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Journal of Electrochemistry ›› 2018, Vol. 24 ›› Issue (1): 20-27.doi: 10.13208/j.electrochem.170441

• Special Issue on Electroplating and Surface Finishing(Guest Editor:Professor Dr. Maozhong An) • Previous Articles     Next Articles

Deposition Mechanism and Coating Characterization for the Trivalent Chromium Electrodeposition in Sulphate Electrolyte

YAN Hui,HUANG Shuai-shuai,YANG Fang-zu*,TIAN Zhong-qun, ZHOU Shao-min   

  1. State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry,College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian, China
  • Received:2017-04-14 Revised:2017-05-17 Online:2018-02-28 Published:2017-05-18
  • Contact: YANG Fang-zu E-mail:fzyang@xmu.edu.cn


Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used to study the electrodeposition mechanism of trivalent chromium on a copper electrode in the novel sulphate electrolyte for thick trivalent chromium plating. The thickness, morphology, composition, microhardness, and structure, as well as the corrosion resistance in 3.5wt% NaCl solution of the trivalent chromium coatings were investigated by X-ray fluorescence gage, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness tester, X-ray diffraction (XRD) and Tafel curve measurements. The results showed that the electrodeposition of trivalent chromium involved two consecutive one electron reduction steps. The first step, Cr3+ + e → Cr2+,is controlled by the electrochemical reduction and diffusion processes, and the second step, Cr2+ + 2e → Cr, is an irreversible process under the diffusion control. The trivalent chromium coating exhibited nodular nanocrystalline structure and contained a small amount of iron (1.10wt%). The microhardness of the coating reached to 789.2 Hv. The corrosion potential (Ecorr) and corrosion current density (jcorr) of the coating in 3.5wt% NaCl solution were determined to be -0.29 V and 9.26×10-5 A·dm-2, respectively.

Key words: Trivalent chromium, Sulphate, Hard chromium, Electrodeposition, Mechanism, Coating Characterization.

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