CHLORINE ON A PORTION OF A SURFACE SUBMERGED IN SALT WATER

TECHNICAL FIELD

The present invention relates to efficient and scalable anfifouling systems and methods that can be applied†o submerged parts ships, either isolated parts, or†o whole hulls. STATE OF TH E ART

Known in the art are methods for generating one or more compounds comprising chlorine with an oxidation number higher than -1 , for example hypochlorous acid, on a portion of a surface submerged in sal† water; the method comprising the steps of:

providing a firs† electrode in the sal† water;

providing a† leas† one second electrode in the sal† water;

causing a direct electric current†o flow between the firs† electrode and the a† leas† one second electrode, such†ha† CF ions of the sal† water in contact with the a† leas† one second electrode are turned into Ch.

For example, US61 73669 discloses a marine fouling prevention system. This document proposes†o generate the chlorine on the surface†o be protected. For this, the anodic and cathodic behavior of the surface †o be protected is alternated during different time intervals, which means anodically polarizing the surface†o be protected during a time interval†o generate the chlorine and then depolarize it. For this purpose the two parts of the hull are electrically separated by an insulator and each part of the ship is polarized alternately, always generating the chlorine on the surface †o be protected, by applying an electric current proportional†o the anodic area†o be protected.

Flowever, when a metal surface is anodically polarized, it can be subjected†o electrolytic corrosion. DESCRIPTION OF THE INVENTION

For overcoming the mentioned drawbacks, the present invention proposes a method of generating one or more compounds comprising chlorine with an oxidation number higher than -1 , for example hypochlorous acid, on a portion of a surface submerged in sal† water; the method comprising the steps of:

providing a firs† electrode in the sal† water;

providing a† leas† a second electrode in the sal† water;

causing a direct electric current†o flow between the firs† electrode and the a† leas† one second electrode, such†ha† CF ions of the sal† water in contact with the a† leas† one second electrode are turned into C ;

wherein the a† leas† one second electrode is arranged under the portion of the surface such†ha† a† leas† par† of the Ch produced by the a† leas† one second electrode rises and contacts the portion of the surface.

The method may be a method of antifouling a portion of a surface, e.g. a portion of a surface of a hull or a portion of a surface of a propeller, when the surface is in sal† water, e.g. submerged in a sea or ocean.

In the present disclosure, antifouling of the portion of the surface should be understood as the inhibition of accumulation of organisms, and in particular the inhibition of accumulation of organisms whose accumulation is detrimental†o the function performed by the portion of the surface.

In the present disclosure, organism should be understood as a living system (i.e. the organism is alive) . The type of organisms whose accumulation is inhibited depends on the type of biocide and on the concentration of biocide on the antifouled portion of the surface. For example, while a low concentration of a particular biocide can be enough†o inhibit accumulation of microorganisms, the inhibition of accumulation of bigger organisms, such as algae or barnacles, may require a higher concentration of the same biocide. In particular, in some embodiments of the invention, the method is used †o inhibit accumulation of organisms which are susceptible (e.g. harmed or troubled) to hypochlorous acid (i.e. HOCI) or to hypochlorite (i.e. OC ) . In the present disclosure, a biocide is a substance which causes harm or troubles an organism susceptible of accumulating on the portion of the surface. In the present disclosure, sal† water is water containing dissolved salts, in particular NaCI and/or other salts having C as anion when dissolved in water.

The differentiating characteristics solve the technical problem posed by the prior ar† devices relating†o the possibility of electrolytic corrosion of the surface†o be protected from the biological incrustation.

The differentiating characteristics solve the technical problem by isolating the surface†o be protected from the biological incrustation of the auxiliary anode, avoiding having†o anodically polarize the surface†o be protected, as done in the prior ar† methods.

The auxiliary anode becomes a fungible and the surface†o be protected does no† suffer corrosion risk. In addition, the need†o control the polarity of the circuit is avoided, so†ha† the elements needed†o power the system are reduced.

