JPS602398B2 - Exterior parts for watches - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to under-plating of a watch exterior part plated with a precious metal.

Conventionally, in the case of exterior parts for watches, the plating composition of products to which precious metal plating is applied is usually as shown in Table 1: under-plating is applied to the base metal such as yellow steel or nickel silver, and the final gold plating is applied on top of it. This was the normal plating configuration.

In this plating configuration, copper or nickel plating is usually used for the bottom finish. However, this underlying Ni plating layer has the following drawbacks due to the characteristics of its material.

In other words, open-deposited Cu and Ni do not have high corrosion resistance by themselves, and in an atmosphere containing sulfides such as sweat, black products of sulfide steel and nickel sulfide are generated, which is used to coat the precious metal on the surface. Easily elutes through the pinhole of
There was a problem in that the appearance deteriorated. Furthermore, Cu
Since Ni and Ni do not have a passive region at any corrosion potential, corrosion progresses to the base material. As a result, the material begins to completely dissolve, and the current situation is that it becomes unusable in terms of appearance. The present invention solves the above problems and significantly improves the corrosion resistance of noble metal plated exterior parts by improving the corrosion resistance of base plating to the same level as chrome plating.

This lower plating was changed to Ni plating, and the Sn content was 60%.
The present invention is characterized in that an alloy containing the above and one or two of Ni and Co is used as an underlay. In addition, the above-mentioned noble metal plating refers to Au alloy (Example A
Refers to u-Ag-Cu and Au-Cu-Cd systems. In general, metal Sn has superior corrosion resistance compared to Ni even in oxidizing and reducing corrosive atmospheres.

However, if pure Sn is electrodeposited, the strength is insufficient and dents occur, and it is easily worn out, so it is alloyed to contain 10% or more of Ni and Co and used as an underplating. Also Sn
By containing 60% or more of the content, the progress of corrosion due to sweat etc. can be completely inhibited. Examples will be described below.

Example 1 Sn was reduced to 80% using the following plating tolerance ingredients and plating conditions.
A watch side was manufactured by electrodepositing 3 mounds of a Sn--Co alloy to form a lower layer, and then electrodepositing 3 mounds of an Au-12.5% Cu-12.5% Ag gold alloy thereon.

When this was immersed in artificial sweat at 40° C. for 24 hours and compared with a conventional Ni undercoated product, the Sn-Co alloy electrodeposited product showed no discoloration at all and had excellent corrosion resistance. Plating component: Potassium pyrophosphate 250 t/d Stannous pyrophosphate 15 t/d Cobalt chloride
30% 1,3-propanediamine 4cc/soPH IO
Temperature: 55°C Cathode locker rotation Cathode current density: 0.5 to 2 A/d Au-Cu-Ag-based finishing bath Ingredients: cyanide, gold, metal, 80m / Messiaen, silver, potassium, 0.5t, cyanide steel
30 cyanizing power 1'
5th evening/so pH
8.5Temp
6 p○ current density IA/d〆Example 2 Under the same plating electrodeposition conditions as Example 1, Sn was 80%
The same excellent corrosion resistance was obtained for watch No. 8, which was coated with a Sn--Ni alloy containing four peaks and was helmet-plated.

Plating ingredients Potassium pyrophosphate 250 ml/Stannous pyrophosphate 15 ml/Nickel sulfamate 40 ml/Tritanolamine 1 cc' The top coating was the same as in Example 1.

(See Table 1) Example 3 Using the same electrodeposition conditions as Example 1, 75% Sn was added.
Electrodeposition was performed on a watch band using the Sn--Co--Ni alloy as an underlay.

Through this under-plating treatment, it was possible to improve the corrosion resistance, which had previously been a problem with watch bands made of nickel silver or stainless steel, as shown in Table 1. Finishing bath ingredients: Potassium pyrophosphate 250 t/stannous pyrophosphate 15 t/s cobalt chloride
30 evening/so nickel chloride
15/Part 1, 3 Propanediamine
4cc/The top attachment is Au-12.
5% Cu-12.5% Cd.

Au-Cu-Cd based plating rich component cyanide gold 6 t's cadmium cyanide potash 1 t/s cyanide steel
8M/potassium cyanide
28 ta'〆PH I
ITemp 60'0 current density
0. The above three examples of ship/d are summarized in Table 1 and shown in comparison with the current product.

In the table, the corrosion resistance of plating was evaluated under the conditions described in Example 1, and the plating adhesion was evaluated by a 900 bending test. In Table 1, 0 for appearance indicates that the gloss is sufficient for decoration and there is no pitting or fogging, and × indicates that the gloss is insufficient and there is roughness or fogging. Corrosion resistance of 0 means that no corrosion or discoloration occurs under the above test conditions, ×
indicates that corrosion or discoloration will occur. Next, adhesion of 0 means that no cracks occur in the above-mentioned bending test;
× indicates that a crack occurs. All the ratios of each of the above components are expressed in % by weight.

Claims (1)

[Claims] 1. An exterior part for a watch, in which the lower plating is made of an Sn alloy consisting of 60% to 90% Sn and one or two of Ni and Co, and the upper layer is plated with a precious metal.