Effect of Sodium Hypophosphite Content in the Electroplating Bath on the Electrochemical Properties of Ni-P Alloy Coatings
Porous Ni-P alloy coatings were prepared by galvanostatic electrodeposition at the deposition current density of jdep = -250 mA cm-2 from the nickel plating bath of the Watts type containing different content of sodium hypophosphite. Investigations of hydrogen evolution reaction (HER) were carried out in 5 M KOH solution at room temperature. Ac impedance behavior of the electrodes was described using electrical equivalent circuits containing two constant-phase elements (two-CPEs electrode model). The results obtained from the EIS and steady-state measurements allowed to determine the Volmer-Heyrovský mechanism and kinetics of the HER. It was found that for the Ni-P alloy coatings deposited from the galvanic baths after addition of sodium hypophosphite in the amount of 5, 10, 20 and 30 g dm-3, the decrease in their catalytic activity towards the HER is observed due to diminishing of intrinsic activity of the electrodes.
M. Popczyk and B. Łosiewicz, "Effect of Sodium Hypophosphite Content in the Electroplating Bath on the Electrochemical Properties of Ni-P Alloy Coatings", Solid State Phenomena, Vol. 228, pp. 246-251, 2015