AZ91D镁合金和2002铝合金在0.5mg/L NaCl溶液中的电偶腐蚀行为研究

Galvanic Corrosion Behavior for Galvanic Couple of AZ91D Mg-alloy/2002 Al-alloy in 0.5 mg/L NaCl Solution

采用电化学方法和表面分析技术研究了AZ91D镁合金与2002铝合金在0.5 mg/L NaCl溶液中的电偶腐蚀行为。对于镁合金,耦合后始终为阳极,腐蚀电位正移,腐蚀速率增加,这可能归结为它们之间的电偶效应显著加速了其阴极过程。对于铝合金,耦合后始终为阴极,腐蚀电位也正移,腐蚀速率增加,这可能归结为它们之间的电偶效应抑制了其表面钝化膜的形成。随着浸泡时间的延长,它们之间的耦合电位先正移后逐渐负移,电偶电流密度先增加后减小,最后逐渐增加并达到相对稳定的状态。为汽车发动机材料的选择、设计及其电偶腐蚀的抑制提供基本理论依据。

The galvanic corrosion behavior for the galvanic pair of AZ91D Mg-alloy/2002 Al-alloy in0.5 mg/L NaCl solution was studied by means of electrochemical methods and surface analysis techniques. For the galvanic pair of AZ91D Mg-alloy/2002 Al-alloy in the NaCl solution, Mg-alloy always acted as anode, thus its corrosion potential positively shifted, while corrosion rate increased. This could be attributed to that the galvanic effect between the two alloys significantly accelerated its cathode process.On the other hand, Al-alloy, always acted as cathode, its corrosion potential also positively shifted, and the corrosion rate increased. This could be ascribed to that the galvanic effect between the two alloys inhibited the formation of the passivation film on its surface. With the extension of immersion time, the coupling potential of the two alloys shifted towards positive first and then gradually negative, and finally reached a relatively stable state. The galvanic current densities increased first and then decreased and increased gradually again, and finally reached a relatively stable state. The research results not only enriched the knowledge of galvanic corrosion, but also provided a theoretical basis for the selection and design of automotive engine materials and the inhibition of the galvanic corrosion of multi-metal pairs.