Effect of tin addition on the electrochemical behavior of pure aluminum

Abstract

The surface analyses and the anodic polarization measurements on Al-0.01%Sn alloys heated at 823K for 6h have been carried out to investigate the relations between the electrochemical properties and the morphology of Sn at the surface layer. After the heating the fine Sn particles were uniformly distributed at the metal-oxide film interface. The rapid current increase was observed at two different potentials in the polarization curves on the alloys. They are attributed to the formation of two different potential layer due to the segregation of Sn at the surface, that is, the potential of surface layer is less noble that of inner one because of more amount of solid solution Sn in the former. On the other hand, the densely distributed finer shallow pits occured in the anodic dissolution at lower current density, the distribution of which approximately corresponded with that of precipitated Sn particles.