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Chromium plating method

a technology of chromium plating and chromium ions, which is applied in the direction of electrodes, etc., can solve the problems of preventing stable plating operation, preventing the practicability of chromium plating, and the plating method with the combined chromium plating bath is almost not used industrially at present, so as to prevent the practical use of chromium plating, prevent the hydrolysis of trivalent chromium ions, and facilitate the maintenance of plating bath

Inactive Publication Date: 2012-11-08
C UYEMURA & CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an industrially advantageous chromium plating method that allows for continued operation with a combined chromium plating bath for a long period of time. The method uses an anode with an iridium oxide-containing coating that prevents the oxidization of trivalent chromium ions into hexavalent chromium ions. However, it was found that lead ions in the plating bath cause the increased concentration of hexavalent chromium ions, which can lead to defective plating and environmental concerns. Therefore, the present invention provides a method that allows for the continued use of the iridium oxide-containing coated anode while maintaining the optimal concentration of hexavalent chromium ions in the plating bath. By controlling the concentration of lead ions in the plating bath, the concentration of hexavalent chromium ions can be kept at an optimal level for stable chromium plating for a long period of time.

Problems solved by technology

However, the conventional plating bath containing a trivalent chromium compound causes troubles when it is contaminated with hexavalent chromium ions (Cr6+).
However, the plating method with the combined chromium plating bath is almost not industrially used at present.
The reason for this is that chromium plating with the conventional combined chromium plating bath proceeds smoothly in its early stage but is liable to cause troubles after a comparatively short period of time, thereby preventing stable plating operation.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0059]The following chromium plating bath was prepared.

[0060]

Chromium oxalate 78 g / L (in terms of Cr3+)Ammonium sulfate120 g / LChromic acid 20 g / LpH 2.2

[0061]The contents of trivalent chromium ions, hexavalent chromium ions, oxalate ions, and sulfate ions were as follows. Incidentally, the content of Pb ions was 1 mg / L.

Trivalent chromium ions 78 g / LHexavalent chromium ions 10 g / LOxalate ions248 g / L (in terms of oxalicacid dihydrate)Sulfate ions 87 g / L

[0062]A composite iridium oxide anode consisting of a titanium plat which was coated with a mixture of iridium oxide and 30 mol % (in terms of metal) of tantalum oxide was used as an anode. An amount of the mixture including iridium oxide in the coating film is 0.5 g / dm2 (in term of iridium metal). A plastic object processed up to a nickel electroplating is used as an object to be plated (cathode). Chromium plating was carried out for 10 minutes under the conditions of 10 A / dm2 of cathode current density and 6 A / dm2 of anode current dens...

example 2

[0068]The same procedure as in Example 1 was repeated to perform chromium plating except that the concentration of hexavalent chromium ions was changed to 20 g / L and the concentration of lead ions was changed to 2 mg / L. The resulting chromium plated film had as good appearance as that of Example 1.

example 3

[0069]The same procedure as in Example 1 was repeated to perform chromium plating except that the composite anode was replaced by an anode made of iridium oxide alone. The resulting chromium plated film had as good appearance as that of Example 1.

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Abstract

A chromium plating method wherein an article to be plated is immersed in an acidic chromium electroplating bath and electrolysis is carried out using a positive electrode that has an iridium oxide-containing film at least on the surface. The acidic chromium electroplating bath contains a trivalent chromium compound and a hexavalent chromium compound at a ratio such that the total chromium concentration of trivalent chromium and hexavalent chromium is 60-140 g / L, the hexavalent chromium concentration is 5-40 g / L, and the ratio of the hexavalent chromium concentration is 5-35% by mass of the total chromium concentration, while containing 50-400 g / L of organic carboxylate ions and having a lead ion concentration of not more than 2 mg / L. By the method, a chromium plating film that is good and stable over a long time period can be obtained. In addition, the plating bath can be controlled extremely easily in the chromium plating method.

Description

TECHNICAL FIELD[0001]The present invention relates to a chromium plating method that employs a plating bath containing a trivalent chromium compound and a hexavalent chromium compound mixed together.BACKGROUND ART[0002]Among well-known conventional chromium plating baths are the one which contains chromic acid (which is a hexavalent chromium compound) as the major component and the one which contains a trivalent chromium compound. The bath containing chromic acid as the major component is widely used as one of them. Beside, the bath containing a trivalent chromium compound is beginning to be used in the environmental point of view. However, the conventional plating bath containing a trivalent chromium compound causes troubles when it is contaminated with hexavalent chromium ions (Cr6+).[0003]On the other hand, there is also known a chromium plating bath which contains a trivalent chromium compound and a hexavalent chromium compound in combination. (This is referred to as a combined ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C25D3/06
CPCC25D3/04C25D3/06C25D17/10C25D3/10C25D3/08
Inventor MURAKAMI, TORUMAEDA, RYOSUHAIMI, HAMIDNURUL, AIDILLAMOHD, MURUSHID
Owner C UYEMURA & CO LTD
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