What Does Localized Corrosion Mean?
Localized corrosion refers to the hastened attack of passive metals in corrosive environments. It is characterized by an intense attack at confined areas on surface components, while the remaining area of the surface corrodes at a much slower rate. This can be due to environmental effects or the component material’s inherent properties, like in the creation of protective film oxide.
In a localized corrosion, the material's surface may be fundamentally under suitable corrosion control, with the corrosion confined at localized sites where the corrosion protection has stopped working.
Corrosionpedia Explains Localized Corrosion
There are several types of localized corrosion:
- Crevice corrosion: The attack may occur in shielded areas and crevices, as well as on metal surfaces prone to corrosives.
- Pitting corrosion: This form of attack results in metal holes. In such cases, the holes may be large or small in diameter. Pits can be close together or isolated, and may appear as a coarse surface. In general, it can be described as cavities with surface diameter almost the same size as their depth.
- Intergranular: Effects of grain boundaries have little or no effect in almost all metal applications. In such cases, metal corrosion results in a uniform attack, since grain boundaries are more reactive compared to the matrix. In some circumstances, grain interfaces are extremely reactive, leading to corrosion.
Corrosive environments that are highly different from the regular environment usually play a role in the propagation and initiation of corrosion pits. This makes the task of prediction tremendously complicated. Hence, it requires sophisticated computational and experimental tools to gain more advanced understanding of localized corrosion.