Simultaneous effect of welding current with post-weld T6 heat-treatment on corrosion susceptibility of Al6013 alloy joined by GTAW

Abstract

Al6013 base metals were joined successfully with ER4047 weld metal by using the GTAW method under different welding currents. Post-weld T6 heat treatment effects on corrosion properties were investigated in terms of open circuit potential (OCP), potentiodynamic polarization (PDS), and electrochemical impedance spectroscopy (EIS) tests. It was determined that corrosion resistance of the post-weld samples increased with increasing welding current, while T6 heat-treatment only effective on 110A and 140A welding current samples (3.61 to 2.08, 2.95 to 2.40, and 1.38 to 2.15 µA·cm-2 for 110, 140, and 170A welding current before and after T6 heat-treatment). The characteristics of the oxide films on the surfaces are revealed with EIS analysis by a two-constant equivalent circuit model which observed that while the passive film originating from Al is formed on the surfaces, on the other hand, it contains a pittings on the surface. It was determined that the pitting resistance of the T6 heat-treated 110A samples increased (3075 to 4562 Ω). Post-corrosion SEM surface morphologies showed that low welding currents lead to more damage with increased exposure to corrosion.