resistance of the treated part Resistance to blackening 171 51 0.92 A A A Example 172 52 0.81 B B A Example 173 53 0.92 B B A Example 174 54 0.85 A A A Example 175 55 0.71 A A A Example 176 56 0.79 A A A Example 177 57 0.79 B B A Example 178 58 0.85 D D C Comparative example 179 59 0.71 D D D Comparative example 180 60 0.93 B B A Example 181 61 0.63 D D C Comparative example 182 62 0.82 A A A Example 183 63 0.95 A A A Example 184 64 0.75 D D D Comparative example 185 65 0.72 D D D Comparative example 186 66 0.78 C D D Comparative example

[0124] Table 21-1

Chemically processed steel sheet No. Solution for chemical treatment No. Precipitated Amount
(mg / m ² ) Drying temperature
(° C) The proportion of each element in a chemically processed film (parts by weight) Category Mo V P 187 67 200 40 1,5 2.0 5,0 Comparative example 188 68 200 80 1,5 2.0 1,0 Comparative example 189 69 200 40 60.0 20,0 5,0 Example 190 70 500 40 39.6 6.0 5,0 Example 191 71 1000 40 7.8 0.8 50,0 Comparative example 192 72 300 40 480.0 160,0 5,0 Comparative example 193 73 fifty 80 188.3 40,0 80.0 Comparative example 194 74 200 40 1,5 2.0 5,0 Comparative example 195 75 200 80 1,5 2.0 1,0 Comparative example 196 76 200 40 60.0 20,0 5,0 Example 197 77 500 40 39.6 6.0 5,0 Comparative example 198 78 1000 40 7.8 0.8 50,0 Comparative example 199 79 300 40 480.0 160,0 5,0 Example 200 80 fifty 80 188.3 40,0 80.0 Comparative example

Table 21-2

Chemically processed steel sheet No. Solution for chemical treatment No. Evaluation results Category V ⁵⁺ / V Corrosion resistance of the flat part Corrosion resistance of the treated part Resistance to blackening 187 67 0.85 D D D Comparative example 188 68 0.81 D D D Comparative example 189 69 0.92 B B A Example 190 70 0.90 A A A Example 191 71 0.68 D D D Comparative example 192 72 0.75 D D D Comparative example 193 73 0.74 D D D Comparative example 194 74 0.81 C D D Comparative example 195 75 0.79 D D D Comparative example 196 76 0.95 B B A Example 197 77 0.84 C D D Comparative example 198 78 0.76 C D D Comparative example 199 79 0.93 A A A Example 200 80 0.78 C D D Comparative example

[0125] As is evident from Tables 16-1, 16-2 and 20-1, 20-2, in chemically treated steel sheets No. 171-177 obtained using, respectively, solutions No. 51-57 for chemical treatment, all of the corrosion resistance of the flat part, the corrosion resistance of the treated part and the resistance to blackening were sufficiently favorable.

[0126] However, as is evident from Tables 17-1, 17-2 and 20-1, 20-2, in chemically treated steel sheets No. 178-184 obtained using, respectively, solutions No. 58-64 for chemical treatments having the same compositions as the compositions of solutions No. 51-57 for chemical treatment, except that they contained a hydrophilic resin, at least one of the corrosion resistance of the flat part, the corrosion resistance of the treated part and the resistance to blackening were sometimes insufficient . More specifically, in chemically treated steel sheets No. 180, 182 and 183 using, respectively, solutions No. 60, 62 and 63 for chemical treatment having a relatively low concentration of hydrophilic resin, all of the corrosion resistance of the flat part, the corrosion resistance of the treated part and resistance to blackening were sufficiently favorable. In contrast, in chemically treated steel sheets No. 178, 179, 181 and 184 obtained using, respectively, solutions No. 58, 59, 61 and 64 for chemical treatment having a relatively high concentration of hydrophilic resin, all of the corrosion resistance of the flat part , the corrosion resistance of the treated part and the resistance to blackening were insufficient. As expected, this is due to the fact that the content of a hydrophilic resin with a relatively high concentration in the solution for chemical treatment inhibits the formation of a two-layer structure in a chemical conversion film.

[0127] Further, in chemically treated steel sheets Nos. 185 and 186, all of the corrosion resistance of the flat part, the corrosion resistance of the treated part, and the resistance to blackening were insufficient. The reason for this is as follows: solutions No. 65 and 66 for chemical treatment contain a hydrophilic resin with a high concentration regardless of the presence / absence of phosphorus, even if the ratios of “Mo / V” and “amine / V” in solutions No. 65 and 66 for chemical treatments are the same, and thus the formation of a two-layer structure in a chemical conversion film is inhibited for the same reason as described above.

[0128] Further, as is evident from Tables 18-1, 18-2 and 21-1, 21-2, in chemically treated steel sheets No. 187-193 obtained using, respectively, solutions No. 67-73 for chemical treatment having the same compositions as the compositions of solutions No. 51-57 for chemical treatment, except that they contained fluoride in the form of a fluoride ion or metal fluoride ion, at least one of the corrosion resistance of the flat part, the corrosion resistance of the treated part and resistance to blackening was sometimes insufficient. More specifically, in chemically treated steel sheets No. 189 and 190 using, respectively, solutions No. 69 and 70 for chemical treatment having a relatively low fluorine concentration, all of the corrosion resistance of the flat part, the corrosion resistance of the treated part, and the resistance to blackening were sufficiently favorable. In contrast, in chemically treated steel sheets No. 187, 188 and 191-193 obtained using, respectively, solutions No. 67, 68 and 71-73 for chemical treatment having a relatively high fluorine concentration, all of the corrosion resistance of the flat part, corrosion resistance of the treated part and resistance to blackening were insufficient. As expected, this is due to the fluorine content with a relatively high concentration in the solutions for chemical treatment, which inhibits the formation of a two-layer structure in a chemical conversion film.

