Anodes for a trivalent chromium electroplating bath

Electrochemical behavior of different anode materials in electrolytes containing trivalent chromium salts was investigated. Some of electrodes (Ti/MnO 2 , platinized titanium, materials based on Ebonex ® ) were shown to be n-type semiconductors. Semiconducting properties of electrodes affects their electrochemical behavior.It was shown that choice of an appropriate anode for a trivalent chromium electroplating bath should be based on compromise between its selectivity and service life. It was found that current efficiency of Сr(VI)-species strongly depends on the nature of anode material. Dimensionally stable anode based on mixture of titanium oxides and ruthenium oxides, PbO 2 , Ti/MnO 2 anodes are characterized by low rates of Cr(VI)-species generation. Nevertheless these materials are not stable in the electrolyte media that limits their application for hard chromium electrodeposition. Composite materials based on platinized titanium or platinized Ebonex ® are recommend as anodes for carbamide-containing electrolytes since they characterized by good service life and admissible values of current efficiency of Сr(VI)-species.