METHOD OF ELECTROCHEMICAL CHROME PLATING OF METALS AND THEIR ALLOYS Russian patent published in 1999 - IPC

FIELD: electroplating. SUBSTANCE: chrome plating is carried out at current density 3 to 300 A/sq.dm and pH 7.1 to 12 in electrolyte containing, mol/l: chromium(III) compound 0.3-1.0 (on conversion to metal), dicarboxylic acid 0.6-3.0, ammonium salt 0.6-4.0 (on conversion to ammonia), surfactant 0.05-1.0 g/l, and, additionally, buffer additive up to 0.7. Molar ratio of chromium(III), dicarboxylic acid, and ammonia is equal to 1:(2-3):(2-4). Chrome plating of profiled objects of copper and its alloys, nickel and steel, including those with copper and nickel coatings is carried out at pH 7-11. Chrome plating of aluminum, zinc, and their alloys is carried out at pH 6-8. Method expands process possibilities for chrome plating of various-metal and -alloy parts having different degree of complexity from the same electrolyte giving bright coatings with bluish shade. Electrolyte is distinguished by high coating capacity. Wide current density range allows screw threads M5 and M8, obtuse, right, and acute angles up to 50 deg. to be coated. Quality of coating on anode-facing ribs is similar to that of coating on surface parallel to anode. . EFFECT: expanded process possibilities. 2 ex