I† is further pointed ou††ha† the circuit can be connected directly†o a renewable energy source, for example solar or continuous motor wind, without the need for conversion elements or signal control. For the antifouling effect, a uniform current over time is no† required. In addition, the possibility of designing the auxiliary anode†o obtain additional functionalities such as propeller protector or stabilizing fin is emphasized, as described in the following variants.

In some embodiments the firs† electrode is a cathode.

In some embodiments, the portion of the surface which comprises the firs† electrode may be made of a material which is corroded when being under sal† water such as steel or aluminium. As a result of behaving as a cathode, corrosion of the firs† electrode is inhibited. In a preferred embodiment, the firs† electrode is partly or completely within or on the portion of the surface where accumulation of organisms is to be inhibited. In other embodiments, the first electrode is positioned near the portion of the surface, such as at a distance of less than 1 m., for example, less than 50, 25, 10 or 5 cm from that surface.

In some embodiments, a plurality of first electrodes behaving as cathodes are provided.

In some embodiments of the invention, the at least one second electrode is an anode. In an embodiment, the at least one second electrode faces said portion of the surface. The at least one second electrode may be made of a material which do not degrade, in particular is not corroded, when the at least one second electrode generates Ch gas, such as graphite, mixed metal oxide, platinum or niobium. In a preferred embodiment, the at least one second electrode is made of titanium coated with mixed metal oxides (Ti MMO electrode), more preferably, the at least one second electrode is made of titanium coated with oxides of precious metals such as for example RuC , IrC and/or P†C>2. Therefore, in some embodiments, the at least one second electrode can permanently act as an anode without requiring much maintenance.

Ch ions of the salt dissolved in the salt water are turned into CI2 through the following reaction which takes place on the at least one second electrode:

The electrons generated by the reaction form part of the aforementioned direct current.

In addition, in an embodiment, the direct current provides a cathodic protection of the first electrode.

The expression “under” is to be understood in the sense that the at least one second electrode is placed in relation to the portion of the surface such that at leas† par† of the Cb produced by the a† leas† one second electrode will rise and thereby contact the portion. “Under” is thus no† intended†o necessarily imply a position vertically below the portion, although this option may often be preferred. In some embodiments of the invention, the C gas generated by/on the a† leas† one second electrode is contained in bubbles which rise due†o their lower density with respect†o sal† wafer. The bubbles separate from the a† leas† one second electrode, rise and, then, contact the portion of the surface. Afterwards the bubbles can move over, such as along and/or across, the portion of the surface. As bubbles separate from the a† leas† one second electrode, they leave space for new CI2 gas†o be produced. As the CI2 gas moves away from the a† leas† one second electrode and over the portion of the surface, it undergoes the following reactions, which generate biocide products, in particular HOCI and OCL·:

CI2 (g) Cl2 (ac), KH=6.2X1 0- ²

Cl ₂ (ac) + H ₂ 0 HOCI + H ⁺ + Ch, KH=4X1 0- ⁴

HOCI^ H ⁺ +OCI-, pKa=7.5

The biocide action of the biocide products is no† restricted †o a conductive portion of the surface, as their production does no† rely on the conductivity of the antifouled portion of the surface. The instability of HOCI and OC restrict their biocide effect †o a vicinity of the region where they are generated, and therefore it is important†ha† the CI2 gas substantially reaches and contacts the portion of the surface. In a preferred embodiment, the anode is near the portion of the surface†o be treated, such as a† a distance of less than 1 m., for example, less than 50, 25, 10 or 5 cm from the portion of the surface.

The present invention is considered†o be potentially energy efficient as the CI2 gas can be produced substantially without interruption, and it is also considered potentially advantageous in†ha† it may provide for cathodic protection of the firs† electrode, which in some embodiments may comprise or consist in par† of a vessel, such as the hull of a boa† or other vessel or part thereof. The CI2 when coming into contact with water generates other species responsible for the biocidal effect. In some embodiments, the surface comprises a† leas† par† of the firs† electrode.

In some embodiments, the firs† electrode is a cathode and the a† leas† one second electrode is an anode.

