JPH03291395A - Nickel plating method ensuring high corrosion resistance - Google Patents

Abstract

PURPOSE:To form Ni plating layers having superior corrosion resistance and fine appearance by successively subjecting the surfaces of parts of an automobile, a motorcycle, etc., to Ni under plating, Ni alloy plating and finish Ni plating. CONSTITUTION:The surfaces of various metallic materials or Cu plated resin products, especially parts of an automobile, a motorcycle, etc., are subjected to Ni under-plating to form semimat or bright Ni plating layers in <10mum thickness and then Ni alloy plating layers whose potential is lower than that of the bright Ni plating layers by 0-50mV, e.g. Ni-Co, Ni-Fe, Ni-Zn or Ni-Mn alloy plating layers are formed in 0.1-1.0mum thickness. Finish Ni plating layers such as bright Ni, microporous bright Ni or microcracked bright Ni plating layers are further formed in <=6mum thickness. Triple Ni plating layers having superior corrosion resistance and fine appearance can be formed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a highly corrosion-resistant nickel plating method, and more particularly, to high corrosion-resistant nickel plating for parts of automobiles, motorcycles, etc. that require both high corrosion resistance and excellent glossy appearance. Regarding a corrosion-resistant nickel plating method.

[Prior Art] Nickel-chromium plating is generally used for parts of automobiles, motorcycles, etc. that are exposed to outdoor wind and rain due to its corrosion resistance and excellent metal appearance.

In normal nickel-chromium plating, corrosion is prevented by passivating the outermost chromium layer, but it is not possible to completely prevent defects (cracks and bores) in the chrome film, and even if it is possible, Even if this happens, it is not possible to prevent the occurrence of defects due to scratches and the like after plating, so corrosion starts from the defective parts. Corrosion that reaches the substrate significantly impairs the appearance of the object being plated, and even if corrosion does not reach the substrate, corrosion of nickel near the surface causes a noticeable deterioration in the appearance of the object that is to be plated, resulting in a decrease in commercial value. was decreasing.

A triple nickel process and a microporous chromium or microcrack chromium process have already been developed as highly corrosion-resistant nickel plating processes that solve these problems and provide corrosion resistance while reducing the thickness of the nickel plating.

[Problems to be Solved by the Invention] Among the highly corrosion-resistant nickel plating processes, the microporous chromium or microcrack chromium method creates defects such as micropores and fine racks in the outermost chromium of the plating surface. These methods reduce the corrosion current density and slow the corrosion rate, but they all have the disadvantage that the initially minute corrosion holes become larger over time, resulting in visually noticeable corrosion holes such as so-called "marbling".

On the other hand, the triple nickel (tri-nickel) process is a double nickel process in which a nickel plating layer with a lower potential (bright nickel plating layer) is applied on top of a nickel plating layer with a lower potential (semi-bright nickel plating layer). This is an improved version of nickel plating, which has a higher sulfur content and a lower potential than the bright nickel layer between the semi-bright nickel layer and the bright nickel layer (hereinafter referred to as "tri-nickel plating").
This tri-nickel plating layer, which has a lower potential, is used as a sacrificial film to protect the bright nickel layer and the substrate from corrosion.

However, this method also has the problem that once the corrosion reaches the tri-nickel plating layer, which is the sacrificial film, the tri-nickel plating layer corrodes quickly, resulting in noticeable large bits.

Therefore, it has been desired to develop a nickel plating process that has excellent corrosion resistance and does not deteriorate the appearance of the plating even if corrosion occurs.

[Measures to Solve the Problems] In order to solve the above problems, the present inventors reexamined the currently available corrosion-resistant plating methods. As a result, they realized that the disadvantage of the tri-nickel process in that large bits occur is because the corrosion of the tri-nickel plating layer, which is an intermediate sacrificial coating, progresses quickly in the lateral direction. Therefore, after further research, it was concluded that the rapid lateral corrosion of the intermediate sacrificial coating could be prevented by dispersing the corrosion within the coating.

It has also been found that dispersion of corrosion within the intermediate sacrificial coating can be achieved by using a nickel alloy plating whose potential is less base than the nickel plating layers on both sides as the intermediate sacrificial coating.

The present invention was completed based on these findings,
The present invention provides a highly corrosion-resistant nickel plating method characterized by sequentially applying base nickel plating, nickel alloy plating, and final nickel plating.

In order to carry out the highly corrosion-resistant nickel plating method of the present invention, it is first necessary to perform base nickel plating on the material to be plated.

