Environmental Stability of Materials—Issues and Opportunities

Abstract

Professor David Kingery, author of the classic text, Introduction to Ceramics, said it well: “Corrosion, like death and taxes in our existence, is inevitable for all materials.” Metals, ceramics, and polymers all undergo change when exposed to the environment. Metals can exhibit electrochemical corrosion, while ceramics and plastics experience primarily chemical corrosion. Although “corrosion” often is used to describe the environmental stability (or instability) of metals, a host of other definitions have been used to characterize the changes that occur in ceramics and polymers.Definitions can become an issue when scientists from various disciplines work together to solve a problem of national/international importance. One such example involves the description of the surface changes that occur when nuclear waste forms are exposed to an aqueous environment (as might occur in a geological repository). The observed surface changes have been referred to as corrosion, leaching, weathering, degradation, and alteration, to name a few. In early symposia on nuclear waste management, sponsored by the Materials Research Society and the American Ceramic Society, definitions and technical issues were discussed extensively by materials scientists, chemists, physicists, geologists, nuclear engineers, and other professionals. Because of this interdisciplinary interaction, significant advances were made (in spite of disagreements over terminology) in understanding the aqueous alteration of these materials. Much of this knowledge will be useful in other applications where environmental stability is important.Although aqueous alteration is an important concept in materials corrosion, the topic of environmental stability is much broader. Other important subtopics are erosion, thermal stability, oxidation and radiation damage, and molten metal, glass, and salt corrosion. Finally, environmental instability need not always be bad. Indeed, there are numerous processes and products that work only because of the material's instability in specific environments.