Enhancement of corrosion resistance of a biomedical grade 316LVM stainless steel by potentiodynamic cyclic polarization

The paper discusses the results on the use of a simple cyclic linear potentiodynamic polarization technique as a method of improving corrosion properties of passive oxide films formed on a biomedical-grade 316LVM stainless steel surface in phosphate buffer. The results demonstrate that the modification of 316LVM surface by cyclic potentiodynamic polarization between the potential of hydrogen and oxygen evolution results in the formation of a passive film that offers significantly increased corrosion resistance (both pitting and general) when compared to the naturally grown passive film. The effect of number of cycles and anodic potential limit on the resulting corrosion properties is discussed. The capacitance analysis demonstrates that the major difference between the electrochemically formed and naturally grown passive film is in the type of semiconductivity in the potential region where pitting on the unmodified surface occurs. The XPS analysis shows that this is due to the presence of Cr(VI)-species in the electrochemically formed passive film, which contribute to the increased density of metal vacancies, and thus to the increased pitting corrosion resistance of the passive film.