Corrosion pits in thin films of stainless steel

Thin stainless steel films were prepared by sputter deposition onto silicon substrates using a 304 stainless steel target. The film composition was es sentially that of 304 stainless steel, but they had a body-centered cubic s tructure and were free of sulfide inclusions. Potentiodynamic polarization curves were obtained for thin films in various chloride-containing solution s and compared to results from conventional stainless steel samples. In add ition, video images of two-dimensional pits in thin films were used to dete rmine the anodic pit current density as functions of potential and chloride concentration. Thin stainless steel films were found to be significantly m ore resistant to pit initiation than their bulk counterparts, but pit propa gation was possible at relatively low potentials. A diffusion-controlled gr owth regime was identified at high potentials, with a transition to mixed a ctivation/ohmic control at lower potentials (just above that required for r epassivation). (C) 1999 The Electrochemical Society. S0013-4651(98)04-038-5 . All rights reserved.