Influence of Surface Treatments on Localized Corrosion Behaviour of Welded AISI 316L Stainless Steel

Stainless steels and corrosion resistant alloys may suffer localised corrosion, such as pitting and crevice corrosion, in chloride containing oxidizing environments. Pitting and crevice initiation occur when chloride ions concentration in solution exceeds a critical value. This value depends principally on materials properties (composition, deformation degree, heat treatment, surface finishing) and environment (temperature, pH, presence of oxidizing environment, flow regime). In this work, influence of different surface treatments on corrosion behaviour of AISI 316L austenitic stainless steel welded by TIG method has been evaluated through potentiodynamic polarisation tests. Surfaces of the welded stainless steel were treated by mechanical methods (grinding, garnet blasting), chemical method (pickling) and combination of both methods. Potentiodynamic polarisation tests were carried out in sodium chloride (NaCl) solutions containing 100 to 3000 ppm Cl- at room temperature. The surfaces of the specimens were examined using optical and scanning electron microscopy (SEM).