METHOD OF PRODUCING OF BLACK WEAR-RESISTANT ANTI-CORROSION COATING ON ALUMINIUM AND ALUMINIUM BASED ALLOYS BY METHOD OF MICROARC OXYDATION Russian patent published in 2015 - IPC C25D11/06 

FIELD: metallurgy.

SUBSTANCE: method includes microarc oxidation of the part in alkali-silicate electrolyte at alternating current density from 8 to 40 A/dm² of microarc oxidation, wherein to the electrolyte additionally alkali metal ferrocyanide and alkali metal hexametaphosphate are added at the following components content, g/l: alkali 1-4, alkali metal ferrocyanide 5-10; alkali metal hexametaphosphate 2-4, technical liquid glass with content of c_tlg=15/m±0.25, where m is modulus of the , technical liquid glass, wherein after electricity passage through one litre of electrolyte in amount of 7.5-8.5 A·h the alkali metal ferrocyanide is added in amount of c_a, determined from ratio c_a=0.13·c_f, where c_f and c_a are initial and added content of the alkali metal ferrocyanide in the alkali-silicate electrolyte, wherein the process of microarc oxidation continues upon completion of the coating growth, and stop of burning of the microarc discharges during time period τ_d, determined as per the equation: τ_d=6000/(|i|·|t|)±1, min, where |i|, |t| are absolute densities of set alternating current in A/dm² and electrolyte temperature in °C, respectively.

EFFECT: increased coating uniformity through thickness, increased corrosion strength, adhesion, coating hardness and duration of the electrolyte operability upon use of simple unit and high process capacity.

4 cl, 2 ex