JPH0285394A - Method for electroplating stainless steel sheet - Google Patents

Abstract

PURPOSE:To form a metal plating layer having superior adhesion on the surface of a stainless steel sheet by activating the surface of the steel sheet by cathodic electrolytic pickling as pretreatment, immersing the steel sheet in a plating soln. without washing and carrying out electroplating with a metal. CONSTITUTION:In the case of a stainless steel sheet contg. easily oxidizable elements such as Al, Cr, Si and Mn, the surface is inactivated by the formation of an oxide coat and the solderability is deteriorated. In order to eliminate this defect, the surface of the steel sheet is activated by electroplating with Ni. When electroplating is carried out, the steel sheet is degreased, washed and subjected to cathodic electrolytic pickling at >=10A/dm<2> current density in a sulfuric acid soln. having 10-20% concn. to dissolve and remove the metal oxide coat. The cleaned steel sheet is immersed in an acidic Ni plating soln. without removing the sulfuric acid soln. sticking to the steel sheet by washing and electroplating is carried out. The surface of the steel sheet is activated by forming an Ni plating film having superior adhesion.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing an electroplated steel sheet with excellent corrosion resistance and heat resistance, and in particular, a method for manufacturing an electroplated steel sheet using a stainless steel sheet as a base steel sheet. It is related to.

(Prior art) When electroplating a stainless steel plate, strike plating is performed in a concentrated hydrochloric acid bath containing a predetermined concentration of metal chloride, and then a predetermined amount of electroplating film is formed in a normal plating bath. A method of producing a stainless steel plate having a plating layer with good adhesion is well known.

(Problem to be solved by the invention) Aj! A stainless steel plate containing a large amount of easily oxidizable elements such as Cr, Si, Mn, etc. has an oxidized film of the easily oxidizable elements on its surface. Therefore, although such stainless steel sheets are resistant to red rust, they have problems such as inert surfaces, poor solderability, high contact resistance, and difficulty in hot-dip plating, making it difficult to take full advantage of their excellent properties. do not have.

As one means for solving such problems, it is known to electroplate a metal such as Ni on the surface of a stainless steel plate. However, even when electroplating a stainless steel W4 plate, the oxide film on its surface has a negative effect on electroplating properties.

In addition, it is difficult to electroplate high-grade stainless steel sheets containing a large amount of Cr%A1, etc., and when electroplating is performed using PROHYS, which is used to plate ordinary mild steel sheets, problems such as poor plating adhesion are likely to occur. It is also a well-known place.

In order to solve such problems, a special pretreatment called strike plating is required, which was mentioned earlier. is strong.

ti) 'N, since the flow efficiency is extremely low, if a soluble anode is used, the elution of Ni will be large and the composition of the treatment bath will change immediately. Additionally, when an insoluble anode is used, toxic and corrosive chlorine gas is generated from the anode.

Due to this problem, it is difficult to perform strike plating using ordinary continuous electroplating equipment. Furthermore, applying such special pretreatment is disadvantageous in terms of: 1st stroke.

The purpose of the present invention is to provide a means for electroplating stainless steel sheets with good adhesion by applying the best pretreatment that can be performed with ordinary electroplating equipment without using strike plating. Ta.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention performs cathodic electrolytic cleaning as a pretreatment of the stainless steel sheet to activate the surface of the steel sheet, and then omit water washing to clean the stainless steel sheet. It is characterized by the fact that electroplating is performed by immersing the steel plate in a plating bath in a post-process plating tank while the surface of the plate remains wet with the pickling solution.

The present invention will be explained in detail below.

The inventors researched a method of electroplating stainless steel sheets with good adhesion using a one-touch pretreatment that does not involve strike plating and can be carried out using ordinary electroplating equipment. When plating in equipment, even if the surface is activated by electrolytic pickling, it is immersed in the plating bath, and before electrolysis, the 1v coating is regenerated on the surface of the steel sheet, and a plating layer is formed on top of this, resulting in poor adhesion. It was found that good plating could not be obtained.

Therefore, we conducted further research and after activating the surface of the steel plate by cathodic electrolytic cleaning, we omitted water washing and immersed the steel plate in a plating bath while the surface of the stainless steel plate remained wet with the pickling solution. The above-mentioned problem was successfully solved by electroplating.

