Abstract
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 readily at 30°C and in all chloride solutions of concentrations ≥10−3 mol·m−3 while 904L SS did not pit at temperatures and concentrations lower than 40°C and 0.6 mol·m−3 NaCl, respectively. Pitting potential (Epit) for 904L SS was much more noble than that obtained for 316L SS while the protection potential (Eprot) values were almost the same for both alloys.
The pitting corrosion inhibition by OH ions was more pronounced for 316L SS and Epit approached that obtained for 904L SS in alkaline solutions.
The alloy with the higher Cr, Ni and Mo content (904L SS) was more sensitive to the temperature effect as compared to 316L SS. It was concluded that Epit was dependent on the alloy composition while Eprot was not affected by the alloy composition.
