JPH11323868A - Arrangement structure of electrode in electrochemical antifouling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the arrangement structure of an electrode in an electrochemical antifouling method, in which the current distribution of an anode surface is equalized and the adhesion of an underwater organism is inhibited or prevented effectively for a prolonged term. SOLUTION: A soluble metal or an insoluble conductive material is installed onto the wall surface of an underwater structure, and connected to the positive electrode of an external DC power and used as an anode 2, and the adhesion of an underwater organism onto the surface of the metal based on the active solution of the metal is inhibited or prevented in the soluble metal and the adhesion of the underwater organism onto the surface of the conductive material based on a bactericidal action by chlorine, hypochlorous ions or generated oxygen formed on the interface of the conductive material is suppressed or obviated in the insoluble conductive material by flowing a current. Latticed, reed screen-shaped, reticulate or spiral metallic conductors consisting of tie plates or linear elements are used as cathodes as the counter electrodes of the anodes 2 (cathode latticed steel wires 31), and arranged at approximately regular intervals from the surfaces of the anodes 2 through a plurality of insulating supporters 231, and the anodes 2 and the cathodes are compounded and unified at that time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to marine organisms (barnacles, mussels) which adhere to the water-contacting surfaces (wall surfaces) of underwater structures, particularly underwater structures, and which grow and inhibit the normal function of the structures. , Seaweeds, etc.) in an electrochemical antifouling method for suppressing or preventing the adhesion of the electrodes. More specifically, the present invention relates to an electrode disposition structure in an electrochemical antifouling method for suppressing or preventing the attachment of marine organisms by direct current electrolysis in seawater using a soluble metal or an insoluble conductive material such as a conductive paint as an anode.

[0002]

BACKGROUND OF THE INVENTION Structures laid underwater are exposed to severe corrosive environments due to seawater. The anticorrosion measures have been researched and developed for many years, and are now almost satisfied with the progress of techniques such as painting, lining, various coatings, and cathodic protection.

On the other hand, measures against dysfunction of marine structures caused by the attachment of marine organisms such as barnacles, mussels, sea squirts, hydroids and seaweeds that inhabit the seawater include the injection of chlorine, copper and tin, etc. Marine organisms have been repelled or killed by toxic substances such as toxic ion-producing antifouling paints and the generation of chlorine, hypochlorite or copper ions by seawater electrolysis.
However, the production of these toxic ions is likely to be in excessive concentration and, in addition, may cause environmental pollution. Research and development of non-polluting marine organism extermination measures or methods (hereinafter referred to as antifouling measures or antifouling methods) are also underway. Some antifouling paints utilizing the water repellency and surface tension of silicone and the anodic electrolysis method of harmless ion-generating metals are already in the stage of practical use, but their life and cost are lower than conventional antifouling technologies. There are issues that need to be solved.

The antifouling means employed in the present invention is an antifouling method utilizing electrochemistry. In other words, this is a method of anodic electrolysis of a metal (mainly steel) in which leached ions are harmless to suppress or prevent the formation of marine organisms on the surface of the metal as the anode. This method is one of the electrochemical means of the conventional antifouling method by seawater electrolysis, but conventionally, chlorine or hypochlorite, which kills marine organisms by electrolyzing seawater. This produces toxic ions such as acid salts. Anodic electrolysis of copper or copper alloys also produces toxic copper ions. In other words, these methods require that the concentration of toxic ions in the environment surrounding the target structure be maintained at a level higher than the concentration at which marine organisms repel, and the amount, flow velocity, water temperature, or Many factors, such as seasonal activity ecology, are inevitably excessive, resulting in secondary environmental pollution, which also kills useful marine organisms.

[0005] On the other hand, the antifouling means employed in the present invention suppresses the adhesion of marine organisms to the metal surface as an anode by anodic electrolysis of a metal having no harmful ions. The higher the applied anode current density is, the more effective it is, but it is not economical because the consumption of the anode and the power consumption increase. Average of 1 A / m ² or less in continuous electrolysis, preferably 0.5 A / m ² or less.
When the anode current density is maintained at around A / m ² , a practically negligible antifouling effect can be obtained. When operated at such an anode electrolytic density, it is possible to design a product with a life of 5 years or more and economically profitable.

