The corrosion behavior of 5083 aluminum magnesium alloy in the NaCl solutions of different pH was studied by the polarization curve method and the AC impedance spectroscopy in scanning electrochemical microscopy(SECM).The results show that in the acid system(pH3~7),with the increase of pH,the corrosion potential shifts positively,the pitting potential is of little difference,the current density reduces,and only one of the electrochemical impedance spectra has a tendency to shrink. At the same time, the impedance and phase angle decrease,the charge transfer resistance increases,and the corrosion resistance increases.In the basic system (pH 9~12),with the increase of pH,the corrosion current density increases gradually,and the corrosion potential decreases, and the corrosion rate increases from 0.000 9 mm/a to 0.025 6 mm/a. There are two capacitive arcs in the electrochemical impedance spectroscopy, showing an anti-arc at pH=12. Meanwhile, the impedance and phase angle decrease, dissolving process of the metal compound particles accelerates, and the corrosion resistance of the alloy reduces.%采用扫描电化学显微镜(SECM)中的极化曲线法和交流阻抗图谱法研究5083铝镁合金在不同pH NaCl溶液中的腐蚀行为,结果表明:在酸性体系(pH为3~7),随着pH的增加,其腐蚀电位正移,点蚀电位相差不大,维钝电流密度减小,电化学阻抗谱中仅有1个容抗弧且呈现收缩趋势.同时,阻抗和相位角减小,电荷传递电阻升高,耐腐蚀性能增大.在碱性体系(pH为9~12),随着pH的增加,腐蚀电流密度增加,而腐蚀电位减小,腐蚀速度由0.0009 mm/a增加到0.0256 mm/a.电化学阻抗谱中有2个容抗弧,在pH=12处出现感抗弧.同时,阻抗和相位角减小,金属化合物颗粒溶解过程加快,合金耐腐蚀性能降低.
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