Corrosion of Mg–Y alloy was studied using electrochemical evaluations, immersion tests and SEM observations. Corrosion mechanisms of Mg-（0.25 and 2.5） Y alloy and Mg-（5, 8, and 15） Y alloy were uniform corrosion and pitting corrosion respectively, and the content of Mg_（24）Y_5 phases determined its effect acting as cathode to accelerate the corrosion or corrosion barrier to inhibit the corrosion. Corrosion resistance of Mg-（0.25, 2.5, 5, 8, and 15） Y alloys was as follows： Rt（Mg-0.25Y） 〈 Rt（Mg-8Y） 〈 Rt（Mg-15Y） 〈 Rt（Mg-5Y） 〈 Rt（Mg-2.5Y）. Y could significantly improve the corrosion resistance of the Mg-Y alloy, but the excess of Y deteriorated the corrosion resistance of the Mg-Y alloy. The optimum content of Y in the studied alloys was 2.5%.
This paper studied the influence of aging treatment on the corrosion behavior and mechanism of Mg-Y alloys with different Y content through corrosion mass loss test, electrochemical test and corrosion morphologies observation. Results show that the peak-aging times of Mg-（0.25, 2.5, 5, 8 and 15） Y alloys at 250 ℃ were 4, 6, 10, 12 and 16 h. The aging treatment reduced the corrosion resistance of Mg-Y alloys, and the corrosion resistance of Mg-Y alloys became worse with increasing of the aging time. The change magnitude of the open circuit potentials for Mg-（0.25, 2.5）Y alloys was greater than that of Mg-（5, 8 and 15）-Y alloys. The polarization curves of Mg （0.25, 2.5, 5, 8 and 15） Y alloys had the similar shape after aging treatment, and the slopes of the anodic branch were greater than those of the cathodic branches. After aging treatment, the corrosion modes of Mg-0.25Y and Mg-（2.5, 5, 8 and 15） Y alloys were uniform corrosion and pitting corrosion with small local deep corrosion.
The influences of the hot extrusion process on the microstructure, corrosion behavior and corrosion mechanism for Mg-Y magnesium alloy were studied by means of the microstructure observation, weight loss test, electrochemical test and corrosion morphology test. The results showed that with increasing of the extrusion ratio, the shear flow line on the vertical section of the extruded alloy increased, the shear bands parallel lines became more clearly visible, and a large number of fine equiaxed grains distributed in parallel with the flow lines. The open circuit potential had a certain degree of improvement after extrusion, the open circuit potential increased with increment of extrusion ratio, and the corrosion potential of the vertical section was higher than that of the same alloy in the same compression ratio. The shift rate of the corrosion potential relatively became larger with increasing of the extrusion ratio, and the cathode corrosion current corresponding to the branch migration shifted to the positive direction. The high frequency capacitive arc increased with increment of the extrusion ratio, and the radius of capacitive arc of the vertical section was slightly larger than that of the transverse section. The corrosion morphologies of Mg-0.25 Y alloy were uniform corrosion, and the corrosion morphologies of Mg-（2.5, 5, 8 and 15） were the pitting corrosion and the small range, deep depth localized corrosion.
