In-situ X-ray diffraction of corrosion products formed on iron surfaces

In-situ X-ray diffraction measurements by synchrotron radiation and conventional X-ray source have been carried out for identifying constituent species of corrosion products, which were formed on the surface of a pure iron and an iron-5 mass% nickel alloy by reaction with aqueous solutions containing sodium chloride or sodium sulfate. A cell has been prepared for in-situ diffraction measurements of the corrosion products. Diffraction patterns from the corrosion products showed that major constituent species of the corrosion products was γ-FeOOH, and the fraction of minor species of α-FeOOH and Fe₃O₄ in the corrosion products depended on corrosion conditions, such as wetting and drying processes, anion species in aqueous solutions and nickel in the sample. An oxide scale thermally formed on the iron surface was also found to affect the formation of corrosion products.