Effects of Y 3+ on properties of electroless NiYP coatings

Abstract

NiYP alloy coatings were prepared on the surface of sintered NdFeB magnets by electroless composite plating. The effects of Y³⁺ concentration on the deposition rate, surface morphologies, element contents and corrosion resistance were investigated. The results showed that the deposition rate of NiYP alloy coatings decreased with the increasing Y³⁺ concentration. A thin NiYP film with adsorbed rare earth yttrium could be formed at higher concentration, which reduced the number of catalytic sites on the surface of intered NdFeB magnets. With the increase in Y³⁺ concentration up to 6 mmol L^− 1, the self-corrosion potential E_corr of the electroless NiYP coatings in 3.5%NaCl solution increased from − 672 to − 513 mV, and the self-corrosion current density I_corr decreased from 28.81 to 1.15 μA cm^− 2. The mechanisms of corrosion resistance of the electroless NiYP coatings modified by Y³⁺ addition were discussed.