JP6928573B2 - Inorganic chemical conversion treatment liquid and inorganic chemical conversion treatment steel sheet - Google Patents

Description

The present invention relates to a chemical conversion treatment liquid for a Zn-based plated steel sheet and a chemical conversion treatment steel sheet.

Zn-based galvanized steel sheets are used in a wide range of applications such as automobiles, building materials, and home appliances. Normally, the surface of a plated steel sheet is subjected to a chrome-free chemical conversion treatment in order to impart corrosion resistance without oiling. Chromium-free chemical conversion treatment is roughly divided into organic treatment and inorganic treatment. The organic treatment forms a thick film containing an organic resin, whereas the inorganic treatment forms a thin film (film thickness: 1 μm or less) in order to obtain spot weldability. The organic treatment can impart relatively high corrosion resistance as compared with the inorganic treatment. Further, even in the inorganic treatment, by using the Al and Mg-containing Zn-based plated steel sheet as the chemical conversion treatment original plate, it is possible to obtain a plated steel sheet exhibiting high corrosion resistance comparable to that of the organic treatment.

Conventionally, as a chemical conversion treatment liquid used for inorganic treatment, titanium-based, zirconium-based, molybdenum-based, and composite systems thereof have been developed depending on the difference in rust preventive. Further, in order to improve corrosion resistance, a system in which a silane coupling agent, silane, or the like is further added has been developed.

Patent Documents 1 to 3 disclose a chemical conversion-treated steel sheet in which a chemical conversion-treated film is formed on the surface of a Zn-based plated steel sheet using a chromium-free chemical conversion treatment liquid containing a Group 4 metal oxygen acid salt or the like. In Patent Document 1, a chemical conversion treatment film is formed on the surface of a Zn-based galvanized steel sheet containing Al with a chromium-free chemical conversion treatment liquid in which a Group 4 metal oxygenate, a molybdate, and a vanadium salt are compounded. , A chemical conversion-treated steel sheet having excellent corrosion resistance and blackening resistance is disclosed. Further, Patent Document 2 discloses a chemical conversion-treated steel plate containing a Group 4 metal oxygenate and a silane coupling agent, and a chemical conversion-treated film formed by a chemical conversion-treated liquid containing various metal elements. Further, Patent Document 3 discloses a chemical conversion-treated steel plate in which a chemical conversion-treated film is formed by a chromium-free chemical conversion treatment liquid containing a group 4 metal oxygenate, silane, silica containing calcium, and vanazine oxide. ..

International Publication No. 2010/070730 Japanese Unexamined Patent Publication No. 2015-117433 Japanese Unexamined Patent Publication No. 2017-14594

However, in the techniques disclosed in Patent Documents 1 to 3 as described above, when the amount of the film adhered is small (the thickness of the film is thin), the corrosion-causing substance easily reaches the Zn-based plating layer, and the corrosion resistance is improved. It will drop. Therefore, it is necessary to have a high barrier property on the surface of the Zn-based plated steel sheet and to increase the amount of the poorly soluble oxide film adhered (thicken the film). However, the chromium-free chemical conversion-treated film containing Group 4 metal oxygenate and the like originally has poor film adhesion to the Zn-based plating layer. Therefore, when processing such as roll forming is performed, film peeling occurs remarkably, and it is necessary to clean the film deposited on the roll. As a result, there is a problem that the productivity in roll forming is lowered.

Further, in the techniques disclosed in Patent Documents 1 and 3 as described above, if the drying temperature is high when the chemical conversion treatment liquid applied to the surface of the Zn-based plated steel sheet is dried, cracks occur in the chemical conversion treatment film. .. As a result, the corrosion resistance of the chemical conversion-treated steel sheet is lowered. Therefore, it is necessary to strictly control the furnace temperature of the drying oven, and there is a problem that the productivity of the chemical conversion-treated steel sheet is lowered.

In one aspect of the present invention, a chemical conversion-treated film having high adhesion to a Zn-based plated steel sheet can be formed, and cracks occur in the chemical conversion-treated film when the drying temperature at the time of forming the chemical conversion-treated film is high. It is an object of the present invention to realize a chemical conversion treatment liquid capable of suppressing the occurrence of zinc conversion. Another aspect of the present invention is to realize a chemical conversion-treated steel sheet having high adhesion between a Zn-based plated steel sheet and a chemical conversion-treated film and high corrosion resistance.

