Fourier-transform infrared studies of the corrosion of nickel in aqueous cyanide media

Abstract

The corrosion of a nickel electrode in aqueous cyanide solutions has been investigated by subtractively normalised interfacial Fourier-transform infrared spectroscopy (SNIFTIRS). At potentials more cathodic than 200 mV vs. SCE, only [Ni(CN)₄]^2– was detected. Cyanide was oxidised to cyanate (OCN^–) and then successively to carbon dioxide at potentials more anodic than 200 mV vs. SCE. Features were assigned to HCN (2094 cm^–1) and HNCO (2256 cm^–1) and their formation was attributed to pH changes associated with the oxidation of cyanide to cyanate, and the decomposition of cyanate (to CO₂ and NH₃). The appearance of a band at ca. 2218 cm^–1 in IR spectra of the thin layer at very high anodic potentials (> 1000 mV vs. SCE) was believed to arise from an unstable nickel(II) isocyanate complex.