Composite fabrication, microstructural analysis and corrosion performance of AA7075-TiB 2 -Si 3 N 4 hybrid composite in hydrochloric acid medium

High-strength AA7075 aluminium alloy reinforced with ceramic particulates such as titanium diboride (TiB 2 ) and silicon nitride (Si 3 N 4 ) offer significant potential for advanced structural applications, yet their corrosion performance in aggressive environments remains challenging. AA7075 hybrid metal matrix composite (AA7075-HMMC) reinforced with TiB 2 and Si 3 N 4 particulates was fabricated using a two-stage stir casting technique to investigate it’s corrosion behaviour in hydrochloric acid environments. Microstructural characterizations using optical microscopy, x-ray diffraction and field emission scanning electron microscopy (FESEM) confirmed the successful incorporation and uniform distribution of reinforcements within the aluminium matrix. The corrosion behaviour of AA7075 alloy and AA7075-HMMC was evaluated in HCl solutions of varying concentrations (0.01–0.5 M) at temperatures of 303–323 K using potentiodynamic polarization and electrochemical impedance spectroscopy. The results revealed increased corrosion rate with increasing acid concentration and temperature for both materials. AA7075-HMMC exhibited comparatively lower corrosion resistance due to reinforcement-induced microstructural heterogeneity and localized galvanic interactions. Activation parameters were determined using Arrhenius and transition state equations. Surface degradations were analysed using SEM, energy-dispersive x-ray spectroscopy and atomic force microscopy (AFM), while water contact angle measurements were employed to evaluate surface wettability. The study provides valuable insights into the corrosion mechanism of aluminium hybrid composite and highlights the need for effective surface protection strategies for their long-term engineering applications.