In effect, all engineering materials are subject to some form of environmental degradation. Further, today’s technology demands materials that are capable of performing under increasingly hostile circumstances (i.e., fusion reactors, high-temperature batteries, MHD channels, etc.). In some cases, suitable materials are not currently available. Although much is currently known (in an empirical sense) regarding the design of materials for corrosion resistant service (e.g., stainless steels), a capacity for designing from first principles and producing new materials on an atomic level is emerging. Before introduction into service situations, the chemical stability of these materials must first be examined.