Corrosion measurement on shear strength of Cu/Sn–9Zn/Cu lap joints

Corrosion of the Cu/Sn–9Zn/Cu lap joints in 3.5 wt.% NaCl solution showed reduction in the ultimate shear strength with increasing immersion time. The highest ultimate shear strength value obtained was at 122.67 MPa before immersion while the lowest value was 85.32 MPa after immersion for 28 days. Corrosion products consist of tin (II) chloride and zinc hydroxide chloride had been obtained due to the active dissolution of tin. The formation of pits observed on the lap joints marked as stress concentration points which are detrimental toward the shear strength. Upon longer immersion period, the pit coalescence and propagation led to the existence of long, deep cracks. The fracture paths nucleates from the cracks clearly established the mechanism of the fracture formation for the Cu/Sn–9Zn/Cu lap joints. The fracture analysis together with the presence of the corrosion by-products fully reiterated that corrosion activities was the main factor for the decrease in shear strength of Cu/Sn–9Zn/Cu lap joints.