Originally Posted by Varley
I don't agree with your last ('aggressively'). The only real meaning of overprotection is to generate gas bubbles and blow off the paint. De-zincification would only occur if it were being sacrificial (ie underprotection).
It is possible to over protect a vessel with an ICCP system, if the voltage is too high for an excessive period of time it will cause Hydrogen embrittlement and as a result of this the likes of valve stems and spades made of lesser noble metals will suffer, reference cells are strategically placed around the vessel to monitor the voltage output but as most ICCP units are placed to the aft of the vessel the reference cells up Fwd will give a lesser reading to the aft reference cells therefore a happy medium must be reached. Once the ICCIP system has been switched on for the first time it will take many days for it to become fully effective and vice versa if it is switched off it will take just as long to UN protect the vessel, Ive heard of some vessels switching off the system from time to time to prevent any problems such as embrittlement.