Effect of Surface Roughness on the Electrochemical Behavior and Corrosion Resistance of TiTaNbZrAg Alloy with Different Amount of Tantalum in Bulk Composition

The corrosion behavior of the TiTaNbZrAg alloys with different amounts of Tantalum (0 %, 10 % and 20%) and with distinct surface topography (smooth and rough) was investigated in phosphate buffer solution (PBS) for long-time immersion (1000 hours). The corrosion resistance was studied by Open circuit potential (OCP), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). From the potentiodynamic investigations, it was observed that all types of samples show good corrosion resistance (i.e. Rcorr < 10µm y-1) and may be used successfully for medical applications. However, the samples with smooth surface and with a certain amount of Ta (10 % and 20%) exhibit the best corrosion performance (Rcorr < 1µm y-1). As regard the samples with rough surface, the results evidenced that they show lower corrosion resistance (1< Rcorr < 3 µm y-1), suggesting that the Ta presence not necessary brings about a very good corrosion protection. Actually, the synergetic effect of both the presence of Ta and surface roughness plays an important role in corrosion behavior. Based on literature reports, we assume that the good corrosion resistance results from the good stability of the film, formed mainly from Ta2O5 and TiO2, formed on the alloy surface during immersion in PBS.