Corrosion Behavior Characterization of the Nugget Zone in Copper/Brass Metals of Dissimilar Friction Stir Welded Lap Joints

The electrochemical behavior of the weld nugget zone (WNZ) in copper-brass plates was studied in this paper. These plates were welded by the friction stir lap welding method in 1M NaCl solution at low heating input (450 rpm-25 mm/min ) and high heating input (710 rpm-16 mm/min) by using the electrochemical impedance spectroscopy (EIS) and Tafel polarization at ambient temperature. The morphology of nugget zone corroded surfaces was analyzed by SEM (scanning electron microscopy) technique. The welding process appeared to decrease the corrosion resistance of the welded nugget regions through increasing the welding heat input. The results from EIS measurements presented the welded joints of NZ which showed higher and lower values respectively than brass and copper. Due to changing of microstructural of weld nugget zone during welding process, the Icorr of nugget zone enhances with increasing welding heat input. In fact, the surface corrosion morphology analysis revealed that the surface of welded sample by high heating input was shielded with a roughly porous corrosion layer rather than the surface of the welded sample at low heating input.