JP2001303265A - Surface-treated steel sheet and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a surface-treated steel sheet which has the excellent corrosion resistance of processed parts on flawed parts not obtainable with only the self-repair effect by hexed chromium and further the surface-treated steel sheet which is excellent in the corrosion resistance of the processed parts, the blackening resistance under a moist environment or the corrosion resistance of the processed parts and the blackening resistance in a stacked state. SOLUTION: The film, in which (A) the chromium is included at 0.1 to 100 mg/2, (B) calcium is included at 0.1 to 200 mg/2 and (C) a compound consisting of either one or two kinds of zinc and aluminum is included in a range of 0.1 to 100 mg/2 in terms of phosphorus, is formed on the surface of the galvanized steel sheet. This film is formed by applying a treating liquid which is a treating liquid containing the water-soluble chromium compound, the calcium and the phosphoric acid and containing (i) 0.1 to 50 g/l hexad chromium ions, (ii) 1 to 50 gel calcium and (iii) 1 to 50 g/l phosphoric acid in the treating liquid described above on the surface of the galvanized steel sheet and heating the steel sheet to a range of the ultimate sheet temperature 60 to 300 deg.C without washing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical conversion coating formed on the surface of a galvanized steel sheet used for home appliances, building materials and the like, and more particularly, to an excellent corrosion resistance in a galvanized steel sheet. The present invention relates to a surface-treated steel sheet provided with a surface treatment, a surface-treated steel sheet further excellent in blackening resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a chromate-treated film has been formed on the surface of a zinc-based plated steel sheet as a primary rust preventive treatment until used by a consumer, but in recent years, it exhibits a high degree of corrosion resistance even after processing parts. Function to do so has come to be required.

[0003] Among zinc-based steel sheets, Zn-Al-based steel sheets obtained by alloying Zn and Al have higher corrosion resistance than galvanized steel sheets, and their demand is increasing mainly in the field of building materials. .

[0004] However, with the recent development of high durability and maintenance-free in the field of building materials, various environments,
With respect to the shape, it has been required that the original appearance surface of a Zn-Al-based plated steel sheet can be maintained for a long period of time. Specifically, the Zn-5% Al alloy-plated steel sheet containing about 5% aluminum, compared to the chromate-treated film that has been formed on the surface as a primary rust prevention treatment until it is used by consumers, (a) The function of exhibiting high corrosion resistance even after processing in a corrosive environment (corrosion resistance of the processed part) and (b) The plating surface becomes black when stored outdoors for several days with the sheet material stacked before the enforcement A function of suppressing the blackening phenomenon (blackening resistance during stacking) has been required. Also contains about 55% aluminum
Zn-55% Al alloy coated steel sheet (a) Function to exhibit high corrosion resistance even after processing in corrosive environment (corrosion resistance of processed part)
And (b) a function of suppressing the blackening phenomenon in which the plated surface is blackened in a humid environment (resistance to blackening in a humid environment) has been required.

[0005] Chromate-treated films are roughly classified into three types. Electrolytic chromate-treated films containing a trivalent chromium compound as a main component, reactive chromate-treated films, and 3 types.
It is divided into a coating type chromate treatment film composed of a compound of chromium (VI) and hexavalent chromium.

[0006] In these chromate-treated films, a trivalent chromium compound which is hardly soluble acts as a barrier to corrosion factors such as chloride ions and oxygen (barrier effect). Hexavalent chromium in the film elutes to the part, and has the effect of suppressing corrosion by passivating the damaged part of the film (self-repair effect).

[0007] For this reason, when corrosion resistance of the processed portion is required, a coating type chromate film is often applied.
Hexavalent chromium has a strong oxidizing property and is easily reduced to trivalent chromium over time. In addition, it is water-soluble and elutes out of the system in a humid environment. In many cases, hexavalent chromium sufficient to exert a repair effect does not remain in the coating, and it was not always possible to obtain a satisfactory corrosion resistance in the processed portion.

There are several known techniques for solving this problem, but they can be roughly classified into the following two methods. For example, JP-A-2-34792 discloses a method of adding a fluorocarbon resin in a chromate film to impart lubricity, and JP-A-10-176280 discloses a method of reducing lubricity. A method of containing a thermoplastic elastomer to impart ductility is disclosed. Both methods reduce the degree of film damage caused by sliding such as press working, and provide a self-repair effect with a smaller amount of hexavalent chromium. The purpose is to get. Method to suppress the amount of hexavalent chromium elution in the coating For example, in Japanese Patent Publication No. 9-800337, by dispersing a hardly soluble chromate in the coating, chromium is not eluted in the healthy part of the coating, The purpose is to elute hexavalent chromium by using a corrosion reaction (pH rise) in the damaged part of the film as a trigger to exert a self-repair effect.

According to the above method, the degree of damage to the film can be reduced with respect to press working or bending, and a certain degree of self-repair effect can be exhibited.
The effect of reducing damage to the film cannot be obtained for a portion that is damaged due to contact with a sharp metal piece or the like. Further, the resin to be contained is expensive, and there is a problem in terms of economy and productivity, such as a decrease in the stability of the processing solution.