In the present disclosure, a cathode is an electrode through which electrons enter the sal† wafer due†o a reduction reaction (e.g. due†o the reduction reaction 4H2O + 4e- -> 2H2 + 40H ) . In the present disclosure, an anode is an electrode through which electrons leave sal† wafer due†o an oxidation reaction (e.g. due†o the oxidation reaction 2CI- -> CI2 + 2e ^_ ) . Therefore, the cathode is the element where reduction reactions fake place and the anode is the element where oxidation reactions take place. In some embodiments, the a† leas† one second electrode is a† a distance from the portion of the surface. In this way, accumulation of organisms can be remotely inhibited on surfaces such as a portion of a surface of a propeller, without requiring the second electrode†o be physically placed on the propeller. In some embodiments, the a† leas† one second electrode comprises turns around a volume for containing the surface. These embodiments are advantageous because they allow†ha† a large portion of the surface introduced in the volume for containing the surface is antifouled by a second electrode wherein the second electrode requires little material, occupies a small volume and does no† require a complex supporting structure. Thereby, these embodiments allow antifouling a large portion of the surface in a cheap manner. In addition, these embodiments can be easily adapted†o surfaces of different sizes.

In these embodiments i† can be considered†ha† the second electrode is helically arranged around the volume for containing a surface. In the context of the present disclosure the expression “helically arranged” or“helical shape” is†o be understood in the sense†ha† the a† leas† one second electrode is wound around a volume having any shape suitable for containing a surface.“Helically arranged” or“helical shape” is thus not intended to necessarily imply that the at least one second electrode is wound around a cylinder-shape or a cone-shape, although one of these options may often be preferred. The extension of surface which is anfifouled in this manner depends, among other factors, on the pitch between the turns of the second electrode and on the electric signal applied†o the second electrode. In general, a lower pitch and/or an electrical signal of higher power will increase the extension of surface which is anfifouled.

In some of these embodiments if is preferable that the second electrode is wire shaped, for example is an electrode which has a length higher than 80, 1 50 or 300 times any one of the width and the thickness of the electrode. Thereby, the electrode requires even less material for anfifouling the surface.

In some preferred embodiments in which the anfifouling a† the surface is particularly enhanced, the second electrode is made of titanium coated with mixed mefal oxides (Ti MMO electrode), more preferably, the a† leas† one second electrode is made of titanium coated with oxides of precious metals such as for example RuC , IrC and/or P†C>2.

In some of these embodiments, in order†o support the second electrode, the a† leas† one second electrode is coupled†o supporting means, for example the a† leas† one second electrode is coupled †o a plurality of wire tighteners and optionally †o one or more wire guides. Thereby simple supporting means are enough†o provide the forces required for keeping the position of the turns of the second electrode. In some of these embodiments, the supporting means may be electrically insulated from the second electrode and, for example, the supporting means may be made of aluminium and/or stainless steel.

The supports can be machined with holes adapted for the passage of the anode wound coils and be provided with means for correctly attaching the turns.

In some of these embodiments the surface is a surface of a propeller of a marine vehicle. In some embodiments, the surface is a surface of a marine vehicle.

In some embodiments, the af leas† one second electrode is arranged inside a housing of a water turbine of the marine vehicle. In these embodiments the a† leas† once second electrode produces CL2 in the interior of a turbine, enhancing antifouling of the interior of the turbine.

In some embodiments, the portion of the surface is a portion of a surface of a propeller of the marine vehicle.

In some embodiments, the propeller is connected †o an auxiliary actuator configured †o move the propeller†o place the propeller over the a† leas† one second electrode. In some embodiments, the a† leas† one second electrode is connected †o an auxiliary actuator configured †o move the a† leas† a second electrode†o place the a† leas† one second electrode under the portion of the surface.

In some embodiments, the a† leas† one second electrode is arranged in a propeller guard of the propeller of the marine vehicle.

