Forms of Corrosion
| General/Uniform
Corrosion: Corrosive attack dominated by uniform thinning due to
even regular loss of metal from the corrosion surface |
Atmospheric |
corrosion
or degradation of material exposed to the air and its pollutants rather
than immersed in a liquid |
| Galvanic |
corrosion
that occurs when a metal or alloy is electrically coupled to another metal
or conducting nonmetal in the same electrolyte |
| Stray-current |
caused
by an externally induced electrical current |
| General
biological |
corrosion
of metals generally over the entire exposed surface in aqueous environments |
| Molten
salt |
corrosion
of metals due to molten or fused salts |
| Liquid
metals |
types
of corrosion found in liquid metal / containment / component combinations |
| High-temperature |
Oxidation |
corrosion
by direct reaction of exposed metals to oxidizing agents at elevated temperatures |
| Sulfidation |
| Carburization |
| Other forms |
| Localized
Corrosion: all or most of the metal loss occurs at discrete areas |
Filiform |
occurs
on metallic surfaces coated with thin organic film, typically .1 mm thick,
characterized by the appearance of fine filaments in semi-random directions
from one or more sources |
| Crevice |
corrosion
in narrow openings or spaces in metal to metal or non-metal to metal component
sites |
| Pitting |
extremely
localized corrosion marked by the development of pits |
| Localized
microbiological |
cases
where biological organisms are the sole cause or an accelerating factor
in the localized corrosion |
| Metallurgically
influenced corrosion: form of attack where metallury plays a significant
role |
Intergranular |
occurs
when the corrosion rate of the grain boundary areas of an alloy exceeds
that of the grain interiors |
| Dealloying |
a form
of corrosion characterized by the preferential removal of one constituent
of an alloy leaving behind an altered residual structure |
| Mechanically
assisted degradation: form of attack where velocity, abrasion,
hydrodynamics etc. play a major role |
Erosion |
removal
of surface material by the action of numerous individual impacts of solid
or liquid particles |
| Fretting |
combined
wear and corrosion between contacting surfaces when motion between the
surfaces is restricted to very small amplitude oscillations |
| Cavitation
& Water drop impingement |
occurs
on a metal surface in contact with a liquid, pressure differentials generate
gas or vapor bubbles which upon encountering high-pressure zones, collapse
and cause explosive shocks to the surface |
| Fatigue |
occurs
in metals as a result of the combined action of a cyclic stress and a corrosive
environment |
| Environmentally
induced cracking: forms of cracking that are produced in the
presence of stress |
Stress
cracking |
service
failures in engineering materials that occur by slow environmentally induced
crack propagation |
| Hydrogen
damage |
results
from the combined action of hydrogen and residual or tensile stress |
| Liquid
metal embrittlement |
brittle
failure of a normally ductile metal when coated with a thin film of a liquid
metal and subsequently stressed in tension |
| Solid
metal embrittlement |
occurs
below the melting point of the solid in certain liquid metal embrittlement
couples |