JPS5823478B2 - Manufacturing method of hard gold alloy coating - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a method for manufacturing a hard gold alloy coating, and in particular, it is used to coat so-called high-end accessories such as watch exteriors and eyeglasses to improve properties, corrosion resistance, gloss, color tone, etc. A method of manufacturing a hard gold alloy coating is provided.

Hardening of the gold plating film not only improves abrasion resistance and scratch resistance and lengthens product life, but also has excellent advantages such as lowering manufacturing costs because it can be expected to have a lower metal phase.

In view of these points, the present invention aims to provide a method for producing a hard gold alloy coating that further improves the thickness, corrosion resistance, gloss, color tone, etc. required for gold plating.

The features of the present invention will be specifically explained below.

First of all, the first feature of the present invention is that the gold alloy electroplating solution used in the present invention produces approximately 58 to
84 wt%, copper 8-25 wt%, Ni.

It is designed to obtain an alloy with a total Co content of 10 to 35 wt%, and when a hard gold alloy film is to be produced by electrodeposition, the electrolyte contains gold sulfite (containing 1 to 309 gold/l), Cyanide-free soluble copper salts (copper o, i
~10 g/IJ), cyanide-free converting nickel salt, cobalt salt (0.1 ~
509/l) and an alkali sulfite content of 10EI/1 or more.

In the present invention, gold, which is the main component by weight of the alloy, is 1 to 30 g/l.
The reason for this is that the multi-component alloy based on the present invention has a suitable alloy composition, such as gold potash cyanide, which is used under ordinary cyanide base or organic acid base, and has a stable luster. This is because it is difficult to obtain.

Father, each salt of a metal is a source of its respective metal component;
Therefore, at a low copper concentration of less than 0.1 g/1, it is difficult to obtain electrodeposition effective for hardening, and even if it is obtained, long-term stable production in an industrial sense is difficult.

In addition, a high concentration of 10 g/1 or more is not only uneconomical, but also causes cloudiness and smearing, and tends to upset the balance of the alloy composition of the electrodeposition. Especially, when copper salts and cobalt salts are in excess, the colorfastness is reduced. This is not preferable because it also causes a decrease in performance.

Here, the soluble copper salt that does not contain cyanide includes many salts such as inorganic salts such as sulfate and sulfamate, as well as organic salts such as enolate EDA complex.

In addition to the reasons for excluding cyanide, there are also reasons to prevent pollution.
This is because there is a tendency to inhibit the stability of the bath.

Further, nickel and cobalt are selected as metal components following gold and copper, and a range of 0.1 to 50 g/l is specified for each, but these are intended to improve the hardness of electrodeposition.

Furthermore, since the alkali sulfite is used as a stabilizer for gold sulfite, if the amount is less than 10 g, the gold sulfite may decompose.

Although there is no problem with %NIJ on the high concentration side, 509/l is considered to be an appropriate amount considering economic efficiency.

pH has the same effect as alkali sulfite, and at pH 7.5 or lower, almost no gold will precipitate, and sometimes gold sulfite may decompose.

Next, the second feature of the present invention is that in the present invention, when the above-mentioned hard gold alloy coating is to be manufactured by electrodeposition, Ag, Cd, Zn, In, Sb, and As are used in the electrolytic solution.

The present invention provides a method for producing a hard gold alloy coating containing 0.001 to 109/l of one or more of the following metals: Se and Te in the form of cyanide-free hemolytic salts.

In this feature, the metal salt additive is added to the electrodeposition for the purpose of improving gloss, preventing brittleness, and improving physical properties.

In the case of Ag, Cd, Zn, In, and Sb, very simple inorganic salts are used, but organic acid salts such as cadmium malate may also be used, and they can be used under the electrolyte conditions shown in the first characteristic. As long as it is soluble, it does not have to be water bathable.

Metals in this group have the effect of lowering the appropriate temperature for heat treatment, and are therefore effective in preserving the mechanical strength of the deposited material.

However, since it has a sensitive effect on the color tone, gloss, etc. of electrodeposition, excessive use may actually impede these effects and is not preferable.

Regarding As, Se, and Te, only sulfite compounds or their alkali salts are effective in improving electrodeposition efficiency and gloss.

Also, this group of additives is very sensitive and excessive use should be avoided as much as possible.

The above are the essential conditions in the electrodeposition process of the present invention, but in addition to the above essential components, the electrolyte solution contains 30 to 30% of sodium citrate.
301. #Add.

