PITTING CORROSION BEHAVIOR OF TYPE SUS904L AND SUS316L STAINLESS-STEELS IN CHLORIDE SOLUTIONS

Pitting Corrosion behaviour of commercial stainless steels (SS) types 904L and 316L has been investigated in pure sodium chloride solutions of different pH values and at different temperatures. Potentiodynamic polarization technique and scanning electron microscopy were utilized. The results indicated that pitting corrosion of 316L SS occurred read ily at 30-degrees-C and in all chloride solutions of concentrations gr eater-than-or-equal-to 10(-3) mol.m-3 while 904L SS did not pit at tem peratures and concentrations lower than 40-degrees-C and 0.6 mol.m-3 N aCl, respectively. Pitting potential (E(pit)) for 904L SS was much mor e noble than that obtained for 316L SS while the protection potential (E(prot)) values were almost the same for both alloys. The pitting cor rosion inhibition by OH ions was more pronounced for 316L SS and E(pit ) approached that obtained for 904L SS in alkaline solutions. The allo y with the higher Cr, Ni and Mo content (904L SS) was more sensitive t o the temperature effect as compared to 316L SS. It was concluded that E(pit) was dependent on the alloy composition while E(prot) was not a ffected by the alloy composition.