In order to solve the above problems, the chemical conversion treatment liquid according to one aspect of the present invention has a chemical conversion treatment film formed on the surface of a zinc-based plated steel sheet having a zinc plating layer containing Al: 0.1 to 22.0% by mass. A chemical conversion treatment liquid for forming, which contains a water-soluble Group 4 metal oxidate, a phosphoric acid compound, a Group 1 metal, a molybdate, and a vanadium salt, and is phosphorus for the Group 4 metal in the chemical conversion treatment liquid. The molar ratio of the group 1 metal to the group 4 metal in the chemical conversion treatment liquid is 0.02 to 0.8, and the molar ratio of 1 to phosphorus in the chemical conversion treatment liquid is 1. The molar ratio of group metals is 0.01 or more.

Further, in the chemical conversion treatment liquid according to one aspect of the present invention, the amount of the Group 4 metal is 35 g / L or less.

In order to solve the above problems, the chemical conversion-treated steel sheet according to one aspect of the present invention includes a zinc-based plated steel sheet having a zinc-plated layer containing Al: 0.1 to 22.0 mass% and the zinc-based plated steel sheet. A chemical conversion-treated steel plate having a chemical conversion-treated film formed on the surface of the above, wherein the chemical conversion-treated film contains a group 4 metal oxygenate, a phosphoric acid compound, a group 1 metal, a molybdenate, and a vanadium salt. It contains 17 to 136 parts by mass of phosphorus with respect to 100 parts by mass of the Group 4 metal, and contains 0.5 to 21 parts by mass of the Group 1 metal with respect to 100 parts by mass of the Group 4 metal, and contains with respect to 100 parts by mass of phosphorus. It contains 0.7 parts by mass or more of Group 1 metal.

Further, in the chemical conversion-treated steel plate according to one aspect of the present invention, the Group 4 metal oxygenate is Zr oxygenate.

According to one aspect of the present invention, a chemical conversion-treated film having high adhesion to a Zn-based plated steel sheet can be formed, and the chemical conversion-treated film cracks when the drying temperature at the time of forming the chemical conversion-treated film is high. It is possible to realize a chemical conversion treatment liquid capable of suppressing the occurrence of. Further, according to one aspect of the present invention, it is possible to realize a chemical conversion-treated steel sheet having high adhesion between a Zn-based plated steel sheet and a chemical conversion-treated film and high corrosion resistance.

It is a table which shows the data of the chemical conversion treatment liquid as an Example and a comparative example of this invention. It is a table which shows the substance described in FIG. It is a table which shows the data of the chemical conversion-treated steel sheet as an Example and a comparative example of this invention.

[Embodiment 1]
Hereinafter, an embodiment of the chemical conversion treatment liquid and the chemical conversion treatment steel sheet of the present invention will be described in detail. The chemical conversion-treated steel sheet of the present embodiment has a Zn (zinc) -based plated steel sheet as an original plate to be subjected to the chemical conversion treatment, and a chemical conversion-treated film formed on the surface of the Zn-based plated steel sheet using a chemical conversion treatment liquid described later. .. In addition, "AB" in this specification means "A or more, B or less".

(Zn-based galvanized steel sheet)
A Zn-based galvanized steel sheet having excellent corrosion resistance and design is used as the original plate to be subjected to the chemical conversion treatment. The “Zn-based plated steel sheet” in the present embodiment means a plated steel sheet having a Zn-based plated layer containing Al: 0.1 to 22.0% by mass and Zn: 50% by mass or more.

The type of base steel sheet of the Zn-based plated steel sheet is not particularly limited, and for example, ordinary steel, low alloy steel, stainless steel, and the like can be used.

(Chemical conversion coating)
The chemical conversion treatment film is a film formed on the surface of a Zn-plated steel sheet using a chemical conversion treatment liquid described later. The chemical conversion-treated film is a film for improving the corrosion resistance and blackening resistance of Zn-based plated steel sheets. As used herein, the term "corrosion resistance" includes at least one of flat portion corrosion resistance and processed portion corrosion resistance. The “processed portion corrosion resistance” is the corrosion resistance of a portion (processed portion) of the chemical conversion-treated steel sheet that has been subjected to processing (for example, bending) to deform the chemical conversion-treated steel sheet. The "flat portion corrosion resistance" is the corrosion resistance of a portion of the chemical conversion-treated steel sheet other than the processed portion.

(Chemical conversion treatment liquid)
The chemical conversion treatment liquid in the present embodiment is a liquid for forming a chemical conversion treatment film on the surface of a Zn-plated steel sheet by being applied to the surface of a Zn-based plated steel sheet and dried. The chemical conversion treatment liquid in the present embodiment contains a water-soluble Group 4 metal oxygenate, a phosphate compound, a Group 1 metal, a molybdate, and a vanadium salt.

