Corrosion Resistance of Electrodeposited Nanocrystalline Ni from Citrate Baths

Gold has been widely used for the contacts in electrical connectors. However, people are searching for the substitute of gold due to its high cost. Nickel is considered as the ideal metal to replace gold since the former has a number of superior properties. Electroplating nickel from Watts bath is the prevalent method for nickel production, but boron compounds are harmful to environment. Sodium citrate can be an environmentally friendly alternative to boric acid. In this research, nanocrystalline Ni deposits with different grain sizes were electrodeposited from citrate bath. The effects of sodium citrate concentration, current density and pH on the electrodeposited Ni properties were analyzed. The cathodic current efficiency decreased with the increase of sodium citrate due to the complexation of Ni
²⁺
and citrate ions. Sodium citrate influenced the orientation and grain size of nickel deposits. The corrosion resistance of nickel deposits from citrate baths is comparable to that of boric acid baths. The corrosion resistance of Ni coatings in 1 mol·L
^-1
H
₂
SO
₄
increased when the grain size decreased from 43.9 nm to 25.7 nm because of the faster formation of Ni(OH)
₂
passive films.