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Mechanism of electroless deposition of Ni–W–P alloys by adding surfactants
Author(s) -
Hamid Z. Abdel
Publication year - 2003
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.1562
Subject(s) - sodium tungstate , adsorption , aqueous solution , tungstate , critical micelle concentration , inorganic chemistry , nickel , chemistry , tungsten , surface tension , metal , salt (chemistry) , pulmonary surfactant , micelle , organic chemistry , biochemistry , physics , quantum mechanics
This paper describes an electroless deposition method for the formation of a thin metallic film containing mainly nickel with significant amounts of tungsten (up to 25%) and phosphorus (5–10%). The film was deposited from an aqueous electrolyte that contained sodium tungstate as a source of tungsten, nickel sulphate as a source of nickel and hypophosphite as the reducing agent and a source of phosphorus. The surfactants were p ‐hexyloxy‐ p ‐sodium sulphonate azobenzene (HSA) with the formula H 13 C 6 OC 6 H 4 N 2 C 6 H 4 SO 3 Na and p ‐hexylbenzyltriethanol ammonium chloride (HBC) with the formula H 13 C 6 H 4 CH 2 N + (C 2 H 4 OH) 3 Cl − , added as stabilizers. In this study the process parameters of typical solutions, such as temperature, pH and concentration of tungstate salt and the concentration of different surfactants, were presented and discussed. Adsorption of the surfactants on a metal surface was dependent, among other things, on the structure of their hydrophobic and hydrophilic portions. The effect of adsorption of these surfactants on a metal surface was examined above and below the critical micelle concentration (CMC). The deposition process involves several reactions that occur simultaneously and are described in detail in this work. The mechanism for interaction of the surfactants with the steel surface was proposed through the isotherm for adsorption from aqueous solution. Furthermore, the surface properties of the surfactants were measured, particularly the CMC, the surface tension reduction and the maximum surface excess Γ max . The tungsten percentage in the deposit layer was strongly influenced by the plating conditions and the critical concentration of each surfactant. The results were discussed according to the surface properties of the additive. The thin film of Ni–W–P achieved high crystal refinement and high hardness, it was smooth and uniform and it exhibited superior corrosion resistance. Copyright © 2003 John Wiley & Sons, Ltd.