Corrosion behaviour of copper cladded steel produced using multi pass friction stir welding process

Thick cladding of copper on mild steel substrate has been produced using a novel multipass friction stir welding (FSW) process, executing several adjacent passes, covering the entire steel substrate. Metallography examination reveals proper bonding between clad copper and steel substrate, with grain refinement for the steel region near the interface, while the copper portion depicts grains coarsening due to multipass action during FSW. The clad copper plates and base copper were tested for their corrosion behaviour in 3.5% NaCl solution through the potentiodynamic polarisation method. The study suggests corrosion rate of cladded plates were nearly same as pure copper, and much lower than the steel substrate. SEM-EDS and XRD examination depicts oxide layer formation for the corroded clad top. Atomic force microscopy reveals the presence of pits and valleys in the corroded clad copper top. The experimental results suggest multipass cladding through FSW does not degrade the corrosion properties of copper to a greater extent, and are comparable to base copper results.