Coarse-grained　(CG),　fine-grained　(FG),　and　ultrafine-grained　(UFG)　Al-2.5　wt%　Cu　(Al-Cu)　alloys　were　respectively　prepared,　with　and　without　0.3　wt%　Sc　addition,　for　comparison.　The　influences　of　minor　Sc　addition　on　the　microstructural　evolution,　tensile　mechanical　properties　and　pitting　corrosion　resistance　were　system.　atically　studied　at　different　grain　scales.　A　significant　Sc　microalloying　effect　on　the　precipitation　was　observed　that　the　minor　Sc　addition　promoted　the　dispersion　of　finer　theta＇-Al2Cu　precipitates　in　the　CG　alloy　and　favored　the　intragranular　theta＇-Al2Cu　precipitation　in　the　FG　and　UFG　alloys,　with　the　smaller　grain　size　leading　to　a　stronger　Sc　microalloying　effect.　The　Sc　addition　induced　convincing　increases　in　the　yield　strength　at　all　the　three　grain　scales,　and　improved　(in　the　CG　and　UFG　Al-Cu　alloys)　or　retained　(in　the　FG　Al-Cu　alloy)　the　pitting　corrosion　resistance　at　the　same　time.　This　indicates　that　the　inverse　strength-pitting　corrosion　correlation　as　usually　observed　can　be　broken　by　minor　Sc　addition.　The　strengthening　mechanisms　were　discussed　and　the　grain　size　dependent　pitting　corrosion　resistance　mediated　by　the　Sc　addition　was　rationalized　in　terms　of　a　competition　between　the　positive　influence　derived　from　the　interfacial　Sc　segregation　and　the　negative　influence　come　from　the　deformation-induced　dislocations.　The　present　findings　provide　a　possible　approach　to　break　the　inverse　strength-pitting　resistance　correlation　in　heat-treatable　Al　alloys　by　modifying　the　precipitate/matrix　interfaces　through　the　suitable　microalloying　atom　segregation.