Suppressing dendrite growth of the cadmium deposits in a high-viscous ethylene glycol solution by pulse electrodeposition

Electrodepositing cadmium in the non-aqueous ethylene glycol solution eliminates the risk of hydrogen embrittlement. However, the high viscosity of ethylene glycol combined with the large ionic radius of cadmium ions leads to significant concentration polarization, resulting in the formation of porous deposits and dendritic growth at the substrate edges. This study employed pulse electrodeposition and compared the effects of different current waveforms (direct current, unidirectional pulse current, and direct current superimposed with bidirectional pulse current) to address these issues. The results demonstrate that pulse currents significantly enhance the nucleation rate during the initial deposition stage, thereby substantially improving the compactness of the coatings. Introducing bidirectional pulse currents onto a DC baseline effectively suppresses dendritic growth at the edges and increases the effective coating thickness. This beneficial effect is achieved through the preferential dissolution of edge dendrites by the anodic current pulses, which weakens the concentration polarization effect. A detailed discussion on the nucleation and growth processes of the deposits under different current waveforms is provided. This work offers a feasible pathway for electrodepositing high-performance, corrosion-resistant coatings in high-viscosity systems.