Failure behaviour of SPR joints after salt spray test

The ageing of steel/aluminium hybrid joints in salt spray environment, obtained by Self-Piercing Riveting technique (in the next SPR), was studied to evaluate their mechanical degradation in these critical environmental conditions. The investigation was carried out on symmetrical or unsymmetrical joints at varying the total thicknesses (i.e. 2, 2.5 and 3 mm). The joint strength was determined by means of shear tests of single-lap joints. Long term ageing tests were performed to evaluate the relationship among failure mechanism, joint configuration and corrosion degradation in salt spray environment. The experimental results evidenced that the corrosion degradation phenomena influence significantly the performances and the failure mechanisms of the joints, inducing premature failure of the joint at lower stress level. Furthermore, the joint configuration influences the durability of the SPR joint. The joints with thick aluminium sheet showed good mechanical stability. Instead poor durability performance in corrosive environment occurred in samples with thin aluminium sheet.