Corrosion properties of duplex treated Ti–6Al–4V alloy in chloride media using electrochemical and positron annihilation spectroscopy techniques

The corrosion properties of duplex-treated and nitrided Ti–6Al–4V have been investigated in 0.025, 0.25 and 2.5 M NaCl using electrochemical techniques, Positron Annihilation Spectroscopy (PAS), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS). The electrochemical results showed a three-fold increase in corrosion rate for every ten-fold increase in chloride concentration. The morphology and surface composition studied by XRD showed the presence of TiN and Ti2N layers. SEM and EDS showed the presence of pitting and the presence of oxide and chloride products. At the lowest concentration of NaCl no aluminum was detected in the surface layers while at the highest concentration no chloride byproducts were detected. PAS indicated that the damage caused by the NaCl changes in nature and becomes shallower as the concentration increases.