On the other hand, according to the above-mentioned method, although the sustainability of the self-repair effect is improved as compared with the case where a water-soluble chromic acid is applied and a film is formed, the self-repair effect is poor due to the poor solubility. , At the same level as immediately after the formation of a film containing a highly water-soluble chromium compound, and in general, a film containing chromate is easily colored, and it is remarkable for members used without painting. Problems such as lowering the product value also occur.

On the other hand, a Zn-Al-based plated steel sheet has both a sacrificial corrosion-preventing ability by Zn and a passivation film-forming ability by Al acting synergistically to obtain excellent corrosion resistance. However, since Al is an active metal by nature, when the passive film is damaged, the blackening phenomenon easily occurs in a wet environment.

Zn-Al containing 4 to 25% by weight of aluminum
(1)
After plating, a method of treating with a solution containing Ni ions or Co ions (JP-A-59-177381), (2) a method of heat treatment after skin pass rolling (JP-A-55-131178), (3) )
Cleaning the plating surface with an alkaline aqueous solution
Japanese Patent Application Laid-Open No. 63-166974) and (4) a method of performing blast treatment after plating and before chromate treatment (JP-A-63-166974).

[0013] In fact, by applying the above-mentioned prior art, the blackening resistance of a Zn-Al-based plated steel sheet containing 4 to 25% by weight of aluminum is improved in a normal wet environment. However, Zn-Al containing 4-25% by weight of aluminum
System plated steel sheet, during the construction period of roofs, outer walls, etc.
When stored outdoors in the form of sheets or roll-formed molding materials (stacked state), the surface of the steel sheet becomes wet due to condensation easily in the natural environment. There is a problem that changes.

Further, all of the above-mentioned methods require special processing equipment, and therefore have problems in terms of economy and productivity.

Further, as a method for suppressing the blackening phenomenon of a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum, Japanese Patent Publication No. 1-53353 discloses a method in which chromic acid and resin are mixed at a certain ratio or more. Chromic acid is prevented from directly reacting with plating by treating with a treatment solution mixed with
A method for improving blackening resistance is disclosed. Also, Zn
As a method for suppressing the blackening phenomenon performed on -5% Al alloy-plated steel sheets and the like, JP-A-59-177381, JP-A-63-65088
A method of treating with Ni or Co is described as a pretreatment for performing chromate treatment after plating described in Japanese Unexamined Patent Publication (Kokai) No. H11-15083.

However, the method of treating with a treatment solution in which chromic acid and a resin are mixed at a certain ratio or more is based on a method in which aluminum is used.
Although the effect of improving the blackening resistance of Zn-Al-based plated steel sheets containing ultra-up to 75% by weight is recognized, it is not complete,
Rather, by mixing the resin in a certain ratio or more, the life of the processing solution is remarkably shortened, and the use of a resin that withstands the strong oxidizing power of chromic acid is disadvantageous in terms of cost.

Further, by performing a pretreatment with Ni, Co or the like, blackening resistance during stacking may be improved.
Since expensive metal is used, it is disadvantageous in terms of cost.

[0018]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned technical problems and provides a surface-treated steel sheet having excellent corrosion resistance at a worked portion and a scratched portion which cannot be obtained only by the self-repair effect of hexavalent chromium. It is an object.

Another object of the present invention is to provide a surface-treated steel sheet which is excellent in corrosion resistance in a processed portion and blackening resistance in a wet environment.

Another object of the present invention is to provide a surface-treated steel sheet which is excellent in corrosion resistance in a processed portion and blackening resistance in a stacked state.

Still another object of the present invention is to provide a method for producing the surface-treated steel sheet.

[0022]

The gist of the present invention for solving the above problems is as follows. (1) 0.1 to 100 mg of (A) chromium on the surface of galvanized steel sheet
/ m ² , (B) calcium is 0.1 to 200 mg / m ² , (C) zinc, a compound consisting of one or two of aluminum and phosphoric acid is 0.1 to 100 mg / m ^{2 in} terms of phosphorus. Surface-treated steel sheet, characterized in that a film contained therein is formed (first
invention).

(2) A zinc-based plated steel sheet contains 4
The surface-treated steel sheet according to the above (1), wherein the steel sheet is a Zn-Al-based plated steel sheet containing up to 25% by weight.

(3) A zinc-based plated steel sheet
The surface-treated steel sheet according to the above (1), wherein the steel sheet is a Zn-Al-based plated steel sheet containing more than 5 to 75% by weight.

(4) In producing the surface-treated steel sheet according to (1) to (3), a water-soluble chromium compound, calcium or a compound thereof, and phosphoric acid or a salt thereof are formed on the surface of a galvanized steel sheet. A processing solution comprising:
(i) hexavalent chromium ion 0.1 to 50 g / l, (ii) calcium 1 to 50 g / l, (iii) phosphoric acid 1 to 50 g / l A method for producing a surface-treated steel sheet, characterized in that a coating is formed by heating in a range of a reached sheet temperature of 60 to 300 ° C (fourth invention).

