Electroplating of copper onto a preanodized 7005Al/Al₂O _3(p) metal matrix composite

The electroplating of copper onto 7005Al/Al₂O_3(P) metal matrix composites (Al MMC) is difficult but becomes feasible if the composites have been preanodized in mineral acids. It is clear that phosphoric (P) acid anodizing is better than oxalic (O) or sulfuric (S) acid anodizing when the morphology of the copper coating and its adhesion to the MMC substrate are considered. Electrochemical studies, such as cyclic anodic potentiodynamic polarization (CAPP), cyclic cathodic potentiodynamic polarization (CCPP) and electrochemical impedance spectroscopy (EIS) are beneficial in delineating the influence of the anodizing pretreatment on the subsequent copper electroplating process. A positive hysteresis of the CAPP curve in phosphoric acid indicates the effective removal of oxide film from the composite. After examining the CCPP curves for the Cu-electroplating bath, for MMC pretreated in various acids, we can understand the morphological differences in the copper coatings and variations in adhesion to the anodized composite. EIS measurements confirm the d.c.-polarization results.