In this study, effect of Mg alloying addition (2-8 wt.%) on corrosion behaviour of Al matrix composites, in 3.5 wt.% NaCl environment, has been investigated. Composites were produced by pressure infiltration technique at 750 degrees C and had a SiC particle (SiCp) volume fraction of similar to 60%. Results were evaluated by using potentiodynamic polarisation measurements, immersion tests, SEM, EDS and XRD analysis. Compared to the pure All matrix, mass loss of the composites decreased with increasing Mg content. Experimental results revealed that intermetallics as a result of reaction between Al-Mg alloy and SiC particle has beneficial effect on corrosion resistance of the composites due to interruption of the continuity of the matrix channels within the pressure infiltrated composites. (C) 2009 Elsevier Ltd. All rights reserved.