Characterisation of high temperature corrosion products on FeAl intermetallics by XPS

FeAl (42 at.% Al) intermetallic compound was exposed to a mixture gas of (9 5% N-2 + 5% H-2) plus 1% H2S at 600 degreesC. The corrosion products on the surface of FeAl specimens were examined by using scanning electron microsc opy, energy dispersive spectroscopy and X-ray photoelectron spectroscopy (X PS). The XPS depth profile revealed that the thin scale consists of two lay ers: a layer of mixture of FeS and Al2O3 on the top and an Al2O3 layer bene ath the mixture. In XPS depth profile analysis, two binding energy referenc es were used to determine the chemical states of Al in the scale: C Is from hydrocarbon contamination and O 1s of the internal standard. The variation of the binding energy difference between C 1s and Al 2p was >1.5 eV depend ing on the scale thickness, while the scatter of the binding energy between the Al 2p and O Is was smaller than 0.4 eV and independent of the scale th ickness. It was also found that FeS decomposes after ion sputtering. (C) 20 01 Elsevier Science Ltd. All rights reserved.