Characterization of roughness and pitting corrosion of surfaces modified by blasting and thermal oxidation

The blasting process generates a renewed surface on the surface of metallic biomaterials with a different topography and a different chemical composition. The impact of particles on the metallic surface increases both the surface roughness and susceptibility pitting corrosion. The aim of this work is to smoothen the sharp edges of blasted Ti6Al4V alloy surfaces by means of oxidation treatment and the evaluation of their susceptibility to pitting corrosion after this thermal oxidation. Oxidation treatments were performed at 500 and 700 °C for 1 h on samples blasted with SiO2/ZrO2 and Al2O3 particles. Compositional, microstructural and topographical characterization of the blasted surfaces were carried out by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), and atomic force microscopy (AFM). The surface reactivity and corrosion behaviour of the samples were assessed by scanning Kelvin probe (SKP) and by anodic polarization curves. The susceptibility to pitting corrosion of the Ti6Al4V blasted surfaces becomes higher as roughness increases. The oxidation treatment of the Ti6Al4V blasted surfaces causes the presence of nuclei of oxides that cover the area free of particles, especially in the samples treated at 700 °C, giving rise to a higher micro-nano roughness. The presence of the oxide, covering the blasted Ti6Al4V, decreases the surface reactivity leading to a lower passive current and wider pasivation region, decreasing the susceptibility to pitting corrosion.