Pitting corrosion in cast 7XXX aluminium alloys and fibre reinforced MMCs

The corrosion behaviour of cast and heat-treated Al–6%Zn–1%Mg and Al–6%Zn–1%Mg–1%Ag alloys and metal matrix composites (MMCs) were investigated using dynamic polarisation techniques, followed by scanning electron microscopy (SEM) and secondary ion mass spectrometry (SIMS). The addition of silver and the incorporation of continuous Altex fibres into the alloys have a positive effect on the materials’ corrosion resistance. It was observed that due to the presence of second phase particles and microsegregation, pitting occurs preferentially at the grain boundary and fibre/matrix interface regions in the cast alloys and composites, respectively.