Pipeline metal surface exposed to the atmosphere, due to the role of water and oxygen damage, known as atmospheric corrosion. The reason is that there is water vapor in the atmosphere, which condenses on the metal surface to form a water film. This kind of water film dissolves the gas and other impurities in the atmosphere, acts as an electrolyte and causes electrochemical corrosion on the metal surface.
The corrosion of metals in the atmosphere is not immersed in a large amount of electrolyte, so the corrosion process is different from the complete immersion of metals in the electrolyte. The characteristics of the corrosion process are that the liquid layer on the metal surface is very thin, the resistance is very small, and the oxygen in the air can be supplied continuously, so the cathodic process is mainly oxygen depolarization. At the same time, due to the thin liquid layer on the metal surface, the process of metal moving towards the ion anode is slow, and the ion concentration increases, and the oxygen passes through the water film to passivate the anode. Therefore, the anode process is hindered to a certain extent and becomes the main control step in the corrosion process. When the liquid layer on the metal surface is thick and the oxygen inlet is blocked, the corrosion is mainly controlled by the cathodic process.
Due to the influence of atmospheric conditions, metal composition, surface shape, orientation, droplet flow, working conditions and other factors, the corrosion behavior and corrosion resistance of metals in the atmosphere are quite different. In addition to pollutants, the main natural factors affecting atmospheric corrosion are climate conditions. In the absence of water, the corrosion effect of many pollutants is very small, but when the relative humidity is greater than 80%, the corrosion rate will increase rapidly. Therefore, the surface of overhead pipeline laid in ditch or wet environment is easy to be corroded.
Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services. Tel: 0539 3712117, 15588026668.