强流脉冲离子束辐照镁合金微弧氧化膜的耐腐蚀性能

采用强流脉冲离子束在束流密度为200 A/cm2、辐照次数为1~10次条件下对AZ31镁合金微弧氧化膜进行辐照改性处理。采用扫描电子显微镜对氧化膜的表面及截面形貌进行表征;在Princeton Applied Research(PAR)2273型电化学工作站测量氧化膜的极化曲线。结果表明:在束流密度200 A/cm2、5次辐照条件下氧化膜表面获得连续、致密的改性层;以3.5%NaCl溶液为腐蚀液,氧化膜表面发生的腐蚀过程由辐照前的活化溶解向辐照后的钝化-孔蚀击穿转变;在束流密度200 A/cm2、5次辐照条件下击穿电位提高到最大值-800 mV(vs SCE)。强流脉冲离子束辐照产生的连续致密改性层是氧化膜耐蚀性改善的主要原因。

Anti-corrosion properties of micro-arc oxidation films on AZ31 magnesium alloy irradiated by high-intensity pulsed ion beam

The microarc oxidation(MAO) films on the AZ31 magnesium alloy were modified by high-intensity pulsed ion beam(HIPIB) at an ion current density of 200 A/cm2 with 1-10 shots.The surface and cross-section morphologies of the MAO films were characterized by scanning electron microscopy(SEM).The polarization curves of the MAO films were measured by Princeton Applied Research 2273.The results show that a continuous and compact sealing layer forms on the MAO films by HIPIB with 5 shots.The polarization curves in 3.5% NaCl solution show that the corrosion behaviors of the MAO films transit from active dissolution of original films to pitting-breakdown of irradiated,and the breakdown potential achieves to -800 mV(vs SCE) at ion current density of 200 A/cm2 with 5 shots.The noticeable improvement in the corrosion properties of MAO films is attributed to the blocking effect of the sealing layer that hinders the process of electrolyte penetrating the MAO films to the magnesium alloy.