SU1161599A1 - Electrolyte and method for nickel-plating of articles of zink alloys - Google Patents

Description

The invention relates to the deposition of electroplated coatings, in particular nickel, from zinc alloys.

It is known that the conditions for coating products from zinc alloys differ significantly from the conditions for coating iron, steel, copper and other products, mainly because of the very negative potential and the high chemical activity of zinc [Ί. Zinc reacts with both acidic and alkaline electrolytes and displaces heavy metals from solutions of their simple salts. The yoke feature is aggravated by the fact that zinc casting is usually porous; the electrolyte is retained in the pores, which then reacts with the base metal, and the reaction products cause peeling of the coating.

It is known to apply a nickel coating directly on a zinc alloy substrate from an electrolyte based on the complex compound c. organic ligand [2 1

However, the electrolyte used is unstable, the accumulating products of oxidation and reduction of the organic acid make nickel coatings friable, porous, prone to flaking from the base metal. After passing through the electrolyte the specific amount of electricity 100-110 A h / l, it is necessary to replace the newly prepared electrolyte.

A known electrolyte for nickel plating of zinc castings containing nickel sulphate, sodium sulphate, ammonium chloride and boric acid [3 1..

A known method of nickel plating of zinc surfaces, including the loading of parts and deposition of the coating at a current density of 1.3-3.9 A / dm ² , electrolyte temperature of 21-27 ° C and pH 5.3-5 ,? [3].

A disadvantage of the known electrolyte and method of nickel plating is that dark uneven porous precipitates are obtained with low adhesion.

The purpose of the invention - preparation of a porous ^one infinite uniform coating with high adhesion at zinc alloys directly nickel-plating.

2

The specified goal is achieved

the fact that the electrolyte nickel plating gray gray nickel, gray ammonium chloride, sodium and boric acid, in addition molybdate prices sodium at the following ratio sulfate components, g nickel Sulphate 80-90 sodium Chloride 140-150 ammonium boric ^! 12-14 acid 12-1.4 Molybdenum sour sodium 0.05-0.1 When nickel plating products from pin

horse alloys from the electrolyte of this composition according to the proposed method, the loading of parts and the first 50-60 seconds of electrolysis is carried out at a current density of 15-20. A / dm ² , <3 precipitation - p.ri '2-4 A / dm ² , the process temperature is maintained at 60-70 ° C.

The introduction of molybdate sodium into the electrolyte together with the use of high current densities (“current push”) during nickel plating provides unorbed even coatings with high adhesion up to 60 microns thick, not containing molybdenum in its composition. The electrolyte used is stable in work ·, correction is necessary after passing the amount of 230-250 Ah / l.

Examples of obtaining coatings for the proposed method of the proposed electrolyte are given in tab.p.1 (the electrolyte composition and modes of the coating deposition process), in table. 2 -. the characteristics of the coatings and electrolyte obtained (for comparison, examples of nickel plating of zinc alloys from a known electrolyte (example 5) are given, as well as using a “current push” (example 6) and sodium molybdate acid additives (example 7) separately in the known method.

Preparation of the surface of the parts before nickel plating is carried out by methods generally accepted for zinc alloys.

Coating strength of coating with 0С7

‘Determine the methods of polishing, heating, applying the grid

scratching and bending, porosity coating

1 161599

paste method (GOST 9.302-79); electrolyte dissipative capacity - according to the Field method; the corrosion resistance of the coating is determined after aging n 3% solution of sodium chloride over. 20 days of the largest frequency indicator (GOST 9.012-73).

When nickel plating of the proposed composition of the electrolyte according to the proposed method, the current efficiency of 80-90%.

The test results show that only a combination of the introduction of an additive of molybdenum sodium, "current shock" and an elevated deposition temperature provides a non-porous, uniform nickel coating with. high adhesion

and corrosion resistance on zinc alloy parts.

Obtained by the proposed method and from the proposed electrolyte coating can be used as a sublayer in a three-layer coating Nickel - brilliant nickel - chrome

Example

Table 1

The composition of the electrolyte (g / l) and mode deposition one • 2 3 four five 6 7 Sulfate nickel 80 80 90 90 75 . ⁷⁵ 80 Sodium Sulphate 140 140 150 150 75 112.5 150 Ammonium chloride 12 12 14 14 15 15 12 Boric acid 12 12 14 14 15 ' 15 12 Molybdate sodium 0.05 0.05 ABOUT,! 0.1 - - 0.08 Current density, A / dm ² 15 15 20 20 KZ 15 s ^ o ("Push current" 2 four 2 four 1,3 1,3 h ° ^ν Primary ' pH 5.0 5.7 5.8 5.6 5.3 5.5 5.5 Temperature, ° С 65 65 65 65 21. 21 60

Ta blitz 2 Examples of electrolyte Scattering ability electrolyte, % Adhesion strength, kg / mm ² Coating thickness, micron The porosity of the coating, the number of pores per 1 DM ² Corrosion resistance of coating,% one 2 3 + Have s 3 four 25 15 0.5 18 one 59 21.9 21 There is no 12

42

" I161599 6 Continued table. 2 one 2 R four five one 60 7 3 four 24 15 0.6 ^nineteen 2 59 18,8 ²¹ There is no 14 42 6 60 - ⁿ - 6 3 ¹ , 5 21 9 0.2 17 3 60 22.0 15 There is no eleven thirty ——  five _h 60 four 3 1.8 ²² 9 .0,4 18 four 60 18.9 15 There is no ten thirty - ⁿ - five 60 _ "_ · four five 42 Does not meet the requirements of GOST 22 38 3 25 40 6 43 8.2 9 20 36 15. 18 32 * h 7 50 1G, 2 15 32

0

Coatings are prone to flaking.

Claims (1)

1. The electrolyte nickel plating products from zinc alloys, containing nickel sulphate, sodium sulphate, ammonium chloride and boron acid, about one hundred percent, with the aim of semi2. Nickel plating of products from zinc alloys from electrolyte , including the loading of parts and electrolytic deposition of the metal, which is the fact that the loading of parts and the first 50-60 seconds of electrolysis is carried out at a current density of 15-20 A / dm ² , and deposition - at 2-4 A / dm ² , the process temperature is maintained at 60-70 ° C. (L with cn with with 1161599