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

Authors

Hui YAN
Shuai-shuai HUANG
Fang-zu YANGFollow
Zhong-qun TIAN
Shao-min ZHOU

Corresponding Author

Fang-zu YANG(fzyang@xmu.edu.cn)

Abstract

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 (E_corr) and corrosion current density (j_corr) of the coating in 3.5wt% NaCl solution were determined to be -0.29 V and 9.26×10^-5 A·dm^-2, respectively.

Graphical Abstract

Keywords

Trivalent chromium, Sulphate, Hard chromium, Electrodeposition, Mechanism, Coating Characterization.

DOI Link

https://doi.org/10.13208/j.electrochem.170441

Publication Date

2018-02-28

Online Available Date

2017-05-18

Revised Date

2017-05-17

Received Date

2017-04-14

Recommended Citation

Hui YAN, Shuai-shuai HUANG, Fang-zu YANG, Zhong-qun TIAN, Shao-min ZHOU. Deposition Mechanism and Coating Characterization for the Trivalent Chromium Electrodeposition in Sulphate Electrolyte[J]. Journal of Electrochemistry, 2018 , 24(1): 170441.
DOI: 10.13208/j.electrochem.170441
Available at: https://jelectrochem.xmu.edu.cn/journal/vol24/iss1/12