SU571528A1 - Electrolyte for depositing zinc-based alloys - Google Patents

Description

one

The invention relates to the field of electroplating, in particular, to electrochemical deposition of alloys of zinc nickel-phosphorus for the restoration of worn-out parts operating under conditions of dynamic alternating loads.

An electrolyte is known for precipitating zinc-containing alloys, for example, nickel-zinc, including zinc sulphate, nickel chloride, acetic acid, or its co.hb fl.

However, such an electrolyte; it cannot be used to produce; of coatings intended for the restoration of worn-out machine parts due to the low thickness of the quality layer of the coating (10-15 µm), while that of the parts being repaired is mostly in the range of 0.25-0.30 mm. In addition, the electrolyte is intended only for coatings used to lock metal metals from corrosion, without taking into account the requirements for coatings applied to worn parts.

The closest to the invention in technical essence and the achieved result is an electrolyte for the deposition of zinc-based alloys, for example, zinc-nickel, containing sulfuric zinc, double nickel-ammonium salt and a buffer additive, for example aluminum sulphate 2.

Coatings derived from such an electrolyte are used to restore the worn surfaces of the mounting holes of the gearbox housing.

However, these coatings have insufficient wear resistance (seizure and adhesion of the coating to the pipe with the surface occurs) and microhardness (120-160 kg / mm). The internal stress of the coating is 100-250 kg / cm.

In order to increase the wear resistance of the coating due to the production of zinc-nickel-phosphorus alloy, the proposed electrolyte additionally contains hypophosphite, sodium, and, as a buffer additive, sodium acetate with the following ratio; srsh1onentov, g / l: CHs sulfate: K230-270

Double ammonium salt nickel 30-50

Hypophosphite sodium 2.5-5.5

Sodium acetate 20-30

The deposition process is recommended to be carried out at a temperature of 18-45 ° C, a cathode current density of 8-12 A / dm and a pH of electrolyte 2; t) -3.5. The incorporation of phosphorus into the zinc nickel coating increases the physicomechanical duplications as a result of the formation of solid phosphorus-nickel compounds in the alloy. These particles, which possess high physicomechanical properties, protrude from meta when rubbed: the metallic matrix and are subjected to the strongest loading. As a result, they prevent adhesion and setting, and also contribute to better lubrication of the rubbing surfaces during their friction, which significantly increases the wear resistance of the zinc-nickel-phosphorus coating compared to the zinc-nickel coating. In addition, the formation of solid compounds of zinc with nickel contributes to an increase in the wear resistance of this coating. In the zinc – nickel – phosphorus coating obtained from the proposed electrolyte composition and electrolysis modes; There is no internal stress, which is the main source of reducing the fatigue strength of the machine parts to be restored. The coating has a good adhesion to the substrate, (steel 40X), since the separation of the coating occurs over the coating itself. The adhesion strength of the coating to the substrate is 700-735 kg / cm. Fatigue limit -33 9 kg / mm .H. Three electrolyte compositions {N 1.2, ZU were prepared for preparation, each of which contains, g / l: zinc sulphate - 250, sulphate; iQ: nickel-ammonium - 40. VKcysit & KHCflorq sodium - 25, differing from each other the content of sodium hypophosphite, equal in each composition in series, g / l: 2.5; 4.0; 5.5. An alloy of each electrolyte composition was obtained separately in an electrolytic bath at acidity pHs 3.0, cathode current density 12 A / dm and temperature 38 ° С. The data on wear resistance and microhardness of the obtained alloys are presented in the table.