Corrosion Improvement of Surgical Grade Stainless Steel by Sol-Gel Hybrid Coatings Containing SiO2 Nanoparticles and Glass-ceramic Particles

S. CERÉ; A. GOMEZ SANCHEZ; G. DUFFO

Niza, Francia

Congreso; 61st Annual Meeting of the International Society of Electrochemistry; 2010

International Society of Electrochemistry

Titanium and its alloys are the most widely used biomaterials for permanent implants applications. Zirconium is presented as an alternative to titanium, based on its excellent corrosion resistance and biocompatibility. Both metals belong to the so called valve metals. Their corrosion resistance is mainly due to a thin surface oxide film present in air and oxygenated electrolytes. These films are strongly adhered to the metal substrates and acts as a barrier against corrosion. Since the implant surface is the region in contact with living tissues, the characterization of the surface film is of great interest since the success or failure of the prosthesis greatly depends of the reactions that can occur on the surface. The surface modifications in order to improve biocompatibility of permanent implant materials are topics of concern in the field of biomaterials. In this study several surface modification processes, such as immersion in concentrated peroxide solution, potentiostatic anodization in phosphoric acid and cathodic electrodeposition of Ca-P compounds, have been conducted on cp titanium (grade 2) and zirconium (Zr 702) in order to determine the best surface conditioning that promote rapid osseointegration on this materials as well as to evaluate the barrier effect against the corrosive environment.  Complementary surface characterization techniques were used to determine the changes on surface after each process.  Electrochemical impedance spectroscopy and potentiodynamic anodic polarization tests were conducted to characterize the electrochemical behavior after each modification process in simulated body fluid solutions (SBF). Equivalent circuit models were developed to characterize de film structure from EIS results. Anodization in phosphoric acid results in thickening of the oxide surface film that increases the corrosion resistance of both materials in SBF solutions. Phosphorous is incorporated to the anodic oxide film as phosphate. Peroxide immersion leads to thickening of titanium oxide film, evidences by change in the surface sample color. In zirconium, no evidences of thickening of oxide film was found, but an improvement of the barrier effect of the surface film was determined by the electrochemical tests. The electrodeposition slightly affects electrochemical response of zirconium, enhancing the passivity range of the material.