Effect of fluoride ions on corrosion behaviour of commercial pure titanium in artificial seawater environment

摘要

The corrosion behaviour of a commercial pure (CP) titanium in artificial seawater with different fluoride ions concentration at pH = 2 were investigated by means of immersion test, corrosion morphology characterization techniques including laser scanning confocal microscope (LSCM) and electron back-scattered diffraction (EBSD) and scanning electronic microscopy (SEM), as well as potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and corrosion product analysis by X-ray photoelectron spectroscopy (XPS). The results indicate that the corrosion resistance of CP titanium decreased with the increase of fluoride ions concentration because the fluoride ions could dissolve the barrier film of CP titanium into porous partly or entirely by forming soluble compound of TiF62-. Additionally, crystal orientation of CP titanium has an influence on corrosion rate and the order of corrosion rate of 6 main crystal orientations is (0 0 0 1) < (1 0<(1)over bar>1)/(1 0 (1) over bar2)/(2 (1) over bar(1) over bar 2) < (1 0 <(1)over bar> 0)/ (2 (1) over bar(1) over bar 0), which results from the influence of structure and energy factors. In the end, ideal mechanisms for the behaviours of passive film interacting with fluoride ions in different concentrations are proposed.