Electrochemical Behavior of Al-5%Zn-0.1%Sn Sacrificial Anode in Aggressive Media: Influence of Its Alloying Elements and the Solidification Structure

The tin and zinc effect on the aluminum activation process produced in the Al-5%Zn-0.1 %Sn alloy in aggressive media was analyzed. Potentiostatic, galvanostatic, and potentiodynamic polarizations, electron microscopic observations, and energy-dispersive x-ray (EDX) analysis were used to analyze the generated attack. The chloride ion influence in this process was studied. Depending on casting conditions and heat treatment, enriched Zn-Sn zones tend to form in determined sites (i.e., interdendritic or grain-boundary zones). These zones control the activation potential, the attack initiation and propagation sites, and the anode efficiency.