Corrosion Behaviour of Mg, Graphite-, B4C and Ti-Reinforced Hybrid Aluminium Composites

Corrosion of metal matrix composite significantly affects the mechanical properties of the composites. Therefore, it is important to analyse the corrosion resistivity of newly developed metal matrix composites. In the current study, corrosion resistivity of newly developed hybrid metal matrix composite was investigated. Composites were developed using aluminium matrix and different reinforcements like Mg, graphite, B4C and Ti. The study was conducted by simple immersion of composite material for 21 days. Three different reagents 3.5% w/v NaOH, 3.5% w/v NaCl and 3.5% w/v HCl with concentration in water were used for the corrosion study. The initial and final weight of the specimens was measured to find out the corrosion rate. Moreover, optical microscopic, scanning electron microscopic (SEM) and electron-dispersive X-ray (EDX) techniques were used to validate the results after the immersion test. It was observed that the initial corrosion rate of MMC (metal matrix composite) is higher compared to pure aluminium due to reinforcement, but afterwards, it reduces due to the formation of the passive oxide layer and higher diffusion path length. Moreover, MMC with high carbon content (B4C and graphite) shows the highest corrosion rate due to the presence of C. However, MMC with high Mg content shows better immunity against corrosion. The pitting corrosion mechanism was found profound in all the composite samples while general corrosion was observed in pure aluminium. Therefore, this study provides in-depth information about the effect of pH, diffusion path and corrosive environment on newly developed aluminium metal matrix composites. © 2022, The Institution of Engineers (India).