JPS6047354B2 - gold plated products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to gold-plated products such as exterior parts for watches, and particularly to gold-plated products that are inexpensive and have excellent corrosion resistance.

Exterior parts for watches (cases, bands, dial rings,
When applying gold plating to tension rings, etc., raw materials such as brass and nickel silver are used, and the type of plating used is gold or gold alloy plating.

Conventionally, such gold plating has been applied to watch case materials 1 made of brass, as shown in Figure 1.
As a base plating, nickel plating 2 is applied to a thickness of about 2 to 8 microns, and on top of that, a 12 to 16 ton gold-silver alloy plating 3 is applied to a thickness of about 3 microns, followed by a 23 ton gold-nickel alloy plating. 4 was applied to a thickness of about 2 microns to form the watch case.

In the case of such watch cases, since gold and gold alloys, which are precious metals, are thickly plated, the problem is that the plating becomes expensive and the cost increases. In addition, if the case is finished with only a mirror surface, there is no particular problem with corrosion resistance, but if a part or most of the case has a streaked finish, it can be used as a traditional base plating for aesthetic appeal. It had the disadvantage of being inferior in corrosion resistance compared to mirror-finished cases in that it could not be plated thickly due to the damage to the surface. Furthermore, even if a type of nickel plating is used that does not impair the aesthetic appearance of the streaks even if the plating is thick, the coverage of the plating to the valleys of the streaks will be poor, and as a result, the corrosion resistance will be affected as well. It had the disadvantage of being inferior. The present invention was made as a result of various studies in order to eliminate the drawbacks listed above, reduce plating costs, and provide a watch exterior part with good corrosion resistance for all surface finished watch exterior parts. Tin 40-45 as a base plate.
% copper-tin alloy plating with a thickness of 2 microns or more, and gold or gold alloy plating as a final plating of 0.2 to 1.
It is characterized by micron coating.

The copper-tin alloy plating containing 40 to 45% tin includes various types of copper-tin plating such as copper cyanide-alkali stannate plating, copper cyanide-tin pyrophosphate plating, or copper pyrophosphate-tin pyrophosphate plating. Obtained from alloy plating bath.

The present inventors conducted various studies on this plating, and found that even with relatively light plating, it yellows slightly due to sweat and the like and is not easily corroded, which led to the present invention. In addition,
Copper-tin alloy plating as a base plating is most preferably a bronze-copper-stannate alkali plating, and is from a tanning bath using a thiocyanate, a polyethyleneimine compound, or a nickel salt as a brightener. , it can be plated thickly without damaging the aesthetic appearance of the surface finish, such as streaks.

The present invention will be explained below using a watch case as an example. As shown in Figure 2, a watch case 1 made of brass material with a partially streaked finish is plated with a copper-tin alloy 5 containing 40 to 45% tin in the following plating bath and plating conditions. 2 micron plating was carried out, and 23 strength gold-nickel alloy plating 4 was further applied to 1 micron as a final plating. (Plating bath) Sodium stannate 100fIe Sodium cyanide 30yIe Copper cyanide
12y1' Sodium hydroxide
10d 1e Sodium thiocyanate 0.

1f11e Polyethyleneimine nickel sulfate (as nickel) 0.1y1e
(Plating bath) Bath temperature 65 C Current density 2 AIdd anode
Carbon plate plating time
The watch case obtained in the above manner and similar watch case materials were plated with conventional nickel plating of 3 microns, 12-16 latt gold and silver alloy plating of 3 µm, and 23 latt gold-nickel alloy plating. When a corrosion resistance test was conducted on a watch case coated with a 2-micron coating using an artificial sweat immersion test, the case of the present invention showed no corrosion or discoloration after 5 days of immersion, but the conventional case showed no corrosion or discoloration in the streaked areas. Some spots of corrosion occurred on the surface.

As described above, according to the present invention, by performing copper-tin alloy plating containing 40 to 45% tin as the base plating, it is possible to reduce the cost by reducing the thickness of the finishing plating. .

Furthermore, it is possible to produce watch exterior parts with good corrosion resistance even with any surface finish. In the embodiments, a watch case has been described, but it goes without saying that the present invention can be applied to other parts as well, and that other materials other than brass are also possible.

It goes without saying that the thicknesses of the final plating and the base plating can be used in any appropriate combination other than those described in the examples.

a Brief Description of the Drawings FIG. 1 is a partial cross-sectional view of a conventional watch case, and FIG. 2 is a partial cross-sectional view of a watch case according to an embodiment of the present invention.

1...Watch case, 2...Nickel plating, 3...12-16 karat gold and silver alloy plating, 4...23 karat gold- Nickel alloy plating, 5... Copper-tin alloy plating containing 40 to 45% tin.

Claims (1)

[Claims] 1. A gold-plated product made by applying copper-tin alloy plating containing 40 to 45% tin to a thickness of 2 microns or more as a base plating, and further applying gold or gold alloy plating to a thickness of 0.2 to 1 micron as a final plating.