The　effect　of　heat　treatment　on　the　long-term　corrosion　resistance　of　Er　containing　5083　aluminum　alloy　was　studied　using　the　micro-hardness　test　and　mass　loss　test.　The　microstructure　was　analyzed　by　TEM.　To　maintain　the　strength,　the　annealing　temperature　was　selected　to　be　100-230.　below　the　recrystallization　onset　temperature　determined　by　the　micro-hardness　test.　The　plot　of　the　annealing　temperature　versus　the　Intergranular　Corrosion　(IGC)　initial　time,　which　is　determined　by　the　Nitric　Acid　Mass　Loss　Test,　showed　a　C-curve.　The　shortest　IGC　initial　time　(similar　to　1h)　happened　at　175　degrees　C,　the　nose　temperature　of　the　C-curve.　When　annealed　at　125-200　degrees　C,　the　samples　were　IGC　sensitive　with　the　initial　time　less　than　3h.　The　entirely　IGC　resistant　(stabilized)　samples　were　obtained　when　annealed　at　220-230　degrees　C.　The　175　degrees　C　sensitized　treatment　was　performed　on　the　220　degrees　C-stabilized　samples,　which　showed　that　the　3-12h　stabilization　could　significantly　improve　the　resistance　for　long-term　corrosion.　TEM　results　showed　that,　for　the　IGC　sensitive　samples,　beta　phases　(Al3Mg2)　grew　along　the　grain　boundary　continuously,　while　for　the　stabilized　samples,　they　were　isolated　on　triangle　grain　boundary　and　phase　boundary.