Comparative study on the electrochemical corrosion behaviour of Al-Fe joints fabricated via compound casting, magnetic pulse welding, and diffusion bonding

In this study, the corrosion behaviour of an aluminium alloy AA6061/mild steel (MS) joint fabricated by solid-liquid (compound casting) and solid-state joining methods (magnetic pulse welding and diffusion bonding) was investigated through electrochemical corrosion in the presence of a 3.5% NaCl solution. In solid-liquid compound casting, applying a coating to MS before joining influenced corrosion behaviour. While Cu-coated MS provided good corrosion resistance, Ni-coated MS showed optimal integrated mechanical and corrosion characteristics. In Magnetic Pulse Welding (MPW), the 14.5 kV MPW joint showed the best corrosion resistance compared to the 14 kV sample, which suffered higher corrosion due to unbonded regions at the joint interface. Optimized welding energy and interface integrity are key to minimizing corrosion in high-impact solid-state welding processes. Corrosion rate during diffusion bonding depends on the process parameters and the interlayer’s effect at the interface. Pitting, IGC, and cracks in the intermetallic compound (IMC) are observed in the SEM-EDS analysis. Irrespective of technique, the interface’s corrosion behavior was found to be banking heavily on bonding parameters, IMC thickness and morphology, and defects in IMCs. Corrosion is mainly due to the anodic dissolution of the aluminium alloy due to a galvanic couple, and voids in the transition region accelerate the corrosion performance.