触变成形AZ91D镁合金在NaCl溶液中腐蚀行为的电化学分析

Electrochemical Analysis of Corrosion Behavior of Thixo-formed AZ91D Magnesium Alloy in NaCl Aqueous Solution

用动电位极化曲线和电化学阻抗谱的方法对触变成形AZ91D镁合金在NaCl水溶液中腐蚀行为进行了研究。结果表明:在相同浓度的NaCl水溶液中,随着腐蚀时间的延长,开路电位逐渐提高(正移),同一腐蚀电位下触变成形AZ91D镁合金的阳极极化电流明显减小,电化学阻抗谱(EIS)显示其容抗减小,腐蚀产物在合金表面沉积,对基体金属具有一定的保护作用,因而其腐蚀速度减小;随着溶液中Cl-浓度的增大,开路电位呈下降(负移)趋势,且其开路电位的正移速度较慢,同一腐蚀电位下触变成形AZ91D镁合金的阳极极化电流增大,EIS显示其线性阻抗减小,腐蚀反应的过程加快,所以腐蚀速度增大。

The corrosion behavior of thixoformed AZ91D magnesium alloys in NaCl solution was studied by using potentiodynamic polarization and impedance measurements. The results showed that the open-circuit potential ( OCP) of thixoformed AZ91 D magnesium alloys was gradually shifted in the positive direction, and its anodic polarization current was decreased evidently. EIS measurements revealed that capacitive resistance was decreased because of the corrosion products formed on the alloy surface were partly protective to the parent metal, and hence the corrosion rates were decreased along with the increase of the corrosion time in NaCl solutions at the same concentration. When the NaCl concentration was increased, the OCP tended to become more negative, and its positively shifting became more slowly. Moreover, the anodic polarization current of thixoformed AZ91D magnesium alloys increased at a given potential. EIS results revealed that linear impedance decreased due to the reactive process of corrosion expedited, and the corrosion rates increased along with the increaseing of concentration of NaCl solution at the same time.