Electrochemical Analysis on Friction Stir Welded and Laser Welded 6XXX Aluminium Alloys T-Joints

Friction Stir Welding (FSW) and Laser Welding (LW) can be successfully employed to weld aluminium alloys, in many cases overcoming the difficulties encountered with more conventional welding processes like MIG or TIG. The corrosion resistance of the welded joint remains, however, an important issue, especially in applications (like in aircrafts), where corrosion can induce structural failure: the weld region has often lower mechanical resistance in comparison with the parent material and a decrease in its corrosion resistance, especially when the corrosion damage can represent a potential crack initiation site, can be unacceptable in components design. In this work the corrosion resistance of welded T-joints produced with FSW and LW on different 6xxx aluminium alloys is investigated. These alloys offer good mechanical properties and high corrosion resistance and are often used in aircraft fuselage components. Processes like FSW or LW, however, can induce, in age-hardenable alloys like the 6xxx ones, significant metallurgical modifications and consequent changes in the electrochemical reactivity. This work proves that, if the alloys and the welding parameters are chosen correctly, for both FSW and LW it is possible to obtain welded joints such that galvanic couple established between the welded region and the parent material results in preferential attack of the latter: this drives corrosion away from the weld region and reduces the cathode/anode area ratio, improving the corrosion performance of the whole weld.