JPH0394073A - Production of electrically conductive coated, black plated steel sheet - Google Patents

Abstract

PURPOSE:To improve electrical conductivity and wettability with solder by chemically treating a Zn-Ni alloy plated steel sheet with an aq. soln. contg. phosphoric acid, etc., and by forming a discontinuous resin coating film on the resulting black plated steel sheet by dispersion coating with org. resin particles. CONSTITUTION:An aq. soln. of pH<=3 contg. 1-20% phosphoric acid, 0.5-10% hydrogen peroxide and 1-4C prim. alcohol is prepd. A Zn-Ni alloy plated steel sheet contg. >=5% Ni in the uppermost layer is chemically treated with the aq. soln. and further chemically treated with an aq. soln. of pH<=1.5 contg. 1-40g/l Cr. A water-dispersible org. resin is atomized with an electrostatic atomizer and a discontinuous coating film is formed on the steel sheet by 0.1-2g/m<2> by dispersion coating with the resulting resin particles. A coated surface on which innumerable exposed parts are locally present is obtd. and electrical conductivity and wettability with solder are ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Use Separation) The present invention relates to a method for producing a painted black-plated steel sheet suitable for use in electrical resistance welding and soldering during processing.

(Junior technology) Black is often used for office supplies, the outer panels of electrical test products, automobile interior parts, etc., as it increases the thickness by -15 m. However, zinc or zinc alloy plated steel sheets have a silvery white or grayish white appearance, and therefore lack a sense of weight and are unsuitable for use in such applications if they are left bare.

Therefore, a method of treating galvanized steel sheets with a chromate treatment solution containing silver ions (Japanese Patent Application Laid-Open No. 1983-455445) was developed to blacken the plating layer, and a method was developed in which a galvanized steel sheet was treated with a chromate treatment solution containing silver ions in an aqueous solution of a metal salt of sulfuric acid and an ammonium salt. A method of anodizing zinc alloy-plated steel sheets such as old Zn alloys (Special.
No. 151491) etc. have been proposed.

(Problems to be Solved by the Invention) However, the former method uses expensive silver, resulting in high manufacturing costs, and the latter method also requires anodization, which requires electric angle treatment. It was expensive and could only produce a greenish black color.

Therefore, the present inventors developed a method for producing an inexpensive black-plated steel sheet using Zn-Ni containing 5% or more Ni in the top layer.
Alloy plated steel plate with 1-20% phosphoric acid and 0.5-1%
Treated with an acidic aqueous solution of +1}13.0 or less in which 0% hydrogen peroxide was dissolved, or an acidic aqueous solution in which 0.1 to 10% of an organic metal ion elution inhibitor was added to this aqueous solution,
A method of forming a blackened film on the surface of a plating layer was previously proposed (Japanese Patent Application No. 83711/1983). The blackening principle of this method is that Ni and Zn in the plating layer dissolved in phosphoric acid are oxidized with hydrogen peroxide to form a film consisting of zinc oxide and zinc phosphate on the surface of the plating layer. This method produces a black leather by fixing metal and Ni oxide on the surface of the surface, and the strong oxidizing power of hydrogen peroxide makes it possible to blacken the surface without anodizing.

However, this black coating does not have good corrosion resistance, so white chains easily occur and the black color is impaired.Also, the strength is weak, so scratches occur during processing, exposing the white plating layer, and the appearance will decrease.

-3- As a countermeasure to this problem, a method has been proposed in which an organic resin film is formed on the black film (Japanese Patent Laid-Open No. 61-227181). However, when using an organic resin film, if the resin film is made thicker, the conductivity is lost, making it impossible to use it for applications such as connecting a ground conductor by electrical resistance welding or soldering.

On the other hand, if the resin film is made thin enough to allow electric resistance welding or soldering, the corrosion resistance will decrease and the resin film itself will exhibit an interference color, changing its appearance.

Further, it is difficult to form a film thin enough to be easily removed by electric resistance welding or soldering using industrial coating methods such as roll coating and curtain coating.

