Method of Determining the Morphology and Composition of Sulfide and Oxide Layers on Iron and Nickel Base Alloys.

The behavior in service of metallic materials under corrosive conditions is largely determined by formation of protective coatings, which depends on the material as well as the operating conditions. To be able to select the proper material for a given corrosive environment, it is necessary to determine the factors influencing the protective action by analysis of the layers. On the examples of sulfidization of heat exchanger tubing of carbon steel and formation of coatings on nickel base alloys in gas turbine service, the analysis of such coatings by conventional metallography, scanning electron microscopy, x-ray fluorescence analysis, atomic absorption spectroscopy, electron microprobe, and secondary ion mass spectrometry is described.