In some embodiments, the propeller rotates while a† leas† par† of the CI2 produced by the a† leas† one second electrode rises and contacts the portion of a surface of the propeller. In these embodiments the rotation of the propeller is advantageous because it allows †ha† a smaller second electrode antifouls the same surface extension of the blades of a propeller. For example, instead of arranging the second electrode under the blades and occupying the whole vertical projection of all the blades in order†o ensure †ha† all the blades are properly antifouled, the propeller rotation allows †ha† the second electrode be arranged under the blades and occupying the vertical projection of jus† one blade. Since the propeller rotates, every blade will eventually occupy the position in which the second electrode antifouls said blade, and hence antifouling of the blades can be achieved with a smaller second electrode. Hence, this rotation changes the orientation of propeller surfaces, which allows moving propeller surfaces†o an orientation wherein a higher amount of CL2 gas produced by the second electrode contacts the surface. For example, propeller surfaces which are initially upwardly oriented may rotate in order†o become downwardly oriented such that these surfaces face toward the second electrode. In addition, a reduced size of the second electrode is advantageous because occupies less space and hence has a lower negative impact on navigation of the marine vehicle. In some of these embodiments the rotation speed of the propeller while the CL2 rises and contacts the propeller is for example of less than 1 rpm, 0.01 6 rpm or 0.0007 rpm. This low speed is advantageous because if allows an appropriate diffusion of biocidal species produced by the CL2, potentially enhancing the anfifouling effect. This appropriate diffusion is achieved because the low rotation speed, when compared with a higher rotation speed, generates low dispersion of these species and minimizes generation of wafer movement near the propeller.

In some of these embodiments, an electric motor provides the required low rotation speed for anfifouling the propeller. An electric motor is advantageous because if may run on electricity from batteries of the marine vehicle and/or from the electrical system of the marine vehicle, and hence the motor does no† require †o be powered by fuel which could generate sudden movement of the vehicle resulting in a vehicle accident.

In some embodiments, the a† leas† one second electrode is mounted on a propeller guard or on a hydrofoil stabilizer or on a hydro-shield. In this way compactness of the propeller accessories is increased. In some embodiments, the electrode is located in a mobile structure†ha† allows its mobility between the working position where it can achieve the antifouling effect on the propeller and a navigation position outside the area of influence on navigation performance. In some embodiments, the electrode anchorage is shaped such†ha† it fits in the sacrificial anode gap. Since the tail is protected by printed current, a protection is provided by using†ha† area†o anchor the anode and keep the propeller clean. In some embodiments, the propeller guard comprises a propeller cover, wherein the propeller cover has an inner face and wherein a† leas† a portion of the inner face comprises the a† leas† one second electrode. In these embodiments the a† leas† one second electrode antifouls no† only blades and par† of the axis of the propeller bu† also the inner face of the propeller cover. Naturally, the inner face of the propeller cover is made of a material suitable for generating CL2 by means of applying an electrical signal †o such material, for example, in some of these embodiments the inner face of the propeller cover is made of sheets of titanium coated with mixed metal oxides (Ti MMO electrode) . In some of these embodiments the propeller guard comprises plates made of the material of the a† leas† one second electrode. Preferably, the second electrode is cylindrically or ring shaped.

In some embodiments, the a† leas† one second electrode is arranged in a full keel.

In some embodiments, the a† leas† one second electrode is attached †o a propeller shat† bracket.

In some embodiments, the a† leas† one second electrode comprises a plurality of second electrodes separated from each other.

In this way, a smaller area of the a† leas† one second electrode with respect†o the area of the portion of the surface can be achieved. The plurality of second electrodes produce CI2 gas a† different locations and the gas will disperse and potentially contact a portion of a surface having a relatively large area in relation †o the total surface area of the plurality second electrodes.

In some embodiments, a† leas† some of the electrodes of the plurality of second electrodes are arranged along the surface and wherein a† leas† one of the electrodes of the plurality of second electrodes is arranged a† a different heigh† than a† leas† another one of the electrodes of the plurality of second electrodes.

