Types of corrosion

According to the point of metal corrosion process can be divided into chemical corrosion and electrochemical corrosion.

Corrosion purely chemical corrosion caused by the chemical action called chemical corrosion. For example, the metal subjected to the air, in the air O2, H2S, SO2, CI2 and other contact, to form the corresponding compound on the metal surface. Metal usually warm dry air is often not corrosion at high temperatures on a single easy to be oxidized to constitute a layer of oxide scale, while undergoing decarburization. In addition, various forms of organic sulfur compounds included in the oil, naphthenic oil pipeline they will produce chemical corrosion of metal.

When the electrochemical corrosion of the metal contact and the electrolyte solution, the corrosion caused by the electrochemical reaction is called electrochemical corrosion. It is distinct from chemical etching, due to the formation of galvanic cells caused. Metal pipes in contact with the atmosphere contain water, soil, lakes and oceans. These media contain CO2, SO2, HCI, NaCI and dust concentration of electrolyte solution is different, The metal itself due to containing impurities, as a result of iron and impurity elements have different potentials, so that when the steel is exposed to moist air, the surface of the adsorption on the iron surface covered with a very thin film of water on.

Underground pipes to prevent corrosion mainly electrochemical corrosion, stray current corrosion and microbial corrosion. Factors influencing the corrosion of metals include metals both nature and the outside media. The metal itself, the more active the metal, the more easily loses electrons and corrode. The impact of external media on metal corrosion is also great, if the metal in the humid air, contact with corrosive gases or electrolyte solution, is prone to corrosion.