Studies of the corrosion resistance properties of bone screws made from 316l stainless steel in ringer’s solution

Stainless steel 316L is one of the most common metallic biomaterials used for implants. Its passive surface provides a good corrosion resistance in the body environment, which can be reduced by surface mechanical damages. This is the reason why the bone screws made of stainless steel 316L were subjected to laboratory analysis in the initial state, after diversified implantation period and after mechanical damage of the surface. The mechanical damages were estimated on the basis of stereoscopic and scanning electron microscope (SEM). In order to estimate the pitting and crevice corrosion resistance, potentiodynamic and potentiostatic examinations were performed. On the basis of obtained results it can be stated that despite the visible damages on the surface, the investigated screws present a good pitting corrosion resistance. However, the way the screws were fastened caused frictional corrosion and existing cavities led to crevice corrosion. Moreover, clear correlation between magnitude of mechanical damages of the surface, implantation time and screws corrosion resistance was observed.