Electrochemical and Corrosion Behavior of Stainless Steel 304L in SULFIRAN Process

In this paper, Corrosion behavior of stainless steel 304L was evaluated in used catalyst solution in Sulfiran plant in temperature range 35-45°C. The electrochemical techniques consisted of polarization curves and electrochemical impedance spectroscopy (EIS) were used in laboratory tests. It was found that the corrosion rate of S.S 304L alloy was predicted to be less than 5mpy. In the meantime, there is possibility of pitting corrosion on stainless steel 304L. The linear polarization resistance (LPR) and weight loss techniques were used for determination of corrosion rate in pilot test. In addition of surface analysis techniques such as XRD, XRF and SEM were applied in this research. The evaluations of metallurgical are carried too. Results of pilot tests confirmed founding’s of laboratory tests. Investigation of metallurgical aspect of stainless steel 304L corrosion showed some corrosion in the from of wide shallow pits. Wet H2S agent was main factor in corrosion induced damages because of sensitization of the investigated SS304L alloy. It seems the alloy has been sensitized during cooling down in solution annealing heat treatment. Corrosion was initiated from sensitized grain boundaries. Presences of O2 in Sulfiran solution reduces corrosion of the alloy through repairmen of iron oxide passive layer. For prevention and mitigation of resulted damage, unsensitized SS304L alloy should be used.