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. (c) 2007 Elsevier B.V. All rights reserved.