JPH04333576A - Production of surface-treated steel sheet having excellent adhesive property - Google Patents

Abstract

PURPOSE:To obtain a surface-treated steel sheet for an adhesive base undergoing no deterioration in the adhesive property even at a high temp. of >=100 deg.C. CONSTITUTION:The surface of a steel sheet or a Zn or Zn alloy plated steel sheet is electroplated with a Zn alloy at 30-200A/dm<2> current density in an acidic plating bath of pH 1-6 contg. 0.05-5g/l, in total, of Ni<2+> and/or Co<2+> and impurities including <=2g/l total Fe and <=2mg/l Pb. The steel sheet is then immersed in a reactive chromate soln. to form a chromate film by 0.5-120mg/m<2> (expressed in terms of Cr) and drying is carried out at >=120 deg.C atmospheric temp. so that the steel sheet attains to 100-300 deg.C. By this method, a surface-treated steel sheet having excellent adhesive property is produced. An org. high molecular compd. soluble or dispersible in water or an org. solvent is further stuck on the surface-treated steel sheet in the form of an org. resin coating film by 0.2-2.0g/m<2> on dry basis to produce another surface-treated steel sheet having excellent adhesive property.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a surface-treated steel plate that has good adhesion as a bonding base when bonding a steel plate to a sheet-like material such as resin or metal.

0002

2. Description of the Related Art Generally, steel plates (laminated steel plates), which are made by pasting a sheet-like resin onto a steel plate with an adhesive, are often used for automobiles, home appliances, and building materials. In recent years, these steel sheets are required to have high corrosion resistance, so zinc-based surface-treated steel sheets are used instead of cold-rolled steel sheets. In particular, electrogalvanized steel sheets, which are easily available and have excellent surface smoothness, are often used.

On the other hand, examples of bonding sheet materials such as metal to steel plates include damping steel plates and steel plates for printed circuit boards, but the situation is similar to laminated steel plates, and when electrogalvanized steel plates are used. There are many.

[0004] When electrogalvanized steel sheets are used as the adhesive base, either phosphate-treated steel sheets (bonde steel sheets) (for example, Japanese Patent Publication No. 58-57511) or chromate-treated steel sheets (chromate steel sheets) are used. For example, JP-A-50-14550) is used.

However, these steel plates do not necessarily have sufficient performance. That is, bonded steel sheets have phosphate crystals formed on their surfaces, but these have poor toughness and are susceptible to deformation, resulting in peeling of the bonded sheets during bending.

[0006] Since the chromate film has a small amount of adhesion, unlike bonded steel sheets, it has good adhesion during bending. However, under high temperature and high humidity conditions of 100° C. or higher, its adhesive properties deteriorate significantly.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a surface-treated steel sheet for use as an adhesive base, which solves the above-mentioned problems and whose adhesive properties do not deteriorate even at high temperatures of 100° C. or higher.

[0008]

[Means for Solving the Problems] The reason why conventional surface-treated steel sheets have poor adhesion is not clear, but the present inventors have discovered that H2O in the chromate film dehydrates during heat bonding and generates gas at the same time. It is estimated that this causes oxidation and corrosion of the underlying plating, resulting in a decrease in adhesive strength and peeling. Therefore, as a result of intensive studies focusing on the activity of the base plating and the drying conditions of the chromate film, the present invention was arrived at.

That is, the present invention contains a total of 0.05 to 5 g/l of Ni2+ and/or Co2+ on the surface of a steel sheet or a galvanized steel sheet, and contains Tota as an impurity.
l In an acidic plating bath with a pH of 1 to 6 in which Fe is limited to 2 g/l or less and Pb is limited to 2 mg/l or less, the current density is 30 to
Electrolytic zinc alloy plating is applied at 200A/dm2, and then immersed in a reactive chromate solution to achieve a Cr conversion of 0.5~
To provide a method for producing a surface-treated steel sheet with excellent adhesiveness, which comprises forming a chromate film of 120 mg/m2 and then drying at an ambient temperature of 120° C. or higher and a final plate temperature in the range of 100 to 300° C. It is something.

