Corrosion behaviour of heterogeneous antimony-copper layers in chloride media

The electrodeposited antimony-copper coatings demonstrate a varying degree of chemical and structural heterogeneity that determines their corrosion behaviour in 0.5M sodium chloride. The electrochemical and corrosion properties of layers at open circuit potential were investigated by electrochemical impedance spectroscopy and optical surface observation. Corrosion polarisation tests revealed that anodic behaviour of Sb-Cu alloys is similar for the all tested samples and depends on the antimony chemical resistance. Under anodic polarisation up to about -0.03 V-Ag/AgCl a multistep process of anodic oxide film transformation was registered. The observations by SEM revealed that at a higher anodic polarisation many submicron-sized pits are formed. The formation of microgalvanic corrosion cells results in preferential dissolution of the antimony phase at both OCP and anodic polarisation.