In this antifouling method, the surface of a target structure is covered with an anode metal (mainly steel), a conductor serving as a cathode is separately installed in the same environment, and the object is connected to an external DC power supply and energized. The point of uniformly dissolving the entire surface of the anode metal is to determine whether the antifouling effect is good or not. When the current density is constant, the size of the anode metal (electrode plate), the contact position of the conducting conductor,
The geometrical arrangement such as the spacing and the size, shape, and interelectrode distance of the cathode serving as the counter electrode greatly affects uniform dissolution.

[0007] Uniform dissolution as viewed from the anode metal is a major factor in the material and composition of the anode metal, but this is left to the material manufacturer and cannot be easily changed.
If they are not readily available, they are consumables and are not economically viable. For example, for steel, SS40
0, an aluminum material is an alloy number 5000 or 6000 series containing a small amount of Mg or Si, and zinc is a galvanic anode material containing 99.99% by weight of zinc or a small amount of Al. The shape of the anode is suitably a rolled plate material that is easy to process in consideration of the target structure. The larger the plate material is, it is desirable because it can be installed and the number of fixing points can be reduced considering the construction on the target structure,
The size of the anode needs to be appropriately changed depending on the shape and size of the target structure, the design life, etc. Per 3 '(about 90
0 mm) × 6 ′ (about 1800 mm) or 4 ′ (about 120 mm)
It is desirable to use a commercially available material that is easily available (0 mm) × 8 ′ (about 2400 mm) as a standard. It is an important factor in the antifouling effect that the outflow current from the plate-shaped anode is uniform from the entire surface of the anode. However, it has been reported that the outflow current tends to concentrate on the edge of the plate-like anode and is several times larger than that in the center. This means that if the current density is adjusted to the edge of the plate anode, the central part will have insufficient current and marine organisms will attach easily, and if the current density is adjusted to the central part, the edge will be reduced. Is promoted, the design life of the plate anode is shortened, and the plate anode may fall off. It is conceivable to gradually increase the thickness of the plate anode from the center to the edge of the plate anode, but it is not easy to change the plate thickness within one plate anode that is a consumable material. Absent.

[0008] An electrochemical antifouling method for suppressing the adhesion of marine organisms living in seawater to the wall surface of a structure in contact with seawater involves producing chlorine or hypochlorous acid on the anode surface by seawater electrolysis. A method for killing marine organisms and covering the surface of the target structure with a soluble metal or insoluble conductive material serving as an anode, and generating only oxygen without generating active dissolution or chlorine by anodic conduction, and forming a marine organism on the anode surface There is a method of suppressing the formation of corn.

In the case of producing toxic ions such as chlorine and copper ions in seawater, if chlorinated and copper ions corresponding to a specified amount of electricity are generated, useful marine organisms are also killed, or excessive concentrations may be caused. Although there is a risk of secondary environmental pollution, the purpose of antifouling is achieved.

In order to suppress the adhesion of marine organisms to the surface of a metal or a conductor serving as an anode, it is necessary that a current uniformly flows from the surface of the anode. That is, it is important that the entire surface of the metal as the anode operates within a predetermined current density. If the current distribution becomes uneven, partial dissolution and generation of oxygen will be different, causing various troubles, and marine organisms will adhere to parts where dissolution and oxygen generation are insufficient, and that part will be used as a nucleus. Promotes the attachment of marine organisms.

Accordingly, an object of the present invention is to provide an electrode disposition structure in an electrochemical antifouling method for making the current distribution on the anode surface uniform and effectively suppressing or preventing the adhesion of aquatic organisms over a long period of time. Is to do.

[0012]

As a result of the study, the present inventors have found that the arrangement of the anode and the cathode, particularly the shape and arrangement of the cathode, is an important factor in the electrochemical antifouling method. .

The present invention has been made on the basis of the above-mentioned findings. By installing a soluble metal or an insoluble conductive material on the wall surface of an underwater structure, connecting it to the positive electrode of an external DC power source to form an anode, and passing an electric current. In the case of the soluble metal, the adhesion of underwater organisms to the surface of the metal based on the active dissolution of the metal is suppressed or prevented, and in the case of the insoluble conductive material, chlorine generated at the interface of the conductive material, In an electrode disposition structure in an electrochemical antifouling method for suppressing or preventing the adhesion of aquatic organisms to the surface of the conductive material based on a bactericidal action by chlorite ions or generated oxygen, a cathode which is a counter electrode of the above-mentioned anode is a strip plate. Or a metal conductor in the form of a grid, wire, mesh or spiral made of a wire, arranged at approximately equal intervals from the surface of the anode via a plurality of insulating supports, and combining the anode with the cathode Conversion There is provided an arrangement structure of an electrode in an electrochemical antifouling method characterized by the.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
An important factor in the method for suppressing or preventing the attachment of marine organisms to the anode surface by anodic electrolysis is that when a predetermined anode current density is applied, current flows uniformly from the entire surface of the anode. Factors such as the material and size of the anode, the distance between the electrodes, the resistance of the circuit, and the like influence. However, once the anode to be used is determined, the uniform distribution of the outflow current is affected by physical dimensions such as the dimensions of the cathode, the distance between the electrodes, and the circuit resistance.

