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Corrosion means of a metal interaction with the environment that surrounds it, producing the consequent deterioration in their physical and chemical properties. The key features of this phenomenon is that only occurs in the presence of an electrolyte, resulting in clearly identified areas, called anode and cathode: a reaction of anodic oxidation is a reaction in which electrons are released by switching to other regions cathode. In the region produce anodic metal dissolution (corrosion) and thus the immunity region of the metal cathode.

Metallic bonds tend to become ionic bonds, the favors that the material can at one time transfer and receive electrons, creating anodes and cathode areas in its structure. The speed at which a material is slowly and continuously corrodes all depending on the environment where it is, as time passes creates a thin layer of material on the surface, which are formed initially as spots until they appear imperfections on the surface of metal.

The best known are the chemical alterations of metals from the air, like the rust of iron and steel or the formation of green patina on copper and its alloys (bronze, brass). However, erosion is a much broader phenomenon that affects all materials (metals, ceramics, polymers ...) and all environments (aqueous media, atmosphere, high temperature ...).

It is an important industrial problem, which can cause accidents (rupture of a piece) and also represents a significant cost, since it is estimated that every few seconds dissolve five tons of steel in the world.

According to the appearance of corroded metal, you can include the following types of corrosion:

- Uniform Corrosion: Where chemical or electrochemical corrosion acts uniformly over the entire surface of the metal.
- Galvanic corrosion: It occurs when dissimilar metals are in contact, the two metals have different electrical potential which favors the emergence of another metal as anode and the cathode, the higher the potential difference the more active material will be the anode.
- Pitting corrosion: This hole or holes are produced by chemical agents.
- Intergranular corrosion: which is located at the grain boundaries, this leads to losses in the resistance to decay the edges of the grains.
- Corrosion effort: It refers to the internal stresses after cold deformation.