THE KINETICS OF NICKEL ELECTRODEPOSITION INHIBITION BY ADSORBED HYDROGEN AND ANIONS

This study investigates the kinetics of nickel electrocrystallization through impedance measurements in strongly acidified chloride electrolytes and with additives such as 2 butyne 1,4 diol and sodium benzenesulfonate. In chloride solutions at pH 0.5, notable inductive effects and a distinct capacitive low-frequency feature were observed, contrasting with less acidified environments. The presence of 2 butyne 1,4 diol demonstrated a more significant inhibiting influence in chloride than in sulfate solutions, extending the range of potential where the inductive low-frequency effect manifests compared to additive-free electrolytes. The addition of sodium benzenesulfonate further revealed both inductive and capacitive low-frequency responses in the electrolytes studied. A proposed reaction mechanism explains these observations, illustrating the effects of various anions on the kinetics. Specifically, in sulfate electrolytes, the interaction between strongly bonded adsorbed hydrogen and intermediate adions is key, while in chloride electrolytes, the slow desorption of an adsorbed anionic species predominates. This mechanistic insight elucidates the impact of additives on nickel deposition kinetics.