Effect of Cerium Chloride on Corrosion Resistance of Chromate Conversion Coatings on Aluminum Alloy 6061

The corrosion resistance of the chromate conversion coatings (CCCs) formed on AA6061 in chromate solutions with cerium chloride (0~60 mg/L) as additive was investigated by electrochemical measurement technology. The results of potentiodynamic polarization curves showed that the values of the pitting corrosion potential (Epit) and corrosion potential (Ecorr) of the CCCs raised greatly by adding a small amount of CeCl3 (20~40 mg/L). The electrochemical impedance spectroscopy (EIS) showed that the values of normalized Rp also greatly increased. The two tests indicate that an appropriate amount of CeCl3(20~40 mg/L) can improve effectively the corrosion resistance of the CCCs, whereas an excessive CeCl3 (e.g 60 mg/L) may deteriorate the property of the CCCs.