<Group 4 metal oxygenate>
Group 4 metal oxygenate is a component for forming a dense chemical conversion-treated film, and improves the corrosion resistance of the chemical conversion-treated steel sheet. It is difficult to form a dense chemical conversion treatment film with a chemical conversion treatment solution containing only molybdate and vanadium salt, which will be described later, but by further adding Group 4 metal oxygenate, Mo and V and the like are crosslinked. Therefore, a chemical conversion treatment film having a high barrier property can be formed.

The Group 4 metal is not particularly limited, and Ti, Zr, or Hf can be used. Oxide is a salt of an inorganic acid containing oxygen. The group 4 metal oxate of the present embodiment is, for example, a hydride, an ammonium salt, an alkali metal salt, an alkaline earth metal salt, or the like, and in particular, an ammonium salt of the group 4 metal oxidate from the viewpoint of corrosion resistance. It is preferably present, and ammonium zirconium carbonate is particularly preferable.

In the chemical conversion treatment liquid of the present embodiment, the concentration of the Group 4 metal is preferably 35 g / L or less. When the concentration of the Group 4 metal in the chemical conversion treatment liquid is higher than 35 g / L, the Group 4 metals are bonded to each other and the chemical conversion treatment liquid is gelled while the chemical conversion treatment liquid is being stored. Therefore, the chemical conversion treatment film cannot be formed satisfactorily. That is, the chemical conversion treatment liquid of the present embodiment has high long-term storage stability because the concentration of the Group 4 metal is 35 g / L or less.

<Phosphoric acid compound>
The phosphoric acid compound is a component for forming a dense chemical conversion-treated film by binding with a group 4 metal oxygenate, and improves the corrosion resistance of the chemical conversion-treated steel sheet. The type of the phosphoric acid compound is not particularly limited, and an inorganic phosphate or an organic phosphate can be used.

Inorganic phosphates include, for example, alkali metal phosphates (eg, sodium diphosphate, potassium diphosphate, sodium tripolyphosphate), alkaline earth metal phosphates (calcium diphosphate, etc.), ammonium phosphate (eg, calcium diphosphate). , Diammonium hydrogen phosphate, ammonium dihydrogen phosphate, triammonium phosphate, etc.) and the like can be used. As the organic phosphate, for example, 1-hydroxyethane-1,1-diphosphonic acid, nitrilotris (methylene-phosphonic acid) and the like can be used.

<Group 1 metal>
Group 1 metal is a component for increasing the number of hydroxyl groups in the chemical conversion coating. When the number of hydroxyl groups in the chemical conversion coating increases, a bond is likely to occur between the chemical conversion coating and the Zn-based plated steel sheet. As a result, the adhesion between the chemical conversion coating and the Zn-based plated steel sheet can be improved.

Further, when the number of hydroxyl groups in the chemical conversion treatment film increases, it is suppressed that water is removed from the chemical conversion treatment film when the chemical conversion treatment liquid is dried. As a result, it is possible to prevent cracks from being generated in the chemical conversion-treated film when the chemical conversion-treated film is formed. As a result, the corrosion resistance of the manufactured chemical conversion-treated steel sheet can be improved.

In addition, the Group 1 metal has a function of improving the long-term storage stability (treatment liquid stability) of the chemical conversion treatment liquid. This is because the inclusion of the Group 1 metal in the chemical conversion treatment liquid increases the amount of hydroxyl groups in the chemical conversion treatment liquid, so that the binding of the Group 4 metal and phosphorus can be suppressed. That is, by including the Group 1 metal in the chemical conversion treatment liquid, it is possible to suppress the chemical conversion treatment liquid from becoming a gel, that is, to improve the long-term storage property of the chemical conversion treatment liquid.

The Group 1 metal may be added to the chemical conversion treatment liquid as the above-mentioned phosphoric acid compound, or may be added to the chemical conversion treatment liquid as another compound (for example, hydroxide).

<Molybdate>
The molybdate stabilizes the valence of V in the chemical conversion treatment liquid and improves the blackening resistance and corrosion resistance of the chemical conversion treatment steel sheet. It is presumed that the molybdate ion stabilizes the valence of V to pentavalent by forming a complex with the pentavalent V ion in the alkaline chemical conversion treatment liquid.

The type of molybdate is not particularly limited, and for example, molybdate, ammonium molybdate, alkali metal molybdate, and the like can be used. In particular, molybdate or ammonium molybdate is preferable from the viewpoint of corrosion resistance.

