When complete in 2001 two French-built fast car/passenger ferries will have a total of nine BAC Corrosion Control impressed current cathodic protection systems between them to safeguard steel hulls and seven water jet propulsion units against corrosion. Installation of the nine systems will be undertaken as a joint venture by BAC France engineers for Chantiers de L’Atlantique, St Nazaire, part of ALSTOM.
The Corsaire 14000 is a 140 metres long vessel with the capacity to carry 1800 passengers and 400 cars at a speed of more than 40 knots. The Corsaire 10000 is 103 metres long and designed to ferry 800 passengers and 190 cars at 35 knots. Both ships are for the Greek company Nel Lines, one of the largest ferry operators in the Aegean, and are being built at ALSTOM’s Lorient and St Malo shipyards in western France.
The Corsaire type 14000 has four water jets, two of 2 metres diameter and two 1.40 metres. The ICCP systems for these two giant jets are the largest that BAC has ever supplied and, together with those for the two smaller units, provide the best solution to protect the jet tunnels and components that are subjected to high velocity water flow and the risk of greater than normal corrosion. There are three water jets each 1.25 metre diameter on the Corsaire 10000.
Impressed current corrosion protection (ICCP) systems offer long term control of corrosion and much reduced maintenance and inspection times for larger vessels, hence their increasing popularity. Such systems, for which BAC is a market leader, use inert (non-galvanic) anodes with an external source of DC power to impress a current from anode to hull (cathode). They operate evenly over the hull to control any corrosion as the coating deteriorates between dry docking schedules.
To control and monitor these ICCP installations, reference electrodes fitted adjacent to the anodes and electrically connected into the system provide a remote control and monitoring facility and an alarm on the bridge. For the two hull and water jet protection systems BAC has used its purpose designed mixed metal oxide(MMO) anodes.
BAC’s MMO anodes comprise a titanium disc with a mixed metal oxide coating that activates the titanium electrically, enabling it to function as an anode. Installation of both anodes and reference electrodes is completed through a welded-in-place gland assembly with watertight teflon seals.