(5) The method for producing a surface-treated steel sheet according to (4), wherein the weight ratio of trivalent chromium ion / (trivalent chromium ion + hexavalent chromium ion) in the treatment liquid is 0.2 to 0.8. (Fifth invention).

(6) In producing the surface-treated steel sheet according to the above (1) to (3), a water-soluble chromium compound in which the chromium compound is a trivalent chromium compound, calcium or A treatment solution containing the compound and phosphoric acid or a salt thereof, wherein the treatment solution contains (i) 0.1 to 50 g / l of trivalent chromium ion and (ii) 1 to 50 g / l of calcium.
And (iii) a surface treatment characterized by applying a treatment solution containing 1 to 50 g / l of phosphoric acid and forming a film by heating at a maximum temperature of 60 to 300 ° C. without washing with water. A method for manufacturing a steel sheet (a sixth invention).

(7) The method for producing a surface-treated steel sheet according to the above (6), wherein the water-soluble chromium compound is chromium carboxylate (seventh invention).

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The base zinc-coated steel sheets include zinc-coated steel sheets, Zn-Ni-coated steel sheets, Zn-Fe-coated steel sheets (electroplating, galvannealed), Zn-Cr-coated steel sheets, Zn-Mn-coated steel sheets, and Zn-coated steel sheets. Co-plated steel sheet, Zn-Co-Cr
Alloy-plated steel sheet, Zn-Ni-Cr-plated steel sheet, Zn-Cr-Fe-plated steel sheet, Zn-Al-based plated steel sheet (eg, Zn-5% Al alloy-plated steel sheet, Zn-55% Al alloy-plated steel sheet), Zn- Mg-plated steel sheet, Z
An n-Al-Mg plated steel sheet, or a zinc-based composite plated steel sheet in which a metal oxide, a polymer, or the like is dispersed (for example, Zn-SiO ₂ dispersed plating) can be used. Further, among the above platings, a multi-layer plated steel sheet obtained by plating two or more layers of the same or different types can be used.

Further, Zn- containing 4 to 25% by weight of aluminum
The Al-based plated steel sheet is a Zn-Al plated steel sheet that contains 4 to 25% by weight of Al as an essential component, and further contains trace elements such as La, Ce, Mg, and Si as needed. This includes a so-called Zn-5% Al alloy plated steel sheet.

Also, it contains more than 25 to 75% by weight of aluminum.
A Zn-Al-based coated steel sheet is an alloy containing Al: more than 25 to 75% by weight as an essential component, and further, if necessary, trace amounts of La, Ce, Mg, Si
It is a Zn-Al plated steel sheet that also contains elements such as So-called Zn-55
% Al alloy plated steel sheet is included in this.

As a method for plating the above-mentioned steel sheet, any practicable method among an electrolytic method, a melting method and a gas phase method may be adopted.

When the film of the present invention is applied to these plating surfaces, any alkali degreasing, solvent degreasing, surface conditioning treatment (alkaline treatment) may be applied to the plating surface in advance, as necessary, so that film defects and unevenness do not occur. Surface conditioning treatment, acidic surface conditioning treatment). Also,
From the viewpoint of further improving the blackening prevention effect of the steel sheet on which the film of the present invention is formed in a use environment, an acid or iron containing iron group metal ion (Ni ion, Co ion, Fe ion) may be previously formed on the plating surface as necessary. An alkaline surface conditioning treatment can also be performed. When electrogalvanizing is used as a base, an iron group metal ion (Ni ion, Co ion, Fe ion) is added to the electroplating bath in order to further improve the blackening prevention effect.
Ion) to make these metals 1p
pm or more. In this case, the upper limit of the iron group metal concentration in the plating film is not particularly limited.

A feature of the present invention is that (A) chromium having a barrier effect, (B) calcium having a self-repairing effect, and (C) any one or both of zinc and aluminum are provided on the surface of a galvanized steel sheet. An object of the present invention is to form a chemical conversion coating containing a compound formed of a seed and phosphoric acid.

Here, the adhesion amount of chromium in the film is preferably 0.1 mg / m ² or more and 100 mg / m ² or less. If it is less than 0.1 mg / m ² , the barrier effect by chromium is not sufficiently exhibited,
On the other hand, if it exceeds 100 mg / m ² , the effect of improving the barrier effect cannot be expected even though the treatment time is extremely long. Desirably, 10mg
More preferably the / m ² or more 70 mg / m ² or less.

