Enhanced Corrosion Properties of Nanostructured 316 Stainless Steel in 0.6 M NaCl Solution

Surface modification through surface mechanical attrition treatment (SMAT) process and annealing were employed to enhance the corrosion properties of 316 stainless steel (SS) in 0.6 M NaCl. SMAT resulted in the formation of a nanocrystalline layer on 316 SS with an average grain size of 20 nm at the depth of about 30 µm from the treated surface. The nanocrystalline microstructure of the surface was characterized by X-ray diffraction and scanning electron microscopy. The micro-hardness of the surface layer of the treated sample was higher than that of the as-received sample by about 100 HV (Vickers hardness) at a depth of 200 µm from the treated surface. By the combined effect of SMAT and low-temperature annealing treatment at 400 °C, the electrochemical tests revealed an improvement in the corrosion properties of 316 SS in terms of corrosion potential and current density. This was attributed to the easy movement of Cr from the material matrix to the surface layer which resulted in the formation of a protective oxide layer on the material surface.