The structure to be stain-proofed has various shapes and sizes. In mounting the anode on the wall of the structure, the type, size, shape, electric conduction or mounting means of the anode are taken into consideration. The anode is placed on the wall of the structure and attached.

Since the cathode serving as the counter electrode is a sink for the current of the electrolytic reaction and is not directly related to the purpose of antifouling, a metal body in the environment surrounding the target structure (for example, a reinforced concrete structure). Is a reinforcing steel bar, a steel structure in the case of such a structure, an attached conductive structure, or the like, or a separate conductor is provided in the environment to serve as a cathode. In other words, it is usual that a nearby conductor is used as the cathode rather than being arranged in consideration of the current distribution.

The inventors of the present invention spread an iron steel sheet around the interface of the structure in order to prevent marine organisms from adhering and fouling the surface of the structure in contact with seawater, and perform anodic active dissolution using the steel sheet as an anode. Thus, it has been found that the formation of marine organisms can be suppressed on the surface of the steel sheet, and the practical development of an electrical antifouling method is being promoted (International Publication No.
4). In the process of practical development, we learned that achieving uniform dissolution of the steel sheet as the anode was the point of practical application, and that the edges of the steel sheet were several times more soluble than the center. And proposed to use an iron steel sheet whose edge portion is gradually thicker than the center portion (Japanese Patent Laid-Open No. 7-30083).
No. 3, JP-A-8-302643).

[0018] However, this improvement has a problem in production of a steel plate (electrode) and attachment and fixation to a structure, which is a practical shackle. In the course of an attempt to improve an electrode that can be easily and uniformly melted for some structures, it was found that the cathode disposition structure was one factor for almost satisfactory uniform melting.

That is, as shown in a test example described later, the cathode is opposed to the anode, the distance between the electrodes is arranged at substantially equal intervals from any part of the anode surface, and the anode is positioned from the center to the edge of the anode surface. It was found that the anode could be uniformly dissolved by disposing the cathode so as to decrease the area density, that is, increasing the circuit resistance, and bringing the anode and the cathode into close proximity and integrally integrating them.

Since the cathode is an inflow current, there is no concern about corrosion and dissolution, so long as it is a conductor, the material is not limited, and a conductive material having strength and workability may be used. A steel material, a copper alloy material, a titanium alloy material, or the like can be considered. Although the shape may be a plate material, when the area ratio with the anode is close to 1: 1, the cathode current density becomes 1 A / m ² or less in consideration of the applied anode current density, and an electrolytic product based on the seawater electrolysis reaction is formed. Being
Marine organisms easily attach to the cathode surface. At a steady anode current density of 1 A / m ² or less, in order to suppress the formation of electrolytic products or the attachment of marine organisms to the cathode surface, the cathode area is preferably 1/10 or less of the anode area. Since it is necessary to make the distances approximately equal and close to each other, it is appropriate that the cathode is made of a material having a small cross-sectional area and processed from an elongated material. For example, it is preferable to manufacture from a strip (strip) or a wire (thin bar). The shape of the cathode may be lattice, screen, mesh or spiral. Depending on the object, the distance between the cathode nets and the like at the center is made dense with respect to the anode surface, and the distance between the cathode nets and the like is made coarse (wide) toward the edge. With this arrangement, the current flow depends on the resistance of the circuit, so that the current distribution between the center and the edge of the electrode is balanced. That is, current flows out almost uniformly from the entire surface of the anode. Since the area of the cathode is 1/10 or less of that of the anode, the cathode current density is high, and the adhesion of electrolytic products and marine organisms is suppressed.

