MECHANISM OF TRIVALENT CHROMIUM ELECTRODEPOSITION USING Cr(III)-CONTAINING BATH WITH AND WITHOUT INORGANIC ADDITIES
Cathodic polarization technique was used for different Cr(III)-containing baths to explore the effect of inorganic additives on the mechanism of trivalent chromium electrodeposition. The presence of cations in the Cr(III)-containing bath can support a good condition for the diffusion of Cr3+ complexes from the bulk electrolyte to the cathode surface, thus improving the reduction of the Cr-complex. On the contrary, effect of anions was more complicated due to the appearance of additional reactions or an increase of viscosity in the bath. Results show that the morphology of the coating depends significantly on the addition of cations and anions. Quality of the coating is much better from the baths with the addition of Na+ or Mg2+ than addition-free, and only SO42- was acceptable to obtain a smooth morphology. In addition, higher current efficiency can be obtained from the baths added with cations of Na+ or Mg2+, and anion of SO42- in comparison with the other baths.
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