Nature of oxygen in the passive film on stainless steels in 0.1 M NaCl solution

Abstract

Three different oxygen species, O²⁻, OH⁻, and H₂O, are introduced into the deconvolution of the oxygen peaks measured in the prior study and their true concentrations are investigated in the depth profile. It is found that H₂O exists mainly in the outermost part of the passive film at the interface of solution and the passive film. OH⁻ and O²⁻ are found throughout the passive film; they have a maximum concentration in the outer layer at around 10 to 20 Å depth, with a concentration of 40 at.% for the stainless steel 29-4-2 and 50 at.% for 18-12. After the maximum the concentrations are sharply reduced with increasing sputtering time and remain at a constant concentration of about 10 at.% at 35 Å depth. Both species still exist at this concentration even after long time sputtering.