Introduction:

Damage to the metal surface caused by the relative movement of two metal surfaces on each other that are under high load is called erosion corrosion.

Erosion corrosion is intensified by mechanical stress and repeated surface movements (vibration). The necessary conditions for erosion corrosion to occur are that first two solids with a low amplitude of oscillation must have a reciprocating or vibrating motion on each other and then the two objects must be under load (mechanical stress).

As a result of this movement, on the one hand, an oxide layer is formed on the surface and on the other hand, this layer is destroyed by the abrasion of the two surfaces on each other. At any moment, the metal surface is exposed to a corrosive environment, and in this way the corrosion rate increases sharply. The damage resulting from erosion corrosion occurs in the form of surface scratches on the metal, in the form of holes, grooves, wear and loosening of assembled components.

Steel plates screwed onto railway tracks, bearings fitted onto shafts, engine components, ball and roller bearings, all demonstrate this type of corrosion.

Mechanisms of Erosive Corrosion

The mechanism of erosive corrosion includes electrochemical and mechanical factors. Due to the relative movement of two surfaces on each other, very fine scratches or surface irregularities are created on the metal surfaces and these defects are converted into oxide particles by electrochemical factors and their accumulation causes subsequent wear. On the other hand, mechanical work and increased pressure of the surfaces on each other cause fine particles to be peeled off from the metal surface and these particles become oxide pieces and the repetition of these steps causes the erosive corrosion of the surfaces in contact with each other.

Methods to reduce or prevent this type of corrosion:

1. Reducing friction: Using greases and oils that have high fluidity, which reduces friction and prevents oxygen from coming into contact with the surfaces. For this purpose, phosphate coatings are sometimes used in conjunction with lubrication.
2. Increasing the pressure applied to the surface to reduce slip between mating surfaces.
3. Using gaskets to reduce (absorb) relative vibrations and prevent air from entering the contact surface.
4. Increasing the hardness of one or both of the objects that are on top of each other. Methods such as sandblasting, shot peening, and cold working can be used to increase the hardness of metal surfaces.