Rudder protection coating launched

Oct 13 2013


Following more than 10 years of strenuous testing, Subsea Industries, a Hydrex company, has launched what it claims is the ultimate rudder protection coating.

Ecoshield was developed specifically for permanent protection against cavitation damage for rudders. The glassflake reinforced coating protects the rudder for the service life of the ship without need for recoating, or major repair. It comes with a 10- year guarantee.

The coating is also suitable for bulbous bows, stabiliser fins, thruster nozzles and other underwater ships’ gear, which needs special protection from corrosion.

Until now, the problem of cavitation damage to rudders, causing erosion, pitting and sometimes complete failure, necessitating very expensive repairs, or replacement, has remained unsolved.

The need for rudder repairs, involving welding and resurfacing in drydock has been almost universal, while the cost of rudder maintenance and the safety hazards connected with worn and failing rudders are out of proportion to the relatively small surface area involved.

Efforts to solve this problem have included redesigning the rudder, changing its position relative to the propeller, trying various materials, including stainless steel, metal facing the surface, cathodic protection and a variety of coatings. But the problem has persisted.

Ecoshield is a specifically reinforced version of the Ecospeed non-toxic underwater vessel hull coating, which is designed for the entire underwater hull of any type of ship.

Small but significant variations of the Ecospeed formula have been tested on rudders since 2002 with extraordinary results. Ships that were experiencing heavy cavitation damage to their rudders, once the glassflake coating was applied, have seen no further cavitation damage erosion for as long as 10 years after application, with no sign that the coating will need replacement during the life of the ship.

 

Newbuilding

Ecoshield is designed to be applied at best at the newbuilding stage, or in drydock for ships already in service. Application is simple, Hydrex said. It requires blasting to create a 75μm profile and a surface preparation of SA 2.5 or SP 10 and then the glassflake paint is applied in two coats to a thickness of at least 1,000 μm DFT, with an overspray time of about three hours minimum and no maximum.

A pitted rudder can be repaired using a thick resin paste (a new, soon-to-be-announced product), which is capable of building up the pitted surface to its original form and which is as tough, or tougher, than the steel it is used to fill.

The heavy glass content of Ecoshield insulates the rudder or other part, making cathodic protection systems, including sacrificial anodes, virtually unnecessary, as evidenced by the very little wear on the anodes when a ship’s rudder, already coated, is inspected in drydock and by the fact that an impressed current can be turned right down with no ill effect.

Evidence of the success of the new product is the number of companies who began by coating one rudder as an experiment and who, after seeing the results in service, have ordered this coating for the rudders on other ships with plans to convert their entire fleet, the company said.

Shipowners who have previously applied Ecospeed to rudders on ships in service are specifying the coating for the rudders and other underwater gear on their newbuildings.

Ecoshield comes with a 10-year guarantee. It is the only coating known to fully protect a rudder from all cavitation damage and is available from Subsea Industries.

A ‘White Paper’ with full details about protecting rudders from cavitation damage is available in the publications/papers section of www.shiphullperformance.org for free download.

Subsea Industries is a Hydrex company, with its main offices in Belgium and the US. The company has over 35 years of experience in all aspects of underwater hull fouling control, hull maintenance and advanced underwater hull cleaning.

Intended to keep ships trading with minimum drydocking and to protect the marine environment, Subsea Industries developed and tested a system, Ecospeed, which combines a completely non-toxic hard hull coating, which lasts the lifetime of the ship, with routine, advanced in-water hull cleaning.

The coating is classified as a surface treated composite (STC), which consists of relatively large glass flakes in a resin base. It is applied in two coats on a grit-blasted hull to a dry film thickness of 1,000 microns.

Once conditioned under water with special tools, the coating provides a very smooth, extremely hard yet flexible protection lasting the life of the ship, requiring only minor touch-ups. The surface improves in hydrodynamic performance with each in-water cleaning, the company explained.



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