The present invention provides a method for producing e7 black-plated steel sheet that can solve these problems.

(Means for Solving the Problems) The present inventors have investigated various ways to obtain painted black-plated steel sheets that can be welded by electric resistance welding or soldered. He discovered that it would be better to make it dispersed, and perfected the invention.

-4 That is, in the present invention, a Zn-Ni alloy plated steel sheet containing 5% or more of Ni in the top layer is coated with 1 to 20% of phosphoric acid and 0.5% of phosphoric acid.
After chemical treatment with an aqueous solution of pH 3 or less in which 5 to 10% hydrogen peroxide and 0.1 to 10% primary alcohol having 1 to 4 carbon atoms are dissolved, p containing 1 to 409/e of C'
ut. Chemically treated with an aqueous solution of s or less, then water-soluble or water-dispersible 8! The resin emulsion is atomized by an electrostatic atomizer, coated so that the emulsion particles are dispersed on the surface, and dried to obtain a dry resin film amount of 0.1 to 2.0 g/II1.
The resin film was manufactured by the method described in No. 2.

Zn-Ni alloy plated steel sheet containing 5% or more of
20% phosphoric acid, 0.5-10% hydrogen peroxide and 0
．． When chemically treated with an aqueous solution of pH 3.0 or less in which 1 to 10% of primary alcohol having 1 to 4 carbon atoms is dissolved, metal Ni and Ni are formed in the film consisting of zinc oxide and zinc phosphate, as described above. A black film with fixed Ni oxide is formed on the surface of the plating layer.

Here, the phosphoric acid concentration of the aqueous solution was set to 1 to 20% because
If it is less than 1%, precipitation of phosphate is insufficient, and 20%
This is because, if it exceeds .tau., the plating will be excessively molten and the corrosion resistance of the plated steel sheet will deteriorate.

In addition, the hydrogen peroxide concentration was set to 0.5 to 10%.
．． If it is less than 5%, the oxidizing power of the aqueous solution will be insufficient and the film will not be sufficiently black, and if it exceeds 10%, the aqueous solution will be difficult to handle.

Furthermore, the reason why the IJ of the aqueous solution is set to 3 or less is that if it is higher than 3, the etching effect on the plating layer and the precipitation of phosphate will be slowed down, resulting in a decrease in productivity.

In addition, the primary alcohol was added to suppress the reaction between iron ions eluted from the plating layer of the steel sheet and hydrogen peroxide. Inhibits reaction with hydrogen peroxide. The reason why alcohol is used as the primary alcohol is that this reaction-inhibiting effect is greater than that of secondary alcohols. If this primary alcohol is less than 0.1%, no anti-1b inhibitory effect will be observed, and if it exceeds 10%, it will be excessively adsorbed on the surface of the plating ζ4 and will hinder the blackening reaction. Moreover, when the number of carbon atoms exceeds 4, the primary alcohol becomes difficult to dissolve in an aqueous solution and is also easily adsorbed on the surface of the plating layer, thereby hindering the blackening reaction.

Table 1 shows 10% phosphoric acid, 5% hydrogen peroxide, 20% iron
0+]1) This shows the hydrogen peroxide residual rate after adding various alcohols to the aqueous solution of II1 and leaving it in the open for 1011 hours.It can be seen that the addition of the primary alcohol is effective in suppressing the reaction.

Table 1 = 7 1,1 containing 1 to 409/c of Cr after black treatment
Treatment with an aqueous solution of 11.5 or less removes the coarse zinc phosphate film on the surface layer, and at the same time forms a chromate film to reduce the black color that leads to white rust. This is for defense 112. If the Cr content is less than 197C, a sufficient chromium 1 film cannot be formed, and 4097
If it exceeds e, it becomes difficult to handle the aqueous solution. Also,
1) If 1] exceeds 1.5, it becomes difficult to dissolve the zinc phosphate crystals.

