Influence of pulse reverse current parameters on electrodeposition of copper-graphene nanocomposite coating

This work focuses on the influence of pulse reverse current parameters such as duty cycle and frequency on the microstructure and properties of graphene reinforced copper nanocomposite (Cu-Gr) coating. Graphene nanosheets were prepared by a liquid phase exfoliation technique and characterized using FE-SEM and Raman spectroscopy. Cu-Gr nanocomposite coating on stainless steel was prepared by pulse reverse electrodeposition method. The influence of pulse reverse current parameters such as duty cycle and frequency on the coating structure and texture was analyzed. By reducing the duty cycle and increasing frequency, a high amount of graphene co-deposition was achieved. A duty cycle of 40%, frequency of 1000 Hz and stirring speed of 500 rpm produced Cu-Gr coatings with maximum graphene codeposition. XRD analysis showed that the change in duty cycle and pulse frequency influenced the crystal structure, preferred orientation, and crystallite size of the deposit. A high pulse frequency improved the compactness of the composite coating, while longer pulse off-time and application of reverse pulse resulted in highly oriented (220) texture of pure Cu and Cu-Gr nanocomposite coatings. Due to graphene co-deposition, the copper grains became more refined, and hence the microhardness of the composite coating showed a tremendous increase compared to pure Cu coating. The Tafel polarization and electrochemical impedance studies revealed that pulse reverse electrodeposited Cu-Gr coating has higher corrosion resistance than pure Cu coating due to strong (220) texture and barrier effect of graphene.