Chemical And Chemical Corrosion

What is Corrosion?

It is the degradation of material properties due to interactions with their environments, and the corrosion of most of the metals (and many materials for that matter) is inevitable. While primarily associated with metallic materials and all the material types are susceptible to the degradation process.

Corrosion is defined as an attack on a material as a result of the chemical and frequently the electrochemical reaction, with the surrounding medium. According to this definition, the term corrosion can also be applied to all of these materials, including the non-metals also. But in practice, the word corrosion is mainly used in conjunction with metallic materials

Chemical and electrochemical corrosion :

Chemical corrosion can be seen as oxidation and occurs by the continuous action of the dry gases and at high temperatures. Electrochemical corrosion on the other hand takes place by the help of electrode reactions, usually in humid environments, i.e. wet corrosion. All metals in dry air are covered by a very thin layer of oxide, about 100Å (10-2µm) thick. This layer is built up by chemical corrosion with the oxygen in the air. At very high optimum temperatures, the reaction of the oxygen in the air can continue without restraint and the metal will rapidly be transformed into an oxide.

These thin layers of oxides are capable to protect the metal against the continued attack, e.g. in a water solution. In actual fact, it is these layers of oxide or products of it forms on the surface of the metal that protect the metal from the continued attack to a far longer extent that this corrosion resistance of the metal