Electrochemical behaviour of high nitrogen bearing stainless steel in acidic chloride solution: Effects of oxygen, acid concentration and surface roughness

The effects of oxygen, H2SO4 concentration and surface roughness on the electrochemical behaviour of high nitrogen bearing stainless steel (HNS) in acidified 0.5 M NaCl solution were investigated using potentiodynamic polarization method. The results revealed three corrosion potentials indicating an unstable system. The number of the potentials was influenced by H2SO4 concentration. Three potentials existed above 0.011 M H2SO4, two between 0.011 and 0.0065 M H2SO4 and one below 0.0065 M H2SO4. Oxygen increased the number of corrosion potential at 0.005 M H2SO4 + 0.5 M NaCl solution while surface roughness had no noticeable influence on the number of potentials but increased the values of the corrosion potentials and passivation current densities with increase in the surface roughness. The corrosion mechanism has been discussed using the ideal polarization curve models.