The chemical conversion treatment liquid of the present embodiment contains, for example, an amount of molybdate having a Mo concentration in the range of 0.01 to 45 g / L in order to obtain excellent corrosion resistance.

<Vanadium salt>
The vanadium salt contributes to the improvement of the corrosion resistance of the chemical conversion-treated steel sheet and the improvement of the blackening resistance of the chemical conversion-treated steel sheet. The type of vanadium salt is not particularly limited, and for example, ammonium metavanadate, sodium metavanadate, potassium metavanadate, vanadate in which vanadium pentoxide is dissolved in amine, and the like can be used. In these vanadium salts, the valence of V is all pentavalent. Among these vanadium salts, vanadate in which ammonium metavanadate or vanadium pentoxide is dissolved in amine is preferable from the viewpoint of corrosion resistance.

The chemical conversion treatment liquid of the present embodiment preferably contains, for example, an amount of molybdate having a V concentration of 8 g / L or less. When the concentration of V is larger than 8 g / L, the stability of the chemical conversion treatment liquid is lowered, and a precipitate may be formed when stored at room temperature for about 1 month.

<Mole ratio>
Next, the molar ratios of the Group 4 metal oxygenate, the phosphoric acid compound, and the Group 1 metal in the chemical conversion treatment liquid of the present embodiment will be described.

In the chemical conversion treatment liquid of the present embodiment, the molar ratio of phosphorus to the group 4 metal is 0.5 to 4, the molar ratio of the group 1 metal to the group 4 metal is 0.02 to 0.8, and phosphorus. The molar ratio of Group 1 metals to to is 0.01 or more.

When the molar ratio of phosphorus to Group 4 metal in the chemical conversion treatment liquid is less than 0.5, and when the molar ratio of phosphorus to Group 4 metal is larger than 4, the chemical conversion treatment film is corroded by chloride ions and the like. Since the film is easy to permeate the factors, the corrosion resistance of the chemical conversion-treated steel sheet is lowered.

When the molar ratio of the Group 4 metal to the Group 4 metal or phosphorus in the chemical conversion treatment liquid is smaller than the above value, the number of hydroxyl groups derived from the Group 1 metal becomes insufficient in the formed chemical conversion treatment film. Therefore, the number of bonds between the chemical conversion-treated film containing Group 4 metal and phosphorus as main components and the Zn-based plated steel sheet is reduced. As a result, the adhesion between the chemical conversion coating and the Zn-based plated steel sheet becomes insufficient.

When the molar ratio of the Group 1 metal to the Group 4 metal in the chemical conversion treatment liquid is larger than 0.8, the chemical conversion treatment film is easily decomposed by the corrosion factor, so that the corrosion resistance of the chemical conversion treatment steel sheet is lowered.

From the viewpoint of long-term storage of the chemical conversion treatment liquid, the molar ratio of the Group 1 metal to the Group 4 metal is 0.5 or more, and the molar ratio of the Group 1 metal to phosphorus is 0.18 or more. Is preferable.

The chemical conversion treatment liquid of the present embodiment has, for example, a group 4 metal concentration of 5 to 35 g / L, a phosphorus concentration of 0.8 to 60 g / L, and a group 1 metal concentration of 0.2 g / L or more. Further, the chemical conversion treatment liquid of the present embodiment may contain an amine, a silane coupling agent, or the like in addition to the above-mentioned substances. The amine dissolves a salt containing vanadium in the chemical conversion treatment liquid while maintaining the valence of V at a pentavalent value, and forms a pentavalent or hexavalent Mo composite oxygenate from the molybdate. The amine is preferably a low boiling point amine having a molecular weight of 80 or less. As the amine, for example, ethanolamine, 1-amino-2-propanol, ethylenediamine and the like can be used.

(Chemical conversion steel sheet)
The chemical conversion-treated steel sheet of the present embodiment is produced by applying the above-mentioned chemical conversion treatment liquid to the surface of a Zn-based plated steel sheet and drying it to form a chemical conversion-treated film.

The method for applying the chemical conversion treatment liquid is not particularly limited, and a method such as a roll coating method, a spin coating method, or a spray method can be used. The amount of the chemical conversion-treated film adhered to the surface of the Zn-based plated steel sheet is preferably in the range of ^{50 to 1000 mg / m 2.} When the adhesion amount is ^{less than 50 mg / m 2} , the thickness of the chemical conversion treatment film becomes thin, so that sufficient corrosion resistance cannot be obtained. On the other hand, if the amount of adhesion is ^{more than 1000 mg / m 2} , the thickness of the chemical conversion coating film becomes too thick, and the corrosion resistance becomes excessive. Considering the spot weldability, the amount of the chemical conversion coating applied to the surface of the Zn-based plated steel sheet is more preferably in the range of ^{50 to 500 mg / m 2.}

The drying temperature of the chemical conversion treatment liquid may be room temperature, but is preferably 30 ° C. or higher from the viewpoint of productivity.

