Corrosion behavior and mechanical performance of AZ31/PEEK joints fabricated by Friction Stir Spot Joining and Self-Piercing Riveting

Abstract

The progression of lightweight materials has introduced significant challenges in joining dissimilar substances such as magnesium alloys and polyether ether ketone (PEEK), particularly for demanding automotive and aerospace applications. This study systematically investigates the comparative performance of Friction Stir Spot Joining (FSpJ) and Self-Piercing Riveting (SPR), two promising techniques for fabricating magnesium-polymer dissimilar material (hybrid) joints. AZ31/PEEK joints were evaluated through detailed microstructural analysis (SEM with EDS), electrochemical corrosion testing (including electrochemical impedance spectroscopy and potentiodynamic polarization), and mechanical performance assessment via pull-out and tensile shear testing. The results show that FSpJ joints exhibited a substantially more positive self-corrosion potential and an ∼81 % reduction in corrosion current density compared to SPR joints during early immersion. Furthermore, FSpJ joints demonstrated superior corrosion resistance with a 10-fold higher charge transfer resistance (1.33 × 10² Ω·cm²) and a 57.8 % increase in initial tensile shear strength (4.13 × 10 ³ N) relative to SPR joints. However, following 192 h of immersion, FSpJ joints experienced a sharp reduction in shear strength (∼74.2 % loss), while SPR joints retained nearly double the residual strength of FSpJ joints, owing to the robustness of their mechanical interlocking design. These findings provide valuable guidance for material selection and joining techniques in the automotive and aerospace industries, where corrosion resistance and joint integrity are critical to ensuring long-term structural reliability in harsh service environments.