The black plated steel sheet produced as described above is atomized with 1 liter of water-soluble or water-dispersible organic resin Emulun using an electrostatic atomizer, and when the coating is applied so that the emulsion particles are dispersed on the surface and dried, a T-continuous resin film is formed. is formed. This lower continuous resin film has countless uncoated parts where the plating layer is locally exposed, so these parts have electrical conductivity and wettability to molten metal, making it suitable for electric resistance welding and soldering. can be attached.

The amount of resin in this tree discontinuous film is 0. i
- Make it 2.0g/to2. 0. 1
If it is less than g/m28, there will be many unpainted parts and the corrosion resistance and fingerprint resistance will be poor.2. If it exceeds 0 g/m2, the film will not be continuous, resulting in resistance welding. 1'-Takashi is in trouble.

For the 8% resin film, it is preferable to apply a fi-resin emulsion containing a fluororesin in order to improve the lubricity during processing into a member.

The fluororesin content used is 0.5 to 30% of the coating resin in the dry coating state. If the 7-base resin content is less than 0.5%, the lubricity improvement effect of the resin film will be small, and if it exceeds 30%, the wettability will be low, and two-coat inspection using silk printing etc. In this case, the adhesion with the second coat of paint decreases.

As the seven resins, polytetrafluoroethylene (P
'FFE), polychlorotri7fluoroethylene (PCT
FE), Te1ra7fluoroethylene-hexa7fluoropropylene copolymer (FEP), Poly7vinylidene fluoride (P
VdF), Poly7vinyl(P■F), Ethylene-7
It may contain a fluoroethylene copolymer, te1-la-7-fluoroethylene-per-7-fluorovinylether (PFA), or the like.

Chromic acid or chromate is added to resin Jl to improve the corrosion resistance of the leather crotch. 12, the bar contains an acrylic copolymer made by copolymerizing one or more of methyl methacrylate, ethyl acrylate, butyl acrylate, and ethylhexyl acrylate, and the copolymer and chromic acid or It is preferable to use an emulsion in which the amount of chromate blended is such that copolymer/total chromium = 2 to 25 in the dry film state. If a copolymer like the one mentioned above is mixed into the resin film, the carboxyl of the copolymer and chromic acid (chromate) will react with each other during heating and drying of the emulsion, resulting in It cross-links and becomes a chromate film of chromate.This chromate film replaces the solder during soldering and promotes the wettability of the solder.

The black color of the plating layer due to chemical treatment may change due to slight differences in the processing conditions or the composition of the plating layer, so in such cases, add black pigment to the resin film. , it is better to make the color tone uniform. Additionally, adding a black pigment to the {M oil film can prevent interference colors that occur when the resin film is thin. As a black pigment,
Carbon black is preferred, and the average particle size is 0.
Fine particles of 1μ16 or less are suitable. Also, the amount added is ノ (m mediator tree 11?? 1 1') O ITj groin ~ lr + tari (). 1 to 10 parts by weight. If it is less than 0.1 part by weight, the color tone will not be uniform enough, and if it exceeds 10 parts by weight, the corrosion resistance and adhesion of the film will decrease.

(Example) A blackened film was formed on a Zn-old alloy plated steel sheet with a Ni content of 12% in an aqueous solution containing 10% phosphoric acid, 5% hydrogen peroxide, and 3% propanol, and then immersed in an aqueous solution containing chromium. processed and dried. Next, a water-soluble or water-friendly organic resin emulsion was atomized onto the black-treated plated steel plate using an electrostatic atomizer, and the coating was applied and dried.

Table 2 shows the resin film coverage, linearity measured by a color difference meter, color unevenness, coefficient of dynamic friction, fingerprint resistance, spot weldability, solder wetting and spreading properties, and corrosion resistance of this painted and plated steel sheet. These investigations were conducted as follows.

(1) Resin film coverage ratio SEM4 true of XiA surface (X 2 (1 0 (1)
wo41i1 Shadow 1-: The resin film portion was measured using an image analyzer.

