JPS5980800A - Stripping method of plating - Google Patents

Abstract

PURPOSE:To strip easily a plating layer of noble metal without damaging a base metal by subjecting the plating layer of noble metal formed on aluminum to an anodization treatment in the stage of stripping said layer. CONSTITUTION:An article 2 wherein gold 5 is plated via copper plating 7 on aluminum or an aluminum alloy 8 is used as an anode and is suspended between cathodes 3 in a bath cell 1 contg. about 15% sulfuric acid in the case of stripping the gold plating 8 having a pinhole 6 in the gold plating 5 from said article 2. When the voltage of a DC power source 4 is set at about 15-20 volts, the current increases gradually, and the copper plating 7 begins to dissolve through the pinhole 6 of the plating 5. When the dissolution of the plating 7 progresses and the aluminum alloy on the base metal 8 exposes, said surface is passivated by an anodization treatment, so that no more current flows and only the plating 7 is dissolved off. The gold plating 5 is dislodged and removed.

Description

[Detailed description of the invention] This invention applies decoration to aluminum or its alloy.

If, for some reason, it becomes necessary to remove the plating layer of a component that has been plated with a precious metal such as gold plating or rhodium plating for the purpose of corrosion protection or to improve electrical conductivity, and then re-plating it, Without damaging the base metal,
There is still no satisfactory method for removing plating. There are chemical methods (dipping and dissolving in a cyanide solution, etc.) and mechanical methods (polishing with emery paper), but it is very difficult to remove them without damaging the base metal.

In such plating removal, the plated parts are electrochemically anodized, and at this time, the plating is indirectly removed, and the base metal is anodized. Therefore, the dissolution loss is suppressed to a very small amount of several microns or less.

This invention will be explained below using FIG. 1 and FIG. 2.

Generally, when precious metal plating is applied to aluminum or its alloy, heavy metals such as copper plating and nickel plating are applied intermediately, rather than directly as decoration. .

10 micron copper plating on aluminum alloy.

On top of that are parts with 1 micron gold plating.

The case of peeling using a sulfuric acid bath will be described.

Figure 1 is a schematic cross-sectional view of a plated part, and Figure 2 is a schematic cross-sectional view of a plated part.
FIG. 3 is a diagram showing an anodizing treatment method.

Use item (2) as the anode in a bathtub with a sulfuric acid concentration of 15% (No. 11).

Cathode (31 (310) suspended between. And DC power supply (4)
The voltage of 15. When set to -20 volts, the current begins to gradually increase.

Although the gold plating (5) itself does not react, the copper plating (7) begins to dissolve through the pinhole (6) in the gold plating due to the following reaction - Cu-+Cu+20 Plating generally has pinholes. The number varies depending on the surface roughness of the surface to be plated, the plating thickness, and the type of plating, but it reaches approximately several to several hundred sides/cIIl. The rougher the surface and the thinner the plating, the greater the number of pinholes and the faster the peeling based on the 9-pin principle.

As the copper plating (7) continues to melt and the aluminum alloy of the base metal (8) is exposed, this surface becomes passivated by anodizing, and at the same time, current no longer flows through this surface, leaving the remaining aluminum alloy exposed. The dissolution of the copper plating progresses, and eventually the copper plating is completely dissolved and removed, and the gold plating falls off in the form of a foil and is removed.

As described above, according to the present invention, a noble metal plating layer on aluminum or an aluminum alloy can be easily peeled off.

Note that rhodium plating and other noble metal plating can be similarly peeled off.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the method of anodizing treatment, Fig. 2 is a schematic cross-sectional view of the plated parts, and (1) is a bathtub. (2) is the product, (3) is the cathode, (4) is the DC power supply, (5
) indicates gold plating, (61 indicates pinhole, (7) indicates copper plating, and (8) indicates base metal. Identical or equivalent parts in the drawings are indicated with the same reference numerals. Agent) Shin Kuzuno

Claims (1)

[Claims] 1. A plating removal method characterized in that a plating layer of a precious metal applied to aluminum or an aluminum alloy is removed by anodizing treatment.