Studies on the corrosion of Fe based alloys for superheater applications

Corrosion resistance of several Fe based alloys during the combustion of K and Cl containing fuels, was evaluated with air cooled probes and with field tests in the temperature range from 450 degrees C up to 590 degrees C. Enhanced corrosion was typically observed in cases where the sulfation of the deposits occurred. Corrosion proceeds along grain boundaries and makes the grains vulnerable to rapid oxidation and subsequent degradation of the alloy. Chlorine seems to activate and accelerate the corrosion of the alloys significantly. Diffusion of Fe and Ni was observed in the alloys. Chromium, on the other hand, seems to form spinels and does not diffuse to a large extent.