JPS6077997A - Electrolytic etching bath for gold or gold alloy - Google Patents

Abstract

PURPOSE:To obtain an electrolytic etching bath for gold or a gold alloy giving a lustrous surface to any of annealed, worked and electroformed articles by specifying the relation among water, hydrochloric acid and acetic acid and the relation between hydrochloric acid and acetic acid. CONSTITUTION:This electrolytic etching bath for gold or a gold alloy consists of water, hydrochloric acid and acetic acid in 1:(0.1-100):(0.1-100) ratio of water: hydrochloric acid:acetic acid and 1:(1-10) ratio of hydrochloric acid:acetic acid. The bath is characterized by acetic acid contained. Luster is not obtd. in a bath consisting of hydrochloric acid and water. In accordance with an increase in the concn. of acetic acid in the bath, the resistance of the bath is increased, and luster is improved. Since the resistance of this bath is low, the bath has low power consumption, and the temp. of the bath is hardly raised. Even when the bath is produced in large quantities, the composition is hardly changed, and the bath maintains its stability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic etching bath for gold or gold alloys, and more particularly to an electrolytic etching bath for all decorative articles such as gold electroformed articles and rolled gold articles.

Conventionally, many electrolytic etching baths have been used that mainly contain harmful substances such as cyanide and chromic acid. A sulfuric acid-phosphoric acid-sodium chloride bath-hydrochloric acid bath is known as a bath that does not use these harmful substances. but,
Although this bath produces a glossy surface when annealed, the processed product lacks luster, and when the shape becomes complex, the concave areas do not become glossy and appear cloudy. moreover,
Because it uses a four-component system of sulfuric acid, phosphoric acid, sodium chloride, and hydrochloric acid, it has the disadvantage that the bath is complex and maintenance is difficult.

The present invention was made in view of the above-mentioned drawbacks, and provides an electrolytic etching bath that does not use harmful substances such as cyanide or chromic acid, and can change the glossy surface of annealed products, processed products, and electroformed products. be.

The electrolytic etching bath in the present invention is a bath consisting of acetic acid, hydrochloric acid, and water, (a) water: hydrochloric acid: acetic acid - 1:0.1 to 100:0.
It is characterized by having a relationship of 1 to 100, and (b) a relationship of hydrochloric acid:acetic acid of 1:1 to 10.

In the present invention, the most significant feature is acetic acid.

In other words, no gloss was obtained with a bath of hydrochloric acid and water, but as the concentration of acetic acid in the system was increased, the bath resistance increased and the gloss improved. However, if the acetic acid concentration in the system becomes too high, the degree of haze in the four low current density areas becomes severe in the case of articles with large irregularities, making it impractical. Therefore, the proportion of acetic acid in the bath is preferably within the ranges (a) and (b) above.

Examples and conventional examples will be described below.

[Example 1] A rolled product (No. 1) of a metal plate of width 101 x length 50 x 0.5 x thickness, an annealed product heat treated at 600°C for 30 minutes (No. 2), and a width 10 An electroformed product (No. 3) of dragon x length 50+u x thickness 50μ was created. Add this to 400ml of acetic acid! .

Water 12ml1. 30V at room temperature in a bath with a composition of 80 mβ of hydrochloric acid.
Electrolytic etching was performed for 2 minutes. Result No. 1~N01
All three were shiny. In particular, the gloss of No. 1 and No. 2 was remarkable (mirror gloss).

[Conventional Example 1] Processed product similar to Example 1 (No. 4), annealed product (No.
, 5) Create an electroformed product (No. 6) and add it to sodium chloride 200g/I), sulfuric acid 100m/Il,
Phosphoric acid 100 nl/12.

5008/di' in a bath of 50 ml/j2 of hydrochloric acid at room temperature.
, electrolytically etched for 20 seconds. Result No. 4
and No. 6 were glossy, but No. 5 annealed products were not glossy. In addition, the processed product No. 4 had inferior gloss compared to No. 1.

