Effects of Y3+ on properties of electroless NiYP coatings

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 6mmolL(-1), the self-corrosion potential E-corr of the electroless NiYP coatings in 3.5%NaCl solution increased from -672 to -513mV, and the self-corrosion current density I-corr decreased from 28.81 to 1.15Acm(-2). The mechanisms of corrosion resistance of the electroless NiYP coatings modified by Y3+ addition were discussed.