If we go back in history, we can understand that the man has involved himself with works and resources of sea from a long time. He has been continuously improving and producing structures for using it in such harsh conditions. Earlier, structures were manufactured by using Iron. After some time, mankind invented steel and started using it in place of Iron. But, very soon, they realized that the sea water promotes corrosion and the structures are at high risk of being corroded because they are in constant touch with this sea water. And thus increased the importance of Hull protection.
The ships/metal buoys/iron structures at sea face a silent enemy ‘corrosion’. This affects ship’s hull, machinery, components and harbour installations. And moreover, it can also deplete the ships/metal buoys/iron structures strength by corroding the structure in its severe form. Any metal which comes in contact with the sea water is affected by corrosion and thus by pitting and perforations. And so, the implementation of schemes for hull protection is very imperative. In addition, it is equally important that these hull protection techniques should be nicely understood so that they are operated and maintained to best possible level. The principle and applications described in most of my posts relate to Cathodic Protection. This widely used and important method of corrosion control for hull protection involves two techniques:
In this, the important principle of bimetallic corrosion is utilized for hull protection. In this type of system, the ship’s hull is forced to become a cathode with respect to electrodes that are positive with respect to the ship’s hull. The electrodes used for this purpose are Zinc, Magnesium and Aluminium, However, in all the three, Zinc is very popular. These electrodes provide galvanic current and in the process get eaten away. They provide protection to the ship hull by sacrificing itself and thus are called as Sacrificial anodes.
It is an electrically powered method for controlling corrosion. This method is loosely based on the functions of Galvanic cell. In this method, the oxidation process is focused on the anode. And thus, the corrosion of cathode is automatically suppressed to facilitate the hull protection.