There are no particular restrictions on the materials to be plated to which the method of the present invention can be applied, and metal substrates such as steel, zinc, aluminum, copper, copper alloys, and plastic substrates such as ABS resin are pretreated by a conventional method. After that, if necessary, it is possible to adopt any of those plated with other metals such as copper.

Further, as the base nickel plating, semi-bright nickel plating, bright nickel plating, semi-bright-bright nickel plating (double nickel plating), etc. can be employed.

Among these base nickel platings, the semi-bright nickel plating has a very small amount of sulfur eutectoid, for example, 0.005% or less, and has a relatively poor potential compared to bright nickel. As the composition of the semi-bright nickel plating bath, any conventionally used known nickel plating bath can be employed. Further, examples of brighteners for semi-bright nickel include chloral hydrate, formalin, and coumarin. Alternatively, for example, N
Commercially available products such as 2E and BTL (manufactured by Ebara Nishilight ■) can also be used.

Furthermore, among the base nickel, bright nickel plating has a sulfur content of, for example, about 0.02 to 0.07, and has a relatively base potential than semi-bright nickel plating. As the composition of the bright nickel plating bath, any of the conventionally used known nickel plating baths can be employed, and as the brightening agent, a known brightening agent such as a 1°5-1. Aromatic sulfonimides such as sodium 6- or 2.5-naphthalene disulfonate, sodium 1,3,6-naphthalene trisulfonate, sodium benzenesulfonate and sodium saccharinate, and sulfinic acids are used alone or in combination. In addition, for the purpose of imparting gloss and leveling, acetylenically unsaturated alcohols and their derivatives such as 1,4-butynediol, and ethylenically unsaturated sulfonates such as sodium vinylsulfonate and sodium allylsulfonate are also used. ,or,
Pyridine-based sulfonic acid sodium salts are used. In place of these, commercially available brightening agents for bright nickel such as "61, #63 (manufactured by Ebara Nishilight ■) may be used.

Preferred conditions for this semi-bright nickel plating and bright nickel plating are shown in Table 1 below.

(Left below) Part ■ Table Range Optimum Value NlSO4・68.0 100-400 g/l
280 g/lNiCl2・6H203G~ 60
g/l 45 g/IH3B03 20
~60 g/l 40 g/l brightener
Appropriate amount Appropriate amount pH 3.5~5.5 4.2 Plating temperature 40~65℃ 55℃ Cathode current density 1~IOA/da24 A/da2 Stirring Air, machine Air, machine The film thickness of this base nickel layer is quite thin. However, in the case of plating on plastic materials,
The thickness is preferably 10 μm or more in order to alleviate thermal shock.

Next, nickel alloy plating is applied.

The nickel alloy plating performed in the method of the present invention is
Basically, it is an alloy plating of nickel and a metal such as cobalt, iron, zinc, or manganese, which has a potential less base than nickel in the so-called corrosion potential series, and the potential of this alloy plating film is higher than the potential of the bright nickel plating film. It only needs to be base, and it may be a two-component alloy plating or an alloy plating consisting of more components.

A preferable nickel alloy plating film has a corrosion potential in a Cath solution that is 0 to 50 mV lower than that of a bright nickel film.
It's vulgar.

Such a nickel alloy plating film can be obtained, for example, by plating an alloy of nickel and metals such as cobalt, iron, zinc, and manganese.

For example, when forming a nickel alloy plating film using Ni-Co alloy plating, the cobalt content is 5 to 60.
% range (nickel metals and nickel salts used industrially contain several % cobalt, and cobalt is also eutectoid in the nickel plating film, but in this specification In this case, such a nickel plating film is used as a 100% nickel plating film.

In addition, when using Ni-Fe alloy plating to form a nickel alloy plating film, the iron content is 1 to 30%.
A nickel-iron alloy plating bath is used.

The nickel alloy plating bath used in the present invention may basically be any nickel alloy plating bath capable of eutectoiding nickel and a metal that satisfies the above conditions, and therefore is constructed based on a known nickel plating bath.

An example of a nickel alloy plating bath based on a Watt type nickel bath that can be used in the present invention is shown in the second example.
Although shown in the table, it goes without saying that the nickel alloy bath that can be used in the present invention is not limited thereto.

In the present invention, the film thickness of the nickel alloy plating is not particularly limited, but the object of the present invention can be achieved by setting the film thickness to about 0.1 to 1 μm.

