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 ag-gressiveness of F-.The acceleration effects of H+ and F-as well as the inhibition effect of Fe3+ on the cor-rosion behavior of TC4 alloy were examined in this work using electrochemical polarization curves mea-surements 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 Fe3+ can somewhat re-duce corrosion of the TC4 alloy.This can be attributable to the fact that the faster cathodic reduction caused by Fe3+ moves the anodic curves from active-passive region to passive region.Meanwhile,F-is consumed by forming a compound with Fe3+,which mitigates the corrosive effect of F-on passive film.
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