The chemical conversion-treated steel sheet produced by the above method contains (1) a group 4 metal oxidate, a phosphoric acid compound, and a group 1 metal, and (2) the chemical conversion-treated film contains a group 4 metal oxidate and a phosphoric acid. It contains compounds, group 1 metals, molybdates, and vanadium salts, and (3) the chemical conversion coating contains 17 to 136 parts by mass of phosphorus with respect to 100 parts by mass of the group 4 metal, and (4) the chemical conversion coating 1 that contains 0.5 to 21 parts by mass of Group 1 metal with respect to 100 parts by mass of Group 4 metal, and (5) the chemical conversion coating is 0.7 parts by mass or more with respect to 100 parts by mass of phosphorus. Contains group metals.

The chemical conversion-treated steel sheet of the present embodiment has the above-mentioned structure, and thus contains a predetermined amount or more of Group 1 elements in the chemical conversion-treated film. As a result, since a predetermined amount or more of hydroxyl groups are present in the chemical conversion-treated film, a bond is likely to occur between the chemical conversion-treated film and the Zn-based plated steel sheet. As a result, the chemical conversion-treated steel sheet of the present embodiment has high adhesion between the Zn-based plated steel sheet and the chemical conversion-treated film.

Further, the chemical conversion-treated steel sheet of the present embodiment contains a predetermined amount or more of hydroxyl groups in the chemical conversion-treated film because it has the above-mentioned structure. As a result, it is possible to suppress the occurrence of cracks in the chemical conversion-treated film during production, so that the chemical conversion-treated steel sheet of the present embodiment has high corrosion resistance.

The amount of Mo contained in the chemical conversion treatment film is preferably 1 to 60 parts by mass with respect to 100 parts by mass of the Group 4 metal (for example, Zr). When the amount of Mo is less than 1 part by mass with respect to 100 parts by mass of the group 4 metal, the blackening resistance is not sufficient. Further, when the amount of Mo is larger than 60 parts by mass with respect to 100 parts by mass of the group 4 metal, the amount of the Zn-based plating layer and the unreacted molybdate may become excessive, and the corrosion resistance of the processed portion may be lowered.

The amount of V contained in the chemical conversion treatment film is preferably 2 to 20 parts by mass with respect to 100 parts by mass of the group 4 metal (for example, Zr). When the amount of V is less than 2 parts by mass with respect to 100 parts by mass of the group 4 metal, the corrosion resistance and blackening resistance are not sufficient. Further, when the amount of V is larger than 20 parts by mass with respect to 100 parts by mass of the group 4 metal, the amount of pentavalent V that has not reacted with the Zn-based plating layer becomes excessive, and the corrosion resistance may decrease.

[Embodiment 2]
Other embodiments of the chemical conversion treatment liquid of the present invention will be described below. Since the matters other than the matters described in the present embodiment are the same as the matters described in the first embodiment, the description thereof will be omitted.

In order to improve the corrosion resistance of the chemical conversion treated steel sheet, it is conceivable to increase the amount of phosphorus contained in the chemical conversion treatment liquid, that is, the amount of phosphate. However, in the conventional chemical conversion treatment liquid, only one of the inorganic phosphate and the organic phosphate is contained as the phosphoric acid compound, and in such a case, if the amount of the phosphate is increased, the chemical formation occurs. While the treatment liquid is being stored, phosphorus binds to each other to form a gel, which causes a problem that the stability of the treatment liquid is lowered.

Therefore, the present inventors have conducted intensive studies to include both an inorganic phosphate and an organic phosphate as a phosphoric acid compound to bond phosphorus to each other during storage of the chemical conversion treatment solution. It was found that it can be suppressed.

Further, the present inventors have found that an inorganic phosphate can improve the corrosion resistance of a chemical conversion-treated steel sheet, and an organic phosphate can improve the blackening resistance of a chemical conversion-treated steel sheet. ..

From the above findings, the chemical conversion treatment liquid of the present embodiment has the following constitution.

