Page 48: of Maritime Reporter Magazine (June 2021)

TECH FEATURE BIOFOULING

Environmentally Friendly Alter he shipping industry has to prevent a heavy buildup of fouling they avoid the cost of added labour and been searching for the next over time. The two main types include extra days of drydock. However, many best solution to control bio- Controlled Depletion Polymer (CDP) jurisdictions strongly regulate in-water fouling ever since 2001, and Self Polishing Copolymer (SPC) cleanings to prevent the release of toxic

Twhen the IMO banned the coatings which vary by the mechanisms substances from antifouling paints dur- use of tributyltin (TBT) as a biocide in they use for leeching toxic chemicals ing cleaning and the spread of invasive [2] antifouling coatings. Biofouling control into the ocean . species. Transversely, in-water hull measures are a high priority investment Soft foul release coatings are an envi- cleanings have been recognized by the for shipowners since fouling growth on ronmentally friendly alternative which International Maritime Organization a ship’s hull can signi? cantly decrease use the sheer force of water to remove (IMO) and the United States Environ- energy ef? ciency. During a ship’s jour- fouling organisms without leeching bio- mental Protection Agency (USEPA) as a ney, fuel consumption constitutes 50- cides into the environment. These low measure to limit the transfer of invasive 60% of its operational cost and this cost friction topcoats are primarily silicone- species when performed appropriately.

is only further increased from fouling’s based and can effectively prevent foul- Historically, antifouling coatings negative impacts on the hull’s drag per- ing under dynamic conditions (when have not been designed to be cleaned formance (84% increase in shaft power the ship is in motion) due to their low by any existing underwater hull groom- [1] [6, 7] for a heavily fouled containership) . surface energy, slip, and elastomeric ing method . After each hull clean-

Currently, the most popular method properties. Soft foul release coatings ing these coatings will mechanically of biofouling control for the underwater have become increasingly popular due degrade which cuts down their lifetime, hulls of marine vessels is to coat them to their inherent fuel savings as they decreases their functionality and pol- with “antifouling coating systems”. The maintain a lower average hull roughness lutes the marine environment. For this [3] drag performance of a vessel’s hull can throughout their lifetime . One draw- reason, ship owners are forced to wait be signi? cantly improved by choos- back is these coatings contain silicon for the next drydock period to clean the ing the proper coating system for the oils (1-10%) which can persist in the hull and re-apply the antifouling sys- [4] intended application and environment. ocean . The long-term environmental tem, sacri? cing their fuel savings and

Each marine coating system is differ- impact of these silicon oils is still not increasing GHG emissions.

ent as they use various mechanisms to fully understood. Soft foul release coatings are heav- protect a ship’s hull from biofouling ily reliant on their ability to maintain a and corrosion. The main type of marine defect-free surface. However, due their Hull Cleanings coating used to protect against fouling Hull cleanings both in drydock and in- weak adhesion between layers and soft- organisms is a biocide-based antifoul- water are effective alternatives to con- ness of the topcoat, they can be dam- ing. These coatings are used for vessels trol biofouling growth. In-water clean- aged during underwater hull cleaning which undergo long stationary periods ings have recently become popular since operations. As a result, shipowners opt

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MR #6 (34-49).indd 48 6/4/2021 5:08:51 PM