Composition, structure, and corrosion-electrochemical properties of chromium coatings deposited from chromium(III) electrolytes containing formic acid and its derivatives

To study electrocatalytic properties of chromium, its deposits are obtained from Cr(III) electrolytes containing formic acid and its four derivatives (formaldehyde, methyl alcohol, formamide, dimethylformamide) and comprehensively examined. Amorphous structure of the deposits is established with an x-ray diffraction analysis. The valence state of chromium and major extrinsic elements is studied by x-ray photoelectron spectroscopy. The carbon reduction degree and the organization of carbon particles in deep layers of the deposits (chainlike or graphite-like structures) is shown to depend on the nature of organic compounds added into the chromium-plating electrolyte. The corrosion-electrochemical behavior of the obtained deposits in 0.5 M H2SO4 is compared to that of polycrystalline chromium and deposits plated from sulfate-oxalate Cr(III) electrolytes.