What is pitting corrosion
- Localized chemical or mechanical damage to the protective oxide film; water chemistry factors which can cause breakdown of a passive film are acidity, low dissolved oxygen concentrations.
- Corrosion of a metal surface, confined to a point or small area, that takes the form of cavities.
- Ratio of the depth of the deepest pit resulting from corrosion divided by the average penetration as calculated from weight loss.
- An empirical relationship to predict the pitting resistance of austenitic and duplex stainless steels.
What is galvanic corrosion?
- Galvanic corrosion (also called ' dissimilar metal corrosion' or wrongly 'electrolysis') refers to corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte.
- A localized form of corrosion usually associated with a stagnant solution on the micro-environmental level.
- An acceleration in the rate of corrosion attack in metal due to the relative motion of a corrosive fluid and a metal surface.
- Corrosion damage induced under load and in the presence of repeated relative surface motion.
What is pack rust?
- Pack rust is often used in relation to bridge inspection to describe built-up members of steel bridges which are already showing signs of rust packing between steel plates.
- Powdered rust particles relatively dense that are commonly used as additives to asphalt to improve the anti sliding properties of the pavement.
- Pack rust is a form a corrosion typical of steel components that develop a crevice into an open atmospheric environment.
- Rust settling as crud in boilers and other devices where the evaporation of water combined with normal corrosion of vessels leads to such accumulation of debris.
What is dealloying?
- Dealloying is the selective leaching of one element from an alloy by corrosion processes.
- Dezincification of unstabilized brass, whereby a weakened, porous copper structure is produced.
- Corrosion attack usually related to the segregation of specific elements or the formation of a compound in the grain boundary regions.
- Graphitic corrosion of the porous graphite network when a gray cast iron is impregnated with insoluble corrosion products.
What can cause stress corrosion cells?
- General thinning.
- Regions within a metal subject to a high local stress.
- Cold work
- Grain boundaries.