METHOD OF MULTILAYER COMPOSITE COATING MANUFACTURING ON STEEL BY CHEMICAL DEPOSITION Russian patent published in 2015 - IPC C23C18/36 C23C18/32 B32B15/00 

FIELD: metallurgy.

SUBSTANCE: under this method on steel surface a multilayer coating is applied, in it nickel-phosphorous layers are applied as odd layers, and cobalt-phosphorous layers are applied as even layers. Ni-P layers are precipitated from the solution with pH 4.1-4.3 and containing: nickel sulphate 10-30 g/l, sodium hypophosphite 15-25 g/l, sodium acetate 10-20 g/l, thiourea 0.005 g/l, acetic acid 13 ml/l. At that Co-P layers are precipitated from solution with pH 8.0-8.5 and containing in g/l: difluoride cobalt 15-35, sodium hypophosphite 10-22, sodium citrate 80-100, ammonium chloride 30-60. The mentioned layers precipitate at temperature 70-92°C.

EFFECT: method ensures making on the steel surface of multilayer composite coatings out of different quantity of alternating layers with increased corrosion resistance and microhardness.

2 cl, 2 tbl, 1 dwg, 4 ex