EFFECTS OF CONCENTRATION OF SODIUM CHLORIDE SOLUTION ON THE PITTING CORROSION BEHAVIOR OF AISI-304L

The pitting corrosion behavior of the austenitic stainless steel in aqueous chlo-ride solution was investigated using electrochemical technique. Corrosion po-tential (Ecorr) measurements, potentiodynamic experiments, potential-hold ex-periments in the passive range, and microscopic examination were used for the evaluation of corrosion characteristics. The experimental parameters were chloride ion concentration, immersion time and anodic-hold potential. Ecorr measurements along with microscopic examinations suggest that in or above 3.5 % NaCl at pH 2 pitting took place on the surface in absence of applied po-tential after 6 hour immersion. The potentiodynamic experiments revealed that Ecorr and pitting potential (Epit) decreased and current density in the passive region increased with the increase of chloride ion concentrations. A linear rela-tionship between Epit and chloride ion concentrations was found in this investi-gation. The analysis of the results suggests that six chloride ions are involved for the dissolution of iron ion in the pitting corrosion process of austenitic stain-less steel