Effects of Mn on Corrosion Resistant Property of AZ91 Alloys

The effect of Mn on the corrosion resistant property of heat-treated AZ91 alloys was investigated by electrochemical, static mass loss tests and salt spray corrosion method. The micromorphologies of the corroded samples of the alloys were studied by scanning electron microscope (SEM), and the phase composition and the corrosion products of the alloys were analyzed by X-ray diffractometer (XRD). Results demonstrate that an independent phase Al6Mn is formed in AZ91 alloy. The solubility of the phase in solid solution of Mg can increase the electrode potential of Mg. Mn addition can increase the corrosion potential, decrease the corrosion current density of AZ91 alloys and reduce corrosion rates. Therefore, the corrosion resistance of alloys is improved. AZ91-0.8Mn alloy shows the best corrosion resistance capacity among all of the specimens among all of the specimens.