Nickel electrodeposition from novel citrate bath

Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes (Fe2+/H2O2, UV/Fe2+/H2O2, and electrolysis/ Fe2+/H2O2) in this study. Comparison of these techniques in oxidation efficiency was undertaken. It was found that Fenton process could not completely degrade citrate in the presence of hypophosphite since it caused a series inhibition. Therefore, UV light (photo-Fenton) or electron current (electro-Fenton) was applied to improve the degradation efficiency of the Fenton process. Results showed that both photo-Fenton and electro-Fenton processes could overcome the inhibition of hypophosphite, especially the electro-Fenton.

Removal of citrate and hypophosphite binary components using Fenton, photo-Fenton and electro-Fenton processes.

Simultaneous biodegradation of Ni-citrate complexes and removal of nickel from solutions by Pseudomonas alcaliphila.

Presence of Fe3+ and Zn2+ promoted biotransformation of Cd-citrate complex and removal of metals from solutions.

The influence of methane sulphonic acid, naphthalene sulphonic acid and phenol sulphonic acid on the electrodeposition of nickel from a citrate buffered nickel bath was investigated. Solution characteristics such as cathode efficiency and throwing power have been assessed, and corrosion resistance of the coatings was measured by electrochemical impedance spectroscopy method. The X-ray diffraction pattern obtained for electrodeposited nickel showed a polycrystalline fcc structure. A uniform and pinhole free surface was observed under SEM analysis.

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Effect of sulphonic acids on electrodeposition of nickel and its structural and corrosion behaviour

Adipate, which is used as a buffer in a citric electroless nickel plating solution, adsorbs on the NiP surface and incorporates into coatings when the plating process takes place. The quantity of adipate incorporated into NiP coatings decreases with increase in hypophosphite and citrate concentrations in plating solution, similarly to the quantity of adipate adsorbed from corresponding solutions without Ni(II) on a freshly plated NiP surface. An increase in Ni(II) ion concentration in plating solution also diminishes the quantity of adipate incorporated into coatings, though any decrease in its adsorption on NiP coatings is not observed from the corresponding solutions without hypophosphite (when plating does not occur). The adsorption of adipate and citrate leads to the decrease in the rate of catalytic hypophosphite oxidation. The deposition of smoother and brighter NiP coatings in the presence of adipate together with Cu(II) ions, which act as a stabilizer, is determined by a stronger adipate interaction with Cu as compared with NiP.

G. Stalnionis

Papers

Adipate adsorption and its incorporation into NiP coatings from citrate electroless nickel plating solutions