The　stray　current　induced　coating　delamination　at　defect　areas　is　complicated　and　with　its　mechanism　uncovered.　In　this　study,　the　delamination　mechanism　of　epoxy　coating　at　defect　areas　under　stray　alternating　current　(AC)　interference　was　investigated　using　electrochemical　methods　and　software　simulation.　The　simulation　results　indicated　that　stray　AC　at　defect　areas　was　not　evenly　distributed.　The　current　density　at　the　defect　edge　was　higher　than　that　at　the　defect　center.　The　electrochemical　results　showed　different　electrochemical　behaviors　on　samples　with　a　various　size　of　defects　as　AC　density　increased.　The　impedance　of　samples　with　small　defects　decreased,　on　the　contrary,　the　impedance　of　samples　with　large　defects　increased.　The　delamination　area　on　samples　with　small　defects　was　larger　than　that　with　large　defects　under　the　same　level　of　AC　interference.　Furthermore,　the　AC　interference　resulted　in　a　more　severe　corrosion　damage　at　the　small　coating　defects.　Small　defects　deserve　particular　attention　in　the　safety　assessment　at　the　presence　of　stray　AC.