In this way, an even smaller area of the a† leas† one second electrode with respect to the area of the portion of the surface can be achieved. Thus, different electrodes can contribute†o the anfifouling effect on different sub-porfions of the surface, for example, on different longitudinal sub-portions of a hull or other part of a vessel.

In some embodiments, the surface is a submerged surface of a hull, a submerged surface of a pipe, a submerged surface of a propeller shaft or a submerged surface of a container. In some embodiments, at least some of the plurality of second electrodes are arranged along a fin keel, and preferably along and/or across the outer surface of a fin keel.

In some embodiments, the at least one second electrode is electrically connected to a third electrode such that a portion of the second electrode current flows through the firs† electrode and another portion of the second electrode current is deviated†o flow through the third electrode. In this way, the firs† electrode is no† subjected†o excessive electric current which could potentially produce a cathodic overpro†ec†ion of the firs† electrode.

The invention also relates†o a device for generating one or more compounds comprising chlorine with an oxidation number higher than -1 , for example hypochlorous acid, on a portion of a surface of a propeller submerged in sal† water, the device comprising:

coupling means for installing the device in a marine vehicle, and

an electrode;

wherein the coupling means are configured for installing the electrode a† leas† in part under a propeller such†ha† a† leas† part of the Ch produced by the electrode rises towards a propeller.

In some embodiments, the device comprises:

an electrode, and

a volume for containing a propeller; wherein the electrode comprises turns around the volume for containing a propeller such that a† leas† par† of the Ch produced by the electrode rises within the volume for containing a propeller.

The invention also relates †o a propeller guard for generating one or more compounds comprising chlorine with an oxidation number higher than -1 , for example hypochlorous acid, on a portion of a surface of a propeller submerged in sal† water, wherein the propeller guard comprises a propeller cover, wherein the propeller cover has an inner face and wherein a† leas† a portion of the inner face comprises an electrode arranged such†ha† a† leas† part of the CI2 produced by the electrode rises within the volume for containing a propeller.

The invention also relates†o a device for generating one or more compounds comprising chlorine with an oxidation number higher than -1 , for example hypochlorous acid, on a portion of a surface of a surface submerged in sal† water, the device comprising:

an electrode, and

a volume for containing a surface;

wherein the electrode comprises turns around the volume for containing a surface such†ha† a† leas† par† of the CI2 produced by the electrode rises within the volume for containing a surface.

The invention also relates†o a system for applying hypochlorous acid on a portion of a surface submerged in sal† water, the system comprising:

an anode;

a cathode; and

a direct current generator electrically connected with the anode and the cathode, arranged †o cause a direct electric current †o flow between the anode and the cathode, wherein:

the anode is arranged under the portion of the surface such †ha† a† leas† part of the CI2 produced by the anode rises and contacts the portion of the surface. In some embodiments, the system comprises a direct current source directly connected to the anode and the cathode, without any other electronic component being placed in the circuit comprising anode, cathode and the direct current source, in particular, no circuit which reverses the current direction or similar.

In some embodiments, there is a mechanical connection between the surface submerged in sal† water and the anode. In some embodiments, the anode is an electrode forming part of a propeller guard or forming par† of a device according†o the invention.

The invention also relates †o a propeller guard comprising a portion helically arranged around a volume for containing a propeller.

These embodiments are advantageous because they protect the propeller with little material, occupying a small volume and without requiring a complex supporting structure for the propeller guard. In these embodiments, the expression “helically arranged” is no† intended †o necessarily imply †ha† the helically arranged portion defines a cylindrical or conical volume, although one of these options may often be preferred. In addition, these embodiments can be easily adapted †o propellers of different sizes. In some of these embodiments, the helically arranged portion is wire-shaped, for example has a length higher than 80, 1 50 or 300 times any one of the width and the thickness the portion. Thereby, the propeller guard requires even less material for protecting the propeller. In some of these embodiments the propeller guard is made of stainless steel or aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS To complete the description and in order†o provide a better understanding of the invention, a se† of drawings is provided. Said drawings form an integral par† of the description and illustrate embodiments of the invention, which should no† be interpreted as restricting the scope of the invention, bu† jus† as an example of how the invention can be carried out. The drawings comprise the following figures:

Figure 1 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a propeller submerged in sal† water in which the anode is substantially arranged in a vertical plane.