The calcium in the film is not particularly limited. In addition to metallic calcium, calcium oxide, calcium hydroxide, calcium silicate, calcium carbonate, calcium phosphate, calcium molybdate and other simple salts containing only calcium as a cation, , Calcium phosphate / zinc, calcium / magnesium phosphate, calcium / zinc molybdate such as double salts containing cations other than calcium and calcium,
These may be mixed. The mechanism of its development is that at the film damaged part in a corrosive environment or a wet environment, calcium that is more noble than the plating metal elutes preferentially, and while the elution of the plating metal is suppressed, the eluted calcium precipitates at the film damaged part. By doing so, a protective film is formed. It is thought that the Zn-Al-based steel sheet containing 4 to 25% by weight of aluminum and the Zn-Al-based steel sheet containing more than 25 to 75% by weight of aluminum exhibit excellent corrosion resistance and blackening resistance in the processed part. Can be

The amount of calcium adhering to the film was 0.1%.
It is preferably from 1 mg / m ^{2 to} 200 mg / m ² . If it is less than 0.1 mg / m ² , the self-repair effect of calcium is poor. In addition, in a Zn-Al-based plated steel sheet containing 4 to 25% by weight of aluminum and a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum, the effect of exhibiting corrosion resistance and blackening resistance due to calcium in the processed part is poor. If it exceeds 200 mg / m ² , the amount of calcium eluted will be excessive, and the corrosion resistance in the healthy film portion (the portion where the film has not been damaged by processing etc.) will be reduced. More preferably, it is more preferably 10 mg / m ² or more and 100 mg / m ² or less.

On the other hand, the compound comprising one or two of zinc and aluminum and phosphoric acid is not limited to the phosphate ion skeleton or the degree of condensation, and may be a normal salt, a dihydrogen salt, Either a hydrogen salt or a phosphite may be used, and the normal salt includes all condensed phosphates such as polyphosphate in addition to orthophosphate. It is thought that the mechanism of its development is that phosphate ions dissociated by hydrolysis cause a complexing reaction with the eluted metal to form a protective film in the damaged part of the film under the corrosive environment, triggered by the elution of the plating metal. .

Either zinc or aluminum in the coating
The amount of the compound consisting of one or two kinds and phosphoric acid is preferably 0.1 mg / m ² or more and 100 mg / m ² or less in terms of phosphorus. If it is less than 0.1 mg / m ² , the self-repairing effect of a compound comprising one or two of zinc and aluminum and phosphoric acid will be poor. 4 to 25% by weight of aluminum
In the case of Zn-Al-based plated steel sheet containing Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum, the corrosion resistance and blackening resistance of the processed part by the compound consisting of one or two of zinc and aluminum and phosphoric acid The effect of denaturation is poor. Ten
If it exceeds 0 mg / m ² , the self-repair improvement effect cannot be expected for the treatment cost increase, and Zn-containing 4 to 25% by weight of aluminum
Al-based plated steel, Zn containing more than 25 to 75% by weight of aluminum
-For Al-plated steel sheets, the effect of improving the corrosion resistance and blackening resistance of the processed part cannot be expected despite the increase in processing cost. More preferably, it is more preferably 1 mg / m ² or more and 50 mg / m ² or less.

Here, of the above three compounds, (A) chromium and (B) calcium, or (A) chromium and (C) one or two of zinc and aluminum, and phosphoric acid Although the inclusion of the compound has the effect of improving the corrosion resistance of the processed portion, the coexistence of the above three compounds can significantly improve the corrosion resistance of the processed portion. A Zn-Al-based plated steel sheet containing 4 to 25% by weight of aluminum and a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum can be expected to have a remarkable improvement in blackening resistance.

The mechanism is as follows. In a corrosive environment, calcium is eluted preferentially over the plating metal. As a result, the hydrolysis reaction of a compound comprising one or two of zinc and aluminum and phosphoric acid is performed. Is considered to be dissociated into phosphate ions, and phosphate ions having a high complexing ability cause a complex formation reaction with calcium ions to form a dense and hardly soluble protective film, and the corrosion reaction occurs earlier. Can be suppressed. In a Zn-Al-based steel sheet containing 4 to 25% by weight of aluminum and a Zn-Al-based steel sheet containing more than 25 to 75% by weight of aluminum, the blackening phenomenon can be suppressed.

Further, in addition to the above-mentioned film constituting substances, oxide fine particles such as silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide and antimony oxide can be further contained.

Further, in addition to the above-mentioned film constituting substances, organic polymer resins such as epoxy resins, polyhydroxy polyether resins, acrylic copolymer resins, ethylene-acrylic acid copolymer resins, alkyd resins , Polybutadiene resin, phenol resin, polyurethane resin,
It may contain a polyamine resin, a polyphenylene resin, and the like.

In the present invention, a treatment solution containing a water-soluble chromium compound, calcium or a compound thereof, and phosphoric acid or a salt thereof, wherein the treatment solution contains (i) hexavalent chromium ion in an amount of 0.1 to 10%. 50 g / l and (ii) calcium from 1 to 50 g / l
And (iii) applying a treatment liquid containing 1 to 50 g / l of phosphoric acid, and forming a chemical conversion treatment film by heating at a maximum sheet temperature of 60 to 300 ° C. without washing with water, thereby forming a corrosion-resistant part in the processed part. It is possible to manufacture a surface-treated steel sheet having excellent heat resistance. Also, any of a Zn-Al-based plated steel sheet containing 4 to 25% by weight of aluminum and a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum are further improved in blackening resistance.

Here, the hexavalent chromium ion concentration is 0.1 g / l
If the amount is less than 0.5 g / l, the coating amount must be significantly increased in order to obtain a desired chromium adhesion amount, coating unevenness is likely to occur, and if it exceeds 50 g / l, the reactivity of the processing solution is extremely high.
The amount of dissolution of the plating film increases, and the stability of the processing solution is lowered, which is not preferable.

