The electrode state changes with the thickening of the coating in Cr(Ⅲ) thick chromium plating. Thedeposition of Cr(Ⅲ) is carried out on the substrate at the beginning of deposition and on the chromiumcoating when the chromium coating becomes thicker. The aim of this work is to study the influence ofthe change of electrode state on the reduction mechanism of trivalent chromium. The electrodepositionmechanism of Cr(Ⅲ) is studied by cyclic voltammetry, electrochemical impendance spectroscopy,chronoamperometry and polarization technique. The results show that the reduction of Cr(Ⅲ) onchromium coating electrode has a negative deposition potential, higher charge transfer resistance,higher activation energy, and lower diffusion coefficient than those on the nickel electrode, thereduction of Cr(Ⅲ) is more difficult on chromium coating electrode. The change of electrode state isone of the reasons for the difficulty in thickening of chromium coating.
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