Studies of passivation, repassivation and metastable pitting of 316L stainless implant in bone solution

摘要

Passivity, its stability and breakdown, leading to localized corrosion such as pitting is the most important phenomenon for austenitic stainless steel in vivo solution. Because growth of it helps to aggravate other forms of corrosion, leading to failure of implant material. All pits, once initiated may not grow. Many of initiated pits are metastable and may be healed by repassivation. Only those of metastable pits which find favorable conditions grow into stable pits. Studies of repassivation and formation and life of metastable pits have been investigated by cyclic polarization and current transients at different fixed potential within passive. Pits were generated by passing anodic currents within passive region and the characteristic studies repassivation leading to death of pits or formation of stable pits have been investigated. It was found a number pits initiate well below pitting potential. Out of them only a few may grow to stable, depending on diffusion of ions and formation of porous plug over the pit mouth and other may live for few seconds, called metastable pits and cease to grow further due to favorable condition of repassivation.