JPH0672410B2 - Antifouling method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents marine organisms and scale from adhering to and contaminating marine structures, ships, pipes or waterways for transporting seawater, fish nets, faucet nets, or seawater intake screens. Regarding antifouling method.

[0002]

2. Description of the Related Art For example, a pipe for transporting seawater for cooling water of a power plant, a screen for seawater intake, a port side of a ship, a pier,
Various seaweeds, barnacles, and other marine organisms such as shellfish adhere to the parts of marine structures such as pontoons and piers that are constantly in contact with seawater, which reduces water intake and reduces the navigation speed of ships. Such problems occur. For this reason, adhering marine life must be regularly removed, which is a difficult task.

The mechanism of adhesion of marine organisms follows the order that microorganisms such as red tide bacteria first adhere to form a biological film, and larvae of large organisms such as barnacles adhere and grow on it. Therefore, preventing the attachment of microorganisms,
Also, preventing the larvae of large organisms from adhering and growing is an effective solution to the above problems, and various techniques have been proposed for that purpose.

[0004] Most of them adopt a method of killing the organism to be attached by generating an organic tin compound, a chlorine ion or a copper ion around the antifouling body. These methods are not preferable because they lead to serious marine pollution depending on their use.

Under these circumstances, a coating layer is provided on the antifouling body with a conductive material, and an electrode material such as titanium and a reference electrode are arranged in seawater so as not to come into contact with the coating layer, and the coating is performed. A DC voltage is applied with the layer as the anode and the electrode material as the cathode, and a weak current is applied while controlling the potential difference between the reference electrode and the anode to a constant value within the range where chlorine is not generated, and the microorganisms that touch the coating layer are electrically charged. A new method for applying a general shock to prevent the adhesion is newly added, and it is attracting attention as a harmless antifouling method.

According to the above antifouling method, it is possible to effectively prevent biological adhesion to the antifouling object without generating harmful substances that pollute the sea. It is not possible to prevent the attachment of particles such as shellfish fragments, excrement of marine organisms, silica, iron and manganese, and scales are formed on the surface of the coating layer.

When the scale covers the surface of the coating layer, the current flow is hindered and the antifouling effect is reduced. This problem is serious in the above antifouling method, which prevents the attachment of organisms by a weak electric current.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide an antifouling method which prevents scale formation and maintains its effect in the above antifouling method for preventing the attachment of organisms by a weak electric current. Especially.

[0009]

The antifouling method of the present invention is a method for preventing pollution due to the adhesion of marine organisms and scales to structures, ships, pipes or nets which come into contact with seawater, and which is to be protected against contamination. A portion of the body that requires antifouling is provided with a coating layer of a conductive material directly or through an insulating layer to form a working electrode,
To prevent contact with this coating layer, provide an insoluble electrode material in seawater as a counter electrode, and then arrange a reference electrode and apply a DC voltage between the working electrode and the counter electrode to reduce the potential difference between the reference electrode and the working electrode. Measured and found to be 1.2 to -0.6V (vs. SCE)
A weak electric current is applied while controlling it to periodically change in the range of to prevent the attachment of marine organisms and scales.

The potential difference between the reference electrode and the working electrode is 1.2 to −
Periodically changing within the range of 0.6 V (vs. SCE) means that the potential difference is in two or more steps within the above range, preferably 4 to
It means that the current is divided into 6 stages, and the current is sequentially applied in a constant cycle or is changed steplessly. However, this cycle does not have to be regular. Such energization can be easily performed using a commercially available DC power supply device (rectifier) to which voltage adjustment and timing means are added.

Since the coating layer has a capacitor effect, the potential of the coating layer does not change immediately even if the output of the power supply device is changed. Therefore, it is meaningless to change the potential difference in a very short time. The energization cycle is set in consideration of the thickness, surface area, material, etc. of the coating layer. In the case of stepwise change, if the energization time at each potential is 1 hour or more, the above problems hardly occur. On the other hand, if the energization cycle is too long, the adherence of the object to the coating layer will gradually become strong, and peeling will be difficult. Although it depends on the substances contained in seawater and their concentrations, it is preferable that the energization time of each potential is within 6 hours.

