Pitting corrosion

Pitting ( in German: " pitting " ) is a term (eg marble) refers to both damage to building materials (pitting ( building damage ) ) and defines the material outbreak and near-surface micro- cracking under tribological stress. This occurs when, for example, bearings and gears.

The pitting in tribological stress is caused by exceeding the local strength of each material due to the Hertzian pressure between the rolling elements and the inner or outer ring of the bearing or the tooth flanks of the gears. The decisive factor is the fact that when the maximum Hertzian contact pressure of the tension member does not occur on the component surface, but in a typical depth below the surface.

Other factors besides the Hertzian pressure, surface hardness and case depth, surface quality, edge defects in shape and peripheral speed ( gears), oil viscosity, Öladditivierung, temperature, etc.

The result of such pitting is very easy to observe with railroad tracks: from time to time they must be reground.

As well as pitting the biting of salt grains in metals is referred to, as it may happen, for example, when salt is added to a pot before the water is hot enough in it.

• Signs of wear