THE PROCESS FOR ELECTRODEPOSITING OF BLACK CHROMIUM COATINGS

摘要

The present invention relates to chemical industry, in particular to production coatings from electrolytes. An object of the invention is the process for electrodepositing, namely an intense black coating electrodepositing method on a steel, nickel, copper and alloys of these. The method may be used for forming solar collectors selective layers and a variety of industrial products or protection parts from corrosion and improvement of appearance (decorativeness). Parts from steel, copper, brass or nickel-plated parts immersed in the electrolyte containing trivalent chromium Cr (III) ions, chloride ions, nitrate ions, boric acid, amino-acetic acid or its salts is added to the electrolyte. Additionally inorganic zinc compound is added and electrolysis carried out using a cathodic current pulses in the range of 20 to 40 A / dm2, where cathodic pulse duration is 0.5 to 2.5 with 10-20 minutes of breaks. Electrolysis is carried out in cycles, starting with the right size of the cathodic current impulse, and after a brief pause, charged a second cathodic impulse. The number of impulses can be between 2 and 6, depending on the desired coating thickness.