Effect of rare earth (Ce, La) compounds in the electroless bath on the plating rate, bath stability and microstructure of the nickel–phosphorus deposits

Effects of added rare earth elements (RE) in the acidic hypophosphite plating bath on the plating rate, bath stability and microstructure of the electroless nickel–phosphorus (EN) deposits were studied. The surface appearance and microstructure were examined under a reflection optical microscope and a scanning electron microscope equipped with an in-situ energy dispersive X-ray spectroscopy, which can evaluate the elemental analysis of deposits. It was demonstrated that the rare earth elements can decrease grain size and refine microstructure.The deposition rate of the Ni–P deposits was estimated by gravimetric, polarization and quartz crystal microbalance (QCM) methods. Results revealed that up to an optimum concentration of rare earth elements, the deposition rate increases. The stability test method was used to determine the stabilization effect of RE on the stability of the bath. It was found that the addition of RE significantly improved the Pd stability of the EN bath.