Jotun has established a close co-operation with the UK based company Cathelco Ltd.
, thus creating the world's largest supplier of Impressed Current Cathodic Protection (ICCP) and Electrolytic AntiFouling (EAF) systems for corrosion prevention and fouling mitigation.
Impressed Current Cathodic Protection (ICCP) systems
ICCP systems should be ranked, technically and economically above SACP systems.
The metal to be protected is coupled to the negative side of a direct current source, while the positive side is coupled to an anode. This anode is inert and
will last for several years even at high current output.
ICCP systems offer smooth hull because the anodes and electrodes are normally recessed. Therefore they do not create drag and are protected against physical damage. They control the hull condition, achieve the correct protection potential and can cope with large paint damage.
ICCP systems can also be retrofitted at drydock and permanent anodes can be easily replaced, even under water. Drydocking periods can be prolonged and the ICCP systems normally have a lifetime corresponding to that of the ship.
Slip Ring Arrangement (SRA) for propeller shaft
A potential difference occurs between the hull and the propeller due to the use of different alloys and the rotation of the propeller, where possible current will go from the propeller shaft to the hull.
This current will vary with the diameter of the propeller and its rotation speed. The flow of the current occurs most often in the shaft bearings and occasionally in the engine main bearings. This current flow may result in a shaft "spark corrosion", a problem which can be solved by the SRA.
A steel ring is accurately machined to fit the
diameter of the specific
propeller shaft. The ring is bolted together in two halves. Two silver-graphite brushes are accomodated in a brush holder and positioned as illustrated in the photograph.
A short length of electrical wire is fitted between the brush-holder and a bolt, welded to the hull. This ensures a low resistance path between the shaft and the hull.
Electrolytic Antifouling (EAF) systems
Fouling is all too familiar to operators of sea water systems on ships. Marine growth, such as mollusca, algae and slime, enters the sea water system and finds a spot where temperature, nutrients, pH and other environmental conditions are right for settling and breeding. This results in problems such as
turbulence and the time consuming and costly business of repair and maintenance.
When installed, the electrolytic antifouling system conditions the sea water. A "floc" is produced in controlled amounts by copper anodes and aluminium or soft iron anodes (dependant on the quality of the material of the seawater line system). The flocs flow with the seawater, through the line system to combat fouling (Cu) and reduce corrosion (Al or Fe). Moreover the electrolytic system has a unique feature for monitoring anode wear. This means simpler and more trouble free life for the operator.
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