The hexavalent chromium ion species is not particularly limited as long as it is water-soluble.
Ammonium chromate and the like correspond to this, and hardly soluble chromium compounds such as zinc chromate, strontium chromate and barium chromate do not correspond thereto.

In the water-soluble chromium compound, the weight ratio of trivalent chromium ion / (trivalent chromium ion + hexavalent chromium ion) (in terms of chromium metal) is more preferably 0.2 to 0.8. A surface-treated steel sheet having excellent corrosion resistance can be manufactured. Add 4 aluminum
Up to 25% by weight Zn-Al plated steel sheet, 25 aluminum
Any Zn-Al-based plated steel sheet containing ultra-up to 75% by weight has better blackening resistance.

If the weight ratio of trivalent chromium ion / (trivalent chromium ion + hexavalent chromium ion) (in terms of metal chromium) is less than 0.2, the hexavalent chromium ion concentration in the film becomes excessive, and the film is hardly soluble. In a corrosive environment, a Zn-Al-based steel sheet containing 4 to 25% by weight of aluminum without contributing to corrosion resistance
In a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight, the amount eluted without contributing to blackening resistance increases, which is not preferable from the viewpoint of economy and environmental compatibility. If it exceeds 0.8, the processing solution is likely to gel, and the stability of the processing solution is significantly reduced.

Further, according to the present invention, there is provided a treatment solution containing a water-soluble chromium compound in which the chromium compound is a trivalent chromium compound, calcium or a compound thereof, and phosphoric acid or a salt thereof. i) 0.1-valent trivalent chromium ion
50 g / l, (ii) calcium 1-50 g / l, and (iii) phosphoric acid
By applying a treatment liquid containing 1 to 50 g / l and heating at a maximum temperature of 60 to 300 ° C. without washing with water to form a chemical conversion treatment film, it has excellent corrosion resistance in the processed part, and aluminum A Zn-Al-based plated steel sheet containing 25% by weight and a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of aluminum have excellent blackening resistance. According to the method of the present invention, since hexavalent chromium ions are not contained in the treatment liquid, the use of
There is no problem of elution of chromium (VI) out of the system, and high self-repairability can be exhibited without relying on hexavalent chromium.

Here, the trivalent chromium ion concentration is 0.1 g / l
If the amount is less than 0.5 g / l, the coating amount must be significantly increased in order to obtain a desired chromium adhesion amount, coating unevenness is likely to occur, and if it exceeds 50 g / l, the reactivity of the processing solution is extremely high.
The amount of dissolution of the plating film increases, and the stability of the processing solution is lowered, which is not preferable.

The trivalent chromium compound is not particularly limited as long as it is a water-soluble compound.
Examples thereof include chromium sulfate, chromium acetate, and chromium formate, and particularly, chromium carboxylate such as chromium acetate and chromium formate is preferable.

The calcium or its compound coexisting with the water-soluble chromium compound is not particularly limited.
In addition to calcium oxide and calcium hydroxide, single salts containing only calcium as a cation such as calcium silicate, calcium carbonate, calcium phosphate and calcium molybdate, as well as calcium and zinc such as calcium and zinc phosphate, calcium and magnesium phosphate, and calcium and zinc molybdate Any of double salts containing cations other than the above may be used, and these may be mixed. Further, a reaction product with another compound in the treatment liquid is included in the reaction liquid, and may be calcium or calcium ion.

When the calcium concentration is less than 1 g / l,
Zn-Al-plated steel sheet containing 4 to 25% by weight of aluminum, cannot contain enough calcium to exhibit sufficient self-repair effect in the formed film, more than 25 to 75 of aluminum
In any of the Zn-Al-based plated steel sheets containing wt%, the formed film cannot contain enough calcium to exhibit sufficient corrosion resistance and blackening resistance in the processed portion. Also, if it exceeds 50 g / l,
It is not preferable because the calcium content in the coating becomes extremely high, and the corrosion resistance of the sound coating is reduced.

The phosphoric acid or a salt thereof coexisting with the water-soluble chromium compound is not particularly limited, and is not limited to a phosphate ion skeleton or a degree of condensation. Any of a hydrogen salt or a phosphite may be used.Furthermore, the normal salt may be any of condensed phosphates such as an orthophosphate and a polyphosphate, or a mixture thereof. Good. Further, phosphate or phosphate ions may be used.

Further, if the phosphoric acid concentration is less than 1 g / l, the formed film cannot contain phosphoric acid enough to exhibit a sufficient self-repair effect, and Zn-Al containing 4 to 25% by weight of aluminum. Over 25% to 75% by weight of aluminum
In any of the Zn-Al-based plated steel sheets containing, the effect of exhibiting the corrosion resistance and blackening resistance of the processed portion due to phosphoric acid is poor. Also, 50
If the amount exceeds g / l, the reactivity of the processing solution is extremely high, so that the amount of the plating film dissolved increases, and the eluted zinc decreases the stability of the processing solution, which is not preferable.

