Mechanical properties and corrosion behavior of galvanized steel/Al dissimilar joints

In this paper, the mechanical properties and corrosion behavior of steel/Al electromagnetic self-pieced riveting, adhesive and hybrid riveted and adhesive joints in the salt-spray environment were compared. These joints were firstly placed in the neutral salt spray environment, and then surface observation, weighting, mechanical properties tests and fractographic analysis were conducted. Results showed that with the increase of ageing time, the peak load of the single riveted joints firstly increased and then decreased, while the peak loads of the other two joints continued to decline. This was because the corrosion products formed in the sheet clearance of the single riveted joint, increasing the frictional resistance during the shear process after a short ageing time (before 20 days). For adhesive and hybrid joints, adhesives prevented the formation of corrosion products in the clearance, but it was vulnerable to damage by chloride ions, which would result in the continuous strength degradation of the joints. Specifically, after ageing for a long time (25 days), the peak load of the riveting, adhesive and hybrid joints, respectively, decreased by 11.2%, 26.3% and 14.4% comparing with the uncorroded joint, which showed the adhesive joint had the worst corrosion resistance. This indicated that the adhesive joint was more affected by environmental factors than the riveted and hybrid joint.