Corrosion Resistance Analysis of Al-3wt%Si Alloy: Effects of Directional Solidification and Microstructural Variations

Objective: This study investigates the influence of solidification thermal conditions on the corrosion resistance of the Al-3wt.%Si alloy, aiming to correlate dendritic refinement with performance in aggressive environments. Method: The alloy was horizontally solidified under unidirectional transient heat extraction. Samples were sectioned at different positions along the ingot, metallographically prepared, and evaluated by immersion mass-loss tests in 10N H₂SO₄ solution at room temperature for 168 h. Microstructural inspection was performed by optical microscopy. Results and Discussion: Corrosion rate increased monotonically with distance from the cooled base, following the transition from refined dendritic structures to coarser morphologies. Near the chilled base, refined microstructures with reduced primary dendritic spacing (λ₁) favored passivation and stability of the Al₂O₃ film, while farther regions showed coarsening, segregation, and higher corrosion rates. The results reinforce the correlation between microstructural refinement and corrosion resistance, in agreement with previous studies. Research Implications: Findings suggest that thermal control during solidification can be strategically applied to enhance corrosion resistance of cast components in aggressive service environments. Originality/Value: This work contributes by establishing the direct relationship between primary dendritic spacing (λ₁) and corrosion resistance in an Al-3wt.%Si alloy, providing insights for microstructural engineering and durability improvement in transportation, energy, and construction sectors.