Current efficiency and crystallization mechanism in pulse plating of hard chromium

The current efficiency of chromium deposition was investigated under conditions of periodic current reversal. It has been demonstrated that the relationship between the anodic and the cathodic charges, Q_a/Q_c, has a strong influence on the current efficiency and the structure of the deposit. A plausible model for the crystallization mechanism during periodic current reversal has been suggested. According to the model, an advantageous chromium structure is maintained during the deposition process because interstitial hydrogen in the chromium lattice is oxidized during the anodic period.Notation F Faraday constant - i _a anodic current density - i _c cathodic current density - m _a mass of dissolved chromium - m _c mass of deposited chromium - M molecular weight of chromium - Q_a anodic charge - Q_c cathodic charge - T cycle time (T _c + T _a) - T _a anodic pulse duration - T _c cathodic pulse duration Greek symbols current efficiency - _a current efficiency of chromium disolution in anodic period - _c current efficiency of chromium deposition in cathodic period - _max maximum current efficiency