The beneficial role of Y-implantation on the aqueous corrosion of stainless steel

The corrosion behaviour of Y-implanted austenitic stainless steel AISI 321 samples was investigated in 0.5 M H2SO4 at ambient temperature using potentiodynamic polarization and cyclic voltammetry. The implantation of 1 × 1016 Y-ions/cm2 of 40 keV energy did not lead to an improvement of the corrosion resistance of the material because of sputtering effects. On the other hand, a significant improvement of the corrosion resistance was observed by increasing of the dose (2 × 1017 Y-ions/cm2 implanted in the presence of oxygen) and the implantation energy (55 and 80 keV). The elemental composition of the near-surface layers of the implanted steel samples prior and after the corrosion attack was determined by Rutherford backscattering spectrometry (RBS) and Nuclear Reaction Analysis (NRA) using alpha particles, protons and deuterons as projectiles. The surface morphology and microstructure of the non-corroded and corroded samples were examined by Scanning Electron Microscopy (SEM). The corrosion resistance of the implanted materials was found to be related with the thickness and the composition of the implanted layer.