Impact of ionic liquid [FPIM]Br on the electrodeposition of Ni and Co from an aqueous sulfate bath

A novel ionic liquid, namely, 1-(4-fluorobenzyl)-3-(4-phenoxybutyl)imidazole-3-ium bromide [FPIM]Br, was used as an additive for cobalt (Co) and nickel (Ni) electrodeposition from acidic sulfate and Watts baths, respectively. The effect of [FPIM]Br on the electrodeposition mechanism of the coatings was investigated by a variety of electrochemical methods (potentiodynamic cathodic polarization, cyclic voltammetry, and anodic linear stripping voltammetry) as well as by morphologic techniques (XRD, SEM, EDX and AFM). The inhibition of Co2+ and Ni2+ ions deposition in the presence of [FPIM]Br was found to lead to finer-grained deposits. Adsorption of [FPIM]+ on the copper substrate is shown, and the process obeys the Langmuir adsorption isotherm. The cathodic current efficiency (CCE%), hardness and corrosion resistance for Co2+ and Ni2+ deposition in the electrodeposition bath were found to increase when additive was included. The resultant surface morphologies demonstrated that the [FPIM]Br additive served as an effective brightener that can produce highly uniform and smooth Co and Ni deposits.