DOI: 10.18503/1995-2732-2022-20-3-130-140
Abstract
Chrome plating is widely used to make the surface of metal parts harder, as well as wear and corrosion resistant. Currently, there exists a number of model approximations for chromium plating using solutions containing both six- and trivalent chromium. It is believed that, even when using hexavalent chromium solutions, quality chromium coatings can only be obtained if trivalent chromium ions are also present, as well as activator ions (sulphate ions, fluo-rides, etc.) and organic components. Chrome plating of titanium parts to be used in aircraft, engine and shipbuilding industries helps enhance the wear and heat resistance of such parts without compromizing any of the advantages offered by this structural material. One can find a rather large amount of experimental data relating to chrome plating of iron, nickel and copper alloys, whereas only limited information is available regarding parts made of titanium. Chrome plating of titanium can be complicated due to the presence of natural protective oxide films on its surface. Of practical interest in this research is the study of the electrochemical behaviour of a titanium electrode in model solutions of six- and trivalent chromium compared with iron and nickel electrodes. The study was carried out in potentiodynamic mode. Two groups of chrome solutions were used: based on trivalent chromium salts (KCr(SO4)2·12H2O, Cr2(SO4)3) and chromium anhydride СrO3. As a result, the current-voltage characteristics of cyclic anode and cathode polarization in the range from –1500 to +1500 mV were obtained. Effects of hexavalent chromium reduction to trivalent chromium on cathode lines and those of partial oxidation of Cr(III)→Cr(VI) on anode lines were established. The titanium electrode was found to be less electrochemically active compared with nickel or iron. This is confirmed by the major cathodic overvoltage of the chromium reduction process.
Keywords
electrolytic chromium plating, titanium, nickel, electrolyte, potential, current density, voltammetry, potentiostatic and potentiodynamic methods, limiting stage, mechanism, polarization
For citation
Gruba O.N., Ardashev D.V. Electrochemical Behaviour of Metal Electrodes in Model Chrome Plating Solutions. Vestnik Magnitogorskogo Gosudarstvennogo Tekhnicheskogo Universiteta im. G.I. Nosova [Vestnik of Nosov Magni-togorsk State Technical University]. 2022, vol. 20, no. 3, pp. 130-140. https://doi.org/10.18503/1995-2732-2022-20-3-130-140
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