Further, boric acid, sulfuric acid,
An inorganic acid such as nitric acid can be contained.

As a method of applying the treatment liquid described above,
Although there is no particular limitation, application by a roll coater or a ringer roll, or application by dipping and air knife drawing may be mentioned.

After coating, it is preferable to heat the sheet at a maximum temperature of 60 to 300 ° C. without washing with water. Here, if the maximum reached plate temperature is less than 60 ° C., the barrier effect is high.
When the chromium (VI) compound is not sufficiently formed, and at temperatures exceeding 300 ° C., numerous cracks are generated to the extent that the self-repair effect does not reach the coating.In both cases, the corrosion resistance of the processed part and the sound part of the coating is remarkable. Will drop.

[0059]

(Example 1) A zinc-plated steel sheet shown in Table 1 was used as a base plate for processing, and coating was performed with a roll coater under the processing solution composition and drying temperature shown in Tables 3 and 4. It was dried by heating without washing with water to form a chemical conversion coating. The amount of adhesion was controlled by the amount of application, the peripheral speed of the roll coater, the amount of reduction, and the like. Here, Table 2 shows the compounds ("Zn, Al-phosphoric acid" in Tables 3 and 4) composed of one or two of zinc and aluminum and phosphoric acid in the chemical conversion treatment film. The quality evaluation of the obtained surface-treated steel sheet was performed as follows.

The Corrosion Resistance of Processed Parts A notch reaching the iron base was cut into the sample surface over a width of 0.3 mm and a length of 5 cm with a cutter knife, and the following composite corrosion test was performed for 200 cycles.

3 wt% salt spray test (30 ° C .; 0.5 hours) ↓ Wet test (30 ° C., 95% RH; 1.5 hours) ↓ Hot air drying test (50 ° C., 20% RH; 2.0 hours) ↓ Hot air drying test (30 (° C, 20% RH; 2.0 hours) The evaluation was performed based on the area ratio of rust generation in a region of 5 mm on both sides of the cut line. The state of rust (color tone)
Depends on the Al concentration of the plating film,
White rust was generated in a Zn-Al-based steel sheet having an Al concentration of 25% by weight or less, and gray to black rust was generated in a Zn-Al-based steel sheet having an Al concentration of more than 25 to 75% by weight. ◎: No rust generation ○ +: Rust generation area rate less than 5% ○: Rust generation area rate 5% or more and less than 10% ○ −: Rust generation area rate 10% or more and less than 25% △: Rust generation area rate 25% or more 50 %: Rust generation area rate 50% or more

Corrosion resistance of the film sound portion The sample not subjected to any processing such as scratching or bending was subjected to the above-described complex corrosion test for 300 cycles, and evaluated based on the same criterion as above based on the rust generation area ratio of the sample surface. The state of rust is the same as in the case of the above-mentioned evaluation of the corrosion resistance of the processed portion.

Blackening Resistance The blackening resistance of a Zn—Al-based plated steel sheet containing 4% by weight or more of Al was evaluated. Specifically, the following according to the Al concentration
Performed in two ways.

(Zn-Al-based plated steel sheet having an Al concentration of 4 to 25% by weight: No. 2 in Table 1) Samples that have not been subjected to any processing such as scratching or bending are placed in a stack state and subjected to a wet test machine (HCT). After standing for 6 days, the appearance of the sample was visually observed, and the resistance to blackening was evaluated according to the following criteria based on the degree of blackening and the area of blackening. ◎: No change in appearance before and after the test. 有 り: Slight change in spot-like appearance after the test (Area: 10%
△: After the test, there is a planar appearance change part (area: 10% or more and 50% or more)
%: ×: There is at least 50% of a black discolored portion or a planar appearance changed portion after the test.

(Zn-Al-based coated steel sheet having an Al concentration of more than 25 to 75% by weight: No. 3 in Table 1) For a sample that has not been subjected to any processing such as scratching or bending, the temperature is 80 ° C. and the relative humidity is 95% RH. Of whiteness (L value) when left in a constant temperature and humidity controlled atmosphere atmosphere for 24 hours ΔL (L value before test-L value after test)
Was measured and evaluated according to the following criteria. ◎: ΔL ≧ −1.0 ○: −1.0> ΔL ≧ −2.0 Δ: −2.0> ΔL ≧ −4.0 ×: −4.0> ΔL The evaluation results are shown in Tables 3 and 4.

[0066]

[Table 1]

[0067]

[Table 2]

[0068]

[Table 3]

[0069]

[Table 4]

From Tables 3 and 4, it can be seen that the steel sheet on which the coating within the first invention range is formed has a sound coating portion as compared with the steel sheet of the comparative example having the coating outside the first invention range. Corrosion resistance in the processed part is significantly improved. Further, in a steel sheet containing 4% by weight or more of Al having a film formed within the scope of the first invention, 4% of Al having a film formed outside the scope of the first invention is contained.
Black discoloration resistance, that is, Al
Of Zn-Al-based plated steel sheet containing 4 to 25% by weight of black has improved resistance to blackening in a stacked state, and Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of Al has improved blackening resistance in a humid environment. I have.