The present invention also provides an organic resin film of a water-soluble, water-dispersible, or organic solvent-based organic polymer compound on the surface-treated steel sheet obtained by the above method, with a dry weight of 0.2 to 2. The present invention provides a method for manufacturing a surface-treated steel sheet with excellent adhesion, characterized by adhesion of 0 g/m 2 .

The present invention will be explained in more detail below.

According to the present invention, a surface-treated steel sheet with excellent paint adhesion is produced by first applying zinc alloy plating on a steel sheet or a zinc alloy-plated steel sheet, and then applying chromate treatment. Furthermore, an organic resin film is formed on the chromate-treated zinc-plated steel sheet thus obtained. Each process and the reason for its limitation will be described below.

(1) Electrolytic zinc alloy plating process In the electrolytic zinc alloy plating process of the present invention, a zinc alloy plated surface that is resistant to oxidation is created by controlling the amount of trace components in the zinc alloy plating bath. The steel plate to be treated is a steel plate or a galvanized steel plate. When using the latter method, either use a steel sheet that has been previously zinc-plated on a separate line, or use an electroplating line with multiple cells to first apply zinc-based plating to the first few cells, and then apply the above alloy plating to at least the last cell. It may be applied.

Ni2+ and/or Co in the plating bath
If the total amount of 2+ is less than 0.05 g/l, the plating surface will be active and extremely susceptible to oxidation, and if it exceeds 5 g/l, it will turn black and spoil the zinc plating appearance, so it is limited to 0.05 to 5 g/l. .

[0015] Total Fe means Fe2+, Fe3
It is the sum of + ions. In a plating bath, Fe2+ is easily oxidized to Fe3+, and it is extremely difficult to control each of Fe2+ and Fe3+, so it is practical to manage total Fe. In addition, Fe2+ and Fe3+ have a larger influence on Fe3+, but Fe2+ also has an influence, so there is no particular problem even if the total Fe is used for management. Total Fe is 2g/l
If this value is exceeded, the zinc surface becomes more susceptible to oxidation.

[0016] There is no particular lower limit to the lower limit, but iron is inevitably included in the plating bath due to the melting of the steel plate, and it is actually extremely difficult to reduce it to zero. For removing iron ions, various methods such as chelate resins can be used.

[0017] When Pb exceeds 2 mg/l, it becomes susceptible to oxidation. This has a large effect even if the potential difference between Zn and Pb is small. Although there is no particular limit on the lower limit, Pb exists as an impurity in Zn, and it is actually extremely difficult to set it to zero. For Pb removal, Ba
A common method is to add CO3 into the bath.

The basic zinc alloy plating bath may be any bath such as a sulfuric acid bath or a chloride bath, as long as it has a pH of 1 to 6, a current density of 30 to 200 A/dm2, and a clean appearance electrolytic zinc alloy plating.

As for the amount of zinc plating, the corrosion resistance will improve in proportion to the larger the area weight, but if we take into account the increase in cost due to the increase in area weight, it will be 5 to 60 g/m2.
is appropriate. Furthermore, it is of course possible to plate the entire plating layer in a bath with controlled trace components as described above, but only the outermost layer of the plating layer can be plated at 0.5g/plating.
If plating is performed over m2, the desired quality can be obtained.

[0020] As a plating aid, KCl, NH4 Cl
It is better to add appropriate amounts of

(2) Chromate treatment In the present invention, the reactive chromate treatment is carried out by a conventional method. Chromate treatment is performed in an aqueous solution containing chromic acid anhydride, chromate, dichromate, etc. as the main ingredients, and sulfate ions, phosphate ions, nitrate ions, chloride ions, fluoride ions, or further fluorine compounds or silicate colloids. A chromium hydrated oxide is formed on the Zn alloy plating by dipping or spraying, washing with water or hot water, and drying at high temperature.

[0022] The amount of chromate film deposited is 0.
Limited to 5-120 mg/m2. The reason is 0.
This is because if it is less than 5 mg/m2, the secondary adhesion after a wet test will be poor, and if it exceeds 120 mg/m2, the amount of Cr6+ contained in the film will increase, causing deterioration of the resin when bonding or applying organic resin. .

If cleaning after the chromate treatment is necessary, washing with water may be sufficient, but washing with hot water is more effective for sufficient cleaning.

