Influence of Sr and Zn additions on corrosion behaviour of Mg–6Sn–5Al–2Si alloys

Abstract In the present work, the effect of Sr and Zn additions on the corrosion behaviour of Mg–6Sn–5Al–2Si (TAS652) alloys was investigated. Microstructure, potentiodynamic polarisation, electrochemical impedance and immersion tests were carried out in 3˙5% NaCl solution to estimate the corrosion behaviour of TAS652 alloys. The TAS652, TAS652–Sr and TAS652–Zn alloys were fabricated by permanent mould casting. The addition of Sr was found to be efficient to modify and refine the microstructure of the TAS652 alloy. A morphology change in Mg2Si particles from Chinese script shape to a polygonal type was observed. Such modified microstructure resulted in significant improvement of the corrosion properties as compared to the TAS652 base alloy. On the other hand, Zn addition caused to slightly increase the volume fraction of Mg17Al12 phases. Since they are cathodic with the matrix, the galvanic corrosion was activated by Zn addition. The addition of small amount Sr was effective to the corrosion resistance of...