Further, when forming a film within the scope of the first invention, the steel sheet manufactured under the conditions within the range of the fourth invention has good film quality. On the other hand, the steel sheet of the comparative example (No. 38, 41) in which a film was formed at a drying temperature outside the range of the fourth invention,
Poor film quality.

(Example 2) A zinc-coated steel sheet shown in Table 1 was used as a base plate for processing, and was applied by a roll coater under the processing solution composition and drying temperature shown in Tables 5 and 6, and washed with water. Without heating and drying, a chemical conversion coating was formed. The amount of adhesion was controlled by the amount of application, the peripheral speed of the roll coater, the amount of reduction, and the like. Here, the compound consisting of phosphoric acid and one or two of zinc and aluminum in the chemical conversion coating ("Zn, Al-phosphoric acid" in Tables 5 and 6) is shown in Table 2.
Shown in The quality evaluation of the obtained surface-treated steel sheet was performed as follows.

Corrosion Resistance of Processed Section A notch reaching the iron base was cut into the sample surface over a width of 0.3 mm and a length of 5 cm with a cutter knife, and a salt spray test in accordance with JIS Z2371 was performed for 200 hours. Evaluation is the rust generation area ratio in the area of 5 mm each side of the score line,
Performed according to the same standard as in Example 1. The state of rust (color)
Is the same as that in the case of the evaluation of the corrosion resistance of the processed portion in Example 1.

The corrosion resistance of the film sound portion was evaluated for the sample which had not been subjected to any processing such as scratching or bending, for 400 hours, and evaluated based on the rust generation area ratio of the sample surface according to the same standard as in Example 1. The state of rust is the same as in the case of the above-mentioned evaluation of the corrosion resistance of the processed portion.

Black Degradation Resistance A Zn—Al-based plated steel sheet containing 4% by weight or more of Al was evaluated for black degradation resistance in the same manner as in Example 1. The evaluation results are shown in Tables 5 and 6.

[0076]

[Table 5]

[0077]

[Table 6]

From Tables 5 and 6, it can be seen that the steel sheet having the coating within the range of the first invention has, as a matter of course, a sound film portion, in comparison with the steel sheet of the comparative example having the coating outside the range of the first invention. Corrosion resistance in the processed part is significantly improved. Further, in a steel sheet containing 4% by weight or more of Al having a film formed within the scope of the first invention, 4% of Al having a film formed outside the scope of the first invention is contained.
Black discoloration resistance, that is, Al
Of Zn-Al-based plated steel sheet containing 4 to 25% by weight of black has improved resistance to blackening in a stacked state, and Zn-Al-based plated steel sheet containing more than 25 to 75% by weight of Al has improved blackening resistance in a humid environment. I have.

Further, when forming a film within the first invention range, the steel sheet formed at a drying temperature within the fourth invention range is a steel sheet of a comparative example formed at a drying temperature outside the fourth invention range. Good film quality is obtained compared to (No. 38, 41). Further, when the treatment liquid having the Cr reduction rate within the range of the fifth invention is used, a better film quality is obtained as compared with the case where the treatment liquid having the Cr reduction rate lower than the fifth invention range is used (No. 42). Have been. In the case of the treatment liquid (No. 45) having a Cr reduction ratio exceeding the range of the fifth invention, the treatment liquid gelled, and thus the quality evaluation of the steel sheet was not performed.

(Example 3) A zinc-plated steel sheet shown in Table 1 was used as a base plate for treatment, and a chromium salt shown in Table 7 was used as a trivalent chromium compound. Originally, the composition was applied by a roll coater and dried by heating without washing with water to form a chemical conversion coating. The amount of adhesion was controlled by the amount of application, the peripheral speed of the roll coater, the amount of reduction, and the like. Here, the compounds ("Zn, Al-phosphoric acid" in Tables 8 and 9) comprising phosphoric acid and one or two of zinc and aluminum in the chemical conversion treatment film are shown in Table 2. The quality evaluation of the obtained surface-treated steel sheet was performed as follows.

Corrosion Resistance of Processed Parts A notch reaching the iron base was cut into the sample surface over a width of 0.3 mm and a length of 5 cm with a cutter knife, and the following composite corrosion test was performed for 200 cycles. 3wt% salt spray test (30 ℃;
0.5 hour) ↓ Wet test (30 ° C., 95% RH; 1.5 hours) The evaluation was performed based on the same criterion as in Example 1 with the rust generation area ratio in a region of 5 mm on both sides of the cut line. The state of rust (color tone) is the same as in the case of the evaluation of the corrosion resistance of the processed portion in Example 1.

Corrosion resistance of the film sound portion The sample not subjected to any processing such as scratching or bending was subjected to the above-mentioned complex corrosion test for 300 cycles, and evaluated based on the same criterion as above based on the rust generation area ratio of the sample surface. The state of rust is the same as in the case of the above-mentioned evaluation of the corrosion resistance of the processed portion.

