ABSTRACT　　　　　　　　　　　　To　improve　the　bonding　strength　of　precision　adhesive　joints,　mechanical　and　electrochemical　surface　treatments　were　combined　to　modify　the　original　bonding　surfaces.　Microgrooves　with　different　aspect　ratios　were　manufactured　on　aluminum-alloy　surfaces　and　phosphoric　acid　anodizing　(PAA)　was　then　applied　to　the　surfaces.　Wettability,　shear　strength,　and　fracture　morphology　were　tested　and　analyzed.　PAA　treatment　could　change　the　original　flat　surface　to　be　hydrophilic,　and　microgrooves　could　further　enhance　these　characteristics.　Compared　with　the　original　flat　surface,　the　shear　strength　of　the　micro-structured　surfaces　without　PAA　treatment　increased　by　8.54%　at　an　aspect　ratio　of　0.02,　but　decreased　by　0.22%　and　1.90%　as　the　aspect　ratio　increased　to　0.04　and　0.08,　respectively.　The　shear　strength　of　the　flat　surface　only　treated　by　PAA　increased　by　22.88%,　while　combining　microgrooves　could　further　improve　the　shear　strength　by　38.17%,　39.09%,　and　42.24%　at　aspect　ratios　of　0.02,　0.04,　and　0.08,　respectively.　Fracture　morphology　analysis　and　observation　of　interfacial　wetting　indicated　that　manufacturing　microgrooves　and　applying　PAA　treatment　on　the　aluminum-alloy　surfaces　could　eliminate　many　tiny　interface　failures　and　greatly　increase　the　effective　bonding　area,　which　significantly　improved　the　shear　strength.