Effects of Sn on Corrosion Resistance of Rare-Earth-Free Mg-2Zn Alloy

Abstract

Alloys of Magnesium metal have attracted the attention of the automobile industries in the past two decades due to their greater specific strength as well as stiffness. However, increasing the corrosion performance of alloys of magnesium has remained a prime concern in order to attain better performance without using expensive rare-earth elements. In this study, the result of Sn addition (0%, 2%, 4%) to hot rolled binary Mg-2Zn alloy was examined in terms of their corrosion and microstructural properties. To understand microstructural features, optical micrography, and SEM-EDX study were conducted. SEM and EDX analysis confirmed the presence of Sn phase after 2% and 4% addition of Sn. The number of particles increased with the gradual increase in the addition of Sn. However, Sn lowered the melting point of Zn precipitates. Thus, the presence of Zn particles was reduced with the addition of Sn. Electrochemical analyses were conducted in order to study the corrosion performance of the selected alloys by submerging it in NaCl (3.5 wt.%) solution, supported by the SEM micrographs of the corroded surface. It was found that adding tin up to 2% increases corrosion resistance. The addition of 4% Sn, on the other hand, introduced large-size particles of Mg2Sn, leading to local corrosion initiation sites, micro galvanic in nature, and hence, reducing corrosion resistance.