Characterization and Mitigation of Galvanic Corrosion of CFRP-AZ31B Dissimilar Joint

Higher specific strength materials are being considered for lightweight vehicle applications to improve the overall energy efficiency. Magnesium (Mg) alloys and carbon fiber reinforced composites (CFRC) present great potential to achieve this goal. However, joining and corrosion (especially for galvanic corrosion) of dissimilar material joints are major technical challenges for automotive applications. In this present, friction self-piercing (F-SPR) rivet process was employed to spot join a CFRC to Mg alloy AZ31B at a coupon scale. Then, unique corrosion testing scheme was developed to study galvanic corrosion of AZ31B at the joint in 0.1 M NaCl solution. Also, polymer coating and oxide self-formation techniques were used to the different rivet materials to mitigate galvanic coupling effect at the rivet/multi-material interfaces as an electrical insulation approach. Optical and electron microscopy techniques were used to characterize the post corroded F-SPR joints. Based on corrosion depth assessment of AZ31B at the joint, the surface oxide layer formed on alloy rivet greatly reduced galvanic corrosion of AZ31B compared to the untreated rivet (control) and polymer coated rivet.