采用SEM观察Al-Zn—Sn-Ga合金微观下孔蚀的发展过程。结合电化学相关理论，模拟计算由组织中第二相优先溶解而形成的点蚀孔内pH值与蚀孔深度之间的函数关系；探讨在中性NaCl溶液的腐蚀条件下，自催化效应对该合金蚀孔发展的影响。结果表明，合金的腐蚀孔内pH值随着腐蚀坑深度的增加而急速变大，但在孔蚀深度为0-10^-4cm数量级时pH值变化却极小，此时合金蚀孔由于Ga汞齐等因素的作用导致阴极反应较快，从而使蚀孔钝化。通过三维形貌仪测得该合金点蚀孔钝化深度约10-5cm数量级，表明理论计算与实验现象吻合较好
The micro developed and passivated process of corrosion pits of Al-Zn-Sn-Ga alloy were investigated by SEM, and the function relationship between pH value and pits depth in corrosion pits was also calculated in order to oxplain the expanded and passivated mechanism of pitting corrosion under the condition of neutral NaC1 solution. The result showed that pH value increased along with the expanding of the depth of corrosion pits. However in the range of 0~10-4 cm, the pH variation was minimal. The cathodic reaction, which could lead to passivation of corrosion pits, gradually became faster because of the activation of Ga amalgam. The passivation depth of corrosion pits was about 10-5 cm.
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