Effect of Cyclic Reaction on Corrosion Behavior of Chromium-Containing Alloys in CO2 Gas at 650 °C

Abstract

In this work, seven commercial alloys (602CA, 310SS, 253MA, F321, F316L, 800H and 304SS) were investigated in Ar–20% CO2 gas at 650 °C under a cyclic condition (1-h reaction and 0.25-h cooling in each cycle) for up to 310 cycles. The corrosion behavior of these alloys in isothermal reaction condition was also carried out for a purpose of comparison. The results showed that nickel-based 602CA alloy stayed protective in both isothermal and cyclic reaction conditions by forming a thin protective alumina scale. However, alloys F321, F316L, 800H and 304SS all formed thick multilayered oxides with external iron-rich oxides and internal spinel oxides in all reaction conditions. Alloys 310SS and 253MA behaved protective in isothermal reaction condition but formed pitting corrosion in cyclic reaction condition. The high corrosion resistance of 310SS and 253MA was attributed to the high Cr content and the effect of other alloying elements, e.g., Si and Mn, forming additional oxide layers to enhance chromia protection. Cyclic reaction created stress on oxide scale during cooling and heating which accelerated the initiation of breakaway corrosion of these alloys. Carburization due to CO2 reaction was identified for F321, F316L and 304SS, but not for other alloys because of the formation of highly protective alumina or chromia scales.