The distance between the anode and the cathode must be as close as possible at equal intervals. Since the anode is laid directly on the wall of the target structure via insulating material or cushioning material,
It is preferable that the anode and the cathode have an integrated structure (composite) in advance in order to arrange the cathode close to and at equal intervals to the anode.

The distance between the poles depends on the size of the target structure and the environmental conditions of the installation sea area. However, the strip or the wire serving as the cathode does not short-circuit with the anode due to external force such as waves or tides. It needs to be close in range. If the fixing insulation support is adjusted to the appropriate length according to the target structure,
The distance between the poles is kept almost constant. Practically, the distance between the poles is 50 to 300 mm, preferably 100 to 200 mm
Is good.

The above description has described in detail the method of arranging a cathode using an anode made of a soluble iron steel sheet. However, the anode is a conductive paint or a noble metal catalyst which generates hypochlorous acid, chlorine or oxygen by seawater electrolysis. Even in the case of an anode comprising a coated insoluble electrode, the electrode arrangement of the present invention, particularly the cathode arrangement structure, is extremely effective, and uniform generation of chlorine, hypochlorous acid or oxygen can be achieved.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments and the like.

[Test Example] (Laboratory test showing difference in dissolution state of anode due to difference in shape and arrangement of cathode) A 1/10 model of concrete box culvert type intake channel 1 was manufactured, A steel plate was attached to the ceiling, connected to the positive electrode of an external DC power supply, and the state of consumption of the steel plate (anode) according to the size, shape, and mounting position of the cathode metal (SUS304) was investigated.

FIG. 1 is a cross-sectional view showing an example of the arrangement of the cathode 3, and the iron steel plate as the anode has a plate shape. In the figure,
1 is a box culvert intake channel, 2: an anode (steel plate),
Reference numeral 3 denotes a cathode, 4 denotes an insulating material, 5 denotes an insulating flange, 6 denotes a hanging bracket, and 7 denotes an insulator.

1 (a) to 1 (d), the arrangement of the cathode 3 is such that the plate-like electrode is located on the bottom surface in FIG. 1 (a), and the round bar or plate is located on the side wall in FIGS. 1 (b) and 1 (d). FIG. 3 (c) shows an example in which a round bar fixed by the hanging bracket 6 is arranged at the center of the section of the box culvert intake channel 1 respectively. In each case, the consumption distribution of the anode 2 was examined when the current was passed for about three months at an average anode current density of 5 A / m ² (10 times or more of the normal).

FIG. 2 is a cross-sectional view showing the distribution of consumption of the anode (iron steel plate) when the cathode (iron steel plate) is energized for about three months by installing the various cathodes shown in FIG. In the figure, the part surrounded by a horizontal line indicates the degree of wear, and the longer the part, the greater the degree of wear. As shown in FIG. 2, the consumption distribution differs depending on the position of the cathode. In each case, the portion near the cathode is greatly consumed, especially when the device is installed on the bottom surface or side surface (FIG. 2A).
(B) and (d)), the unevenness of consumption is remarkable. When the cathode is installed in the center of the cross section of the water channel (FIG. 2 (c)),
The anode is almost uniformly consumed.

[Examples and Comparative Examples] In order to confirm the results of the test examples, an apparatus of a cathode arrangement type was installed in the practical intake channel screen room, and the anode (iron steel plate) attached to the wall surface of the intake channel screen room was melted. The situation was investigated.

FIGS. 3 and 4 show perspective views of typical electrode arrangements. In addition, FIGS. 5 and 6 show the dissolution distribution of the anode (iron steel plate) in FIGS. 3 and 4, reference numeral 8 denotes a DC power supply, 9 denotes wiring, 11 denotes a screen room, 23 denotes a composite electrode, 231 denotes an insulating support frame, and 31 denotes a cathode grid steel wire.

FIG. 3 shows that a SUS pipe of 150 mmφ is installed as a cathode 3 in the center of the space of the screen room showing an appropriate anode consumption distribution in the test example, and a trapezoidal anode (iron steel plate) 2 is attached to both side walls of the screen room. FIG. 3 shows a perspective view (Comparative Example).

FIG. 4 is a perspective view of the composite electrode according to the present invention (embodiment). 3 is different from FIG. 3 in that the cylindrical cathode 3 in the center of the screen chamber 11 is not provided. Instead, the surface of the anode 2 is interposed via an insulating support 231 so that the distance between the anode 2 and the cathode 3 is constant. Thus, a composite electrode 23 in which an anode and a cathode are integrated, in which a 4.2 mmφ steel wire (cathode) is stretched in a grid 31.