Black Degradation Resistance For a Zn—Al-based plated steel sheet containing 4% by weight or more of Al, black degradation resistance was evaluated in the same manner as in Example 1. The evaluation results are shown in Tables 8 and 9.

[0084]

[Table 7]

[0085]

[Table 8]

[0086]

[Table 9]

From Tables 8 and 9, it can be seen that the steel sheet on which the coating within the first invention range is formed has, as a matter of course, not only the film sound portion but also the comparative steel sheet on which the coating is out of the first invention range. Corrosion resistance in the processed part is significantly improved. No.29,42
As can be seen from the comparison of Nos. To 44, when chromium carboxylate is used as the trivalent chromium compound (Nos. 29 and 44), the corrosion resistance and the blackening resistance are more excellent.

Further, a film within the scope of the first invention was formed.
The steel sheet containing 4% by weight or more of Al has a blackening resistance, that is, Zn-Al containing 4 to 25% by weight of Al, compared to the steel sheet of the comparative example containing 4% by weight or more of Al having a coating outside the scope of the first invention. The resistance to blackening in a stacked state is improved in a system-coated steel sheet, and the resistance to blackening in a wet environment is improved in a Zn-Al-based steel sheet containing more than 25 to 75% by weight of Al.

Further, when forming a film within the scope of the first invention, the steel sheet manufactured under the conditions within the scope of the sixth invention has good film quality. On the other hand, the steel sheet of the comparative example (No. 38, 41) in which the film was formed at a drying temperature outside the range of the sixth invention was inferior in film quality.

[0090]

According to the present invention, it is possible to obtain a surface-treated steel sheet having excellent corrosion resistance of a worked portion and a flaw, which cannot be obtained only by the self-repair effect of hexavalent chromium.

[0091] The zinc-based galvanized steel sheet converts aluminum.
In the case of a Zn-Al-based plated steel sheet containing 4 to 25% by weight, a surface-treated steel sheet having excellent corrosion resistance in a processed portion and further excellent blackening resistance in a stacked state can be obtained.

[0092] Further, the zinc-based plated steel sheet converts aluminum.
In the case of a Zn-Al-based plated steel sheet containing more than 25 to 75% by weight, a surface-treated steel sheet having excellent corrosion resistance in a processed portion and further excellent blackening resistance in a humid environment can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C23C 22/30 C23C 22/30 28/00 28/00 C (72) Inventor Masaaki Yamashita Marunouchi, Chiyoda-ku, Tokyo 1-2-2 Nihon Kokan Co., Ltd. F-term (reference) 4K026 AA02 AA12 AA13 AA22 BA03 BA04 BA07 BB08 CA16 CA19 CA20 CA23 CA26 DA02 EB11 4K027 AA05 AA22 AB05 AB43 AB44 AC82 4K044 AA02 AB02 BA10 BA11 BA12 BA03 BA17 CA11 CA16 CA18 CA53

Claims (7)

[Claims] Claims: 1. A surface of a galvanized steel sheet, wherein (A) chromium is 0.1 to 100 mg / m ² , (B) calcium is 0.1 to 200 mg / m ² , (C)
A surface-treated steel sheet comprising a film containing a compound comprising one or two of zinc and aluminum and phosphoric acid in a range of 0.1 to 100 mg / m ^{2 in} terms of phosphorus. 2. A galvanized steel sheet containing 4 aluminum.
The surface-treated steel sheet according to claim 1, wherein the steel sheet is a Zn-Al-based plated steel sheet containing up to 25% by weight. 3. A galvanized steel sheet comprising 25 aluminum.
The surface-treated steel sheet according to claim 1, wherein the steel sheet is a Zn-Al-based plated steel sheet containing more than 75% by weight. 4. A treatment liquid comprising a water-soluble chromium compound, calcium or a compound thereof, and phosphoric acid or a salt thereof on the surface of a galvanized steel sheet for producing the surface-treated steel sheet according to claim 1. Wherein in the treatment solution,
(i) hexavalent chromium ion 0.1 to 50 g / l, (ii) calcium 1 to 50 g / l, (iii) phosphoric acid 1 to 50 g / l A method for producing a surface-treated steel sheet, characterized in that a coating is formed by heating at an ultimate sheet temperature of 60 to 300 ° C. 5. The method for producing a surface-treated steel sheet according to claim 4, wherein the weight ratio of trivalent chromium ion / (trivalent chromium ion + hexavalent chromium ion) in the treatment liquid is 0.2 to 0.8. 6. In the production of the surface-treated steel sheet according to claim 1, a chromium compound comprising a water-soluble chromium compound comprising a trivalent chromium compound, calcium or a compound thereof, A treatment solution containing phosphoric acid or a salt thereof, wherein (i) 0.1 to 50 g / l of trivalent chromium ion and (ii) 1 to 50 g / l of calcium
And (iii) a surface treatment characterized by applying a treatment solution containing 1 to 50 g / l of phosphoric acid and forming a film by heating at a maximum temperature of 60 to 300 ° C. without washing with water. Steel plate manufacturing method. 7. The method for producing a surface-treated steel sheet according to claim 6, wherein the water-soluble chromium compound is chromium carboxylate.