Surface nanocrystallization of EN8 steel: Correlation of change in material characteristics with corrosion behavior

The present paper addresses the influence of surface mechanical attrition treatment on the characteristic properties of EN8 steel and, to analyze the correlation between the change in properties of the treated steels with their corrosion behavior in 0.6 M NaCl and borate buffer, evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy studies. Surface mechanical attrition treatment of EN8 steel induced plastic deformation, enabled surface nanocrystallization, increased the surface roughness, microstrain and defects/dislocations and, imparted compressive residual stresses. The change in properties of EN8 steel following treatment has caused a deleterious influence on its corrosion resistance in 0.6 M NaCl but an improvement in corrosion behavior in borate buffer. The possible reasons for the change in corrosion behavior of the treated EN8 steel are suggested. Pictorial models are proposed to explain the evolution of surface roughness and the mechanism of corrosion attack of the treated EN8 steels in 0.6 M NaCl and borate buffer.