Effects of serum proteins on corrosion behavior of ISO 5832-9 alloy modified by titania coatings

Stainless steel ISO 5832-9 type is often used to perform implants which operate in protein-containing physiological environments. The interaction between proteins and surface of the implant may affect its corrosive properties. The aim of this work was to study the effect of selected serum proteins (albumin and gamma-globulins) on the corrosion of ISO 5832-9 alloy (trade name M30NW) which surface was modified by titania coatings. These coatings were obtained by sol-gel method and heated at temperatures of 400 and 800 A degrees C. To evaluate the effect of the proteins, the corrosion tests were performed with and without the addition of proteins with concentration of 1 g L-1 to the physiological saline solution (0.9 % NaCl, pH 7.4) at 37 A degrees C. The tests were carried out within 7 days. The following electrochemical methods were used: open circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy. In addition, surface analysis by optical microscopy and X-ray photoelectron spectroscopy (XPS) method was done at the end of weekly corrosion tests. The results of corrosion tests showed that M30NW alloy both uncoated and modified with titania coatings exhibits a very good corrosion resistance during weekly exposition to corrosion medium. The best corrosion resistance in 0.9 % NaCl solution is shown by alloy samples modified by titania coating annealed at 400 A degrees C. The serum proteins have no significant effect onto corrosion of investigated biomedical steel. The XPS results confirmed the presence of proteins on the alloy surface after 7 days of immersion in protein-containing solutions.