SURFACE SPECTROSCOPIC ANALYSIS OF HCN/NH₃ CORROSION PRODUCTS ON IRON BY FOURIER TRANSFORM INFRARED PHOTOACOUSTIC SPECTROSCOPY AND X-RAY PHOTOELECTRON SPECTROSCOPY.

Surface analysis of the corrosion products formed on iron metal exposed to off gas from a HCN production process has been performed. The atmosphere contains HCN(g), NH//3(g), and H//2O(g) plus trace gases. Iron gratings exposed to the atmosphere form a dark blue coating which pits the surface of the iron. Samples of the corroded iron surface were analyzed by FT-IR/photoacoustic spectroscopy (PAS) and x-ray photoelectron spectroscopy (XPS or ESCA). The mid-IR spectrum from PAS yielded peaks due to NH//4** plus , CN** minus , and H//2O. ESCA analysis confirmed that the surface iron was divalent, coordinated to cyanide, and no iron(II) oxide was present. Relative quantitation from ESCA showed a 1:4 ratio of NH//4/CN type nitrogen, thus a specific single stoichiometry was not postulated for the corrosion product. This study illustrates the detailed structural information obtainable from FT-IR/PAS with ESCA and the applicability of FT-IR/PAS to corrosion problems.