Tribocorrosion of Type 316L Stainless Steel with Nanopore Arrays in Stimulated Body Fluid

Abstract

Type 316L stainless steel is widely used as a biomaterial because of high corrosion resistance owing to the passive films that form spontaneously on the surface. However, if the passive films are broken by mechanical damages corrosion will be accelerated in the body, resulting in the failure of the integrity. Wear causes the breakdown of passive films, which accelerates corrosion of metallic implant, as a result so-called tribocorrosion is induced. In order to suppress tribocorrosion, friction between materials should be well-controlled. For the control of friction, various surface treatments have been reported. Recently we reported the formation of nanopore arrays on Type 316L stainless steel by a simple anodization.In the present work, we examined tribocorrosion of Type 316L stainless steel with nanopore arrays in simulated body fluid. The tribocorrosion of Type 316L stainless steel was examined in pin-on-disk wear test. UHMWPE (ultrahigh molecular weight polyethylene) and Type 316L stainless steel were used as a pin and disk materials, respectively. Two different surface morphologies were prepared for the disk of the stainless steel; mirror and nanopore arrays. The nanopore arrays were formed by anodization in an ethylene glycol containing sodium perchlorate. The pin-on-disk wear test was carried out in 0.9% NaCl solution or 30% FBS (fetal bovine serum) at 37 °C. During the test, the friction coefficient and the corrosion potential of the disk specimen were monitored simultaneously with time. The corrosion potential decreased immediately after the test was commenced and then recovered gradually with time. After the test wear debris with the size of several micrometers was observed on the surface. In the presentation, the effects of surface nanostuture and organic components included in FBS on the tribocorrosion behavior of Type 316L stainless steel will be discussed.