(2> Using a color unevenness color difference meter) The maximum and minimum L values were investigated and evaluated on the next base wall.6 ◎ The maximum and minimum L values are less than ±0.5 of the average value. The maximum value and minimum value of L value are ±1 or less of the average value Δ The maximum value and minimum value of L value are ±2 or less of the average value 3) Anti-fingerprint adhesion Artificial sweat was applied to an artificial finger, and it was pressed against a test piece for a certain period of time at a pressure of 1 kg/m2, and the state of fingerprint adhesion to the test piece was evaluated according to the following criteria.

◎ No fingerprints attached ○ Very slight fingerprints attached 12 △ More than 50% of the fingerprints are young × Entire fingerprints attached (4) Spot weldability 4. 5 Pressure force 2 with +n+nφ-CF electrode 5
Welding was performed at 0 Kgf and 12 cycles of current flow, and the tensile strength of the welded portion was measured.

◎ Tensile strength 351 Kgf or more ○ Tensile strength 251 to 350 Kgf△ Tensile strength 25
Less than 0 KHf × Unable to weld (5) Solder wettability Floating the steel plate in a 300°C solder bath, dropping 0.5 g of solder (containing pine resin 2.2'U+t%) onto it, and soldering after 30 seconds. The spread area was measured.

◎ Spread area is 1. (Exceeds l cm2○ Spreading area is 0.5-1.0cm2Δ Spreading area is O
y5 c ``Less than I12 × No solder adhesion (6) Corrosion resistance ■ Flat area. ++5 Planted on Z 2371 and conducted 10 Hanasui spray tests.
The test was carried out for 0 hours, and the state of occurrence of white rust was evaluated on the following base walls.

◎ No white rust ○ Very slight white rust ∆ The area where white rust occurs is less than 10% of the whole x The area where white chains occur is more than 10% of the whole - 12 ■ Pressure force at the processing part 2 0 0 Kgf, Pulling speed 500m
After removing the drawbead sliding force under the conditions of m/+nin, Hanasui Fountain Test (JIS Z 2371) 2 4
Applying the same technique to the white button, the condition of the white button is the same as the flat area.
It was equalized.

-15 (Effect of the invention) As shown in I-I-2, the present invention has the advantage of forming a discontinuous film of iso resin in which countless thin unpainted parts of the black film are formed. Therefore, electric resistance welding and soldering can be performed even if the resin film is made thicker.

Furthermore, since the organic resin film is formed using an electrostatic atomizer, its formation is easy.

Claims (4)

[Claims] (1) A Zn-Ni alloy plated steel sheet containing 5% or more Ni in the top layer is coated with 1 to 20% phosphoric acid, 0.5 to 10% hydrogen peroxide, and 0.1 to 10% carbon number 1 to 20%. After chemical treatment with an aqueous solution of pH 3 or less in which four primary alcohols are dissolved, chemical treatment is performed with an aqueous solution of pH 1.5 or less containing 1 to 40 g/l of Cr, and then a water-soluble or water-dispersible organic resin emulsion is prepared. is atomized by an electrostatic atomizer, coated so that emulsion particles are dispersed on the surface, and dried to form a resin film with a dry resin film amount of 0.1 to 2.0 g/m^2. A method for manufacturing a black-coated steel sheet. (2) As an organic resin emulsion, it contains a fluororesin, and its content is 0.5 to 3 of the resin content in the dry film state.
The method for manufacturing a conductive painted black-plated steel sheet according to claim 1, characterized in that the coating is performed so that the conductive coating is 0%. (3) The organic resin emulsion contains an acrylic copolymer obtained by copolymerizing one or more of methyl methacrylate, ethyl acrylate, butyl acrylate, and ethylhexyl acrylate and chromic acid or chromate; The content of chromic acid or chromate in the dry film state is copolymer/total chromium = 2 to 2
5. The method for producing a conductive painted black-plated steel sheet according to claim 1, characterized in that the conductive black-plated steel sheet is coated with the same color as that of 5. (4) The electrically conductive coated black plated steel sheet according to claim 1, wherein the organic resin emulsion contains 0.1 to 10 parts by weight of a black pigment per 100 parts by weight of resin. manufacturing method.