Abstract: The invention relates to a method of obtaining friable and relatively inert TR Fe B type magnetic materials in divided form which lead to magnets having improved corrosion resistance. This method involves treating the material in an atmosphere containing (or capable of containing) hydrogen under the following conditions of absolute pressure (P) and of temperature (T.degree. C.): if P.ltoreq.Pa, 250<T<550; and if P>Pa, 250+100 log (P/Pa)<T<250+100 log (P/Pa) log base 10, Pa being atmospheric pressure. The invention is used for obtaining sintered TR Fe B magnets having improved corrosion resistance.