[0129] Further, as is evident from Tables 19-1, 19-2 and 21-1, 21-2, in chemically treated steel sheets No. 194-200, obtained using, respectively, solutions No. 74-80 for chemical processing having the same compositions as the compositions of solutions No. 51-57 for chemical treatment, except that they contained silicon due to the silanol group, at least one of the corrosion resistance of the flat part, the corrosion resistance of the treated part and the resistance to blackening at times were insufficient. More specifically, in chemically treated steel sheets No. 196 and 199 using, respectively, solutions No. 76 and 79 for chemical treatment having a relatively low concentration of silicon, all of the corrosion resistance of the flat part, the corrosion resistance of the treated part and the resistance to blackening were sufficiently favorable. In contrast, in chemically treated steel sheets No. 194, 195, 197, 198, and 200, obtained using, respectively, solutions No. 74, 75, 77, 78, and 80 for chemical treatment having a relatively high concentration of silicon, all of the corrosion the resistance of the flat part, the corrosion resistance of the treated part and the resistance to blackening were insufficient. It is assumed that this is due to the fact that the silicon content with a relatively high concentration in the solution for chemical treatment inhibits the formation of a two-layer structure in a chemical conversion film.

[0130] As described above, it can be shown that a chemically treated steel sheet having excellent corrosion resistance of the machined part and resistance to blackening can be obtained by applying to the zinc-based cladding steel sheet having a zinc-based cladding layer, containing from 0.1 to 22.0 wt.% aluminum, a solution for chemical treatment containing water-soluble molybdate, vanadium salt, amine, oxoate of an element of group 4 elements of the Periodic table of chemical elements and a phosphate compound, wherein the molar ratio of molybdenum to vanadium is from 0.4 to 5.5, and the molar ratio of amine to vanadium is 0.3 or more; and the hydrophilic resin content is not more than 100 wt.%, the fluorine concentration is not more than 30 wt.%, or the silicon concentration is not more than 50 wt.%, calculated on the total amount of vanadium and molybdenum, even when the solution for chemical treatment is dried at low temperature and for a short period of time.

[0131] This application claims the priority of Japanese Patent Application No. 2013-235543, filed November 14, 2013, and Japanese Patent Application No. 2014-231275, filed November 14, 2014, the full contents of which, including the description and drawings, are incorporated herein by reference .

Industrial applicability

[0132] The chemically treated steel sheet according to the present invention has excellent corrosion and blackening resistance, and is therefore useful for use in a wide variety of applications, such as, for example, automobiles, building materials, and household electrical appliances.

Claims (20)

1. A solution for the chemical treatment of a zinc-plated cladding steel sheet having a zinc-based cladding layer with an aluminum content of 0.1 to 22.0 wt.%, Said solution for chemical treatment containing: water soluble molybdate; vanadium salt; amine; oxoate element 4 groups of the Periodic table of chemical elements; and phosphate compound while the molar ratio of molybdenum to vanadium in the solution for chemical treatment is from 0.4 to 5.5, the molar ratio of amine to vanadium in the solution for chemical treatment is 0.3 or more, the content of the hydrophilic resin in the solution for chemical treatment is not more than 100 wt.% based on the total amount of vanadium and molybdenum in the solution for chemical treatment, the total fluorine content due to the fluorine ion or metal fluoride ion in the solution for chemical treatment is not more than 30 wt.% based on the total amount of vanadium and molybdenum in the solution for chemical treatment, and the silicon content due to the silanol group in the solution for chemical treatment is not more than 50 wt.% based on the total amount of vanadium and molybdenum in the solution for chemical treatment. 2. The chemical treatment solution of claim 1, wherein the amine has a molecular weight of 80 or less. 3. A steel sheet with a zinc-based cladding coating having a zinc-based cladding layer containing from 0.1 to 22.0 wt.% Aluminum and a chemical conversion film disposed thereon, wherein: the chemical conversion film includes a first chemical conversion layer located on the surface of the zinc-based cladding coating and containing vanadium, molybdenum and phosphorus, and a second chemical conversion layer located on the first chemical conversion layer and containing an oxoate of an element of group 4 of the Periodic Table of Chemical Elements, moreover the percentage of pentavalent vanadium calculated as mixed valence vanadium in the chemical conversion film is 0.7 or more. 4. The steel sheet according to claim 3, in which: the oxoate of element 4 of the group of the Periodic table of chemical elements is zirconium oxoate, moreover the chemical conversion film contains from 1 to 60 parts by weight of molybdenum, from 2 to 20 parts by weight of vanadium and from 10 to 50 parts by weight of phosphorus per 100 parts by weight of zirconium. 5. The steel sheet according to claim 3 or 4, wherein the zinc-clad steel sheet is a hot dip galvanized aluminum and zinc-containing galvanized steel sheet having a hot dip galvanized aluminum and magnesium clad layer containing from 0 , 1 to 22.0 wt.% Aluminum and from 1.5 to 10.0 wt.% Magnesium.

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