JPS6217196A - Method for plating stainless steel - Google Patents

Abstract

PURPOSE:To improve the adhesion and appearance of plating by electrolyzing a cleaned stainless steel stock as the cathode in an aqueous soln. contg. nickel sulfate and sulfuric acid and by carrying out desired plating. CONSTITUTION:A stainless steel stock is cleaned and electrolyzed as the cathode in an aqueous soln. contg. nickel sulfate and sulfuric acid. The soln. contains 100-300g/l NiSO4.6H2O and 20-150ml/l H2SO4(98vol%). An insoluble electrode is used as the anode. The preferred temp. of the electrolytic bath is room temp.-about 40 deg.C, the preferred cathode current density is bout 4-20A/dm<2>, and the preferred electrolysis time is about 20sec-3min. Desired plating is then carried out on the stainless steel stock. Plating having satisfactory adhesion and fine appearance is formed on the surface of the stock.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for plating stainless steel materials, and in particular to a method for plating stainless steel that has made plating with good adhesion possible due to the failure of the activation treatment method. Depends on the method.

<Prior Art> Generally, in order to plate a stainless steel material with good adhesion, an activation treatment is required to remove a passivation film that is firmly formed on the surface of the material.

For this reason, conventional methods include surface etching by chemical polishing or electrolytic polishing using an acid bath, and a combination of these with cathodic electrolytic activation, or nickel track plating using a nickel chloride/hydrochloric acid bath (Wood bath). There is.

However, these activation treatment methods have the following drawbacks. First, the former etching method requires the use of highly concentrated and high temperature acids to completely remove the oxide film.
Furthermore, since the processing time needs to be long, roughness of the substrate is likely to occur due to over-etching. Furthermore, once the oxide film has been removed, the stainless steel surface tends to become passivated again, and in the case of plating that requires a high degree of adhesion, the activation effect may be insufficient.

Also, the latter Wood nickel strike method involves cathode electrolysis.
Taking advantage of the low rate, the hydrogen gas generated on the cathode surface reduces and activates the oxide film, and at the same time deposits a thin nickel base plating with good adhesion, making the activated material surface re-passivated. However, the mist containing highly corrosive hydrochloric acid is likely to scatter, leading to deterioration of the working environment and severe corrosion of peripheral devices and equipment. In addition, in order to prevent the generation of chlorine gas due to anodic oxidation of chlorine ions in the bath, it is necessary to use a soluble nickel anode, but the cathode current efficiency is significantly lower than the anode current efficiency.
There is a problem in that the nickel concentration in the bath tends to increase and the bath concentration must be corrected or updated frequently.

<Problems to be Solved by the Invention> The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art and provide a new activation treatment method for stainless steel materials, which eliminates the scattering of hydrochloric acid mist and improves adhesion. The purpose of the present invention is to provide a method of plating stainless steel that can obtain good plating.

Means for Solving the Problems> The present invention aims to achieve the above objects by subjecting pre-cleaned stainless steel material to cathodic electrolysis treatment in an aqueous solution containing nickel sulfate and sulfuric acid, and then subjecting it to desired plating. This is a method of plating stainless steel.

Here, in the cathodic electrolytic treatment, it is preferable that the anode used be an insoluble anode.

Further, the aqueous solution containing nickel sulfate and sulfuric acid may be NiS
O4・6H2O, 100-300g/l, )+2S
04.98voJZ! 20-150 ml
/ It is preferable that the solution is an aqueous solution containing II.

The present invention will be explained in more detail below.

The stainless steel used in the method of the present invention is not particularly limited, and any type of stainless steel such as 5tJS304 may be used, and the stainless steel may be in any shape such as a plate, a bar, or a wire.

Prior to cathodic electrolytic treatment, the stainless steel material is cleaned by conventional cleaning treatments such as anodic electrolytic degreasing, pickling, water washing, and volatile organic solvent immersion.

The composition of the cathode electrolysis solution used in the method of the present invention is nickel sulfate (as hexahydrate) 100 to 300 g/Il, sulfuric acid (
98voj2! k) 20-150 nll/
fl is preferable; if the nickel sulfate concentration is too high or the sulfuric acid concentration is too low, the throwing power will be poor and the adhesion will locally decrease depending on the shape of the material. In addition, in the opposite case, the throwing power will be good, but if the
Processing time must be increased to obtain r properties, resulting in lower workability.

In addition, processing conditions vary depending on the type of material, etc.
Usually, the bath temperature is room temperature to about 40℃, and the cathode current density is 4 to 20℃.
A/d time is preferably in the range of 20 seconds to 3 minutes. Before regular plating, plating is performed for a short period of time at a relatively high current density to create a uniform, very thin nickel-plated surface with good adhesion, which reduces the amount of plating that is slow to coat. This is to prevent the surface from being eroded by liquid and to clean the surface by generating hydrogen.