Figure 2 is a perspective view of an embodiment of a system applied †o the surface of a propeller and par† of the surface of a propeller guard and in which the anode extends in a horizontal plane and is integrated with the propeller guard.

Figure 3 is a perspective view of an embodiment wherein the support comprises a cathode and in which the anode extends in a horizontal plane. Figure 4 is a perspective view of an embodiment in which the anode extends surrounding the propeller.

Figure 5 is a perspective view of an embodiment of a system in which the anode is integrated in a fin-shaped support.

Figures 6 to 8 are perspective views of embodiments of a system in which an optional sacrificial anode is shown.

Figure 9 is a perspective view of an embodiment of a system wherein the propeller is connected †o the hull of a ship through a propeller shat†, in which the hull comprises a cathode, in which the anode is mechanically connected †o the propeller shat† and in which the anode extends in the vertically.

Figure 10 is similar†o figure 9, bu† the anode extends in the horizontally.

Figure 1 1 is similar†o figures 9 or 10, bu† here the anode extends parabolically surrounding the propeller. Figure 12 is a perspective view of an embodiment wherein the propeller is supported by the end keel of a ship, in which the hull comprises a cathode and in which the anode is in the end keel. Figure 13 is a side view of an embodiment wherein the portion of the surface includes part almost the whole hull of a marine vehicle, wherein a plurality of anodes are on the surface of the hull and extend along if af different heights thereof. Figure 14 shows the effect of applying the method of the present invention†o a lower portion of a ship's hull.

Figure 15 shows a perspective view of an embodiment wherein an anode wire is arranged around a volume for containing a propeller.

Figure 1 6 shows a schematics or the mobile electrode, between res† and navigation configurations.

DESCRIPTION OF A WAY OF CARRYING OUT THE INVENTION

Next, several embodiments of the invention will be explained, which differ basically in their geometry, since†ha† is the essence of the invention, specifically how the surfaces†o be protected are arranged as a function of the arrangement of the electrodes.

Finally, a†es† of the high efficiency of the system object of the present invention will also be presented.

Firs†, with reference†o Figure 1 , we highlight the basic elements of the invention.

The method of generating hypochlorous acid on a portion 6 of a surface 3 submerged in sal† water comprises the steps of: providing a firs† electrode 7 in the sal† water;

providing a† leas† one second electrode 2 in the salt water;

causing a direct electric current to flow between the first electrode 7 and the at least one second electrode 2, such that CF ions of the salt water in contact with the at least one second electrode 2 are turned into Ch, which is labelled with the reference d.

According to the invention, the second electrode 2 is arranged under the portion 6 of the surface 3 such that at least part of the Ch 5 produced by the second electrode 2 rises and contacts the portion 6 of the surface 3.

Specifically, Figure 1 is a perspective view of an embodiment of a system for applying hypochlorous acid to a portion of a surface 6 submerged in salt water according to the invention, wherein the portion of the surface 6 includes part of the surface of a propeller 3.

The propeller is mechanically connected to a support which is the hull of a marine vehicle, wherein said support comprises a cathode 7 and in which the anode extends in a vertical plane.

Fig. 2 is a perspective view of an embodiment of a system for applying hypochlorous acid to a portion of a surface 3 submerged in salt water according to the invention, wherein the portion of the surface 3 includes part of the surface of a propeller 6 and part the surface of a propeller guard, the propeller being mechanically connected to hull 1 7 of a marine vehicle, wherein said support comprises a cathode 7 and in which the anode 2 extends in a plane 10 horizontal and is integrated with the propeller guard.

