Metallic materials in contact with physiological fluids are subjected to the aggressive action of organic and inorganic anions. The interaction may result in a tarnishing action with subsequent aesthetic modifications of the device; modification of the surface polishing degree; corrosive attack more or less localized and deep, that leads to a loss of performance or to a failure of a component (Fraker and Griffin, 1985). The specific environment in which these phenomena may occur must be taken into consideration. In certain environments, such as the oral cavity, extremely low limits of the corrosion products may be tolerated. Large amounts of corrosion products may lead to necrosis, cellular modifications, or poisoning. Notwithstanding the specificity of the environment in which metallic materials are put, the behavior falls within the general phenomenon of metallic corrosion briefly described below.