阳极氧化AZ91D镁合金在氯化钠稀溶液中的腐蚀行为

利用盐雾实验、极化曲线扫描、电化学阻抗谱和电化学噪声技术等电化学研究方法结合扫描电镜表面观测技术对AZ91D镁合金氧化膜在1%(w)氯化钠溶液中的耐蚀性能进行了评价. 结果表明, 氧化前后的镁合金腐蚀行为发生明显改变, 如未封孔的阳极氧化膜耐中性5%氯化钠盐雾试验时间超过200 h; 氧化后的镁合金自腐蚀电位明显正移, 点蚀诱导期延长; 阳极氧化膜的高频阻抗约为裸露镁合金的数千倍, 这些变化证明阳极氧化处理使镁合金获取了十分优异的耐蚀性能. 首次利用分形维数Df的变化规律初步描述氧化后AZ91D镁合金的腐蚀过程. 可以发现随着浸泡时间的延长, Df呈现出初期快速增长, 随后出现波动, 最后稍有降低的变化过程. 这种现象对应于氧化后AZ91D 镁合金在1%氯化钠溶液中腐蚀的三个阶段.

Corrosion Behavior of Anodized AZ91D Magnesium Alloy in NaCI Aqueous Solution

The corrosion behavior of anodized AZ91D magnesium alloy in neutral 1%(w) NaCl aqueous solution was investigated by salt spray test, polarization curve, electrochemical impedance spectroscopy (EIS), electrochemical noise (EN) and scanning electron microscope (SEM). The results showed that the corrosion behavior of Mg alloy presented characteristic changes due to anodization. For example, the unsealed anodic film could be sustained in 5% NaCl salt spray beyond 200 h, Ecorr of anodized magnesium alloy shifted up and the inductive period for pitting corrosion was obviously prolonged, and the impedance modules in high frequency of anodized alloy were several thousand times those of unanodized alloy. All these proved that anodization process made the alloy gain excellent property of anti-corrosion. The evolution of fractal dimension (Df) was first utilized to depict the corrosion process of anodized AZ91D magnesium alloy and shown as rapid increasing in the initial, fluctuating in the medium and decreasing in the last. This evolution was related with the three different corrosion stages of anodized AZ91D magnesiumalloy in 1%NaCl solution.