CORROSION OF METAL-MATRIX COMPOSITES

The corrosion of metal matrix composites (MMCs) is reviewed with empha sis on relating MMC corrosion behaviour to the electrochemical and che mical properties of MMC constituents. Galvanic corrosion between the r einforcement constituent and the metal matrix governs the corrosion be haviour of many MMCs. Other factors such as residual contaminants of M MC processing and the formation of interphases between reinforcement a nd matrix can also have pronounced effects on MMC corrosion behaviour. The lack of inherent resistance to corrosion of some MMCs requires th at they be coated with organic or inorganic coatings for protection. A lthough the ultimate goal is to engineer and design MMCs to have good inherent resistance to corrosion (while maintaining excellent mechanic al properties), no significant breakthroughs have been achieved in thi s area for MMCs that are typically prone to corrosion (e.g. graphite-a luminium MMCs), In this review, aluminium, magnesium, lead, depleted u ranium, and stainless steel MMCs are evaluated. Reinforcement constitu ents used in the above MMCs include boron, graphite, silicon carbide, alumina, mica, and tungsten.