Common applications of cathodic protection


Common applications of cathodic protection to protect various structures from corrosion:

Cathodic protection system is used in all steel structures buried in electrolyte. Below is a description of some of the most common structures in contact with the electrolyte:

  • Buried pipelines in electrolyte:

Due to the fact that the coating of the pipelines in contact with the electrolyte is not implemented in an ideal way and has holes in the surface of the coating. In addition, during the implementation of the pipeline, its coating may be damaged, to protect the mentioned points against corrosion, a cathodic protection system is used. For the cathodic protection of pipelines, two sacrificial methods (galvanic) and current injection can be used. In the sacrificial method, according to the characteristics of the electrolyte and environmental conditions, magnesium and zinc anodes are usually used, in current injection systems, silicon anodes, MMO are used in tubular, ribbon, wire, etc. models. . The types of anodic beds are selected according to different environmental conditions, such as surface bed, scattered bed, well bed, round bed, etc.

کاربردهای متداول حفاظت کاتدیک

  • Above ground tanks:

Above ground tanks may need internal corrosion protection due to the storage liquid inside. The bottom of the tanks in contact with the electrolyte is also protected from corrosion. Tanks containing acid are cathodic or anodic protection according to the acidic materials inside. The cathodic protection inside the tanks and the bottom of the tanks in contact with the electrolyte is done by the sacrificial (galvanic) method and current injection. Aluminum anodes, lead base are usually used in the cathodic protection inside the tanks, in current injection systems from silicon anodes. MMO is used in ribbon, wire, etc. models. The types of anodic beds are selected according to different environmental conditions, such as surface bed, scattered bed, well bed, round bed, etc. If there is a geomembrane layer in the foundation of the bottom of the tanks, it is inevitable to use the bed near the bottom of the tanks.

  • Buried tanks:

The outer surface of the buried tanks and, if necessary, the inner surface of the said tanks are protected by two methods: galvanic and current injection. In the internal protection of the tanks, aluminum anodes, lead base, etc. are usually used. In the current injection method, all the common substrates in the cathodic protection system, including: near substrate, well, round bed, etc., can be used. Anodes used in the aforementioned substrates are selected from silicon, MMO (wire, ribbon) and… In tanks buried in concrete pits, it should be used from the nearby bed to protect the external surface of the tanks.

  • sea ​​structures:

Corrosion protection in the sea has different parts, such as: the foundation of docks, oil platforms, seabed pipes, hulls of vessels and ships, etc. This corrosion protection is done in two methods: galvanic and current injection. Due to the presence of salt and chlorine in sea water, aluminum anodes or lead base are used in the sacrificial system. Due to compliance with environmental issues (preventing the entry of metal impurities, especially lead into the water), it is used in flow injection systems, MMO and platinized anodes, etc. Due to the very high charging current in marine structures, near beds are used.

  • Boilers and heat exchangers:

The internal surface of the metal structures of boilers are exposed to severe corrosion due to being in contact with high-pressure and high-temperature water, and considering that the power generation cycle in power plants depends on the correct operation of boilers, the corrosion protection of the internal surface of the structure High boiler is very important. Corrosion protection in boilers is done using the sacrificial method (using magnesium anode).

  • Concrete reinforcement:

In the construction and civil engineering industry, concrete structures are considered the base and foundation of buildings, considering that metal rebars are one of the main components of concrete structures and corrosion or damage to the rebars causes the destruction of the concrete structure, and This destruction may cause irreparable human and financial damage (such as the foundations of bridges or the foundations of skyscrapers). In order to protect the corrosion of rebars in contact with concrete, various methods are used such as: anti-corrosion coating of rebars, use of inhibitors, cathodic protection, etc. Cathodic protection of rebars in concrete is done by sacrificial method or current injection, in the current injection method, MMO anodes with strip, mesh-ribbon, net shapes are usually used using transformers, usual cathodic protection rectifiers or transformers. A special pulse is performed.