Effect of Zr Content on the Microstructure and Corrosion Behavior of 1235D Aluminum Alloy

This study investigated 1235D aluminum alloys with varying Zr additions to elucidate how Zr content affects the alloy microstructure and corrosion resistance. The results showed that Al₃Zr precipitates refined the grains by pinning grain boundaries. The 0.06% Zr alloy exhibited the finest grain structure, the lowest fraction of low-angle grain boundaries, the lowest geometrically necessary dislocation density, and the fewest microstructural defects susceptible to corrosion. Electrochemical and immersion corrosion tests indicated that the corrosion resistance followed the order 0.06% Zr > 0.12% Zr > 0.02% Zr. The 0.06% Zr alloy exhibited the highest polarization resistance and formed a dense, stable passive film that effectively hindered Cl^- penetration, thereby minimizing matrix dissolution and the formation of loose hydroxide corrosion products. An insufficient Zr content provided limited grain refinement, whereas excessive Zr promoted precipitate agglomeration; both conditions intensified localized corrosion. Considering both microstructural evolution and corrosion behavior, 0.06% was identified as the optimal Zr addition for this alloy system. These findings provide a theoretical basis for optimizing the Zr content and improving the corrosion resistance of 1235D aluminum alloys in industrial production.