Black nickel electrodeposition from a modified Watts bath

Abstract

Black nickel coatings were electrodeposited on to steel substrates from a Watts bath containing potassium nitrate. The best operating conditions necessary to produce smooth and highly adherent black nickel were found to be NiSO4 Æ 6H2O 0.63 M, NiCl2 Æ 6H2O 0.09 M, H3BO3 0.3 M and KNO3 0.2 M at pH of 4.6, i=0.5 A dm)2, T=25 C and t=10 min. The modified Watts bath has a throwing power (TP) of 61%, which is higher than that reported, not only for nickel, but also for many other metals electrodeposited from different baths. The potentiostatic current– time transients indicate instantaneous nucleation. X-ray diffraction (XRD) analysis shows that the black nickel deposit is pure metallic nickel with Ni(111) preferred orientation.