Effects of surface state on the electrochemical corrosion behavior of nuclear grade 316LN stainless steel

Differences between the ground and mechanically polished 316LN stainless steel were characterized on the surface topography, surface residual strain and electron work function. The electrochemical behavior of the stainless steel was investigated in a borate buffer solution. The ground 316LN stainless steel is featured by a rougher surface with scratches along the grinding direction. Compared with the mechanically polished sample, a thicker cold-worked layer (~50 μm) is imparted by surface grinding, indicating that the residual strain on the ground surface is much higher. The ground surface is more electrochemically active and exhibits a larger corrosion rate in the borate buffer solution, because of its rougher surface topography and a higher residual strain. The passive film on the mechanically polished sample is more compact and protective, due to the decrease of acceptor and donor density and the increase of total impedance of the passive film.