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1¡¢ Suspended anode system
In this system, the auxiliary anode is installed in the insulated frame, and then it is suspended freely from the bottom of the protective tube on the water to the specified depth in the water. Under the action of waves and so on, anode failure will occur periodically, but the replacement cost is very low, which can be easily recovered and replaced. This can be a feasible method for shallow water structures with relatively short life expectancy and medium to high current demand.
2¡¢ Gravity sliding anodes
The auxiliary anode is fixed on the sliding base in grid type and sunk to the seabed, and connected by submarine cable. The system is very reliable under the condition of ensuring the safety of submarine cable and reliable waterproof of anode to cable connector.
3¡¢ Fixed anode system
The anode base is directly installed on the steel structure, and in order to avoid over protection, it is necessary to brush the anode shielding layer. Due to the complexity of excessive welding installation and anode shielding layer, the system is not suitable for the life extension of old platform, but more suitable for new platform, wharf or offshore facilities.
4¡¢ Floating remote anode system
It is very similar to the gravity sliding anodes system described above, except that the auxiliary anode elements are connected to the seafloor base by buoys (usually integrated with the anode) and float in the water. The advantages of this method are: if the debris on the sea surface sinks to the sea bottom and hits the anode, as the anode is floating, the risk of damage is greatly reduced.
5¡¢ Stretching anode system
The system uses tensioned auxiliary anode strings, usually mixed metal oxide (MMO) anodes or platinum plated niobium anodes. As the anode string grows longer and longer in deeper water, great tension is required to minimize the movement of the rope in waves or currents, or multiple intermediate limiting devices are required to limit movement. This system and floating anodes are the most widely used systems in the field of ocean engineering ICCP. Compared with the floating anode system, the potential distribution is more uniform, the polarization time is shorter, the performance is reliable and the cost is lower.
6¡¢ Joint protection system
Combined protection system is a combination of impressed current cathodic protection and sacrificial anode. The ICCP provides a large amount of current at the early stage of polarization, which helps to rapidly polarize to - 900 MV and form a dense calcium magnesium deposit. This current is usually 80-90% of the total demand. Strategic positioning of sacrificial anode is distributed in the area where the applied current is difficult to polarize, which can alleviate and compensate the shielding effect of impressed current cathodic protection. The service life of the sacrificial anode can be greatly prolonged by adding an external current system to the original offshore platform to form a joint protection.