Effects of NaOH and KOH activator agents on the aluminization process

This study investigates the role of sodium hydroxide (NaOH) and potassium hydroxide (KOH) as alkali activators for modifying agro-marine residue ash used as reinforcement in aluminum matrix composites (AMMCs). The core challenge addressed is the inconsistent surface characteristics of bio-derived ashes, which compromise interfacial bonding and limit industrial adoption of eco-composites. Using SEM, EDS, FTIR, and XRD analyses, the study compares the physicochemical changes induced by NaOH and KOH treatments. NaOH-treated particles developed smoother, more uniform surfaces with higher hydroxylation and crystallinity, supporting enhanced wettability and interfacial adhesion. In contrast, KOH-treated particles exhibited denser, rougher morphologies with greater microporosity, favoring mechanical interlocking and improved thermal resistance. FTIR confirmed hydroxyl functionalization in the 3200–3600 cm−1 region, and EDS revealed increased surface oxygen content in both treatments. XRD analysis highlighted a significant increase in crystallinity, especially for NaOH + heat-treated samples, which reached peak intensities of up to 76.4%. Although mechanical properties were not directly measured, the microstructural and chemical modifications observed are strong predictors of improved structural integrity and performance in metal matrix systems. Optimal processing conditions were identified at 4 M concentration, with NaOH requiring shorter activation times (30–60 min) compared to KOH (60–120 min). These findings establish a foundation for designing application-specific, functionally graded composites. By valorizing agro-marine waste and enabling surface engineering through selective alkali activation, this work supports the development of cost-effective, sustainable, and high-performance composites suitable for lightweight, thermally stable, and wear-resistant industrial applications.