Interpretation of electrochemical behavior of nickel-implanted type-430 stainless steel using x-ray photoelectron spectroscopy and transmission electron microscopy

Multiple implantations of Ni⁺ ions into annealed type-430 stainless steel were carried out at energies of 25 and 75 keV in order to produce a surface alloy. X-ray photoelectron spectroscopy, coupled with argon ion etching, was used to characterize the surface composition and chemical depth profiles of the implanted species prior to electrochemical studies. Radiation damage and alloy phase structure were evaluated using transmission electron microscopy. Potentio-kinetic studies were carried out in 1 N H₂SO₄ deaerated by hydrogen. Nickel implantations reduced both the critical and passive current densities. The open-circuit potential was not altered and a change was observed in the primary passivation potential only at the highest concentration of nickel. Potentio-kinetic studies in hydrogen-saturated 1 M NaCl revealed a general enhancement of pitting resistance due to nickel implantation.