Modeling, optimization, and comparative analysis of trivalent chromium electrodeposition from aqueous glycine and formic acid baths

Trivalent chromium electrodeposition has been studied as an alternative to hazardous hexavalent chromium electroplating. Although limited by inability to deposit thick coatings with acceptable quality, it is useful for decorative chromium electroplating. In the present work, we illustrate the application of statistical design of experiments (DOE) in empirical modeling and optimization of electrodeposition of trivalent chromium from baths of chromium complexed with glycine. DOE shows that variations in current efficiency with glycine and chromium chloride concentrations can be explained by a quadratic model. The composition of the bath was optimized with respect to current efficiency to obtain faster deposition. We compare the effects of process parameters (pH, temperature, current density, and pulsed current) on current efficiency and deposit characteristics for both glycine and formic acid-containing baths. Experiments reveal that whether pulsed current increases or decreases current efficiency is determined by how current density influences current efficiency, and the range of lower and upper current density levels. (c) 2005 The Electrochemical Society. All rights reserved.