Enhanced corrosion resistance of Mg-Sn-Zn-Al alloy by Y microalloying

A significant enhancement in corrosion resistance by Y microalloying was achieved for the Mg-8Sn-1Zn-1Al (wt %) alloy in the extruded condition. Average corrosion rates obtained by immersion tests in 0.6 M NaCI solution at 25 degrees C were 42 and 12.7 mm y(-1) for the alloys with and without microalloying with 0.04 wt%Y, respectively. Microstructural investigations indicated that the enhanced corrosion resistance is a result of a transition in a type of second-phase particles toward lowering the difference in electrochemical nobility between the alpha-Mg and these particles, thereby reducing the susceptibility of the alloy to microgalvanic corrosion. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.