Figure 3 is a perspective view of an embodiment of a system for applying hypochlorous acid to a portion of a surface submerged in salt water according to the invention, wherein the portion of the surface includes part of the surface of a propeller, the propeller being mechanically connected to the hull 1 7 of a marine vehicle, wherein said support comprises a cathode 7 and in which the anode 2 extends in a horizontal plane 83.

Figure 4 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface 3 submerged in sal† water according †o the invention, wherein the portion of the surface includes part of the surface 3 of a propeller 6, the propeller 6 being mechanically connected†o the hull 1 7 of a marine vehicle, wherein said support comprises a cathode 7 and in which the anode 2 extends parabolically surrounding the propeller. In this embodiment there is a support 1 1 for arranging the anodes 2.

Figure 5 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface 3 includes par† of the surface of a propeller 6, the propeller 6 being mechanically connected †o the hull 1 7 of a marine vehicle, in which the hull 1 7 comprises a cathode 7 and in which the anode 2 is integrated in a fin-shaped support 85.

Figure 6 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface includes par† of the surface of a propeller 6, the propeller 6 being mechanically connected †o a support 7, the anode 2 extending in the vertical direction and in which a sacrificial anode 13 is shown which can be dispensed with. Figure 7 is a perspective view of an embodiment according†o the invention of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water, wherein the portion of the surface 6 includes par† of the surface of a propeller 3, the anode 2 extending in a horizontal plane 87 and showing a sacrificial anode 13 that can be dispensed with. The sacrificial anode is connected†o a cable 4.

Figure 8 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface includes par† of the surface of a propeller, in which the anode 2 parabolically extends around the propeller 3 and in which is shown an anode of sacrifice 13 that can be dispensed with. Figure 9 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface 6 submerged in sal† water according †o the invention, wherein the portion of the surface 6 includes par† of the surface of a propeller 3, the propeller 3 being connected†o the hull of a ship through a propeller shat†, in which the hull comprises a cathode 7, in which the anode 2 is mechanically connected †o the propeller shat† and in which the anode 2 is arranged in a vertical plane 89.

Figure 10 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface includes par† of the surface of a propeller, the propeller being connected†o the hull of a ship through a propeller shat†, in which the hull comprises a cathode, in which the anode is mechanically connected†o the propeller shat† and in which the anode extends in the horizontal direction.

Figure 1 1 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface includes par† of the surface of a propeller , the propeller being connected†o the hull of a ship through a propeller shat†, in which the hull comprises a cathode, in which the anode is mechanically connected†o the propeller shat† and in which the anode extends parabolically surrounding the propeller .

Figure 12 is a perspective view of an embodiment of a system for applying hypochlorous acid†o a portion of a surface submerged in sal† water according†o the invention, wherein the portion of the surface includes par† of the surface of a propeller, the propeller being supported by the end keel of a ship, in which the hull comprises a cathode and in which the anode is in the end keel. Figure 13 is a side view of an embodiment of a system for applying hypochlorous acid †o the hull 1 7 of a ship, wherein a plurality of linear anodes 2 are on the surface of the hull 1 7 and extend along if af different heights thereof.

Figure 14 shows the effect of applying the method of the present invention†o a lower portion of a ship's hull. The photos show an area that has been exposed†o chlorine gas generated by electrodes. Figure 15 is a perspective view of an embodiment of a system 20 for applying hypochlorous acid to a portion of a surface of a propeller, wherein the system comprises an anode wire 21 helically arranged around a volume 22 for containing a propeller. In order†o support the anode wire 21 , the system 20 for example comprises wire tighteners 23 and optionally at least one wire guide 24.

Figure 1 6 shows an embodiment where the electrode is located in a mobile structure (rotating element ST linked to the main structure by means of an articulation AR and connected via a connection cable CC - the rotating element is preferably a hollow profile or tube) that allows its mobility between the working position where it can achieve the antifouling effect on the propeller and a navigation position outside the area of influence on navigation performance.

In this text, the term “comprises” and its derivations (such as “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements.

The invention is obviously not limited to the specific embodiments described herein, but also encompasses any variations that may be considered by any person skilled in the art within the general scope of the invention as defined in the claims.