Micro-galvanic　corrosion,　driven　by　potential　differences　between　strengthening　phases　and　the　matrix,　is　a　major　concern　for　Mg　alloys　in　NaCl　solution.　Intriguingly,　we　find　that　the　micro-galvanic　corrosion,　dominated　by　the　nobler　18R-LPSO　phase,　is　suppressed　in　Na2SO4　solution,　where　both　the　LPSO　and　Mg　matrix　are　corroded　simultaneously.　Since　the　LPSO　phase　contains　more　Er/Zn　atoms　than　matrix,　higher　proportion　of　Er3+/Zn2+　could　be　released　in　SO42--affected　corrosion,　eventually　forming　a　more　protective　corrosion　film　containing　Er2O3/ZnO/ZnS.　These　findings　highlight　the　specific　corrosion　behavior　of　Mg　alloys　in　Na2SO4　solution,　offering　valuable　insights　for　corrosion　mitigation　strategies.