Infrared spectroscopic studies of surface oxides

Investigations have recently been performed in our laboratory with the object of developing non-destructive optical techniques for the chemical characterization of non-metallic films on metals. Our initial studies were on oxidized samples of 310 stainless steel with minor titanium additions exposed to low P o2 atmospheres ( P o2 ≈ 10 −15 atm). As the exposure time was increased from 0.5 to 139 h the oxide scale was observed to contain increasing amounts of complex oxide phases such as MnCr 2O 4, FeCr 2O 4 and MnTiO 3. Binary oxides of titanium and chromium were observed at all exposure times. A series of reference spectra were also obtained for comparison with corrosion scale spectra. We consider that Fourier transform IR reflection spectroscopy is an extremely useful tool characterizing non-metallic films. It will be quite valuable in supplementing X-ray diffraction for very thin films and will provide complementary information to data obtained by light scattering and electron spectroscopic techniques.