The use of XPS for study of the surface layers of CrNi alloys electrodeposited from the Cr(III)+Ni(II) bath

► The morphology of Ni-rich and Cr-rich alloy coatings was found to have a nodular structure, however, Cr-rich deposits had nanoscale cracks. ► The passive film on CrNi alloys consists of Cr(OH)3, Cr(OH)O, Cr2O3 and low amounts of both NiO and organic substances. ► Nickel is incorporated in bulk of CrNi alloys as metallic Ni0, whereas, chromium is present as metallic and carbide phases. This paper reviews the CrNi alloys electrodeposited from Cr(III) oxalate bath containing NiSO4. Ni-rich and Cr-rich alloy coatings were shown to have a nodular structure with smaller size of nodules for the Ni-rich alloy compared to those for the Cr-rich one which has a nanoscale cracked morphology. The chemical composition of the top layers of CrNi alloys electrodeposited from Cr(III)+Ni(II) bath was studied by the X-ray photoelectron spectroscopy method. Analysis of XPS spectra has shown that the surfaces of both Ni-rich and Cr-rich alloys are covered with the oxide films consisting mainly of Cr(OH)3, Cr(OH)O and Cr2O3 with minor amounts of both NiO and organic substances. The data obtained suggest that Cr(OH)3 and Cr(OH)O dominate outside, whereas, Cr2O3 dominates inside the film. It has been found that nickel is incorporated in bulk of the deposits as metallic Ni0, whereas, chromium is present as metallic Cr0 and chromium carbides.