This is a conventional method for gold plating, and has the effect of improving conductivity and stabilizing the pH of the bath.

Of course, similar chemicals such as sodium tartrate and Lotusel salt can be used, but we are currently conducting research on sodium citrate, which is a typical example and is highly effective.

Also, the optimum concentration is 200 g/l! It's nearby.

The bath temperature can range from 35°C to 70°C, but the optimal range is 45°C.
°C to 55 °C.

Although titanium-platinum electrodes were used in all experiments, other materials may also be used.

The current density may be 0.5 to 2 A/d m', but in the industrial production stage it should be 0.8 to IA/d to prevent burns.
It is better to implement it with i.

Under these conditions the deposition rate is 3-4 minutes per micrometer.

The hardness, which is the main purpose of the invention, differs from gold to gold,
The gold alloy coating of each gold component is roughly as follows.

400-450Hv on 14th to 16th, 300-4 on 18th
00 Hv, 20 to 250 to 350 Hvo.The hardness was measured using a Witzkers hardness tester using a specified diamond indenter.

The corrosion resistance of the electrodeposition is good, and we were able to achieve above-standard results in various tests commonly used in the watch industry, such as ammonia aeration tests and artificial sweat immersion tests.

The following will be explained based on examples.

Example 1 Gold sulfite (5 g/e as gold) Copper sulfate (79/l as copper) Nickel sulfamate (20 g/l as nickel)
Cobalt sulfamate (3 g/l as cobalt
) Sodium citrate 200 g/l Sodium sulfite 50 p/1 The above solution was adjusted to pH 9.2 with NaOH and heated to a temperature of 5.
As a result of plating a nickel silver plate for 20 minutes at a current density of 0°C I A/d m'', a pinkish Hamilton-colored gold plating was obtained, and chemical analysis showed that the coating was 60% Au.
, Cu 15%, Ni 22%, and Co 3%.

Further, the thickness of the gold alloy coating was 5.5 μm, and the hardness of the coating with respect to the gold component, that is, 14.4, was 409 Hv.

Example 2 1g7e of indium sulfate was added to the plating solution used in Example 1, and plating was carried out for 40 minutes under the same conditions as in the previous example.

The resulting deposit was a bright gold alloy that was slightly whiter than the previous example.

The measurement data regarding this electrodeposition is as follows.

(However, the heat treatment method is the same as the previous example) Thickness 10.0μ Alloy composition Au58.5%Cu 15%N122%Co
3% In 1.5% Hardness 441Hv (14,04K) Artificial sweat 24H Good In the above examples, only the case where In was added as a soluble salt was given, but there is no difference even if other metals are used.

However, there is a difference between metal components in that metals with lower deposition potential precipitate more; for example, Ag, Cd,
The alloy composition is 15% for Zn addition amount of 0.5-1g7i
, other Sb, As, Se.

Te is 0.15% for the added amount of 0.01-0.19/l
The amount of precipitation is about 100%.

This is naturally expected since the deposition potentials change in substantially the same order up to A g −+T e.

Claims (1)

[Scope of Claims] 1. A method for producing a hard gold alloy film, in which the electrolytic solution and electrolytic operation satisfy the following conditions axg when producing the hard gold alloy film by electrodeposition. a, gold sulfite (containing 1 to 309 gold/l), b,
Soluble copper salts that do not contain cyanide (containing 0.1 to 10 g/l copper), C, soluble nickel salts that do not contain cyanide, cobalt salts (
d. Contain 10 g/1 or more of alkali sulfite; e. Contain 30-300 S/l of sodium citrate; f. Liquid temperature or room temperature. ~70℃, current density 0.5~2A/d
g-pH is 6.8 to 11. 2. A method for producing a hard gold alloy film by electrodeposition, in which the electrolytic solution and electrolytic operation satisfy the following conditions a"-h. a. Gold sulfite (containing gold 1 to 30 fj/11) (to do)
, b, cyanide-free soluble copper salt (copper 0.1-10g
/IJ), C, cyanide-free soluble nickel salt, cobalt salt (
each in the range of 0.1 to 50 g/l), d. Containing alkali sulfite of 109/1 or more, e. Containing sodium citrate 30 to 3009/l, f. Ag, Cd, Zn, In, Sb, As, Se, Te
0.001 to 10 g/l of one or more of the following metals in the form of soluble salts that do not contain cyanide. g, liquid temperature to room temperature to 70°C, current density 0.5 to 2 A/d
i. h. pH is 6.8-11.