Microstructure and Corrosion Properties of Mg-xSn-5Al-1Zn (x=0, 1, 5 and 9 mass%) Alloys

Abstract

In the present work, the corrosion properties of Mg-xSn-5Al-1Zn (x=0, 1, 5 and 9 mass%) alloys have been investigated. Potentiodynamic polarization and immersion tests were carried out in 3.5% NaCl solution of pH 7.2 at room temperature to measure the corrosion properties of Mg-xSn-5Al-1Zn (x=0, 1, 5, and 9 mass%) alloys. Microstrucral analysis shows the Mg₁₇Al₁₂ and Mg₂Sn phase were mainly precipitated along grain boundaries. With increase of the Sn contents, the volume fraction of the secondary phases, i.e. Mg₁₇Al₁₂ and Mg₂Sn phase, was increased. The corrosion resistance of Mg-xSn-5Al-1Zn alloys was improved by the Sn addition. Especially, the AZ51-5 mass%Sn alloy characterized the superior corrosion resistance in the studied alloys. It seems that the presence of Sn stabilized the Mg(OH)₂ layers on the surface of Mg alloys and the secondary phases effectively formed semi-continuous structures, resulting in a drastic improvement of corrosion resistance of the Mg alloys.