Effects of Fe rust deposits on the corrosion behavior of Al-Zn-Mg-Cu alloy

This paper investigates the corrosion behavior of the Al-Zn-Mg-Cu alloy under deposits of three typical iron rusts (Fe 2 O 3 , Fe 3 O 4 , and α-FeOOH) using electrochemical measurements, immersion corrosion experiments, and molecular dynamics (MD) simulations. The results demonstrate that the three rust deposits exert markedly different effects on the corrosion behavior of the aluminum alloy. Specifically, Fe 2 O 3 deposits decrease the surface potential of the aluminum alloy, inducing galvanic corrosion with the adjacent bare areas and thereby accelerating localized dissolution in the deposited regions. In contrast, the Fe 3 O 4 deposits show negligible influence on the overall corrosion process. Remarkably, α-FeOOH deposits act as a protective barrier that captures aggressive Cl⁻ ions and promotes the formation of a stable corrosion product layer on the alloy surface, thus substantially retarding the corrosion of the alloy. In industrial practice, when steel and aluminum alloy components share the same water circulation system, corrosion products containing Fe, particularly Fe 2 O 3 and Fe 3 O 4 , in the pipelines must be removed regularly to prevent their deposition on aluminum alloy surfaces, which otherwise triggers severe localized corrosion. For water treatment systems containing aluminum alloy components where iron oxide adsorbents are used, α-FeOOH and Fe 3 O 4 (preferably α-FeOOH) are recommended, whereas Fe 2 O 3 is not advised.