RU2205901C1 - Method of electrodeposition of zinc - Google Patents

Abstract

FIELD: electroplating; electrochemical deposition of zinc; corrosion protection of parts. SUBSTANCE: proposed method consists in deposition of zinc in electrolyte containing zinc sulfate, aluminum sulfate and sodium sulfate. Besides that, butynediol 1,4 (35-%) is introduced into electrolyte for obtaining smooth bright surface at the following relationship of components, g/l: zinc sulfate, 200-250; aluminum sulfate, 20-30; sodium sulfate, 50-100; butynediol 1,4 (35-%), 30-40; electroplating is performed at pH equal to 3-4 and temperature of 15-30 C, cathode current density of 1-6 A/sq dm at current efficiency of 93-98% at continuous mixing of electrolyte. EFFECT: enhanced efficiency. 1 tbl

Description

The invention relates to electroplating, in particular to electrochemical deposition of zinc, and can be used in various industries for coating parts in order to protect them from corrosion. For the electrodeposition of zinc, a large number of electrolytes is known [1]. To cover parts of a simple configuration, acid galvanizing electrolytes are usually used. Of acidic electrolytes, sulfate electrolytes containing various organic substances are quite widely used [1]. Closest to the invention is a zinc sulfate electrolyte of the following composition [1], g / l:
Zinc Sulfate - 200-250
Aluminum Sulphate - 20-30
Sodium Sulfate - 50-100
Dextrin - 8-10
pH - 3.6-4.4
Deposition mode:
Temperature, ^o С - 15-30
Cathode current density, A / dm ² - 1-4
Current efficiency,% - 95-98
The disadvantages of this electrolyte are:
1. Since dextrin is produced in the industry with an uneven, indefinite composition, therefore, in order to avoid electrolyte damage, it is necessary to check the suitability of dextrin in a small laboratory bath.

 2. Matte coatings are obtained.

 3. The electrolyte does not have a leveling ability.

 4. With prolonged standing of the bath without current, flocculent clots (fungi) form on the surface of the electrolyte. In this case, the precipitation is dark, rough. To obtain high-quality coatings in this case, it is necessary to study the electrolyte.

 5. Requires prior study.

 The objective of the invention is the development of a stable galvanizing electrolyte, which would allow to obtain shiny coatings with a level surface without prior study.

The problem is achieved in that in the galvanizing electrolyte containing zinc sulfate, aluminum sulfate, sodium sulfate, butynediol 1.4 (35% solution) is introduced in the following ratio of components, g / l:
Zinc Sulfate - 200 - 250
Aluminum Sulphate - 20-30
Sodium Sulfate - 50-100
Butindiol 1.4 (35% solution), ml / l - 30-40
pH 3-4
Temperature, ^o С - 15-30
Cathode current density, A / dm ² - 1-6
Current efficiency,% - 93-98
The process is carried out with stirring of the electrolyte.

 Aluminum sulfate is a buffering agent to maintain pH (pH 3-4).

 At pH <3, brilliant coatings with a low current efficiency are obtained. At pH> 4, silver coatings are obtained, the electrolyte is unstable. Sodium sulfate is introduced into the electrolyte to increase electrical conductivity. Butindiol 1.4 is a brightening and leveling additive. Its concentration in the electrolyte should vary between 30-40 ml / l. Deviation from these limits results in silvery coatings.

 As anodes, zinc of the grade Ts0 or C1 is used. To avoid contamination of the electrolyte with anode sludge, zinc anodes should be enclosed in covers made of polypropylene fabric. Correction of the electrolyte for zinc sulfate, aluminum sulfate, sodium sulfate, butinediol 1.4 is carried out according to chemical analysis.

Prepare the electrolyte as follows. The required amount of zinc sulfate, aluminum sulfate, sodium sulfate is dissolved in distilled water in separate containers at a temperature of 60 ^o C. The prepared solutions are poured through a filter into a working bath. After that, butynediol 1.4 (35% solution) is added to the electrolyte, topped up with distilled water to a predetermined level, and the electrolyte is mixed. Check the pH value, adjusting it with a 2-3% solution of sulfuric acid or caustic soda.

 The table shows the proposed (1-3) and known (4-5) electrolyte compositions and the conditions of electrodeposition of zinc coatings.

 As can be seen from the table, the proposed electrolyte (1-3) allows you to get shiny coatings. The electrolyte is stable in operation, has a leveling ability and does not require prior study. The resulting shiny coatings of the proposed electrolyte have a beautiful decorative appearance, a fine crystalline structure, are firmly bonded to the base metal.

Sources of information
1. Electroplating. Ref. ed. Azhogin F.F., Belenky M.A., Gall I.E. et al. M.: Metallurgy, 1987, 736 p.

 2. Kruglikov S.S. Surface leveling during electrodeposition of metals. Results of science and technology. Series Chemistry. Electrochemistry. VINITI Publishing House. 1965, p. 117-147.

Claims (1)

The method of electrodeposition of zinc in an electrolyte containing zinc sulfate, aluminum sulfate, sodium sulfate, characterized in that to produce a stable galvanizing electrolyte, which allows to obtain shiny coatings with a level surface without prior study, butynediol 1.4 (35%) is introduced into the electrolyte in the following ratio of components, g / l:
Zinc Sulfate - 200-250
Aluminum Sulphate - 20-30
Sodium Sulfate - 50-100
Butindiol 1.4 (35%), ml / l - 30-40
while electrodeposition is carried out at
pH 3-4
Temperature, ^o С - 15-30
Cathodic current density, A / dm ² - 1-6
With current output,% - 93-98
while stirring the electrolyte.

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