Electrodeposition of iron-rich Ni-Fe alloys from sulphate and chloride baths

Abstract

The electrodeposition of iron-rich Ni-Fe alloy deposits from both sulphate and chloride baths and their mechanical properties (hardness, ductility and internal stress) are discussed in detail as a function of bath composition and current density. The current efficiencies of Ni-Fe alloy deposition in the sulphate and chloride baths were found to be 85%–95% and 46%–65% respectively. The composition of the Ni-Fe alloy deposits changed markedly with increasing current density. The hardness of the Ni-Fe alloy deposits with nickel contents above 20 wt.% was 400–500 HV. Large internal stresses were observed in the pure iron and Ni-Fe alloy deposits obtained from both sulphate and chloride baths. However, the Ni-Fe alloy deposits have no cracks. The ductility of the Ni-Fe alloy deposits obtained from the sulphate bath ([Fe]/[Ni] = 1) increased with increasing current density. The electroplated iron had a textured structure. However, addition of Ni 2+ ions to the iron plating bath led to a fine-grained lamellar structure.