Role of a Pb²⁺ Stabilizer in the Electroless Nickel Plating System:  A Theoretical Exploration

Abstract

The electroless nickel plating process involves multiple chemical reactions that interrelate mutually in intricate ways and take place almost simultaneously. This work attempts to provide a theoretical template for understanding this complicated system from the role of heavy metal stabilizers. Pb 2+ ion was selected for the study because it is the most effective species in this category. A theoretical expression of the nickel deposition rate is created by envisioning the Stern-Grahame electrical double layer presumably attached to the plating frontier (the inner Helmholtz plane) as a one-dimensional potential well and the electron transfer from the Fermi level of plating frontier to Ni 2+ ions at the outer Helmholtz plane as the quantum tunneling effect. The deposition of P atoms is assumed to go through the oxidative-addition of hypophosphite (H 2 PO 2 -) ions at Ni atoms on the plating frontier and on this basis its theoretical deposition rate is developed. Another adsorption state of H 2 PO 2on the surface Ni atoms is proposed to form by its two oxygen atoms, and the P(I) center supplies electrons to the plating frontier through these two oxygen bridges. Establishing the relationship between Pb 2+ -ion concentration and the Fermi level of the plating frontier (i.e., inside the solid Ni-P alloy deposition layer on the plating substrate) is an important step for deriving the nickel and element phosphorus deposition rates. The stabilizing effect of the lead ion is attributed to its participation as the neutral atom in the lattice of the Ni-P film at the plating frontier, which results in the ascension of Fermi energy. Thus, the oxidation of hypophosphite at the plating frontier is retarded, which in turn slows down the deposition of both Ni and P that needs electrons. The dependence of the deposition rates of Ni and P on concentrations of Pb 2+ ion was experimentally examined. It is found that the theoretical models predict well the experimental trends. The parameters designated in the theoretical model are determined through a self-consistent computation procedure.

Electroless Ni–Cu–P plating onto open cell stainless steel foam

“…Hence, the addition of CuSO 4 Á5H 2 O will inhibit Ni reduction resulting in deposition rate decrease [20]. The recent studies found that Cu played three different roles: as a stabilizer (due to the reduction of adsorbed Cu +2 to Cu and Cu + ); as an accelerator (due to the catalytic properties of Ni-Cu alloys); and as affecting the solution stability (due to the formation of randomly dispersed copper particles in the solution) [16,[23][24][25][26][27].…”

Synthesis of nickel nanoparticles supported on metal oxides using electroless plating: Controlling the dispersion and size of nickel nanoparticles

“…1 shows two reaction routes for the formation of nickel nuclei. First, the diffusion of nickel colloidal particles from the plating solution during the electroless Ni-P plating on the glass substrates has been reported by Yin et al and other researchers [20][21][22][23][24]. As shown in Fig.…”

“…Yin has reported the formation of nickel colloids in the plating solution [20,21]. To study the formation of new nuclei, an experiment on electroless nickel-plating on Ag/Al 2 O 3 bars was carried out.…”

Metallosomes: artificial cell membranes with ultrathin metallic surfaces derived from cationic cerasomes through electroless plating

“…The deposition of Ni on the cerasome surface was confirmed using EDX analyses: after the plating, the peak of Ni is clearly apparent in the EDX spectra. The EDX spectra of the Ni-metallosomes also contained the peak of P. The incorporation of P, derived from H 2 PO -2 in the plating solution, into the resultant Ni layer generally occurred in the cases of electroless Ni plating systems, 15), 23) which is reasonable when considering the plating mechanism. 23) As confirmed from the SEM observations of several different samples, all of the Ni components were found to bind to the cerasome surface, which indicates that Ni was deposited selectively on the cerasome surface in the regions where the Pd catalyst was immobilized, but not in the bulk solution.…”