Ionics

, Volume 19, Issue 6, pp 911–918

Effect of sodium citrate as complexing on electrochemical behavior and speciation diagrams of CoFeNiCu baths

Original Paper

DOI: 10.1007/s11581-012-0815-8

Cite this article as:
Mehrizi, S., Sohi, M.H. & Saremi, M. Ionics (2013) 19: 911. doi:10.1007/s11581-012-0815-8

Abstract

In this study, the effects of addition of sodium citrate dosages and different pH levels on the electrochemical behavior of CoFeNiCu alloy baths (electrolytes containing metal ions) were investigated. Stability (Pourbiax) diagrams and also speciation diagrams of cobalt, iron, nickel and copper, in conventional and citrate-added CoFeNiCu bath, were calculated by ChemEQL V.3.0 software. Stability diagrams showed that addition of 20 g L−1 sodium citrate to the bath increased the pH of formed detrimental metal hydroxides (especially Fe(OH)3 from pH 3.4 to pH ~ 6.9) through forming stable complexed species that were more stable than metal hydroxides at low pH levels (< ~3). According to the speciation diagrams, both pH level and sodium citrate dosage had noticeable effect on the distribution of species in the baths. Generally, at low pH level and/or sodium citrate dosage, Co++, Fe++, Ni++, and Cu++ species were dominant. The concentration of complexed species of Co(C6H5O7) ( at pH > ~ 7.5 or sodium citrate dosage > ~ 30 g L−1), Fe(C6H5O7) (at pH > ~ 5.5 or sodium citrate dosage > ~ 25 g L−1), Ni(C6H5O7) (at pH > ~ 6 or sodium citrate dosage > ~ 30 g L−1), and Cu(OHC6H5O7)2− ( at pH > ~ 8 or sodium citrate dosage > ~ 20 g L−1) became significant. The effects of sodium citrate and reverse potential (Eλ) on cyclic voltammetry curves were also studied. The addition of sodium citrate in the bath shifted the reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt, iron, and nickel simultaneously with copper, it was necessary to increase Eλ value gradually with sodium citrate dosage; otherwise, only copper would have deposited from citrate-added CoFeNiCu bath. The study of speciation diagrams showed that reduction of metals from CoFeNiCu bath with natural pH (no acid or base is added to adjust pH and it was ~ 5.2) and containing 20 g L−1 of sodium citrate mainly occurred directly from complexed species.

Keywords

CoFeNiCuCitrateElectrochemicalPourbiax diagramSpeciation diagram

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  1. 1.School of Metallurgy and Materials Engineering, College of EngineeringUniversity of TehranTehranIran