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Marine ICCP - Impressed Current Cathodic Protection, application and advantages on board ship

The metal lying underneath the water are affected the electrolytic or galvanic corrosion. This will leads to the reduction of the thickness of the steel plate. The corrosion takes place as a result of the flow of current between one metal and other metal in a solution. Here the solution is sea water and the metals are the dissimilar metal area and the appendages of the hull. This will lead to formation of an anode and cathode. Current will flow from the anode to the cathode. Likely the ions from anode get deposited on the cathode. The flow of current takes place from Anode to cathode and the respective position of the metals in the galvanic series decide between anode and cathode.

These anodic and cathodic areas exist in the ship’s structure due coupling of metals of different compositions and potentials, physical difference in grades, deterioration of metal or non-uniformity in painting. Once such an area is formed, then the rate of corrosion accelerates very fast. So as far as from owner’s viewpoint, it’s very important to avoid the corrosion of the hull

The best method to avoid this issue is by introducing an additional metal, which is more anodic to the existing metals on the ship’s hull. The additional anode which will ultimately be sacrificed may consist of a metal at the negative end of the galvanic series that is more electro negative to the existing metals. This can be an ally of Aluminium, Zinc or Magnesium. The basic principle is that the anode loose metal and cathode metal receives the current and will remain intact and corrosion free.

A Direct Current is introduced into these metals. ICCP stand for Impressed Current Cathodic Protection. The system consists of Anodes, reference electrode and a controller power unit.

With the main hull protected, consideration should be given to protect the propeller, exposed shaft and the rudder. They are made electrically common to the hull. The propeller and the exposed shaft are protected by grounding the shaft to hull with a slip ring. The rudder is grounded by bonding the rudder stock to the hull.

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