Fouling — the disease and treatment

The problem of fouling is much worse than it might seem at first glance. It is estimated by American scientists that annually to combat the fouling about 500 million dollars is spent in the world. According to the same professionals the reduction of speed due to fouling is 8-15% and increase of fuel consumption — up to 20-35% for the period. Under favorable conditions for marine organisms that foul, their weight on the hull could reach 200 tons for two months.

Fouling is a process in which part of the hull, or a stationary floating structure located in the water, is covering by a layer of marine plants and animals. It is accompanied by a decrease in the speed of ships, increase of fuel consumption, enhance of wear of mechanisms and, consequently, by increase in operating costs.
Fouling may cause difficulty in feeding water to the ship’s lines, it destroys protective coatings, reinforces corrosion of metal. The intensity of fouling depends on the area of navigation, as well as the quality of anti-fouling coatings used to protect the underwater part of the hull.

Fouling vessels occurs primarily while sites in the ports, where larvae and spores are carried by flowing to the courts. Fouling during the course there is very rarely, with the controversy of algae and germs balyanuses (a kind of fouling organisms) attached to the vessel, moving no more than 0,5-1 knots. Embryo tube worms, mshank, hydroids and some other fouling organisms can be affixed, and at higher speeds. Disputes of algae and larvae, hitting on the hull, are attached so well that even the strongest blows waves cannot disrupt them. Larvae-established non-toxic paint or unpainted surfaces develop into an adult organism; larvae settled on the toxic paint, do not develop, not enough stick and are easily washed while vessel’s moving.

Observations show that the less intensive fouling is a characteristic of the actively used ships: passenger, cargo, service, port and similar to them. If overlook the speed and intensity of fouling of the ship, those which stand in the picol, took the first place. Even more seriously affected by the phenomenon of underwater stationary offshore structures and equipment: drilling platforms, piers, booms, buoys, etc.

In fresh water, until recently there were few organisms belonging to the foulings. However, development of a number of freshwater seas, appearing of canals that connect rivers with lakes and seas creates the conditions for appearing of fouling organisms in those places where until recently they were not. In the Caspian Sea, for example, balyanuses and tree spoilers appeared; in Volga, Dnieper, Danube stormily developed shells and algae. Underwater part of a boat was photographed after the one-year of work in the Danube, shows the nature of fouling in the absence of protection against it.

Typically, fouling begins with the appearance of zones of light that prefer green algae, which are beginning to grow at a variable waterline, bordering the water, where the amount of light, and oxygen is sufficient for their lives. Below this zone usually begins fouling balyanuses amount of which increases with the increase of depth and reduction of illumination. In the middle and stern of the vessel fouling is stronger, since the bow of the water moves more intensively. If the brass screw is not insulated from the shaft and the hull, its intense fouling occurs after 4-6 weeks of running of the vessel on the water.

Long-term studies have shown that the most effective way to combat the fouling of modern ships — is the use of anti-fouling paints, the more so that the coating used to protect against corrosion of the underwater part of the body, often damaged or even completely destroyed, while if not used anti-colors.
The choice of antifouling self polish paints depends on:

• types of ships on which they are to be applied;
• conditions of usage of ships (sea, river-sea, freshwater sea, lakes, rivers);
• the length of the navigation period;
• sailing vessel areas (north, a temperate climate, the south, subtropical);
• the nature of fouling in the area of navigation, and timing of production of ships in dock.

The composition of anti-fouling paints is: film basis, the components to prevent fouling painted surfaces, pigments, fillers and related solvents. Anti-fouling paint should differ from anticorrosive paint in color, it allows to control the correctness of applying them to the anticorrosive coating. It is strictly prohibited to add soot ink (any kind)to anti-fouling paint: in this case, the sharp deterioration of their protective properties comes. Anti-fouling effects of paints are determined by the speed with which preventing fouling components move from painted surfaces in water. The rate of leaching of these components depends not only on their solubility, but also of how these components relate to the film foundation paints. It is known that the rate of leaching from the paint changes from the time of their contact with water. For example, copper, a required component of anti-fouling paints, released at a rate greater than 10 mg/cm per day, prevents fouling of algae balyanus and other fouling organisms. The rate of leaching of the paint of good quality decreases very slowly in comparison with their initial value. Other colors are very effective at first, after several weeks the average leaching rate becomes almost stable, but after several months of sharp falls below the required level. The ability of paints to maintain uniformly the required rate of leaching in the long term depends on the membrane base.

On the territory of Ukraine Silta-Color Ltd proposes anti-fouling systems manufactured by CJSC EmLak, which compete with the excellent products of foreign manufacturers and are the best alternative to imported systems.

Anti-fouling enamel “Emagard” is non-tin covering of a high-quality, based on semi-soluble binders, where the inorganic compounds of metals and fine biocides function as the main anti-toxins. In contact with water, through a process of diffusion and leaching toxins are released slowly into laminar layer around the hull.
Enamel “Emagard” refers to the type of organotion-free ablative type. Anti-fouling Systems on the basis of enamel Emagard meets the requirements of an international convention on quality control systems of the protection of vessels from the harmful biological fouling — “IMO Anti-fouling System-Convention compliant (AFS/CONF/26)”.
The expiration term of anti-corrosion coatings is determined by the conditions of the system, thickness of layers of operation, speed of the vessel, the area of navigation, etc.