Corrosion behavior of AISI 316L stainless steel and ODS FeAl aluminide in eutectic Li2CO3-K2CO3 molten carbonates under flowing CO2-O-2 gas mixtures

A kinetics study on AISI 316L stainless steel and ODS (Oxide-Dispersion-Str enghtened) FeAl iron aluminide was conducted concerning its corrosion behav ior in molten Li2CO3-K2CO3 eutectic at 650 degrees C in flowing CO2-O-2 gas mixtures. The corrosion resistance of FeAl ODS was demonstrated to be sign ificantly superior to that of austenitic AISI 316L steel under all gas cond itions tested in this work. At low CO2 partial pressure (PCO2 = 0.3 atm) th e corrosion rate of both alloys decreased with time due to the formation of a protective oxide layer. In dry CO2 gas, corrosion of AISI steel proceede d at a near-linear rate, indicative of a surface-controlled reaction. FeAl corroded initially following parabolic behavior, but, on further reaction, exhibited some weight loss. A similar behavior was also observed in a 67CO( 2)-33O(2) gas mixture. Corrosion of FeAl in high CO2 gas has been postulate d to initiate by acidic fluxing of yttria particles. The attack then develo ps as pitting and leads to further reaction by general corrosion as a conse quence of the formation of active-passive electrochemical cells between the interior of pits and the external surface. The weight loss of AISI 316L in 67CO(2)-33O(2) gas can be ascribed to the high oxidizing power of the gas causing a continuous dissolution of the Cr2O3 layer into a soluble chromate .