Corrosion resistant sintered material, especially a sintered rare earth permanent magnet, is produced by pickling to remove adhering surface particles and surface passivation prior to metal coating

摘要

Corrosion resistant sintered material production, comprises pickling to remove adhering surface particles and surface passivation prior to metal coating. A corrosion resistant sintered material production process comprises surface activation, metal coating and heat treatment, the activation stage involving: (a) pickling to remove adhering surface particles; (b) surface passivation with a hydrophilic solvent, a phosphating solution, a chromating solution or a dewatering liquid or by heat treatment; and (c) drying. An Independent claim is also included for a rare earth-containing magnetic body with a corrosion inhibiting metal surface layer having a specified corrosion resistance as determined by the HAST test (highly accelerated steam test). Preferred Features: Pickling is carried out using an aqueous 0.2-25 wt.% acid solution. The metal coating contains /-75 wt.% aluminum and is applied by physical vapor deposition (PVD).