SU945252A1 - Composition for chrome-plating cadmium electroplated surfaces - Google Patents

Description

one

The invention relates to the final processing (finishing) of mechanical products, in particular, to solutions for applying a chromate coating on brilliant cadmium electroplating.

Solutions for the chemical formation of cadmium surfaces based on hexavalent chromium compounds, sulfates and acetates lj and z are known.

However, to obtain a colorless decorative coating using these solutions, subsequent surface treatment is necessary either with an alkali solution or applying a colorless enamel.

A known solution for forming a transparent chromate film on cadmium, containing a hexavalent chromium compound, sodium sulfate and nitrate, and cetate (or borate) Cz1.

The disadvantage of this solution is the inability to obtain a uniform transparent chromate film.

when chroming brilliant cadmium electroplating, since brilliant cadmium electroplating is obtained from electrolytes containing organic brighteners, and are active due to the incorporation of carbon into their composition.

The aim of the invention is to create a solution for chromatizing the brilliance of Q and t of cadmium coatings to produce a colorless chromate film that preserves their decorative appearance and is highly corrosion resistant. J5 Set goal achieved

the fact that in a solution containing hexavalent chromium compounds, sulphate and sodium nitrate, 1/3 of the main chromium bichromate is additionally introduced at 20 with the following ratio of components, g / l: Chromic anhydride in terms of Cr (VI)

Sodium sulfate

8 terms

on, 7-12

Sodium nitrate

in terms of

on, 5-20

1/3 primary

chromium dichromate 0.5-10

1/3 of the main chromium dichromate ZH-jO is well dissolved in water.

452524

The chromate solution is prepared by simply mixing the components. Temperature TV-ZO С, pH О, 4-1.3 Time of surface treatment 10-60 s. 5 According to the invention, articles having a shiny cadmium coating are immersed in a chromate solution for a certain time, then washed with water and dried. Then the processing of products with a brilliant cadmium coating is performed.

The results are shown in Table. one.

Table 1

Compound Cr (VI)

Sodium sulfate

Sodium nitrate

Sodium Acetic Nitric Acid

1/3 of the main chromium bichromate In solutions 2-4, the concentration is indicated in terms of Cr (VI), SO / G N0, respectively. o In a solution of composition 1 cadmium, the surface is covered with an uneven dull chromate film. In solutions 2-k on a shiny cadmium surface, a colorless chromate film is obtained, which does not change the decorative appearance of the treated cadmium surface. The results of testing the corrosion resistance of the films are given in Table. 2 Table 2 Composition of the solution Indicators Time to the appearance of the first signs of corrosion Kad3, 0 10.0 8.0 9, mi, days

5 0.7

10 12 20 0.5

ten

Claims (1)

0.5 The use of the solution according to the invention makes it possible to carry out a cheap finishing protective and decorative finish of brilliant cadmium electroplating on articles of the automotive and radio electronic industry. Claim solution for chromate cadmium electroplating containing hexavalent chromium compound, sulfate and sodium nitrate, characterized in that, in order to obtain on brilliant cadmium electroplating, colorless chromate film that retains their decorative appearance and has high corrosion resistance additionally introduced 1/3 of the main chromium bichromate in the following ratio of components, g / l: Chromic anhydride in terms of Cr (VI) 5 Sodium sulfate in terms of S040.7-12 Sodium nitrate in terms of on N0 {0,5-20 1/3 basic dichromate hroma0,5-10 9 52526 Sources of information received note in the examination № 1. U.S. Patent 2,376,158, cl. 1 8-621, publ. 52. US patent No. 2796372, cl. 1 8-621, publ. 1957. 3. US Patent No. 3121032,, cl. 1TS8-6.2, pub. 196A (prototype).