The influence of the surface finishing on the electrochemical behaviour of DIN 1.4404 and DIN 1.4410 steels

it is well known that the breakdown potential (eb) and the open circuit potential (eocp) are important parameters to evaluate the resistance of metallic materials against corrosion. nevertheless, the literature presents scattered values of these parameters for stainless steels (ss). many factors may contribute to this dispersion of published eb and eocp values. it has been proposed that the finishing and/or final treatment of the surface is one of those factors. to address this question, the influence of the surface finishing on the average roughness (ra), residual stress (t) and electrochemical behaviour of din 1.4404 and din 1.4410 have been considered. samples from both steels were prepared with different finishing degrees with sic paper. roughness, residual stress and electrochemical tests were performed on samples with various surface finishing. electrochemical studies were conducted in an avesta cell and steel electrodes immersed in 1 m nacl or 0.5 m mgcl2 aqueous solutions. we found that when steels are immersed in sodium chloride or magnesium chloride aqueous solutions there is no significant change in the variation of the eocp and eb values as the average roughness increases and therefore we can conclude that these parameters are not affected by the final treatment or by the solution composition.