A comparative study of primary and secondary passive films formed on AM355 stainless steel in 0.1Â M NaOH

In this study, the structure and composition of primary and secondary passive films formed on AM355 martensitic stainless steel were characterized and compared. The film composition analysis revealed that the Fe/Cr ratio in the secondary passive film is significantly lower than that in the metal matrix. Both the primary and secondary passive films are composed of nanoscale particles, and some pores are present in the secondary passive film. Compared to the secondary passive film, the primary passive film exhibits reduced donor density, with a more positive formation potential.