镁合金阳极氧化膜在NaCl溶液中的腐蚀行为

利用盐水浸泡实验研究了AZ91D镁合金阳极氧化膜层在3．5％NaCl溶液中的腐蚀行为。结果表明：AZ91D镁合金阳极氧化膜层不论封闭与否,在中性NaCl溶液中浸泡出现第一个腐蚀点后,膜层表面均很少再出现新的腐蚀点,而是原有的腐蚀点向纵、横两个方向扩展形成腐蚀坑,表面呈“树枝”状腐蚀形貌;浸泡溶液的pH值对阳极氧化膜层的耐蚀性影响很大,酸性溶液中的腐蚀速率明显大于中、碱性溶液的;随浸泡溶液温度的升高阳极氧化膜层的腐蚀速率加快。据此,提出了AZ91D镁合金阳极氧化膜层在NaCl溶液中腐蚀过程的模型。

CORROSION BEHAVIOR OF ANODIC FILM ON MAGNESIUM ALLOY IN NaCl SOLUTION

The corrosion behavior of anodic film on the AZ91D magnesium alloy in 3.5% NaCl aqueous solution was investigated by the saline immersion test.The results show that new corrosion points seldom occur on the surface of the said anodic film over the immersion time in 3.5% NaCl neutral aqueous solution after the first macroscopic corrosion point appeared on the anodic film whether it was sealed or not,while the previous corrosion point extends vertically and horizontally and turns into a corrosion pit which is in form of "dendrite". The pH value and temperature of the test solution affect substantially on the corrosion resistance of the anodic film. The corrosion rate in acidic solution is obviously faster than that in neutral or alkaline solutions, and the corrosion rate increases with increasing of the immersion solution temperature.A possible model about the corrosion process of the anodic film on the AZ91D magnesium alloy is therefore proposed based on the above experimental results.