Sulphidation behaviour of FeAl intermetallics in an atmosphere containing low concentration of H2S

The high temperature corrosion behaviour of FeAl (42at.%Al) intermetallics in a mixture gas, (95%N-2+5%H-2) plus 1%H2S, was studied by thermogravimetr ic analysis at 600 degrees C. The corrosion products were examined by using scanning electron microscopy (SEM) with energy dispersive spectroscopy (ED S), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS ). The experimental results show that FeAl has excellent corrosion resistan ce in this atmosphere and the mass gain of FeAl is less than 0.15 mg/cm(2) after exposure to the atmosphere for 90 hours at 600 degrees C. The depth p rofile of XPS analysis indicated that the thin scale formed on the samples consists of two sub-layers: a layer of mixture of FeS and Al2O3 on the top surface and an Al2O3 layer on the bottom. The formation of the corrosion pr oducts is discussed based on the thermodynamic and kinetic analysis includi ng the partial pressures of sulphur and oxygen under the test condition and the selective oxidation of Al. The excellent corrosion resistance of FeAl in sulphur containing atmosphere can be attributed to the selective oxidati on products of Al2O3 sub-layer.