Examples of the finishing nickel plating in the method of the present invention include bright nickel plating, bright nickel-microporous plating, bright nickel-microcrack plating, and the like.

Of this finish plating, bright nickel can be performed using the same bath composition, conditions, and brightener as those described for base nickel plating.

Further, microporous plating and microcrack plating applied on bright nickel plating can also be performed according to known compositions and conditions.

The thickness of the final plating is not particularly limited as long as it gives the desired gloss to the plated object, but -a is 6 μm.
It is about m or more.

The material to be plated which has been subjected to highly corrosion-resistant nickel plating by the method of the present invention is further subjected to final plating if necessary.

The final plating is generally chromium in the case of parts for outdoor use, but is not limited to this, and other metals such as gold, gold alloys, etc. can also be used.

[For creation]

Although the reason why excellent corrosion resistance is obtained by the method of the present invention is not yet clear, it is presumed as follows.

That is, when corrosion from metal surface defects reaches the nickel alloy plating layer, selective corrosion of eutectoid metals other than nickel occurs, and the corrosion is dispersed. In conventional tri-nickel plating, since the sacrificial layer is a single layer, corrosion progresses uniformly, and when it reaches a certain size, the upper layer is pushed up by the corrosion products, causing corrosion blisters at an early stage. In this case, only a portion of the nickel alloy layer corrodes and dissolves, so no force is generated to form corrosion blisters. Furthermore, the nickel in the alloy plating layer that has undergone selective corrosion has the same properties as bright nickel, and forms a finely porous film. It is thought that this non-uniform coating provides a starting point for corrosion, induces and disperses subsequent corrosion, and thereby provides excellent corrosion resistance.

[Effects of the Invention] According to the method of the present invention, a nickel plating film having excellent corrosion resistance can be obtained as shown in the examples below, so it is an excellent method for corrosion-resistant plating of articles used under harsh outdoor conditions. be.

In particular, since the method of the present invention retains corrosion inside the plating film, corrosion defects do not occur on the plating surface for a long period of time, and it is suitable for use in automotive exterior parts where not only material corrosion but also surface corrosion is not acceptable as a change in appearance. Can be well used in parts that require high corrosion resistance.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples in any way.

Example 1 A copper-plated ABS resin plate (
10C11X 5 cm) was used as a test plate, semi-bright nickel plating (12 μm), Ni-Co alloy plating (Co content 20 wt%; 1 μm), bright nickel plating (12 μm), and chrome plating (0.5 μm) were sequentially applied. A corrosion resistance test piece was then obtained. CASS test M (JIS 0201) was performed on this test piece to evaluate its corrosion resistance. As a result, the surface had no corrosion defects and had the same appearance as before the test.

The composition and conditions of each nickel plating bath used are shown in Table 3, the composition of the nickel alloy plating bath is shown in Table 4, and the composition of the chromium plating bath is shown in Table 5.

Nickel plating bath composition and plating conditions: 3rd
Surface semi-bright nickel bath Bright nickel bath N15O, 6H1O NiC1*15HmO 00g71 45g/1 00g71 75g/l Photo-IR agent, additives and amount used (0.1g/l) (2-Og/1) 2-1 tin -1゜4-Diol Temperature Stirring # Pole Current Density 55℃ N2 Air 4^/da" 55℃ Air 4^/ds" Nickel Alloy Plating Bath Composition and Plating Conditions: Table 4 Conditions N i SO <・6 H2O N i C1z・6 H2O Co S O4・77H2 O300/1 45g/1 12.5g/l Brightener, added saccharin (2.0g/l) H Temperature stirring Stirring cathode current density 3.0 55℃ Cool A 4 A/da2 Chromium plating bath and plating conditions: Conditions Chromic anhydride (Cry') 250 g/l Trivalent chromium (Cr") 2.0 g/l sulfur
Acid 2.5g/l Temperature
45℃ cathode current density
15 A/da" Example 2 Ni-Co alloy plating with a Co content of 60% and a film thickness of 6 μm
Plating was carried out in the same manner as in Example 1 except that the thickness of the bright nickel was changed to 6 μm to obtain a corrosion-resistant sample piece.

A CASS test was conducted on this product, and the same excellent gloss and appearance as in Example 1 were maintained even after 160 hours.

Example 3 Plating was carried out in the same manner as in Example 1 except that Ni--Co alloy plating was changed to Ni--Fe alloy plating using the following composition bath to obtain a corrosion-resistant sample piece.

A CASS test was conducted on this product, and the same excellent gloss and appearance as in Example 1 were maintained even after 160 hours.

