In situ corrosion monitoring of Ti-6Al-4V alloy in H2SO4/HCl mixed solution using electrochemical AFM

Electrochemical atomic force microscope (ECAFM) was employed for in situ observation of corrosion of solution annealed and furnace cooled Ti-6Al-4V titanium alloy in 0.5 mol l-1 H2SO4 + 1 mol l-1 HCl mixed solution. A scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) was also used for microstructure examination and chemical composition analysis. For solution annealed followed by furnace-cooled Ti-6Al-4V titanium alloy, selective corrosion of α phase and galvanic effect at α/β interface could be clearly observed at open circuit potential under ECAFM. A higher dissolution rate was also found in α phase than β phase on the bare Ti-6Al-4V titanium alloy. The effect of potential on the corrosion behavior was also explored. Negligible corrosion was found after potentiostatic etching at -0.5 and -0.85 VPt for 120 min. However, selective dissolution of α phase with respect to β phase occurred when the potential was controlled at -0.9 VPt. The polarity inversion during potentiostatic etching at -0.9 VPt was also found and discussed in this study.