Oxidation behavior of trivalent chromium ions on boron-doped diamond electrodes

Boron-doped diamond (BDD) films (boron content: 17,000 ppm) were grown by hot-filament chemical vapor deposition. To investigate whether BDD films are suitable anode materials in the chromium electroplating process, the oxidation behavior from Cr3+ to Cr6+ was investigated on a BDD electrode. The current efficiency of the BDD electrode for Cr3+ oxidation was similar to that of lead alloy anode, the conventional anode in chromium electroplating processes. In strong acid solution (pH = −0.39), Cr3+ ions were readily oxidized on the BDD and lead alloy electrodes but were not oxidized on platinum and iridium oxide electrodes. Furthermore, during electrolysis for 50 h using the BDD anode in a hexavalent chromium electroplating bath, the Cr3+ ion concentration was maintained below 1.5 g/L. According to these results, the BDD anode is a feasible alternative to lead alloy in hexavalent chromium electroplating.