Metal matrix composites (MMCs) are metals that are usually reinforced with particles or bers to achieve a combination of properties that are not normally available from existing metallic alloys. e achievement of superior properties such as high specic stiness and strength is generally realized by the rule of mixtures (ROMs) (Piggott 1980), where MMC properties are proportional, to some degree, to that of the relative volume percentages of the reinforcement material and matrix alloy phases. While the ROMs can be used with some success in predicting certain mechanical and physical properties, corrosion resistance is normally compromised and less than that of the individual MMC constituents.