(Left below) Table 6 Conditions N i S 04.6 H2O NiC1,.6H20 F e S O4.7 HzO 105g/1 60g/1 2.0 g/l Complexing agent 20g/l Saccharin 2.0 g/l Sodium allylsulfonate 5.0 g/lH Temperature stirring Stirring cathode current density 3.3 60°C Air 4 A/d 2 Example 4 Ni-Co alloy plating was performed using the following composition bath for Ni-Fe-
Plating was carried out in the same manner as in Example 1 except that Co ternary alloy plating was used to obtain a corrosion resistance test piece.

A CASS test was conducted on this product, and the same excellent gloss and appearance as in Example 1 were maintained even after 160 hours.

(Leaves below) Table 7 Conditions N15O, ・6H2O NiC12・6H20 COS o, ・7 H2O Fe5O4='yH, 0 05 0 9,5 2,0 g/1 g/1 g/1 g/l Leading agent 20g/l
Saccharin 2.0 g/l Sodium allylsulfonate 5.0 g/lH Temperature stirring Stirring cathode current density 3.3 60°C Air 4 A/ds+2 Example 5 Ni-Co alloy plating was performed using the following composition bath. Plating was carried out in the same manner as in Example 1 except that Zn alloy plating was used to obtain a corrosion resistance test piece.

A CASS test was conducted on this product, and the same excellent gloss and appearance as in Example 1 were maintained even after 160 hours.

(Leaving space below) Table 8 Conditions N i S O4・6 H2O N i Cl 2・6H20 ZnSO4・7H20 50g71 45g/1 1.1g/l #63J” 15ml/1H Temperature stirring Stirring cathode current density 4.0 55°C Air 3 A/d equipment Example 6 Ni-Co alloy plating was performed using Ni-M using the following composition bath.
Plating was carried out in the same manner as in Example 1 except that n-alloy plating was used to obtain a corrosion resistance test piece.

A CASS test was conducted on this product, and the same excellent gloss and appearance as in Example 1 were maintained even after 160 hours.

(Left below) Table 9 Conditions N15O, 6H2O Ni Cl 2 6 N20 M n S O4 4~6 H20 50g71 5g71 25g/l Saccharin 0.5g/l H Temperature stirring Stirring cathode current density 4.0 55°C Air 5 A/d@” Comparative Example 1 A test piece plated with copper in the same manner as in Example 1 was coated with semi-bright nickel plating (12 μm) and bright nickel plating (
13 μm) and chromium plating (0.5 μm) were sequentially applied to obtain a corrosion resistance test piece.

When I conducted a CASS test on this item, I found that it was 80.
After a period of time, undesirable corroded bits had already formed. Further, although material corrosion did not occur, the gloss and appearance were significantly impaired.

Comparative Example 2 A corrosion resistance test piece was obtained in the same manner as in Example 1 except that the Ni-Co alloy plating was changed to the tri-nickel plating shown in Table 9.

After 80 hours of the CASS test, this product had already developed corrosion and blistering, and its gloss and appearance were significantly impaired.

(Margin below)

Claims (8)

[Claims] (1) A highly corrosion-resistant nickel plating method characterized by sequentially applying base nickel plating, nickel alloy plating, and final nickel plating. (2) The highly corrosion-resistant nickel plating method according to claim 1, wherein the potential of the alloy plating film formed by nickel alloy plating is 0 to 50 mV less base than the potential of the bright nickel plating film. (3) The highly corrosion-resistant nickel plating method according to claim 1 or 2, wherein the nickel alloy plating consists of nickel and one or more metals selected from cobalt, iron, zinc, and manganese. (4) The highly corrosion-resistant nickel plating method according to any one of claims 1 to 3, wherein the base nickel plating is semi-bright nickel and the finishing nickel plating is bright nickel plating. (5) The highly corrosion-resistant nickel plating method according to any one of claims 1 to 3, wherein the base nickel plating is double nickel plating and the finishing nickel plating is bright nickel plating. (6) The highly corrosion-resistant nickel plating method according to any one of claims 1 to 3, wherein both the base nickel plating and the finish nickel plating are bright nickel plating. (7) The highly corrosion-resistant nickel plating method according to any one of claims 1 to 3, wherein the final nickel plating is bright nickel-microporous nickel plating. (8) The highly corrosion-resistant nickel plating method according to any one of claims 1 to 3, wherein the final nickel plating is bright nickel-microcrack nickel plating.