Although nickel may be used as the anode for cathodic electrolytic treatment, if an insoluble anode such as platinum, platinum-plated titanium, or carbon electrode is used, changes in the concentration of the treatment solution can be significantly reduced, and the bath concentration can be corrected. Moreover, there is almost no need to replace the bath solution, and the management of the cathode electrolysis treatment solution is inexpensive and easy even when used repeatedly over a long period of time. When using the cathode electrolysis treatment solution, which is an aqueous solution containing nickel sulfate and sulfuric acid, unlike the conventionally used Wood's nickel strike bath, it contains virtually no chlorine ions, so harmful chlorine is not generated even when an insoluble anode is used. There is no.

After cathodic electrolytic treatment, a wide variety of conventional plating methods such as bright nickel plating, silver plating, gold plating, and solder plating can be successfully performed.

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

Example 1 Stainless steel (5O5) with a thickness of 0.12 mm and a width of 15 mm
A plate of No. 304) was prepared and nickel plated according to the following steps.

(1) Anodic electrolytic degreasing: sodium hydroxide 30g/2,
Sodium carbonate 30g, l, surfactant 0.5g/R,
in a degreasing solution at 60°C, anode current density 58/drn',
Anodic electrolytic degreasing was performed under conditions of a treatment time of 30 seconds.

(2) Pickling: 1Ovojll in hydrochloric acid for 30 minutes at room temperature.
I soaked it for a second.

(3) Activation by cathodic electrolytic treatment: NiSO4/6
H20240g/It, H2S04 (98vo
ffi*) 2 in 50 mM/1 activation treatment solution
Cathode electrolytic treatment was performed at 5° C. and cathode current density of 10 A/drn for 2.1 minutes. A carbon electrode was used as the anode.

(4) Bright nickel plating: Nickel sulfate 240g/
L, nickel chloride 45g/u, boric acid 40g/fi, brightener made by Ebara Nijin Light $610.4 r*l/l
, #63, 10 companies/2, plating with a bright nickel plating solution of pH 3.6 at 55°C and cathode current density of 58/drn for 2.3 minutes, resulting in bright nickel plating with a uniform appearance and a thickness of approximately 3μ. Got the board.

Bending the above bright nickel plated stainless steel plate 61
As a result of bending back three times at 90 degrees, no peeling of the plating was observed and the adhesion was good. Further, even after heating for 3 minutes on a hot plate heated to 450° C., no abnormalities such as blistering or peeling of the plating were observed.

Example 2 Diameter 1. Onon stainless steel wire was prepared and silver plated according to the following steps.

(1) to (3) Same as (1) to (3) of Example 1.

(4) Copper strike plating copper dianide 50g/l'
, Potassium cyanide 83g/ffi, Roise JL/
Copper strike plating was performed using an alkaline steel plating solution containing 40 g/l of salt at 50° C. and a cathode current density of 28/drn' for 30 seconds.

(5) Silver plating After performing strike plating with a silver strike plating solution containing 2 g/l of silver dianide and 70 g/IL of potassium cyanide at room temperature and a cathode current density of 4 A/dm' for 5 seconds, successively plating with 50 g/fi of silver cyanide , potassium cyanide 80g/I1. Plating was carried out for 2.4 minutes at room temperature with a silver plating solution at a cathode current density of 2 A/drn, and the thickness was approximately 5.
A μ silver plated wire was obtained.

The above silver-plated stainless steel wire was subjected to a bending and heating test in the same manner as in Example 1, but no abnormalities such as peeling of the plating or blistering were observed, and the adhesion was good.

It should be noted that the activation treatment solution of Example 1.2 showed very little variation in bath composition even after repeated use.

<Effects of the Invention> According to the method of plating stainless steel of the present invention, desired plating can be performed after cathodic electrolytic treatment in an aqueous solution containing nickel sulfate and sulfuric acid, so that the surface of the stainless steel material has good adhesion and Various types of plating with good appearance are possible, and the following effects can also be obtained.

(1) There is no appearance defect due to roughness of the substrate, which is often seen when the activation treatment method using conventional chemical polishing or electrolytic polishing is used.

(2) Unlike the Wood Nickel Strike method, highly corrosive hydrochloric acid is not used, so there is less negative impact on the working environment and less damage to peripheral devices and equipment.

(3) Since an insoluble anode can be used as the anode for catholytic electrolytic treatment, fluctuations in the composition of the activation treatment bath can be kept to a minimum, and bath management of the catholyte and the like becomes easy.

Applicant: Hitachi Cable, Ltd.

Claims (3)

[Claims] (1) A method for plating stainless steel, which comprises subjecting a pre-cleaned stainless steel material to cathodic electrolysis treatment in an aqueous solution containing nickel sulfate and sulfuric acid, and then subjecting it to desired plating. (2) The method for plating stainless steel according to claim 1, wherein the anode used in the cathodic electrolytic treatment is an insoluble anode. (3) The aqueous solution containing nickel sulfate and sulfuric acid is NiS
O_4・6H_2O, 100-300g/l)H_2S
The method for plating stainless steel according to claim 1 or 2, which is an aqueous solution containing 20 to 150 ml/l of O_4, 98 vol%.