Local　corrosion　at　a　defect　on　a　pipeline　was　assessed　using　both　2-dimensional　(2D)　and　3-dimensional　(3D)　finite　element　models　under　mechano-electrochemical　(M-E)　interaction.　While　the　M-E　interaction　increases　corrosion　activity　at　the　defect,　the　assessment　of　M-E　interaction　would　have　different　results　using　2D　and　3D　models.　Compared　with　the　3D　model,　the　2D　model　produces　a　greater　local　stress,　a　higher　local　plastic　strain,　a　more　negative　corrosion　potential　and　a　higher　anodic　current　density　at　the　defect,　and　thus,　a　lower　threshold　internal　pressure　causing　local　yielding.　The　3D　model　is　more　conservative　for　corrosion　rate　prediction　of　corroded　pipelines.　A　new　concept,　rAZ　(the　ratio　of　the　anodic　zone　length　to　defect　length　in　the　2D　model,　or　the　ratio　of　the　anodic　zone　area　to　the　defect　area　in　the　3D　model),　is　proposed　to　define　growth　mode　of　the　corrosion　defect.　There　is　a　smaller　rAZ　produced　in　2D　model.　At　specific　internal　pressures,　the　2D　model　predicts　an　ellipsoidal　defect　center　area　experiencing　accelerated　corrosion　and　potentially　resulting　in　pipeline　leaking.　©　2021　National　Assoc.　of　Corrosion　Engineers　International.　All　rights　reserved.