In the early spring, the electrodes shown in FIGS.
Approximately seven months before the mid-autumn period, continuous energization was performed at an anode current density of 0.5 A / m ² . After seven months of energization, deposits and dissolved products (red rusts) on the surface of the anode (iron steel plate) were removed, and the thickness of the plate was measured with an ultrasonic film thickness meter to examine the consumption distribution of the anode 2.

FIGS. 5 and 6 show the dissolution state of the anode (steel plate) in FIGS.
6A shows the consumption distribution of the anode (steel plate) attached to the right wall with respect to the flow of seawater, and FIGS. 5B and 6B show the distribution with respect to the flow of seawater. And the consumption distribution of the anode (steel plate) attached to the left wall. In each case, a 2.3 mmt steel plate ([upper bottom 3
60 cm + lower bottom 480 cm] × height 540 cm). Since current is supplied for about 7 months at an average anode current density of 0.5 A / m ² , the consumption is theoretically 0.35 to 0.4 mm.

FIG. 5 shows an anode (steel plate) in which a cylindrical cathode 3 is installed at the center of the screen chamber 11 based on a cathode arrangement test for dissolving the anode (steel plate) 2 of FIG. 1 more uniformly. 2) The dissolution and consumption distribution of 2 shows that although the uniform dissolution is exhibited as compared with the conventional cathode installation, in the actual line, the consumption of the anode (iron steel plate) 2 surface near the cylindrical cathode 3 is prioritized. I have.

FIG. 6 shows the case where the composite electrode 23 is used, and the entire surface of the anode (steel plate) 2 is almost uniformly consumed.
It became clear that the electrode arrangement in which the anode (iron steel plate) 2 and the cathode grid steel wire 31 were combined and integrated at regular intervals showed an excellent melting state.

[0037]

As described above, by the arrangement of the electrodes in the electrochemical antifouling method of the present invention, the current distribution on the anode surface is made uniform and the adhesion of aquatic organisms is effectively suppressed for a long time. Alternatively, it can be prevented. In addition, such an electrode arrangement structure makes it possible to produce electrodes in a factory, thereby facilitating on-site construction work and reducing man-hours.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in which various cathodes are installed on a model of a concrete box culvert.

FIG. 2 is a cross-sectional view showing the distribution of consumption of an anode (iron steel plate) by installing various kinds of cathodes in FIG.

FIG. 3 is a perspective view in which a cylindrical cathode is installed at the center of an intake screen room;

FIG. 4 is a perspective view in which a composite electrode is installed in the intake channel screen chamber according to the present invention.

FIG. 5 is a view showing a dissolution and consumption distribution of an anode (iron steel plate) after energization in FIG. 3;

FIG. 6 is a diagram showing the dissolution and consumption distribution of the anode (steel plate) after the current supply in FIG.

[Explanation of symbols]

1: Box culvert intake channel, 2: Anode (steel plate),
3: cathode, 4: insulating material, 5: insulating flange, 6: hanging bracket, 7: insulator, 8: DC power supply, 9: wiring,
11: Screen room, 23: Composite electrode, 231: Insulating support frame, 31: Cathode grid steel wire.

Claims (2)

[Claims] 1. A soluble metal or an insoluble conductive material is provided on the wall of an underwater structure, connected to a positive electrode of an external DC power source to form an anode, and an electric current is applied. Inhibition or prevention of underwater organisms from adhering to the surface of the metal due to active dissolution, and in the case of the insoluble conductive material, it is effective for disinfection by chlorine, hypochlorite ion or generated oxygen generated at the interface of the conductive material. In the electrode disposition structure in the electrochemical antifouling method for suppressing or preventing the adhesion of aquatic organisms to the surface of the conductive material based on the above, the cathode as a counter electrode of the above-mentioned anode is a grid-like, cord-like, net-like made of a strip or wire Alternatively, it is a helical metal conductor, and is disposed at substantially equal intervals from the surface of the anode via a plurality of insulating supports, and the anode and the cathode are combined into a single body. To dirty law Arrangement of that electrode. 2. The cathode is arranged so that the total area ratio of the cathode to the anode is 1/10 or less, and the area density of the cathode decreases from the center of the surface of the anode toward the edge. 2. An electrode arrangement structure in the electrochemical antifouling method according to 1.