Electrochemical Analysis of the Corrosion Resistance of the Al-Alloy EN AW-5454-D and Its Welded Joints

An electrochemical evaluation of the corrosion resistance of the Al-alloy EN AW-5454-D and its welded joints made by MIG (Metal Inert Gas) and by laser hybrid (LH) welding was performed in this study. All the tested samples had a thickness of 4 mm, whereby all the samples’ surfaces were cleaned with a plasma cleaning process before the electrochemical testing to reduce the impact of contamination. The electrochemical behaviour was investigated in a 3.5 wt.% NaCl electrolyte over exposure periods of 1 h, 7 days, and 30 days using electrochemical methods and surface examination. The results demonstrate that the welding processes (MIG and LH) caused microstructural heterogeneities that reduce the corrosion resistance of the weld. The MIG-welded specimen showed worse properties than the LH-welded specimen in the electrochemical tests, as it had a higher corrosion current density, lower polarisation resistance, and higher layer capacitance. Due to long-term exposure to the immersion solution, despite the reduced susceptibility to uniform corrosion, the Al-alloy samples and their welds remained susceptible to pitting corrosion.