JPS60262994A - Method for plating stainless steel bar - Google Patents

Abstract

PURPOSE:To form a desired metallic layer with superior adhesion by plating when a stainless steel bar is continuously plated at a high speed, by forming an Ni layer by stricking in an Ni striking bath having a specified low concn. before plating. CONSTITUTION:A stainless steel bar is electrolytically degreased to clean to surface, and it is stcuck in an Ni striking bath contg. 150-180g/l NiCl2, 6H2O and 70-90ml/l 12N concd. hydrochloric acid at 15-30 deg.C and 10-30A/dm<2> cathode current density for 5-30sec. The resulting Ni layer is electroplated with a noble metal such as Ay or Ag, Sn, an Sn alloy or the like according to the purpose. Even in case of a stainless steel bar having a passive film on which a film with superior adhesion is difficult to form by plating, a desired metallic film with superior adhesion can be formed by this plating method at a high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION In applications where stainless steel is used as a material for electronic components, there is a demand for electroplating of precious metals or other materials on the surface of stainless steel.

Stainless steel is a material that is difficult to plate with good adhesion because it has a strong passive skin on its surface.
In particular, there are many problems in continuously plating stainless steel strips, making industrial mass production difficult.

Many methods have been proposed for plating stainless steel. For example, as a method for gold plating stainless steel strips for electronic parts, stainless steel strips are plated in a bath containing a mixed acid of an inorganic acid and an organic acid with additives such as a surfactant and an amine corrosion inhibitor. A method has been proposed in which gold plating is performed after surface activation by chemical polishing and cathodic electrolysis.

However, when a mixture of multiple inorganic acids and organic acids and organic compounds with complex structures such as surfactants and amine corrosion inhibitors are used as a treatment bath, it is difficult to analyze and manage the mixture. Because it is difficult to maintain and control the bath composition, it is difficult to mass-produce products of stable quality on an industrial scale. However, there is a drawback that increasing the thickness of the plating film results in poor adhesion and peeling.

This is because, after the stainless steel surface is activated, the passive film is slightly regenerated in the water washing process before plating, so complete adhesion cannot be achieved.

Currently, the Wood Nickel Strike method is a technically established method for plating stainless steel with complete adhesion.

This method was developed and put into practical use in the aerospace industry in the United States, and involves dissolving the passive film on the stainless steel surface in a nickel chloride bath with strong hydrochloric acid, and simultaneously performing nickel strike plating. When using this method, plating with perfect adhesion to the stainless steel surface can be obtained.

However, although this method is effective for plating stainless steel parts, it is difficult to perform continuous high-speed plating on stainless steel strips.

Example Process Specification B of Heha Hoing Company
In AC5746, nickel chloride 240 g/13
Concentrated hydrochloric acid 85.8rrd! /l bath, anodic electrolysis was first performed for 2 minutes at a current density of 8.24 A/dm with stainless steel as the anode, and then the polarity was changed to a current density of 8.24 A/dm with stainless steel as the cathode. A nickel strike method is specified in which electrolysis is carried out for 4 minutes.

On the other hand, according to the overhaul manual of Blatt & Whitney Aircraft Company, stainless steel parts are
After being immersed in 5% by volume hydrochloric acid for 80 seconds to 1 minute at room temperature, it was struck for 5 minutes at a current density of 6.5 A/dm2 in a nickel strike bath containing 210 ml/l of nickel chloride and 111 ml/l of concentrated hydrochloric acid. It is prescribed to do so.

It has been demonstrated that these methods form a nickel strike plating layer with perfect adhesion on the stainless steel surface, and any desired plating can be applied on top of this with perfect adhesion. However, such a method is not suitable for industrially mass-producing stamped steel strip products using a continuous high-speed plating method for stainless steel strips.

That is, the Boeing method requires polarity reversal in which stainless steel is electrolyzed first as an anode and then as a cathode, and is difficult to apply to continuous plating of stainless steel strips. Also, the method of Blatt & Whitney Aircraft Company, 6
It is necessary to immerse the product in 5% by volume hydrochloric acid for 30 seconds to 1 minute, but such highly concentrated hydrochloric acid generates hydrogen chloride gas, which is environmentally unfavorable, and the electrolysis time is as long as 5 minutes. In the case of high-speed continuous plating of stainless steel strips, a long treatment tank is required, which is industrially disadvantageous.

From the above-mentioned viewpoint, the present inventor conducted extensive research with the aim of developing a nickel strike bath suitable for continuous high-speed plating. In order to completely dissolve and remove the passive film of stainless steel and perform strike plating in an extremely short time, it is believed that extremely high concentrations of both hydrochloric acid and nickel chloride are required, but research Results Contrary to expectations, it has been discovered that this objective is achieved over a specific range of bath compositions at low concentrations.

