Repassivating tantalum/tantalum oxide surface modification on stainless steel implants

Medical implants that require ductility, high mechanical strength and endur ance are commonly made of stainless steel (AISI 316L). Depending on environ ment and function steel surfaces may be attacked by pitting corrosion leadi ng to post-operative complications. However, the electrochemical surface pr operties of austenitic steel can be modified for higher corrosion resistanc e. In this work, steel surfaces are coated with a sandwich layer of tantalu m and tantalum oxide, using a PVD sputter process. Mechanical stability is tested and crack generation of the modified material is determined by a fou r-point bending test connected with a corrosion current measurement using p hysiological saline solution as the electrolyte. The mechanical stability a nd repassivation properties of the material are guaranteed up to the onset of substrate plastic deformation. While biocompatibility is obtained by tan talum oxide the ductility is achieved by the tantalum interface which at th e same time ensures continued film adhesion, even after plastic deformation of the steel substrate. (C) 2001 Elsevier Science BN. All rights reserved.