Mechanism of zinc electroplating in alkaline zincate solution

Abstract

The cathodic deposition properties and mechanism of Zn in alkaline zincate solution were studied by electrochemical techniques. The results show that Zn²⁺ exists in the alkaline solution in the form of Zn(OH)₄²⁻. The apparent activation energy of the electrode reaction is 38.93 kJ/mol, which indicates that the discharge of Zn(OH)₄²⁻ on cathode is controlled by electrochemical polarization, and accompanied by a preceding chemical reaction. The diffusion coefficient of Zn(OH)₄²⁻ is 2.452 × 10⁻⁶ cm²/s. Zn(OH)₂ is the species directly discharged on the cathode surface. Based on the above results the mechanism of zinc electroplating in alkaline zincate solution was put forward. The discharged species is Zn(OH)₂ formed from the preceding chemical reaction, which becomes Zn(OH)_ad when gaining one electron, and then gaining the second electron to become Zn. The first electron gaining step is rate determining one.

Keywords

Zn electroplating / mechanism / alkaline / zincate

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