[Example 2] Annealed product (N
o, 7 to No., 10) were made into a cylindrical shape with 5 fins φ and electrolytically etched in the same bath as in Example 1 under the conditions shown in the left column of the table below, and the degree of gloss and amount of cloudy etching were examined. I got the results in the column.

Here, ◎ indicates specular gloss.

[Example 3] Next, pure blunt products similar to those in Example 2 (No. 11 to No. 1
6) was etched in the same bath as in Example 1 at 5 A and 30 V for varying etching times, and the results shown in the table below were obtained.

[Example 4] Next, processed products similar to Example 2 (No. 17 to No. 19
) was carried out in the same bath as in Example 1 under the conditions shown in the right column of the table below, and the results shown in the left column of the table below were obtained.

[Conventional Example 2] A processed product (No. 20) having the same shape as in Example 2 was subjected to the same bath as in Conventional Example 2 under the conditions shown in the right column of the table below, and the results shown in the left column of the table below were obtained.

(Left below) [Example 5] Next, the same processed products as in Example 2 (No. 21 to No. 23)
), acetic acid 200mj2, hydrochloric acid 100n+42, water 200mj! When the test was carried out under the conditions shown in the right column of the table below, the results shown in the left column of the table below were obtained.

[Example 6] 300 nl of acetic acid, 100 nl of hydrochloric acid, Loom water
A processed product (NO024) and an electroformed product (No. 25) were subjected to the same conditions as No. 21 in Example 5, except that the etching was performed with the exception that the outside gloss was ◎, the inside was not cloudy, and the etching amount was 7. A result of .7μ (0g074) was obtained.

[Example 7] Eighteen gold-silver-copper alloy rings were electrolytically etched in a bath with the same composition conditions as in Example 6 (2 cm 2140 OA).
/dm', 60 seconds) The outer gloss was specular, and there was no inner haze.

As is clear from the above examples, the present invention has the following advantages over conventional baths.

■ Rings, bracelets, etc. can be produced using non-explosion fusible products, such as rings and bracelets, as it is possible to produce mirror-like luster on processed gold or gold alloy products, such as rolled ones, which cannot be obtained with conventional baths.

This electrolytic etching bath is ideal for decorative items such as pendants, brooches, watch sides and frames, and eyeglass frames.

■ Compared to conventional baths, non-exploitable fusible baths are less cloudy even in areas with poor electrolytic conditions where it is difficult for current to flow, so they are suitable for products with complex shapes such as products cast by the lost wax method or electroformed products with thick gold. It can also be electrolytically etched uniformly.

■ Non-exploitable soluble baths have lower bath resistance than conventional baths, so they consume less power and cause less rise in bath temperature.

Therefore, even if the etching bath is produced in large quantities, there is little change in the structure of the water evaporation bath due to temperature rise, resulting in a stable etching bath.

Furthermore, non-exploitable solubles have the following characteristics.

■ For non-exploitable fusible materials, the higher the current density, the better the gloss, but conversely, if the current density is too high, the current density distribution becomes more uneven, and the so-called shadow areas (low current density areas) tend to become cloudy. Therefore, when electrolytically etching ornaments with complex shapes, the current density is not very high.

■ For non-exploitable soluble materials, the longer the etching time, the better the gloss will be, but the longer the etching time, the more likely it will become cloudy in the shadows, as in ■. Therefore, it is necessary to consider the etching time depending on the etching shape.

■ For non-exploitable solubles, when the acetic acid concentration becomes thinner and the bath resistance decreases, the degree of cloudiness in the shaded areas decreases, and when the acetic acid concentration becomes thicker and the bath resistance increases, the gloss improves (Applicant: Tanaka Kikinzoku) Industrial Co., Ltd.

Claims (1)

[Claims] A bath consisting of acetic acid, hydrochloric acid, and water, (a) water: hydrochloric acid: acetic acid = l: 0.1 to 100: 0.
1. An electrolytic etching bath for gold or gold alloy, characterized in that there is a relationship of 1 to 100, and (b) hydrochloric acid:acetic acid=1:1 to 10.