23 Feb 2021
Just what are antifouling coatings?
(from a simple diver's assessment)
Antifouling coatings are specialised paints applied to vessel hulls in order to slow the growth of invasive aquatic species (IAS) on vessel structures, specifically below the water line which affects both the durability and performance of a ship or fleet.
These coatings not only prevent marine growth but acts as a protective barrier against corrosion of the hull which weakens and degrades the metal which causes expensive steel repairs.
A concern from the very start of sailing, vessels have long suffered from the growth of marine organisms. As a result, thin metal sheets made from alloys such as copper were attached to the vessel hulls in order to stave off the growth of these species.
In the early 1970s, tributyltin (TBT) became the dominant antifouling paint applied. For the next 40 years, TBT was used as a biocide in antifouling paint, more commonly known as bottom paint, applied to the hulls of sea vessels.
Due to the strong ecotoxicity of the biocide, TBT slowly began leaching out into the marine environment where its high toxicity created negative ecological effects globally.
Although the effectiveness of TBT was high, so too was the risk of altering precious marine life. As a result, the TBT coating was prohibited by the Marine Environment Protection Committee (MEPC) of the International Maritime Organisation (IMO) in 1998, followed by a stringent ban by the IMO in 2003.
WHY DO SHIPS NEED ANTIFOULING SYSTEMS?
Hulls are prime real estate for these biofouling critters, which is why putting preventative measures in place is essential to the longevity of a ship’s capabilities. Marine growth affects the performance of a vessel in many ways:
Slowing corrosion: a natural process of material degradation can be eliminated or suppressed using two principal methods, coating and cathodic protection systems (often used in conjunction with coating systems)
Speed decline: as a ship’s hull becomes fouled with marine growth, the maximum speed of the vessel decreases and increases fuel requirements.
Cost implications: a heavier hull creates a drag weighing down vessels and increasing their fuel consumption by up to 40%.
Transporting AIS: ships may transport marine hitchhikers to other areas which can cause detrimental impacts on local fauna and flora by altering the ecosystem.
When one of the first anti-fouling paints was tested in the early 1990’s and found to yield a substantial result, ways of preventing hull damage as a result of marine growth revolutionised.
With proper planning, shipowners are able to ensure vessels are operating at maximum performance and are cost-efficient while still preserving the condition of their assets. Deterioration is a direct result of poor surface preparation with the only solution being to remove the paint and start from scratch.
Unfortunately repairing coatings through drydocking can be up to 100 times the cost of the initial coating. Drydocking means the entire vessel is brought to dry land or the shipyard in order to inspect and/or repair submerged surfaces such as the hull, propeller etc. This service not only costs an arm and a leg but also means less time in the water.
PROTECTING YOUR HULL
When it comes to managing hull performance, monitoring is critical and should include ship speed, location in the world’s oceans and its activities to gain accurate insights. Choosing the right antifouling process is complex as antifouling paint alone is not enough to fend off these invasive marine organisms. Hull cleaning is key to maintaining a clean bottom, slowing the build-up of marine fouling and optimum vessel performance
Traditional Hull Cleaning:
Conventional ways of cleaning hulls include using divers with brushes/kart systems to dislodge attached organisms. These methods may get the job done but at what cost? Traditional methods of hull cleaning are:
Although brush cleaning serves the same purpose, hull cleaning using HullWiper promises an efficient, cost-effective and is not only better for your pocket but better for the environment too.
How does the HullWiper ROV work?
While the vessel is in port, a support vessel will come to berth or alongside. Once the ROV supervisor has given vessel staff a thorough safety brief, the team begins setting up the HullWiper to start the underwater cleaning process. HullWiper’s adjustable seawater jet pressure is adjusted to variable cleaning speeds depending on the biofouling and coating condition.
The speedy ROV performs a clean in less time than divers and has no nighttime restrictions. An ROV operator on-board the vessel guides the ROV to approach the ship and engages the cleaning mechanism once in position. Removed fouling is captured by HullWiper’s onboard retrieval units, allowing only clean water to be released back to sea. The process is monitored throughout the entire cleaning operation and residues collected during the clean are disposed of ashore in an environmentally approved manner. All these details are recorded in a waste material log.
A hull cleaned by HullWiper has proven countless times to improve vessel speed leading to large savings on fuel which can amount to 40% on a single voyage.
HullWiper’s ability to clean without harm to a ship’s coating is confirmed by many international ship painting companies including:
With operations bases in Dubai including key locations across the Middle East, Sweden, Norway, Denmark, Singapore, Spain, Egypt, Australia, Panama, Mauritius and most recently Namibia, ship owners and operators can proactively manage the effects of hull fouling on vessel hulls and reduce costs easily. Korea and Sri Lanka coming soon!