Offshore Oil Platform And Offshore Wind Power
In offshore wind power projects, the foundation piles immersed in seawater will be corroded by seawater. To increase the service life of steel piles, it is inevitable to carry out anti-corrosion protection for them. At present, it is mainly a combination of physical anti-corrosion (coatings) and electrochemical anti-corrosion (cathodic protection).
The principle of cathodic protection: It is to replenish a large number of electrons to the metal, so that the entire protected metal is in a state of electron excess, and all points on the metal surface reach the same negative potential.
Cathodic protection currently mainly consists of two schemes: one is sacrificial anode cathodic protection, and the other is impressed current cathodic protection.
cathodic protection with sacrificial anode impressed current cathodic protection
Sacrificial anode protection method：
The sacrificial anode method is a technique that electrically connects a metal or alloy with a potential more active than that of the metal to be protected to the metal to be protected. The current generated by the continuous corrosion and dissolution of the metal is used to protect other metals.
Sacrificial anode in seawater is mainly aluminum alloy.
- Advantages and disadvantages:
- Advantages:
The sacrificial anode protection method is a one-time investment and basically requires no maintenance costs during operation. The utilization rate of the protection current is relatively high and over-protection will not occur.
- Disadvantage:
- The driving potential is low. After Marine organisms attach and anodic corrosion occurs, the adjustment range of the protection current becomes narrower and narrower. A large number of sacrificial anodes need to be welded on the steel piles.
- The effective cathodic protection period is limited by the lifespan of the sacrificial anode and is generally 10 to 15 years.
- During the protection process, a large amount of heavy metal pollution is released into the ocean. The installation was time-consuming and laborious, which added extra weight to the steel pile body.
- General cathodic protection is mainly used when the coating of the steel pile body is damaged in the later stage, and replacement in the later stage is almost impossible.
Impressed current cathodic protection method：
The impressed current cathodic protection method involves inserting a direct current power supply in series in the circuit and, with the aid of an auxiliary electrode, applying direct current to the metal to be protected to achieve protection.
The impressed current cathodic protection system is arranged and designed based on different wind turbine foundation structures, providing an overall and optimized design solution and the best protection effect for the equipment of offshore wind power projects.
- Advantages and disadvantages:
- Advantages:
- It features a high driving voltage and can flexibly control the output of cathodic protection current within a wide range.
- It is also applicable in harsh corrosive conditions or environments with high resistivity. The protection range is large. When the quality of the anti-corrosion coating of the pipeline is good, two sets of impressed current cathodic protection systems can protect the entire steel pile.
- The impressed current cathodic protection system is designed to have a long service life and can provide protection for a long time.
- It causes no pollution to the environment. The impressed current cathodic protection system will not release heavy metal harmful substances into the ocean.
- It is easy to install and only requires flange connection installation, without the need for welding installation.
- Disadvantage:
- During operation, it cannot do without an external power supply and requires continuous power supply throughout the year.
- During the operation of cathodic protection systems, strict professional maintenance and management are required.
Composition of the impressed current cathodic protection system:
- Transformer rectifier
- Auxiliary anode
- Reference electrode
- Remote monitoring system