Effect of tin modification on corrosion of AM70 magnesium alloy

In this study, AM70 magnesium alloys with and without 2 wt.% Sn addition are compared for their corrosion performance. They are found to have similar corrosion rates in the first 70 h in 5 wt.% NaCl solution, but in extended immersion test the Sn modified AM70 exhibits accelerated overall corrosion. Nevertheless, Sn modification significantly decreases the susceptibility of the alloy to localized corrosion attack. Polarization curve measurements further indicate that the Sn modified AM70 is likely to have worse galvanic corrosion than AM70 in terms of the loss of metal, but again the Sn modification makes the galvanic corrosion less localized, which is an improvement aspect of the galvanic corrosion performance. The effect of Sn addition on the corrosion behavior appears to be associated with the presence of Sn-containing particles and the solute Sn in the matrix phase, which may change the electrochemical anodic and cathodic polarization behavior of the alloy.