NL1021789C2 - Anti-fouling device. - Google Patents

Description

Anti-fouling device 5 The invention relates to a device for inhibiting the growth of organism on a submerged surface of a body, such as a ship, which device comprises at least a direct current source and an anode and cathode connected thereto for obtaining a electrolytic process.

Growth of organism in shipping is also referred to by the term "fouling". Fouling is the result of the growth of algae, shellfish and mussels on the underwater surfaces of ship hulls.

It is known from the prior art to provide the hull with an anti-fouling paint. Such a paint contains toxic pigments, such as "coppery oxide" or mercury mixtures. It has been found that "coppery oxides" leached from the paint have a highly toxic effect on the growth of algae, shellfish, mussels and the like. A drawback of this anti-fouling method is that the effectiveness is strongly dependent on the oxidation and leaching capacity of the paint. This anti-fouling method is no longer permitted in the Netherlands, at least because of its high environmental impact. In addition, this is a non-manageable process.

Another known anti-fouling method is based on the principle of an imposed current system, in which copper and aluminum anodes are used. Reduction of anti-fouling can also be more or less achieved if the hull is made of copper / nickel or a solid copper / nickel alloy or is provided with copper / nickel steel skin plates 1021789 H. The ship's hull serves as a cathode in the electrolytic process. The system is based on the same principle as the use of anti-fouling paints, where copper pigments are used to provide a toxic medium. This anti-fouling method finds application in the internal cooling water system of ships to keep it free from organisms.

To prevent fouling of submerged surfaces of bodies, for example the hull of a ship, an independent anode cathode device is proposed according to the invention. This means that - in contrast to the known anti-fouling system that is used for cooling water systems of ships - the body itself is not a cathode. The anti-fouling device according to the invention can therefore also be offered for polyester, wooden and aluminum hulls of boats, yachts, sailing boats and the like.

It seems that the use of copper only as an anode may not be desirable. Corrosion cells can be formed when dissolved copper comes out of solution and deposits again on steel surfaces. However, this possibility does not occur and cannot occur under conditions of use according to the invention, since firstly the amounts of copper that go into solution are negligibly small and secondly this copper is not left behind as dissolved copper, but directly oxidizes in copper oxides that are insoluble.

I Both copper-like oxides and copper oxides are I insoluble, so that the amount of copper ions in water I cannot be found and is far below so-called natural levels I (see "Government Gazette", 16 June 2000, no. 114 - Table 1 - I page 18./ target value (dissolved) for copper 0.5 pg / l, or I maximum permissible risk of 1.5 Ug / 1.

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According to a preferred embodiment of the invention, an aluminum anode is also used in addition to a copper anode. Direct decomposition of aluminum alloys results in the formation of colloidal solutions and hydrated aluminum oxides or emulsions that are gelatinous and encapsulate the precipitated copper oxides so that they can be removed as an "innocent" slurry.

Since coppery oxides are continuously formed on the anode surface and oxidize directly to insoluble oxides, they are not free to react with residual chemicals with equivalent reductions in process efficiency. In natural waters, at pH 7 or even in the range of pH 5 to pH 9, there is no adverse effect on the efficiency of the anode system.

The device according to the invention has the following advantages. The anti-fouling system is a safe system. Not only because of the corrosion hazards, but it will not pose a danger to people who come into contact with the system nor will it mean any pollution risk to the water. The anti-fouling device according to the invention will require little attention and maintenance and, apart from replacing spent anodes, will operate fully automatically. The device according to the invention is inexpensive and operating costs are low due to low consumption, since the system operates at low voltage (approximately 1.5-28 Volt DC and max. 1 Amp for copper and 0.25 Amp - 0.5 Amp for aluminum). Accordingly, the main operating costs are the replacement of the copper and possibly aluminum anodes, which are relatively low costs in comparison with other known anti-fouling systems.

1021789 H With anti-fouling paints, leaching rates of "copper oxide" can be more than 10-15 pg / cm2.24 hours. This means that a surface area of 1 m2 with approximately 40 grams of copper oxide per year can be kept clean from 5 biological fouling. Smaller amounts of copper oxide are effective in the system according to the invention. While anti-fouling paints are only active during the period that the leaching rate is above the given amount, in the system according to the invention "copper oxides" are continuously formed in controllable amounts and accordingly anti-fouling of algae, mussels and shellfish continuously.

An exemplary embodiment of the device according to the invention is shown in the accompanying drawing. The drawing shows a perspective view of a device for inhibiting the growth of organism on submerged surfaces. The device comprises an I housing 1, in which a copper anode 2, an aluminum anode 3 and a steel cathode 4 are mounted. The housing comprises a cover 5. The housing and the cover are preferably made of plastic. The anodes 2,3 and the cathode 4 are connected to a direct current source (not shown), which is arranged in the housing 1. Furthermore, control means (not shown) are provided to enable remote control of the electrolytic process, for example whether the anodes are still sufficiently effective.

The device can be placed at the bottom of a (yacht) port I to protect the ships that dock at the port against fouling. It is also possible to carry the device 30 aboard a ship and if the ship is anchored this device can be lowered under the ship as fouling prevention.

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Claims (5)

1. Device for inhibiting the growth of organism on a submerged surface of a body, such as a ship, which device comprises at least a direct current source and an anode and cathode connected thereto for obtaining an electrolytic process, characterized in that neither neither the anode nor the cathode is connected to the submerged surface of the body. The device of claim 1, wherein the anode is a copper anode. The device of claim 2, further comprising a second anode of aluminum. Device as claimed in any of the claims 1-3, wherein the cathode is a steel cathode. Device as claimed in any of the claims 1-4, further comprising checking means for remotely controlling the electrolytic process. 20 25 30 1021789