The use of XPS for study of the surface layers of Cr–Co alloy electrodeposited from Cr(III) formate–urea baths

The chemical composition of the top layers of Cr–Co alloy electrodeposited from Cr(III) formate–urea baths with various concentrations of CoCl2 was studied by the X-ray photoelectron spectroscopy method. The quantity of each element in at.% was calculated from the single Cr2p3, Co2p3, C1s, O1s and N1s peak areas. Analysis of XPS spectra has shown that the surface of Cr–Co alloy is covered with the thick oxide film (about 20 nm) and the bulk of the deposit consists of two phases: carbide and metallic of both chromium (about 60 at.%) and cobalt (about 3 at.%). A low percentage (about 3 at.%) of nitrogen in the bulk of the deposit suggests the presence of chromium nitrides, which may be formed along with carbides during electrodeposition owing to reduction of chromium–carbamide complexes and an extremely high electrocatalytic activity of chromium in the cathodic processes.