Corrosion performance of various deformed surfaces of implant steel for coronary stent applications: Effect of protein concentration.

This work was done to systematically elucidate the corrosion behavior of austenitic stainless steel subjected to various degree of cold deformation (10 %, 20 % & 30 %). The experiments were performed in phosphate buffer saline (PBS) solution having different concentrations of bovine serum albumin (0.2, 0.5, 1.0, 2.0, 4.0 g L). Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) analysis were performed to obtain the corrosion parameters. Scanning electron microscopy with energy dispersive X-ray (SEM-EDX), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface morphologies and chemical compositions of the surface films. Contact angle analysis was also used to detect the hydrophilic character of sample surfaces. The BSA had a considerable effect of inhibition on the corrosion of SSs in annealed as well as in deformed state due to its adsorption on surface of steel. For annealed samples, at 4.0 g LBSA concentration, the corrosion resistance was drastically decreased but interestingly not for sample with more than 10 % deformation and the concentration effect of BSA is also not very significant after 0.5 g L for deformed surfaces. The breakdown potential for 30 % deformed sample is quite higher in presence of BSA even at 4.0 g L while it is lowest for annealed samples in the same condition. The variation in contact angle with deformation is very less after adsorption of BSA. On the basis of the obtained results, mechanism aspect for corrosion of steel in presence of protein is also deliberated.