The reason why the high temperature drying conditions for chromate was limited to an ambient temperature of 120° C. or higher is as follows. If it is less than 120°C, it will be difficult to reach the dry plate temperature, resulting in poor productivity. The drying plate temperature should be in the range of 100 to 300°C. If the drying plate temperature is less than 100°C, the H2O remaining in the chromate film will corrode the plating layer or generate bubbles during resin adhesion and coating, so it will not adhere well. It causes sexual defects. When the temperature exceeds 300° C., alloying of the plating begins, and the plating becomes brittle and adhesiveness decreases.

(3) Organic resin treatment Furthermore, a water-soluble, water-dispersible, or solvent-based organic resin is applied onto the chromate film. Examples of the resin in this case include high molecular compounds such as alkyd resins, aminoalkyd resins, acrylic resins, epoxy ester resins, urethane resins, and acid-modified polyester resins. A sol of silicon, titanium, aluminum, etc. may be added to this polymer compound for the purpose of improving corrosion resistance.

[0026] The amount of resin deposited is limited to 0.2 to 2.0 g/m2. The reason for this is that if the resin content is less than 0.2 g/m2, the corrosion resistance after adhesion is poor. Also, 2.0g/m2
This is because if it exceeds this, it becomes difficult to vent gas during bonding. Note that the method for applying these may be any commonly used method.

[0027]

EXAMPLES The present invention will be specifically explained below based on examples.

(Example 1) Electrolytic zinc alloy plating and reactive chromate treatment were carried out under the conditions shown in Table 1, and a resin film was formed on some of them, and an adhesion test was conducted on them by the following method. evaluated. Note that the same procedure was conducted for a steel plate on which no resin film was formed.

(Test Method 1) A polyester adhesive was used to adhere a vinyl chloride sheet to the surface-treated steel sheet obtained as shown in Table 1 to obtain a test piece. A cutter was used to cut a 2 mm grid pattern down to the base steel plate, and cellophane tape was peeled off, and the following 4-level evaluation was performed based on the degree of peeling. ■ Forced removal of cellophane tape ■ After 120 hours of humidity (60°C, 95% or higher humidity) 3
Peel test within 0 minutes

(Test Method 2) An epoxy resin sheet for printed circuit boards (100 μm) was heat-bonded to the surface-treated steel sheet obtained as shown in Table 1 at 180° C. for 20 minutes to obtain a test piece. A cutter was used to cut a 2 mm grid pattern down to the base steel plate, and cellophane tape was peeled off, and the following 4-level evaluation was performed based on the degree of peeling. ■ After being left in a vapor pressure of 3 atm at 134°C for 24 hours,
Peel test within minutes■ After 120 hours of humidity (temperature of 60℃ or higher than 90%)2
Peeling test after 1 minute immersion in a 60°C solder bath ◎ - No peeling at all. ○-Small peeling. △- Severe peeling. × - Already peeled off before making the cut.

[Table 1]

[Table 2]

[Table 3]

[0031]

Effects of the Invention: According to the method of the present invention, trace components in the zinc alloy plating solution are controlled, and after reactive chromate treatment, high temperature drying is performed under selected conditions, resulting in surface treatment with excellent adhesion. A steel plate is obtained.

Claims (2)

[Claims] Claim 1: A total of 0.05 to 0.05% of Ni2+ and/or Co2+ is added to the surface of the steel plate or zinc-based plated steel plate.
Contains 5 g/l and 2 Total Fe as impurities.
g/l or less, pH 1 ~ with Pb limited to 2 mg/l or less
Current density 30-200A/dm in acidic plating bath No. 6
2, electrolytic zinc alloy plating is applied, and then immersed in a reactive chromate solution to give a concentration of 0.5 to 120 mg/m in terms of Cr.
After forming the chromate film in step 2, the ambient temperature was 120°C.
A method for producing a surface-treated steel sheet with excellent adhesiveness, characterized by drying at a temperature of 100 to 300°C at a temperature of 100 to 300°C. 2. A water-soluble, water-dispersible, or organic solvent-based organic polymer compound is applied as an organic resin film on the surface-treated steel sheet obtained by the method according to claim 1 in a dry weight of 0.2 to 2. A method for manufacturing a surface-treated steel sheet with excellent adhesion, characterized by adhesion of .0 g/m2.