Corrosion Study on Laser Shock Peened 316L Stainless Steel in Simulated Body Fluid and Chloride Medium

In the present work, corrosion behavior of laser shock peened 316 L stainless steel was evaluated and compared with unpeened specimen in Hank solution (simulated body fluid) and chloride medium. Laser shock peening (LSP) was used for surface modification using Q-switched Nd-YAG laser. In the corrosion study, different electrochemical experiments such as open circuit potential (OCP)-time measurements, potentiodynamic anodic polarization, electrochemical impedance spectroscopy (EIS) measurements were performed in 0.5 M NaCl and Hank solution to examine the corrosion resistance of unpeened and laser peened 316 L SS specimens. The results of corrosion study demonstrated that LSP improved the pitting corrosion resistance despite marginally higher roughness (Ra = 1.01 μm) for laser peened surface than unpeened surface (Ra = 0.54 μm). Improvement in pitting corrosion resistance was indicated by ennoblement of OCP, more noble (anodic) value of pitting potential (Epit) and lower corrosion current density (Icorr). Conductivity and pH of NaCl and Hank solution increased after every polarization experiments which indicate the ionic dissolution during corrosion experiments. Qualitative analysis of Nyquist plots obtained from electrochemical impedance spectroscopy (EIS) results also showed higher arc radius (higher polarization resistance) for laser peened specimen than unpeened, which is indicative of more protective passive film and hence improved corrosion resistance. Further, microstructural examination after polarization experiments in both NaCl and Hank solution showed less pitting sites in laser peened specimens than unpeened surfaces. These microstructural observations are in line with the results obtained in polarization experiments. The results of the study are important with respect to medical implants and their biocompatibility in the human body. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.