The semiconducting properties of passive films formed on AISI 316 L and AISI 321 stainless steels: A test of the point defect model (PDM)

The semiconductor properties of passive films formed on AISI 316L in 1 M H2SO4 in three temperatures and AISI 321 in 0.5 M H2SO4 were studied by employing Mott–Schottky analysis in conjunction with the point defect model (PDM). Based on the Mott–Schottky analysis in conjunction with PDM, it was shown that the calculated donor density decreases exponentially with increasing passive film formation potential. Also, the results indicated that donor densities increased with temperature. By assuming that the donors are oxygen ion vacancies and/or cation interstitials, the diffusion coefficients of the donors for two stainless steels are calculated.

► Diffusion of point defects is a key parameter in describing the passive film growth.
► It was shown that donor density decreases exponentially with increasing potential.
► The results revealed that donor densities increased with solution temperature.
► These observations were consistent with the predictions of the point defect model.
► Also, the calculated diffusivity of defect was in the range of 10−16 cm2/s.