Al: A chemical conversion treatment liquid for forming a chemical conversion treatment film on the surface of a zinc-based plated steel plate having a zinc plating layer containing 0.1 to 22.0% by mass, which is a water-soluble Group 4 metal oxyphosphate. It contains a phosphate compound, and as a phosphate compound, it contains both an inorganic phosphate and an organic phosphate.

According to the above configuration, by including both an inorganic phosphate and an organic phosphate as the phosphoric acid compound, it is possible to suppress the binding of phosphorus to each other during storage of the chemical conversion treatment liquid. Further, since it contains both an inorganic phosphate that improves corrosion resistance and an organic phosphate that improves blackening resistance, it is possible to impart corrosion resistance and blackening resistance to the chemical-treated steel sheet.

Examples of the inorganic phosphate in the present embodiment include alkali metal phosphate salts (for example, sodium diphosphate, potassium diphosphate, sodium tripolyphosphate), alkaline earth metal phosphate salts (calcium diphosphate, etc.), and phosphorus. Ammonium phosphate (for example, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, triammonium phosphate, etc.) can be used. In particular, diammonium hydrogen phosphate is preferable because it can suppress the bond between phosphorus during storage of the chemical conversion treatment liquid.

As the organic phosphate in the present embodiment, for example, 1-hydroxyethane-1,1-diphosphonic acid, nitrilotris (methylene-phosphonic acid) and the like can be used. In particular, nitrilotris (methylene-phosphonic acid) is preferable because it can suppress the binding between phosphorus during storage of the chemical conversion treatment liquid.

Further, in the present embodiment, it is preferable to mix 100 to 1500 parts by mass of organic phosphate with 100 parts by mass of inorganic phosphate. When the mass part of the organic phosphate is less than 100 parts by mass with respect to 100 parts by mass of the inorganic phosphate, and the mass part of the organic phosphate with respect to 100 parts by mass of the inorganic phosphate is from 1500 parts by mass. If there are too many, it is not preferable because the chemical treatment steel plate tends to be discolored.

Examples of the present invention will be described below.

FIG. 1 is a table showing data of a chemical conversion treatment liquid as an example and a comparative example of the present invention. In the table shown in FIG. 1, the experimental results of long-term storage property of the chemical conversion treatment liquid described later are also described.

In this example, ammonium zirconium carbonate as a water-soluble Group 4 metal oxate, phosphate, Group 1 metal-containing phosphate, Group 1 metal compound, ammonium molybdate as a molybdate, vanadium salt, and The chemical conversion treatment solutions 1 to 26 shown in FIG. 1 were prepared by dissolving the amine in water. Note that P1 to P5, PN1 to PN5, PC1, N1 and N2 shown in FIG. 1 are substances shown in the table shown in FIG. The amounts of ammonium molybdate, vanadium salt, and amine were dissolved in water in an amount of 8 g / L, 4.5 g / L, and 3 g / L, respectively.

FIG. 3 is a table showing data of a chemical conversion-treated steel sheet as an example and a comparative example of the present invention. In the table shown in FIG. 3, the experimental results of the adhesion of the chemical conversion-treated film to the Zn-based plated steel sheet, which will be described later, and the results of the corrosion resistance test of the chemical conversion-treated steel sheet are also described.

In this embodiment, as the original plate of the chemical conversion-treated steel sheet, (1) molten Zn-6 mass% Al-3 mass% Mg-0.020 mass% Si-0.020 mass% Ti-0.0005 mass% B alloy plating Chemical-treated steel sheets 1 to 34 were produced using a steel sheet (chemical conversion-treated original plate A shown in FIG. 3) or (2) molten Zn-0.18 mass% Al-plated steel sheet (chemical-converted steel sheet B shown in FIG. 3). .. These original plates were produced on a continuous hot-dip galvanizing production line using a steel strip of ultra-low carbon Ti-added steel having a plate thickness of 0.5 mm as a base material. As shown in FIG. 3, the chemical conversion treatment liquids 1 to 26 are used for the chemical conversion treatment steel sheets 1 to 26, the chemical conversion treatment liquid 8 is used for the chemical conversion treatment steel sheets 27 and 30, and the chemical conversion treatment liquid 12 is used for the chemical conversion treatment steel plates 28, 31, 33. , The chemical conversion treatment liquid 13 was used for the chemical conversion treatment steel sheets 29, 32, and 34, respectively.

The chemical conversion treated steel sheets 1 to 34 were produced as follows. First, the surface of the original plate of the above-mentioned chemical conversion-treated steel sheet was degreased and dried. Next, the above chemical conversion treatment liquid was applied to the surface of the original plate, and immediately after that, the temperature of the original plate was raised to 80 ° C. or 200 ° C. using an automatic discharge type electric hot air oven and dried by heating. As a result, a chemical conversion-treated film was formed on the surface of the original plate to prepare chemical conversion-treated steel sheets 1 to 34.

