Atmospheric corrosion behavior of wire arc additive manufactured Mg-Gd-Y-Zn-Zr alloy in tropical marine environment: Comparison with casting

The atmospheric corrosion of wire arc additive manufactured (WAAM) Mg-10Gd-4Y-2Zn-0.5Zr alloy was comparatively studied against the cast alloy after one year of exposure to tropical marine atmosphere, and weight loss measurements, morphological characterization and corrosion product analysis were performed. The results show that corrosion rates for both samples initially decreased before increasing with exposure time. Throughout the exposure period, the WAAM sample consistently exhibited higher corrosion rates than the cast sample. Corrosion products for both alloys mainly consisted of Mg₅(CO₃)₄(OH)₂·xH₂O, MgO, and Mg(OH)₂. Notably, magnesium carbonate content increased substantially in corrosion product layers after six months. Internal stress within the corrosion product caused them to crack and fall off. Punctate detachment dominated in the cast alloy, whereas blocky spallation prevailed in the WAAM sample. The corrosion morphology after removal of corrosion products reveals that the corrosion form of cast alloy evolved from pitting to uniform corrosion, with the 3–6 month period representing a critical transition phase. Conversely, the WAAM alloy developed a distinctive wavy corrosion morphology. Furthermore, these divergent evolution patterns are discussed in relation to microstructure features, including grain size, second phase characteristics, and periodic layered structure inherent to WAAM sample.