Water jet tunnels are particularly vulnerable to corrosion because they are constructed from dissimilar metals, typically aluminium and stainless steel or high tensile steel and stainless steel. Problems can arise at the interface of these materials resulting in rapid corrosion which can put the safety and structural integrity of the vessel at risk. Most high speed craft are fitted with ‘isolation’ systems to prevent corrosive activity between the dissimilar metals.
However, many have a history of repeated failure, indicating that ‘isolation’ is not a particularly efficient or successful method of preventing galvanic corrosion.
Jettek – The solution
The Jettek system has been designed to protect the ‘interface’ of the dissimilar metals. It consists of an arrangement of anodes which are flush mounted within the water jet tunnel which are carefully monitored by reference cells which raise or lower the anode output via the control panel. This maintains the optimum level of protection at all times, without affecting the flow or the efficiency of the propulsion unit.
A number of ‘fail safe’ features are built into the Jettek system including an aluminium shield sensor which automatically detects any breakdown in the di-electric shield. There is also a monitoring reference cell on the edge of the di-electric shield. Both of these devices prevent the risk of ‘over protection’.