Superior corrosion resistance and corrosion mechanism of dual-main-phase (Ce15Nd85)30FebalB1M magnets in different solutions

The electrochemical corrosion behavior of both (Ce₁₅Nd₈₅)₃₀Fe_balB₁M sintered magnets prepared with dual-main-phase method and N45-type magnets was studied in 3.5 wt% NaCl, 1.1 wt% NaH₂PO₄, and 2.5 wt% NaOH solutions, respectively. The (Ce₁₅Nd₈₅)₃₀Fe_balB₁M sintered magnets perform superior corrosion resistance than N45-type magnets in the tested solutions. In general, two kinds of magnets exhibit the best corrosion resistance property in 2.5 wt% NaOH solution, while the worst in 3.5 wt% NaCl solution. Microstructures of samples before and after corrosion were investigated. With the addition of Ce by means of dual-main-phase method, which is conducive to facilitating low-temperature sintering and grain refinement, uniform grain size and (Nd, Ce)-rich phase distribution form, give rise to narrow and thin corrosion channels. Moreover, the corrosion rate of the (Nd, Ce)-rich phase is lower than that of Nd-rich one. Accordingly, corrosion resistance of (Ce₁₅Nd₈₅)₃₀Fe_balB₁M sintered magnet is superior when compared with the commercial N45-type magnet which has comparable magnetic properties.