SUPER AUSTENITIC STAINLESS-STEELS - A PROMISING REPLACEMENT FOR THE CURRENTLY USED TYPE 316L STAINLESS-STEEL AS THE CONSTRUCTION MATERIAL FOR FLUE-GAS DESULFURIZATION PLANT

Potentiodynamic anodic cyclic polarization experiments on type 316L st ainless steel and 6Mo super austenitic stainless steels were carried o ut in simulated flue-gas desulphurization (FGD) environment in order t o assess the localized corrosion resistance. The pitting corrosion res istance was higher in the case of the super austenitic stainless steel containing 6Mo and a higher amount of nitrogen. The pit-protection po tential of these alloys was more noble than the corrosion potential, i ndicating the higher repassivation tendency of actively growing pits i n these alloys. The accelerated leaching study conducted for the above alloys showed that the super austenitic stainless steels have a littl e tendency for leaching of metal ions such as iron, chromium and nicke l at different impressed potentials. This may be due to surface segreg ation of nitrogen as CrN, which would, in turn, enrich a chromium and molybdenum mixed oxide film and thus impedes the release of metal ions . The present study indicates that the 6Mo super austenitics can be ad opted as a promising replacement for the currently used type 316L stai nless steel as the construction material for FGD plants.