不同离子对TC4钛合金电化学腐蚀行为的协同作用机制

Synergistic Effect Mechanism of Different Ions on the Electrochemical Corrosion Behavior of TC4 Titanium Alloy

采用电化学方法研究了H^(+)、F^(-)及其2者协同作用加速TC4钛合金腐蚀的机制,以及添加Fe^(3+)后TC4钛合金腐蚀的缓蚀机理。结果表明,H^(+)对TC4钛合金表面钝化膜的破坏作用较小,而F^(-)对钝化膜破坏作用极大,尤其当F^(-)和H^(+)共存时协同加速TC4钛合金的腐蚀,但加入一定浓度的Fe^(3+)后,对TC4钛合金的腐蚀起到抑制作用,原因是Fe^(3+)加速阴极还原反应,使阳极从活化-钝化区转移到钝化区,同时溶液中Fe^(3+)通过络合作用消耗F^(-),减弱了F^(-)对钝化膜的破坏作用。

Due to the compact passive film,titanium alloys exhibit excellent corrosion resistance.However,during practical applications,the passive film is inevitably damaged by aggressive ions.Among the common ions,F^(-)is the most harmful to the passive film because of its high complexation with Ti.However,the destructiveness of F^(-)varies with pH.Moreover,there are inhibitory ions that reduce the aggressiveness of F^(-).The acceleration effects of H^(+)and F^(-)as well as the inhibition effect of Fe^(3+)on the corrosion behavior of TC4 alloy were examined in this work using electrochemical polarization curves measurements and electrochemical impedance spectroscopy (EIS).The results reveal that whereas H^(+)has slight destructive effect on the passive film,F^(-)has a considerable aggressive effect.In particular,F^(-)and H^(+)work synergistically to accelerate the corrosion of the TC4 alloy.The addition of Fe^(3+)can somewhat reduce corrosion of the TC4 alloy.This can be attributable to the fact that the faster cathodic reduction caused by Fe^(3+)moves the anodic curves from active-passive region to passive region.Meanwhile,F^(-)is consumed by forming a compound with Fe^(3+),which mitigates the corrosive effect of F^(-)on passive film.