Study on mechanical degradation and corrosion behavior of pre-holed self-piercing riveted-bonded hybrid joints under salt spray condition☆

The improved process of pre-holed self-piercing riveted-bonded (PH-SPR-bonded) is proposed to improve the mechanical properties and corrosion prevention of the high-strength steel and aluminum alloy sheets. In this paper, four types of joints are designed, including PH-SPR joint, electrophoretic PH-SPR (EPH-SPR) joint, PH-SPR-bonded joint, and electrophoretic PH-SPRbonded (EPH-SPR-bonded) joint, to investigate the mechanical degradation and corrosion behaviors of PH-SPR-bonded joints under a salt spray condition. The surface quality, weight variation, mechanical properties, corrosion behaviors, and corrosion mechanisms of the four types of joints after various corrosion durations are discussed in detail. The results show that the weight variations of the specimens initially increase and then decrease with the increase in corrosion duration. The increase in weight variation is primarily due to surface corrosion. The peak force of the non-bonded PH-SPR and EPH-SPR joints initially increases and then decreases with increasing corrosion duration. At 720 h of corrosion, the peak force of the PH-SPR joint is 27.4% lower than that of the joint without corrosion, while the EPH-SPR joint remains higher than the joint without corrosion. For the PH-SPR-bonded joints, the peak force decreases with increasing corrosion duration, while the EPH-SPR-bonded joints are generally unaffected by corrosion. Although the PH-SPR-bonded joints are significantly affected by corrosion, their peak force and energy absorption are still 70.2% higher than the PH-SPR joints without corrosion. The electrophoretic coating and adhesive bonding can significantly enhance the corrosion prevention of the joints, reflected in both surface quality and mechanical properties of joints.