That is, nickel chloride (NiC12.6H20) 150g ~
xsogA, concentrated hydrochloric acid (12NH (J) 70ml to 90n
M! Using a nickel strike bath with a bath composition in the range of bath temperature 15° to 30°C, cathode current density 10A to 80A/a.
By carrying out a strike for 5 to 30 seconds under electrolytic conditions of m, a completely adhesive nickel strike layer is formed on the stainless steel surface, and any plating can be applied on the stainless steel surface by a known method with complete adhesion. The present invention was completed by discovering that the present invention can be applied.

``Such a high current density and short time with a nickel strike bath with such a low concentration bath composition is a completely unexpected fact that was previously unknown, and is a novel invention. υ, it is an extremely advantageous method for continuously plating stainless steel strips at high speed and industrially mass producing plated stainless steel strips.

The nickel strike of the present invention can be plated with precious metals such as gold and silver, as well as tin and tin alloy plating, and can be plated with any base metal. Adding electrical conductivity, etc.K
This makes it possible to develop many uses.

Furthermore, the nickel strike bath according to the present invention is easy to maintain and manage through analysis, and is therefore extremely advantageous in terms of product quality control.

Not suitable, suitable range is 15og/l to 180g/1
1 and preferably 160 g/l. The concentration range of concentrated hydrochloric acid is 10ml to 90rrJ/l, preferably 80ml.
J/A! It is.

If it is less than 70 ml/l, the activation of the stainless steel surface will be insufficient and the adhesion will be poor when thick plating is applied. Moreover, if it is more than 90 m1/1, fume containing electrolytic raw hydrogen chloride gas will be generated, which is not preferable. Bath temperature is 15° ~
Although it can be used at room temperature at 80°C, the adhesion of plating is adversely affected outside this temperature range. Current density is IOA~80
If the A/dm2 is less than 10A/dm2, the required electrolysis time will be longer and it is unsuitable for high-speed continuous plating, and 30A/d.
If the rr is 12 or more, the adhesion will decrease, which is not preferable.

The electrolysis time is 5 to 80 seconds, and if it is less than 5 seconds, the adhesion will be poor, and if it is more than 80 seconds, the line speed will be slow in continuous plating, which is not preferable.

Next, the present invention will be explained by giving examples.

Example 1 After performing a strike for 5 seconds at a polar current density of 20 A/drr 12, a hard gold plating bath stamp book N-7 manufactured by Engelhard Co., Ltd.
7 acidic bright plating bath) at a bath temperature of 40℃ and a current density of 6A/d.
Plating was carried out for 60 seconds at m2 to obtain a gold-plated stainless steel strip with a film thickness of 1.5 μm.

This gold plating exhibited perfect adhesion, with no peeling observed even after the material was broken by repeated 180° bending. This gold-plated stainless steel strip could be used as an electrical contact in a connector.

Example 2 A SUS 410 stainless steel strip with a thickness of 0.15 mm and a width of 40 mm was electrolytically degreased by a known method, and then heated to a bath temperature of 80 ml in a nickel strike bath containing nickel chloride xsog// and concentrated hydrochloric acid 90 ml/l. °C, cathode current density 3oA
Electrolysis was performed for 10 seconds at a current density of 2OA/drn at /dn12 to demonstrate stainless wire bonding properties.

Example 3 After electrolytically degreasing a 5US410 stainless steel strip with a thickness of 0.8 mm and a width of 4 Q cm, 150 g/A' of nickel chloride and 70 m of concentrated hydrochloric acid were applied! A nickel strike was performed by electrolyzing for 15 seconds at a bath temperature of 2oC and a cathode current density of 10A/drn2 in a nickel strike bath containing /l, followed by white tin-copper alloy plating in a coating bath.Stannic acid + )l]um Na25n03'8H20100g
Sodium cyanide NaCN Bog/l Copper cyanide CnCN 12g/l Sodium hydroxide NaOHLOg/l Ansodium dione Na CNS 35 g/l Bath temperature 60℃ PH
A white tin-copper alloy plating containing about 50% tin was obtained on a stainless steel strip for 60 seconds at 18,510 people/dm2. This white tin-copper alloy plating exhibited perfect adhesion and excellent solderability. Ta.

As is clear from the above examples, the present invention allows stainless steel strips to be plated with any type of plating with excellent adhesion using a continuous plating method, thereby expanding the industrial use of stainless steel strips over a wide range of areas. This is an industrially significant invention.

Claims (1)

[Claims] In the process of continuous plating on stainless steel strips, 150g to 180g/l of nickel chloride and 70ml of concentrated hydrochloric acid are used.
It is characterized by performing arbitrary electroplating after performing a strike for 5 to 80 seconds in a nickel strike bath containing 0 m1/l under electrolytic conditions of a bath temperature of 15°C to 80°C and a cathode current density of 10A to 30A/dm. A method of plating stainless steel strips.