The local corrosion behaviour and the mechanism of a low-Sn bronze alloy segregation area were studied. The results showed that segregation has a higher Sn content but a lower surface potential than the dendritic stem, forming a microregion galvanic couple, which not only induces corrosion initiation, but also accelerates the corrosion of the segregation region. In contrast, the corrosion products of the dendrites were mainly Cu2O and SnO2, while the segregation gradually changed from Cu2O and SnO2 to Cu(OH)2, Cu2(OH)2CO3 and Cu2(OH)3Cl, which provided poor protection against local metals. The late pitting effect also accelerated corrosion in the segregated area.