Most of the ships were owned by different companies, but they all experienced the same problems. Cavitation corrosion damage had appeared on the rudders of their ships. Often a rudder is not given the proper protection against cavitation and the resulting erosion and corrosion damage. In those cases the financial consequences can be extensive for the owner.
Tests in a flow channel, carried out in Grenoble, have confirmed that Ecoshield performs extremely well under severe cavitation. The coating will prevent corrosion damage from reoccurring on an existing ship, or can protect the rudder(s) of a newbuilding against cavitation and corrosion damage from the very start of its life. It is the only known coating that can provide this type of full protection, claimed Subsea Industries.
Rudder protection is best begun at the newbuilding stage. When a vessel enters drydock, maintenance of its stern area, especially cavitation damage repair, can take a long time. There are strict procedures concerning blasting, painting, welding and propeller and stern tube seal work. Painting is assigned to the end of the schedule and as a consequence, it may be rushed, or not get done at all, or else prolongs the stay in drydock.
With an Ecoshield application, these problems can be avoided from day one, as the underwater gear will not need to be repainted during future drydockings. Ecoshield will remain intact for the lifetime of the vessel and is guaranteed for 10 years. At the most, quick and easy touch-ups amounting to less than 1% of the surface area will be required. Planning the maintenance of the vessel’s stern area therefore becomes much easier.
The coating can also be used to protect vessels that have been in service for some time and are already facing cavitation and corrosion damage, similar to the vessels coated over the few last months.
Flexibility
Ecoshield’s flexibility makes it easy to adapt the application schedule to the rest of the activities planned at the shipyard, or drydock, in a way which does not interfere with them.
Overcoating time can be as short as three hours, which means that for smaller surfaces, such as rudders, or bow thrusters, the two coats required can usually be applied in one single day, the company said.
The return on investment in a coating system that offers full protection from day one is claimed to be fast. This becomes very clear when the costs of the temporary underwater repairs is taken into account and the regular inspections required by a condition of class, not to mention the extra costs associated with rudder repair and recoating in drydock, the company said.
Another product
Subsea Industries has also unveiled a new product for filling and building up a corroded and pitted steel surface to its original condition, prior to recoating with Ecoshield.
Ecofix is claimed to be as tough as the steel itself, able to be machined and can be used to repair most pitting, or corrosion damage on rudders, stabiliser fins, thrusters and other underwater gear.
It is used in combination with Ecoshield. When a rudder, or another piece of underwater ships’ gear, has not been properly protected, the surface will become corroded.
Cavitation damage can cause severe pitting. The steel needs to be restored to its original shape with a smooth surface, prior to recoating.
This is where Ecofix comes in, Subsea Industries said. It is a tested and proven filler.
Because it uses the same basic resin as Ecoshield, the coating can be applied in only one hour after the filler. The company claimed that this is the effective alternative to metal facing, or very expensive alternative fillers. And because it is part of the Ecospeed/Ecoshield family, it is fully compatible with the coating.
Underwater gear
Ecoshield and Ecofix are also suitable for stabiliser fins, thrusters, nozzles and other underwater ships’ gear, which needs special protection from corrosion. These items can now also be repaired, prior to recoating where other, less effective coatings have permitted corrosion and cavitation damage to occur.
With the launch of the new product, Subsea Industries offers a full package; Ecofix restores the surface of the rudder, or other underwater gear and Ecoshield will protect the area from suffering corrosion and cavitation damage, the company concluded.