The effect of Zn concentration on the corrosion behavior of Mg–xZn alloys

► The corrosion resistance of Mg–xZn alloys reduces with increasing Zn content. ► The corrosion of Mg–5Zn preferentially initiates from other precipitation phases. ► The MgxZny second phases play a key role in the propagation stage of corrosion. ► The very fine MgxZny second phases dominate the corrosion around the boundaries. The effect of Zn concentration on the corrosion behavior of Mg–xZn alloys is investigated. The microstructure is observed by scanning electron microscopy (SEM). The corrosion resistance is evaluated by electrochemical and immersion tests. The initiation and propagation of corrosion are analyzed based on the electrochemical measurements and corrosion morphologies observation. It is found that the MgxZny second phases are precipitated on the boundaries and their volume fractions rise with increasing Zn concentration. As a result, the corrosion resistance of Mg–xZn alloys reduces with increasing Zn concentration, which is greatly associated with the micro-cathodic effect of the MgxZny second phases.