On the Possibility of Replacing Standard Chromium-Plating Electrolytes with Sulfate-Oxalate Solutions of Cr(III)

A method for preparing sulfate-oxalate chromium-plating solutions by reducing Cr(VI) from industrial chromium-plating electrolytes to Cr(III) with a Na₂SO₃ solution is proposed.     

Solution of a problem of mendeleev type and the estimation of the derivatives of polynomials in the laguerre weighted space L2

Translated from Matematicheskie Zametki, Vol. 50, No. 1, pp. 10–18, July, 1991.     

Corrosion–Electrochemical Behavior of Chromium Deposits Obtained from Sulfuric Acid Solutions Containing Oxalates

The corrosion–electrochemical behavior of chromium electrodeposits, which are formed in sulfuric acid solutions of Cr(III) containing oxalates, is studied by taking steady-state polarization measurements in a 0.5 M H₂SO₄ solution. No region of the metal's active dissolution is observed for such coatings, and the open-circuit potential is localized in the passivity region, i.e. it is substantially displaced in the positive direction as compared with that for metallurgic chromium or the coatings deposited from standard chromium-plating electrolytes. According to XPS data, the surface layer of the passive metal a few nanometers thick includes oxide compounds of chromium and also carbides formed during the coating electrodeposition. Specific features of the corrosion–electrochemical behavior of the deposits are attributed to the presence of carbide compounds of chromium in them, with the compounds playing the role of a cathodic alloying agent.     

Distribution of components of binary nickel—chromium alloys electrodeposited from sulfate—oxalate solutions

The composition and distribution of elements over the thickness of electrodeposited nickel—chromium layers are studied by x-ray photoelectron and Auger electron spectroscopy techniques. During a layer-by-layer etching, the Cr : Ni ratio varies with a period of 2–5 nm. This period and the amplitude of the ratio of concentrations of components increases with the current density. During alloy deposition on a copper cathode, the first to deposit is nickel, which exerts a catalytic effect on the chromium deposition, which in turn exerts a catalytic effect on the oxalate reduction to carbon. Once a deposit thicknesses of ~100 nm is reached, the alloy composition becomes constant. The deposits contain considerable amounts of carbon (in the form of graphitized structures and carbides), which increases from 0.6 to 2 wt % with the current density. The surface of the growing alloy 50–70 nm thick is rich in nickel and chromium hydroxides and organic compounds containing carboxyl groups.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1481–1486.Original Russian Text Copyright © 2004 by Edigaryan, 4, Lubnin, Polukarov.     

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.     

Electrodeposition of Multilayered Ni–Cr Films from Sulfate–Oxalate Electrolytes

As shown by scanning Auger electron microscopy and Auger electron spectroscopy, multilayered Ni–Cr thin films can be deposited under the action of periodic currents from sulfate–oxalate solutions containing nickel and chromium ions. The chromium-rich layers have an amorphous structure. In the nickel/chromium interphase region, the carbon content is elevated. Nickel layers contain admixtures of a hydroxide nature.