Durability of the Ecospeed coatings

How long should a ship hull coating last? Is it enough for it to stay on the hull for two and a half to five years and be replaced at the next drydocking? Or should it in fact last the life of the ship without the need to repaint, 25 years or more?

Current situation with coating durability

Some coatings, such as antifouling or foul release coatings, are not expected to last very long before they need to be replaced. Ships typically spend many days in drydock with the coating scheme being patched up and spot repaired and then the full topcoat of antifouling or foul release paint being completely reapplied.

There are downsides to this approach:

The cost to the owner of repainting is high – not only materials and labor but also drydock fees and, above all, off-hire time.

There is an environmental penalty. Where does the antifouling or foul release coating go in  between drydockings? The ship leaves drydock with a new coat of paint. It comes back into drydock with that coating mostly disappeared. The toxic and polluting paint with heavy metals, biocides, silicone oils, PFAS and microplastics has come off and disappeared into the sea, where it drops to the bottom and settles in the sediment. No wonder there is such a huge, planetary-wide problem with highly contaminated sediment.

Because traditional ship and boat hull paint is not very durable, the protection offered is only partial. On rudders and running gear, for example, the coating can be destroyed by cavitation, leaving the bare steel to erode and corrode unprotected. This in turn can result in the need for hot work in drydock, which itself is very time-consuming and expensive. Scrubbers and scrubber outlets are another example of poor protection provided by traditional coatings which quickly disappear under the onslaught of the highly acidic effluents from scrubbers. This affects the recycling tank, the overboard pipes and the entire area of the hull around the overboard pipe.

The cycle of replacing the topcoat every 2.5 – 5 years is generally repeated for several drydockings until the coating is so rough that the hull needs to be completely blasted back to bare steel and the entire coating scheme replaced, usually every 10 – 15 years.

Another philosophy and approach

With its Ecospeed family of hard, non-toxic coatings, Subsea Industries has operated on the basis that the hull paint should provide lifelong protection for the hull without the need to repaint. Touch-ups of mechanical damage may be required, but these are very quick to carry out, and they leave the coating as good as new and, perhaps more importantly, as smooth as when the original coating was applied.

This, in addition to the requirement that the coatings be entirely non-toxic, was the philosophy and business model behind Ecospeed and later Ecoshield and Ecolock. They are all designed, manufactured and applied with durability in mind, as well as no harmful impact on the marine environment.

Cases in point

The RRS Ernest Shackleton, now the RV Laura Bassi is an icebreaking Antarctic research and supply ship that routinely breaks 2.5 meter ice on its missions to stations in the polar regions every year.

The traditional ice class coating that the ship was using was found to be unsatisfactory and needed frequent replacing. The British Antarctic Survey who were operating the ship at the time found Ecospeed Ice in 2008 and the coating was applied. It has remained intact all the way to the present, needing only touch-ups of mechanical damage to the coating during routing drydocking.

When OGS acquired the ship in 2019, Mr. Rosario Martino, Naval Architect and Marine Engineer for the vessel’s ship managers, ARGO s.r.l. said, “It was impressive to see the Ecospeed paint in an excellent condition even after so many years of service. We have performed only touch-ups in the bow area affected by the impacts with the ice layer.” He added, “When Laura Bassi returned from her first Arctic campaign, during which she encountered quite a few icy areas, it was clear that the Ecospeed paint did its job impeccably.”

Oceanex’s dry bulk cargo ship Oceanex Sanderling sails in ice off the coast of Nova Scotia in very harsh conditions. The conventional coating originally applied needed extensive repair annually due to the abrasion of floating ice, often containing sand, grit, lava and gravel. The wear and tear on the paint was leaving the hull bare and exposed to the corrosive effects of salt water and air. The ship was coated with Ecospeed in 2011 and the coating has not been replaced since. When she was in drydock in Amsterdam in 2022, the hull coating was still in excellent condition and only very minor repairs were needed to restore the coating to as good as new.

A small cruise ship that mostly sails in the Caribbean and has long periods laid up, was coated with Ecospeed in 2008. The hull is cleaned by divers on the ship’s crew. The original coating is still intact and only touch-ups have been carried out in the intervening 16 years, for example when welding on the hull was needed in order to make modifications to the interior of the ship. The coating is very easy to repair when needed and has remained smooth.

Conventional coatings on rudders and running gear are notoriously short lived. But a thousand or more rudders, thruster tunnels, propellers, boot tops, bulbous bows, stabilizer fins and other running gear have been very successfully coated with Ecoshield and not needed to be recoated in later drydockings. The durability of Ecoshield is unparalleled in this type of application, and more and more major shipping companies are turning to the coating to protect their rudders and running gear and reduce time in drydock.

Offshore stationery assets such as FLNGs, FSRUs and others are a special case. They are often stationed in a particular location for 20 – 40 years without going to drydock. They may need to be cleaned on site in order to reduce weight from too much biofouling or in order to facilitate UWILD inspections by class. Ecolock has proved to be an excellent solution, and more and more owners are turning to this coating to protect their assets, especially when they learn that it can come with a 35-year warranty.

How we can accomplish this longevity

It starts with the idea that hull coatings can  last a long time if the manufacturer wants them to. After that it’s a matter of using the best resin for the purposes, vinyl ester. It does not become brittle over time as is the case with epoxies. It is acknowledged as the most long-lasting and durable base for this type of coating. To that we add a high proportion of special, large aspect ratio glass platelets and bonding agents. The result is a tough, durable, long-lasting, non-toxic coating.

A key factor in the durability of the coating on a ship’s hull is the preparation. Our coatings are only guaranteed to last if the preparation and application requirements are adhered to. This means grit blasting the steel to a roughness of 75 microns (about 3 mil) and a cleanliness of SA 2.5 or equivalent, which is near white steel. Application conditions are quite lenient as far as temperature, humidity and so on.

Ecospeed coatings are applied in two coats (sometimes three) of 500µm/20 mil each with an overcoat time of 3 hours minimum but no maximum. Total dry film thickness is 1000 µm/40 mil or, for a longer warranty especially in the case of Ecolock, 1500µm/60 mil. Subsea Industries sends a knowledgeable coatings inspector to guide the application, ensure the preparation is correct and that the final DFT is achieved.

Ours is a new and different approach to hull coating – one that is designed to be environmentally safe as well as cost-effective for ship and boat owners.