Application of cathodic protection technology

Cathodic protection is an electrochemical protection technology used to prevent metal corrosion in dielectric (seawater, fresh water, soil and other media). The basic principle of this technology is to apply a certain DC current to the protected metal surface to produce cathodic polarization. When the potential of the metal is negative to a certain potential value, the anodic dissolution process of corrosion will be effectively suppressed.

According to the different ways of providing cathodic current, cathodic protection is divided into sacrificial anode method and external current method. The former is to connect a metal with more negative potential (such as magnesium, aluminum, zinc, etc.) with the protected metal structure, and provide protection current to the protected object through the continuous dissolution and consumption of the negative metal or alloy, so as to protect the metal structure. The latter is to change the external alternating current into low-voltage direct current, and transfer the protection current to the protected metal structure through the auxiliary anode, so as to inhibit the corrosion. Whether it is sacrificial anode method or external current method, its effective and reasonable design and application can obtain good protection effect.

The combined application of cathodic protection and coating can make the underground or underwater metal structures obtain the most economical and effective protection. Good coating can protect more than 99% of the external surface of the structure from corrosion. Underground or underwater metal structures are usually coated with protective coating before use to insulate the metal from the dielectric environment. If the metal structure can be completely electrically insulated and isolated, the corrosion of metal in the dielectric will be restrained, and the corrosion current will not be generated, so as to prevent metal corrosion.

However, the perfect coating does not exist. Due to the transportation, installation and joint coating, thermal stress and soil stress, aging of coating and the existence of micro pinholes in the coating, there will always be some defects in the outer coating of metal structures, which will eventually lead to local corrosion of metal. The combination of cathodic protection technology and coating can effectively solve this problem. On the one hand, cathodic protection can effectively prevent the corrosion of the damaged coating and prolong the service life of the coating. On the other hand, the coating can greatly reduce the demand of protection current, improve the distribution of protection current, and increase the protection radius, making cathodic protection more economical and effective. For underground or underwater metal structures with bare or poor anticorrosive coating, cathodic protection even corrodes The only alternative means of protection.

The cost of cathodic protection usually only accounts for 1% - 5% of the cost of the protected metal structure, and the service life of the structure can be prolonged by several times or even dozens of times. Therefore, this technology has been widely recognized by people, and has been more and more widely used in shipbuilding, port facilities, marine engineering, petrochemical, electric power, municipal and other fields.

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.