This will be explained in more detail below.

First, as the stainless steel plate, one that has been rolled, annealed, and pickled in a conventional manner or one that is as rolled is used. After degreasing and washing with water, the steel plate is cathodic electrolytically pickled in a sulfuric acid bath. The treatment conditions at this time need to be stronger than those for ordinary pickling of mild steel. The sulfuric acid concentration is 1
0% or more, preferably about 15 to 20% or more. Although it is better to have a high bath temperature, if it is too high, there is a risk that the steel plate will dry out before the subsequent electrolytic process. Therefore, in consideration of the plating equipment, a bath temperature of 40 to 70°C is desirable.

According to the findings of the present inventors, long-time electrolysis at high current density is desirable as the electrolytic conditions, and as described in the examples, in order to ensure plating adhesion, at least 10 A/dt.
A conductive layer of a”×1.5 sec is required.

The polarity of electrolysis is cathode 4. - Good plating adhesion cannot be obtained by anodic electrolysis, anodic/cathodic electrolysis, etc.

The electrolytically pickled steel sheet is immersed in a pickling plating bath without being washed with water after the adhering pickling liquid is removed by roll squeezing, and then electroplated immediately. At that time, it is important to keep the distance between electrolytic pickling and electroplating as short as possible so as not to give time for the oxide film on the surface of the steel sheet to regenerate.

From this point of view, it is necessary to adjust the arrangement of the electrolytic bath, line speed, and bath surface height.

In addition, when electroplating a rust-free steel plate according to the present invention,
A small amount of sulfuric acid was brought into the plating bath. Depending on the type of plating solution, this small amount of sulfuric acid may not be acceptable. In such cases, the steel plate should not be rinsed with water after electrolytic pickling, but plated for a short time in a sulfuric acid plating bath, etc. to completely coat the surface, then rinsed with water, and then coated with water as necessary using a specified plating bath. 1 piece of electroplating. According to the knowledge of the present inventors, the electrolytic conditions at this time are at least lOA/
d+w”X O, 2 seconds are required.

That is, in this method, short-time plating without water washing after electrolytic pickling can be used as a substitute for strike plating.

The various electrolytic conditions listed above are only within the knowledge of the inventors, and may need to be changed depending on the surface condition of the rust-free steel sheet. This is to be expected, given that it is subject to change.

Hereinafter, the present invention will be specifically explained with reference to Examples.

(Example 1) As a plating original plate, a cold-rolled 18-8 stainless steel plate (0.6 mm') was used, and after degreasing and washing with water,
After pretreatment was performed under the conditions shown in 1, Ni plating was performed in a Watts bath. The results are shown in Table 1, and when Ni plating was performed using this method and when pretreatment for strike plating was performed, contact surface Ni plating: Watt bath, 50°C.

Cathodic electrolytic pickling: 10% sulfuric acid, 60°C.

Strike Ni plating: 10% hydrochloric acid, 50 g/l nickel chloride Surface properties were good, but adhesion was poor when plated with normal electrolytic pickling pretreatment.

(Example 2) As a plating original plate, a cold-rolled llCr stainless steel plate (0.8 mmt) was used, which was degreased and washed with water.
After pretreatment under the conditions shown in 2, Pb was removed in a gay fluoride bath.
-3n alloy plating was performed. The results are shown in Table 2. Adhesion was good when Pb-3n plating was performed after Ni plating pretreatment using this method, and when strike Ni plating pretreatment was performed, but When plating was performed with electrolytic pickling pretreatment, the adhesion was poor.

(Effects of the Invention) According to the present invention, electroplating with excellent adhesion can be achieved by applying a large amount of highly oxidizing elements in continuous electroplating equipment that processes ordinary mild steel sheets, by simply performing in-shell pretreatment. ■It can be applied to stainless steel sheets containing
This has a significant effect on equipment maintenance, work environment, etc.

Claims (1)

[Claims] A method of electroplating stainless steel sheets containing easily oxidizable elements, in which the steel sheet is electroplated by cathodic electrolytic pickling and then immersed in a plating bath while wet with pickling solution without rinsing with water. A method for electroplating stainless steel sheets, characterized by: