Corrosion of Nickel by Hydrogen Sulfide

The combined techniques of reflection electron diffraction and X-ray diffractometry were found useful in determining the chemical composition and crystallographic orientation of nickel sulfide scales. The corrosion products produced below the Ni3S2-Ni eutectic temperature (637 C, 1179 F) consist of a thick inner layer of Ni3S2 and a thin outer layer of NiS. Polycrystalline nickel yields polycrystalline products with random orientation. Single crystal nickel with the (001) plane exposed yields preferred orientation in both layers. The inner layer of Ni3S2 grows with the (00.1) plane parallel to Ni (001). The millerite and nickel arsenide type forms of NiS grow with their (11.0) planes parallel to Ni (001). Small amounts of α-Ni7S6 and β-Ni7S6 are produced.