Reducing corrosion, the Schottel way

Schottel ProAnode on an azimuth thruster Schottel ProAnode on an azimuth thruster
Industry Database

German propulsion and steering system manufacturer Schottel Group has introduced a new anode aimed at extending the lifecycle of azimuthing thrusters along with other advantages including fuel savings.

Fighting the problem of corrosion to ship’s hulls and underwater components from static charges formed by the flow of water and other phenomenon with consequential effects on dissimilar metals is an age-old (and complex) problem. It was back in 1824 that Sir Humphry Davy attempted to reduce the effects of electrolytic action on ship hulls and came up with the idea of introducing sacrificial anodes made from more electrically reactive, less noble metals into the ‘electrical’ circuit of the hull and appendages, the principle being that you replace the anodes as they degrade rather than the hull, propeller and rudder.

Azimuthing thrusters, popular with shiphandling tugs are prone to this effect and Schottel has introduced a newly developed and patented system called ProAnode which the company claims sets higher standards in corrosion protection, thereby extending the lifecycle of the thruster.

The basic idea behind the ProAnode appears at first sight to be a simple one and involves moving the anode from the outside of the nozzle, where they are prone to be damaged and even knocked off by flotsam such as wood and ice, something that can also be caused by ground contact. Damage to or loss of the anodes may only come to light during routine drydockings and dependent on the time factor, corrosion may already have started to happen.

An additional feature with the new anode claimed by Schottel is that depending on the nozzle’s diameter and the anode’s material, anodes providing up to five years of protection against corrosion can be integrated into the nozzle. This can allow a reduction in the number of additional anodes for the hull or other thruster components.

Those involved in the design, building, maintenance and operation of tugs be they the actual shipyard itself or the myriad component suppliers are under constant pressure to improve on the operational efficiency of the vessel by the prospective or existing owner and Schottel claim its ProAnode contributes to this battle.

The new position in the tail of the nozzle not only shields the anode from potential damage, but also offers additional operational potential as it contributes to the optimal hydrodynamic flow of the nozzle. As the smooth overall surface of the anode reduces flow interference, it meets the customer’s need for high efficiency from the propulsion system. It is claimed this results in lower fuel consumption and pays off in terms of reduced operating costs. The Schottel ProAnode is now a standard fit with its new Rudderpropellers although owners can opt for the conventional anode arrangement upon request.

By Peter Barker

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