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通过循环极化确定纯Al和Al-7Zn-0.1Sn-0.015Ga(质量分数,%)合金在3.5%Na Cl溶液中的自腐蚀电位Ecorr、点蚀电位Epit、点蚀转变电位Eptp和保护电位Erp,并通过Al和铝合金在这些特征电位的点蚀形貌研究了它们的点蚀行为及点蚀扩展机理。结果表明:在点蚀电位时开始出现点蚀坑,随着电位升高点蚀坑迅速向横向和纵向扩展直至保护电位;纯Al的点蚀坑为窄而深的方形点蚀形貌,蚀坑内部为粗糙的结晶状结构,且表面出现明显的丝状腐蚀。Al-7Zn-0.1Sn-0.015Ga合金的点蚀形貌为宽而浅的圆形腐蚀坑,蚀坑内部比较光滑,且丝状腐蚀消失。合金元素能明显活化合金,降低点蚀坑深度,改善其腐蚀形貌。
The corrosion potentials Ecorr, pitting corrosion potential Epit, pitting corrosion potential Eptp and protective potential of pure Al and Al-7Zn-0.1Sn-0.015Ga (mass fraction) alloys in 3.5% NaCl solution were determined by cyclic polarization Erp, and their pitting behavior and pitting corrosion mechanism were studied by the pitting morphology of Al and Al alloy at these characteristic potentials. The results show that pitting pits begin to appear at the pitting potential and pitting pits rapidly expand to the protective potential in both horizontal and vertical directions as the potential increases. The pits of pure Al are narrow and deep pitting patterns, The interior of the pit is a rough, crystalline structure with obvious filiform corrosion on the surface. The pitting morphology of Al-7Zn-0.1Sn-0.015Ga alloy is wide and shallow circular corrosion pits, the interior of the pits is relatively smooth, and the filiform corrosion disappears. Alloying elements can significantly activate the alloy, reducing pitting pit depth, improve the corrosion morphology.