3rd TAGRA

The 7xxx series aluminum alloy AA 7020 is widely used in engineering applications because of its low density, high strength, good corrosion resistance, and weldability. AA 7020 reaches its maximum strength in the T6 temper. Although AA 7020-T6 is readily weldable, the heat generated during welding can alter the microstructure near the weld, particularly in the heat-affected zone (HAZ), and increase its susceptibility to stress corrosion cracking (SCC). This susceptibility limits the use of welded AA 7020-T6 in corrosive environments. Electric arc spray coating (EASC) is a thermal spraying process used for corrosion protection. It is valued for its relatively low cost and broad range of applications. In this study, aluminum-based Al99.99, AlMg5, and AlZn2 coatings were applied to welded AA 7020-T6 specimens by EASC to investigate whether they could reduce SCC susceptibility. After welding, the AA 7020-T6 specimens were divided into four groups. The control specimens were left uncoated, while the three experimental groups were coated with Al99.99 (commercially pure aluminum), AlMg5, and AlZn2, respectively. SCC tests were conducted based on ISO 7539. For each group, the ductility ratio was calculated by dividing the elongation at break in the corrosive environment by the elongation at break in the dry laboratory environment. The uncoated control group exhibited the lowest SCC resistance. Among the coated groups, SCC resistance followed the order AlZn2 > Al99.99 > AlMg5.