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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~(-4) cm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~(-5)cm数量级,表明理论计算与实验现象吻合较好
The development of microscopic pitting corrosion in Al-Zn-Sn-Ga alloy was observed by SEM. Combined with the electrochemical theory, the relationship between pH value and depth of pits in the pitting hole formed by the preferential dissolution of the second phase in the microstructure was simulated. In the condition of neutral NaCl solution corrosion, the effect of autocatalytic effect The impact of the development of the alloy pitting corrosion. The results show that the pH value of the corrosion pores of the alloy rapidly increases with the increase of the depth of the corrosion pits, but the pH value changes very little when the pitting depth is in the range of 0 ~ 10 ~ (-4) cm. At this time, The hole due to Ga amalgam and other factors lead to the cathode reaction faster, so that the hole passivation. The passivation depth of the pitting hole of this alloy was about 10 ~ (-5) cm measured by three-dimensional topograph, which shows that the theoretical calculation is in good agreement with the experimental one