<Measurement of adhesion amount of chemical conversion coating>
The amount of Zr adhered to the chemical conversion-treated steel sheets 1 to 34 was measured by a fluorescent X-ray apparatus. The result is shown in FIG.

<Adhesion test of chemical conversion coating>
Adhesion tests of the formed chemical conversion-treated coatings on the surface of the original plate of the chemical conversion-treated steel sheets 1 to 34 were performed. The adhesion test was performed as follows. First, in accordance with JIS Z2248, test pieces of each chemical conversion-treated steel sheet 1-31 were bent at a bending angle of 90 ° using a push metal fitting having a tip of 1 mmR. Next, a cellophane adhesive tape was attached to the outer surface of the bent portion of the test piece in accordance with JIS Z1522, and then the cellophane adhesive tape was peeled off. Next, the peeled adhesive tape was observed with a scanning electron microscope (SEM), the amount of the chemical conversion treatment film (that is, the amount of peeling of the chemical conversion treatment film) was calculated, and the peeling rate of the chemical conversion treatment film was calculated. The table shown in FIG. 3 shows the results of the adhesion test. In this adhesion test, if the peeling rate of the chemical conversion coating is 3% or less, it is "◎", if it is larger than 3% and 5% or less, it is "○", and if it is larger than 5% and less than 10%, it is "△". When it was 10% or more, it was evaluated as "x".

<Corrosion resistance of chemical conversion treated steel sheet>
Corrosion resistance tests were performed on the chemical conversion treated steel sheets 1 to 34. The corrosion resistance test was conducted as follows. First, the end face of a 70 mm × 150 mm test piece of a chemical conversion-treated steel sheet was sealed, and a salt spray test was carried out for 120 hours in accordance with JIS Z2371. Next, white rust generated on the surface of the test piece was observed. The table shown in FIG. 3 shows the results of the corrosion resistance test. In this corrosion resistance test, when the area ratio of white rust is 5% or less, it is "◎", when it is larger than 5% and 10% or less, it is "○", and when it is larger than 10% and less than 30%, it is "△". When it was 30% or more, it was evaluated as "x".

As shown in FIG. 3, "the molar ratio of phosphorus to Zr in the chemical conversion treatment liquid is 0.5 to 4 (condition 1)", and "the molar ratio of the group 1 metal to Zr in the chemical conversion treatment liquid is 0. It is prepared using a chemical conversion treatment solution that satisfies all of "02 to 0.8 (Condition 2)" and "The molar ratio of the Group 1 metal to phosphorus in the chemical conversion treatment solution is 0.01 or more (Condition 3)". In the chemical conversion-treated steel sheet, the adhesion of the chemical conversion-treated film was high and the corrosion resistance was high. On the other hand, in the chemical conversion-treated steel sheet produced by using the chemical conversion treatment liquid which does not satisfy at least one of the conditions 1 to 3, the adhesion of the chemical conversion treatment film is low, or the corrosion resistance is low, or the adhesion and adhesion are low. Both corrosion resistance was low.

It is considered that this is because when a chemical conversion treatment liquid satisfying all of the conditions 1 to 3 is used, a bond is formed between the chemical conversion treatment film and the original plate because there are many hydroxyl groups in the chemical conversion treatment film formed. It is considered that this makes it difficult for the chemical conversion coating film to peel off from the original plate, and improves the adhesion between the chemical conversion coating film and the Zn-based plated steel sheet. Further, when a chemical conversion treatment liquid satisfying all of the conditions 1 to 3 is used, it is suppressed that water is removed from the chemical conversion treatment film when the chemical conversion treatment liquid is dried, and when the chemical conversion treatment film is formed, the chemical conversion treatment film is formed. It is considered that this is because cracks did not occur or hardly occurred in the chemical conversion coating.

Further, when the chemical conversion treatment liquid 21 in which the molar ratio of the group 1 metal to Zr in the chemical conversion treatment liquid is 0.9, which is larger than 0.8, is used, the chemical conversion treatment film is decomposed by the corrosion factor, so that the chemical conversion treatment is performed. The corrosion resistance of the steel sheet was low.

