METHOD OF ELECTROCHEMICAL OXIDATION OF COATINGS ON VALVE METALS OR ALLOYS Russian patent published in 2020 - IPC C25D11/02 

FIELD: technological processes.

SUBSTANCE: invention relates to electrochemical oxidation of coatings on valve metals or alloys. According to the method, a process layer is formed on the surface of the processed part; the layer thickness provides heat dissipation between the electrolyte and the formed coating and as a result, hot heated spark channels are formed to carry out mass transfer. Lastly, growth of main working layer between part surface and process layer is initiated. At that part is processed in micro-arc oxidation mode. From said mode, thermal separation is immediately achieved, or, while in micro-arc oxidation mode, thickness of process layer is increased and main working layer is formed in parallel. In the second case, growth of the process layer leaves the said mode and ceases to achieve thickness thereof, which leads to termination of occurrence of heated sparkless current channels for mass transfer and domination of the sparkdown mechanism. Output is performed by increasing cathode current. Due to this, the anode, molding voltage drop relative to the maximum voltage value achieved in the micro-arc oxidation mode is provided, to a value which is sufficient to suppress micro-arc oxidisation and at the same time prevents the predominance of etching of the coating over its growth during formation. This leads to increased anode current. Then, avoiding transition to micro-arc oxidation mode, reduction of cathode current is performed and growth of anode voltage is provided. In this mode, the main working layer is formed, increasing its thickness to the required value.

EFFECT: high homogeneity of the coating based on microhardness and corrosion resistance.

4 cl, 2 dwg, 6 ex