Gaseous corrosion resistance of Fe-Al-based alloys containing Cr additions

Iron-aluminum-based weld overlay claddings have recently been considered as corrosion resistant coatings. In this particular study, 10 alloys were exposed at 500 °C to three different corrosive environments ranging from a highly sulfidizing to an oxidizing atmosphere. Corrosion kinetics were determined for exposed alloys and cross-sectional microscopy was used to relate the corrosion products to the corrosion rates. It was found that critical aluminum and chromium concentrations were required to prevent rapid corrosion kinetics during 100 h of exposure. Titanium was found to help the corrosion resistance of a Fe-Al-Cr alloy when exposed to a highly sulfidizing environment, but had an insignificant effect on the corrosion kinetics of alloys exposed to a mixed oxidizing/sulfidizing and an oxidizing atmosphere. The total aluminum and chromium concentration was taken as the alloy content factor (ϕ = at% Al + at% Cr) in order to numerically represent alloys based on the alloying elements. Critical alloying content values were found for each environment based on the corrosion kinetics. It was determined that 19 at% Al and 1 at% Cr was required to prevent rapid corrosion kinetics in all three corrosive environments.