In the chemical conversion treated steel sheet prepared by using the chemical conversion treatment liquid satisfying all the conditions 1 to 3, the mass part of phosphorus in the chemical conversion treatment film is 17 to 136 parts by mass with respect to 100 parts by mass of (1) group 4 metal. Yes, (2) The mass part of the Group 1 metal is 0.5 to 21 parts by mass with respect to 100 parts by mass of the Group 4 metal, and the mass part of the Group 1 metal with respect to 100 parts by mass of phosphorus is 0.7 parts by mass or more. there were. That is, the mass part of phosphorus in the chemical conversion film is 17 to 136 parts by mass with respect to 100 parts by mass of the group 4 metal, and (2) the mass part of the group 1 metal with respect to 100 parts by mass of the group 4 metal is 0.5 to 21 parts by mass. The chemical conversion-treated steel sheet, which is a mass part and the mass part of the group 1 metal with respect to 100 parts by mass of phosphorus is 0.7 parts by mass or more, has high adhesion between the Zn-based plated steel sheet and the chemical conversion-treated film and has corrosion resistance. It was a high steel plate.

<Long-term storage test of chemical conversion treatment liquid>
Next, a long-term storage test was performed on the chemical conversion treatment liquids 1 to 26. In this test, the chemical conversion treatment liquids 1 to 26 were stored in a constant temperature layer at 25 ° C. for 1 month, and then the state of the chemical conversion treatment liquids 1 to 26 was visually observed. The results of this long-term storage test are shown in FIG. In this long-term storage test, if there is no change from the time of manufacture of the chemical conversion treatment liquid, it is "◎", if a very small amount of precipitate is observed, it is "○", and if the viscosity is higher than that at the time of adjustment, or it is gelled. In the case, it was evaluated as "x".

As shown in FIG. 1, when the contents of Zr and P in the chemical conversion treatment liquid are equivalent (for example, "chemical conversion treatment liquid 15 to 17", "chemical conversion treatment liquid 18 to 21", "chemical conversion treatment liquid 22 to" 23 ”) The long-term storage property of the chemical conversion treatment liquid having a large amount of Group 1 metal was high. It is considered that this is because the amount of hydroxyl groups in the chemical conversion treatment liquid increased by containing a large amount of Group 1 metal, and the binding of Group 4 metal and phosphorus could be suppressed. That is, it is considered that the chemical conversion treatment liquid could be prevented from becoming a gel by containing a large amount of Group 1 metal.

Further, when the chemical conversion treatment liquid 13 and the chemical conversion treatment liquid 26 were compared, the long-term storage property of the chemical conversion treatment liquid 26 was low even though the amounts of phosphorus and Group 1 elements in the chemical conversion treatment liquid were almost the same. It is considered that this is because the chemical conversion treatment liquid 26 has a high content of Zr. From this result, it can be seen that it is effective to set the concentration of the Group 4 metal in the chemical conversion treatment liquid to 35 g / L or less in order to improve the long-term storage property of the chemical conversion treatment liquid.

Claims (2)

Al: An inorganic chemical conversion treatment liquid for forming an inorganic chemical conversion treatment film on the surface of a galvanized steel sheet having a zinc plating layer containing 0.1 to 22.0% by mass.
Contains water-soluble Group 4 metal oxidates, phosphate compounds, Group 1 metals, molybdates, and vanadium salts.
The molar ratio of phosphorus to the Group 4 metal in the inorganic chemical conversion treatment liquid is 0.5 to 4.
The molar ratio of the Group 1 metal to the Group 4 metal in the inorganic chemical conversion treatment liquid is 0.02 to 0.8.
The molar ratio of the Group 1 metal to phosphorus in the inorganic chemical conversion treatment liquid is 0.01 or more.
An inorganic chemical conversion treatment liquid characterized in that the amount of the Group 4 metal is 35 g / L or less. Al: An inorganic chemical conversion-treated steel sheet having a zinc-based plated steel sheet having a zinc-plated layer containing 0.1 to 22.0% by mass and an inorganic chemical conversion-treated film formed on the surface of the galvanized steel sheet. hand,
The inorganic chemical conversion treatment film is
Includes Group 4 Metal Oxates, Phosphates, Group 1 Metals, Molybdates, and Vanadium Salts.
It contains 67.9 to 136 parts by mass of phosphorus with respect to 100 parts by mass of Group 4 metal.
Contains 10.1 to 21 parts by mass of Group 1 metal with respect to 100 parts by mass of Group 4 metal.
Against phosphate 100 parts by weight, viewed contains 0.7 parts by mass or more of Group 1 metal,
The Group 4 metal oxate is Zr oxate and is
The group 1 metal is an inorganic chemical conversion-treated steel sheet, which is characterized by being sodium or potassium.

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