Alloy degradation under oxidizing-sulfidizing conditions at elevated temperatures

Abstract

Exposure of high-temperature alloys to a low-P O2 oxidizing-sulfidizing environment above about 550 °C is often characterized by an initial period of protective oxidation followed by more rapid corrosion. This paper will provide a brief overview of alloy corrosion in oxidizing-sulfidizing atmospheres, with specific consideration given to the thermodynamic and kinetic aspects of the process, resulting modes of degradation, and alloy selection. The concept of a "critical microstructure" in the subsurface of the alloy as a prerequisite to initiating protective scale breakdown will also be discussed. The paper will conclude with a specific example of alloy development for the filtration of hot oxidizing-sulfidizing gases

Enhanced High Temperature Corrosion Resistance in Advanced Fossil Energy Systems by Nano-Passive Layer Formation

“…Iron sulfide blocks, nodules and continuous film ( Figure 15d, e, and f, respectively) were found primarily on the binary alloy samples. These morphologies are similar to those reported previously in the literature 10,31,32,35,36,37 .…”

“…This concentration is also close to the critical composition required to form an external Al 2 O 3 layer 8,9,10 . It has been shown that additions of chromium reduce this critical concentration of aluminum 11 in oxidizing conditions, but other researchers have reported detrimental effects of adding chromium to iron aluminum alloys 12 with respect to sulfidation resistance.…”

“…Similar minimal weight gains for FeAlCr alloys in sulfur-bearing environments have been observed by other researchers. Banovic et al 10 exposed iron aluminum alloys to a 1%H 2 S-Ar atmosphere at 700°C for up to 100 hours and found that alloys with more than 10wt% aluminum exhibited weight gains of less than 1mg/cm 2 .…”

Final Report, Materials for Industrial Heat Recovery Systems, Tasks 3 and 4 Materials for Heat Recovery in Recovery Boilers

“…The main competing reactions for sulfidation and oxidation of carbon steel at high temperatures are given in the following equations [18][19][20][21] temperatures. Figures 6 and 7 show the calculated partial pressures of O 2 and S 2 in gas samples taken from each port during different days.…”

“…It is known that the oxide scale formed on the carbon steel surface at typical waterwall boiler tube temperatures is much more protective than the sulfide scale [9,[18][19][20][21]. If the gas composition cycles between a sulfidizing and an oxidizing composition, the resulting scale may not be very protective, resulting in a high corrosion rate [5].…”