Selected　area　grain　boundary　diffusion　(SAGBD)　will　introduce　microstructural　inhomogeneity　into　Nd-Fe-B　magnets,　it　remains　unclear　whether　this　inhomogeneity　affects　the　service　performance　of　the　magnets　remains　unclear.　In　this　paper,　the　micro-area　electrochemical　behavior　of　corrosion　in　SAGBD　magnets　has　been　studied　by　scanning　vibrating　electrode　technique　(SVET),　and　the　results　indicate　that　the　galvanic　corrosion　occurs　in　the　SAGBD　magnets,　which　the　diffused　areas　(cathodes)　are　at　a　higher　potential　while　the　undiffused　areas　(anodes)　corrode　preferentially,　indicating　that　anode–cathode　reversal　occurs　in　SAGBD　magnets.　Moreover,　the　synchronous　improvement　of　magnetic　properties　and　corrosion　resistance　could　be　achieved　by　adjusting　the　ratio　of　diffused　and　undiffused　areas.　This　work　may　supply　an　anti-corrosion　method　based　on　galvanic　corrosion　mechanism　in　the　SAGBD　magnet.　©　2025