ELECTROLYTE FOR DEPOSITING BLACK CHROMIUM COATINGS Russian patent published in 1997 - IPC

FIELD: electrodeposition of protective coatings. SUBSTANCE: deposition of coatings is performed from electrolyte containing, g/l: chromium(VI) oxide, 300-600; sodium tetraborate, 20-50; sodium nitrate, 2-4; potassium silicofluoride, 0.4-1.5; and saturated monatomic alcohol, 0.5-1.5. Deposition is carried out with current density 20-150 A/sq.dm at 15-40 C, deposition velocity being 20-25 mcm/h. Electrolyte enables formation of high-quality black chromium coatings with absorption coefficient higher than 98% and microhardness more than 630 kg/sq.mm. Coatings are highly porous and exhibit elevated corrosion resistance. Electrolyte does not lose activity after passing quantity of electricity equal to 1600 A-h/l. EFFECT: improved quality of coatings. 2 tbl