Corrosion characterisation of alumina–magnesium metal matrix composites

Alumina magnesium metal matrix composites are a precious alternative for aerospace and automotive applications because of their high stiffness-to-weight ratio. A considerable deal of investigations had been devoted to their processing and mechanical properties, while the corrosion behaviour is still uncertain. In this study, the corrosion behaviour of Al2O3 fibres strengthened magnesium AS41 composite, in aqueous solutions containing various concentrations of NaCl at different pH values, was studied and compared with the behaviour of pure AS41 magnesium matrix alloy using electrochemical techniques, hydrogen evolution test, optical microscopy, and scanning electron microscopy (SEM) coupled with EDX and WDX capabilities. The results showed that the corrosion behaviour of the composite was comparable to its pure matrix alloy, yet a reduction in the corrosion resistance was observed in the composite at higher chloride concentrations. The corrosion mechanism involved, as well as the corrosion characteristics, was extensively discussed in terms of the effect of Al2O3 fibres. Also, an appropriate model describing the corrosion mechanism was proposed.