Electrochemical behaviour of surface modified AISI 304 grade stainless steel in ringer’s solution

Stainless steels are widely used as orthopedic implant materials. The main problems with these implant materials are fatigue fracture, fretting fatigue, wear and corrosion. Surface mechanical attrition treatment (SMAT) is a newly developed method to improve the materials properties and performance. In the present study, AISI 304 SS was subjected to SMAT using 2, 5 and 8 mm Ø 316L SS balls for 15, 30, 45 and 60 min. at 50 Hz under vacuum. SMAT of 304 SS increased the surface roughness, induced the formation of mechanical twins, strain induced martensite phase, and increased the defect density, which is a function of the size of the balls and treatment time. SMAT using 5 and 8 mm Ø balls significantly decreased the corrosion resistance whereas treatment using 2 mm Ø balls enabled an anodic shift in Ecorr and a marginal decrease in icorr. However, increase in surface roughness leads to the formation of a defective passive film and a decrease in breakdown potential.