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

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.