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Sat 20 Dec 2008 04:00 AM

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Ask the expert: Stein Kjølberg

How can anti-fouling products help the marine industry cut costs and protect the environment?

How can anti-fouling products help the marine industry cut costs and protect the environment?

Explaining anti-fouling

Anti-fouling products reduce the roughness of a ship's hull, helping to decrease the fuel consumption, which means less greenhouse gases (GHG), including carbon dioxide, nitrogen oxides and sulphur oxides are produced. There are two kinds of hull roughness; physical and biological.

When anti-fouling products are used, there is a 2-5% reduction in fuel consumption.

Biological roughness is typically derived from animal and weed fouling, whereas physical damage is produced by corrosion of the hull. By increasing hull roughness, the drag resistance (propulsion resistance) increases, which requires a greater degree of fuel consumption to maintain the ship's speed, thereby allowing more GHG to be released into the water.

Biocides technology

Biocides are found in anti-fouling products and the biocide that has proved most effective is copper. This is because it has an effect on most fouling species and is accepted as an environmentally protective biocide.

Copper is an essential nutrient for marine life and is safe to handle. At the moment the European Union is examining and approving products containing biocides and anti-fouling paints are among the first on the list.

There are other technologies in the market like FRC (Fouling Release Coatings) and Hard Coatings, but ship-owners repeatedly experienced that those biocide-free technologies' performance depends on the regular cleaning of the hull to remove slime and gain speed.

The recent ban on Tributylin (TBT) anti-fouling has led to a confusing number of new products on the market, and it is essential that each vessel is evaluated before product selection is made.

How it works

The biocide (copperomadine) in our SeaQuantum product dissolves in seawater from the surface of the anti-fouling preventing marine growth. Once the non-toxic silyl group in SeaQuantum is released, the polymer backbone, which is soluble in seawater, will then dissolve leaving the paint surface exposed; the process is repeated until the vessel re-enters drydock.

Hull roughness, anti-fouling performance and, consequently, the reduction in fuel consumption remains constant until the total anti-fouling film has been polished away. We estimate that this product can provide 60 months of truly efficient service.

Becoming cost-effective

When anti-fouling products are used there is a 2-5% reduction in fuel consumption (depending on the way the product is used and the vessel's sailing pattern). This has a direct and positive economical impact, despite the fact that the vessel is still travelling at the same speed.

The premium range of anti-fouling products containing copper biocides costs around US$30-35 per litre and we estimate that an investment of $60,000 in a SeaQuantum system can be returned in just 20 months.

How Jotun has evolved: A systematic approach

Jotun began as a supplier for marine coatings in 1920. Based in Norway, a entrepreneur named Odd Gleditsch opened a paint distribution shop at a time when the whaling industry was rife.

Over the years, Jotun has secured operational contracts with companies all over the world and developed technologies for decorative purposes and surface protection. In 1999, our environmental anti-fouling product, SeaQuantum, was launched.

It is my opinion that no other product can match the lasting performance of self-smoothing, self-polishing and hydrolysis of SeaQuantum. We also cater specifically to vessels trading in cold water and ships that have hulls made of aluminium.

Doing the math

We do encourage ship-owners to use anti-fouling paints based on environmentally acceptable biocide because of its minimal impact on the environment (air and sea). If carbon dioxide gas dissolves in any water in the pores, it reacts with the cement to form carbonates that reduce the pH in the concrete.

Carbonation can be a problem in reinforced concrete as a pH of around 7 can cause corrosion of steel. And when the steel starts to corrode, its volume increases by around four-six times - resulting in enormous pressure on its surroundings, causing cracks and ruptures in the concrete.

Water will then penetrate, the concrete is further weakened and the steel corrodes even more. Another benefit is that when anti-fouling products are used, carbon dioxide emissions are reduced by around 20% after the sailing period.

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