The aim of this study was to investigate the corrosion performance of AZ31 alloy in 3.5% sodium chloride water solution.Optical microscopy and X-ray diffraction analysis were performed to examine microstructure of AZ31 alloys before and after hot extrusion. The corrosion behavior of the alloys prepared by as-casting and extrusion were investigated in 3.5%NaCl aqueous solution by immersion and electrochemical tests.The results indicated that the hot extrusion can obviously reduce the grain size of AZ31 alloy.The average grain size of the as-cast alloy was about 111 m,and the average size of the hot extruded alloy was about 9 m.There was no surface passivation at the initial stage during immersion corrosion of the AZ31 alloy in 3.5% sodium chloride water solution. The corrosion potential of the AZ31 alloy at as-cast state was-1.55 V,and increased to-1.52 V at extruded state. When the AZ31 was immersed for 72 h,the average corrosion rates of as-cast and extruded alloys were 4.293 mm/a and 2.957 mm/a,respectively. Hot extrusion can improve the corrosion resistance of AZ31 alloy in 3.5%NaCl solution.%目的：研究铸态和挤压态AZ31镁合金在3.5%NaCl溶液中的腐蚀性能。方法采用光学显微镜和X射线衍射分析了铸态AZ31镁合金挤压前后的显微组织。利用静态浸泡失重实验和电化学实验研究了铸态和挤压态AZ31镁合金在3.5%NaCl溶液中的腐蚀性能。结果热挤压可有效细化AZ31合金的晶粒，铸态试样的平均晶粒大小约为111μm，挤压态试样的平均晶粒大小约为9μm。AZ31镁合金在3.5%NaCl溶液中的腐蚀初期，合金表面没有发生钝化。挤压后合金的自腐蚀电位从铸态的-1.55 V提高到-1.52 V。浸泡72 h后，铸态试样的腐蚀速率为4.293 mm/a，挤压态试样的腐蚀速率为2.957 mm/a。结论挤压提高了AZ31镁合金在3.5%NaCl溶液中的腐蚀性能。
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