The apparatus for carrying out the antifouling method of the present invention may be constructed appropriately according to the type of the antifouling object and the surrounding environmental conditions. The coating layer may be directly provided on the antifouling body,
If the body to be soiled requires insulation, an insulating layer may be provided between the two. Also, for concrete waterways, bridge piers, ships, etc., where it is difficult to directly provide a coating layer on the anti-fouling body, form a coating layer on a suitable power supply and attach them to the surface of the anti-fouling body. It may be placed at.

As for the coating layer, a lined conductive rubber sheet is preferred when there is a risk of abrasion such as where the flow of seawater is fast, and when there is almost no flow of seawater, a conductive paint is used. A coating will suffice. It is advisable to form a coating layer on an antifouling object such as a net by a powder lining method using a composition comprising a powder of a thermoplastic resin and a powder of a conductive substance.

As the electrode material, a titanium base material plated with a noble metal or a noble metal oxide coated,
Alternatively, a rod-shaped body made of a silver-lead alloy or a carbon-based material is suitable.
It is necessary to dispose the electrode material and the coating layer so as not to come into direct contact with each other, and it is preferable to partially cover the electrode material with an insulating tube or the like.

[0015]

[Function] Various objects such as particles of minerals are suspended in seawater in addition to microorganisms. There is a potential difference called zeta potential at the interface between seawater and floating particles. Therefore, when an electric field is applied, the particles are adsorbed to the electrodes by electrophoresis and form a scale. The zeta potential depends on the composition and pH of seawater. As an example,
FIG. 1 shows the relationship between the pH of the Al ₂ O ₃ particles in the NaCl solution and the zeta potential. As shown in FIG. 1, the zeta potential becomes 0 at a certain pH, which is called the isoelectric point. At the isoelectric point, the adsorption energy of the object on the electrode is also zero. From FIG. 1, the particles of Al ₂ O ₃ are p
It can be seen that when H is 9.5, the zeta potential becomes 0, and the zeta potential does not adhere to the electrode.

As described above, particles of various substances are suspended in seawater, and the isoelectric point varies depending on the substance forming each particle. For this reason, when electricity is continued with the potential kept constant, particles of a substance other than the substance having a pH that is the isoelectric point given by the current attachment adheres to the electrode, and they gradually grow to a strong scale.

When the potential of the coating layer with respect to the reference electrode is changed in the operation of the antifouling device, the pH of seawater in the portion in contact with the coating layer also changes. Where seawater is retained, change the potential of the coating layer from 1.2 V (against SCE) to -0.6
When changed to V (against SCE), the pH of seawater in the portion in contact with the coating layer changes from 3 to 11.

Most objects floating in seawater have a pH
Since it has an isoelectric point in the range of 3 to 11, when the potential of the coating layer is changed in this range, the zeta potential may become 0 for virtually all particles within one cycle. Adsorption force is lost for particles with a zeta potential of 0,
The particles detach from the coating layer. Therefore, even if the particles of the mineral substance adhere to the coating layer, the potential of the coating layer is not dropped and accumulated during one cycle change, and the scale is not formed.

The electric potential of the coating layer is 1.2 to -0.6 V (vs. S).
Choosing in the range of (CE) is the most noble potential of 1.2 V (against SCE) at which seawater is not electrolyzed to generate chlorine.
Therefore, the most base electric potential at which hydrogen is not generated −0.6
There is also a reason for V (against SCE).

[0020]

[Example] A steel pipe having flanges at both ends (caliber "100"
Ten "A" lengths of 1 m) were prepared. A conductive rubber sheet extruded by kneading 30 parts by weight of carbon black and 40 parts by weight of graphite with 100 parts by weight of chloroprene rubber was lined on the inner surface of each to provide a conductive coating layer (3). Sheet thickness after vulcanization is 5m
m. All parts of the conductive sheet without lining, such as the flange surface and outer peripheral surface of the steel pipe, were covered with an insulating material.

A cylindrical reference electrode made of silver, in which a hole is formed near each flange of the coated steel pipe, the side surface and the rear end are covered with an insulating material, and a small hole is formed in the insulating material at the rear end, the tip is a tube. It was inserted and fixed so that it protruded slightly inside.

An electrode material was prepared by plating platinum on a titanium donut-shaped plate having a surface having the same shape and dimensions as the flange portion.

As shown in FIG. 2, the above steel pipe was flange-joined with an electrode material (4) sandwiched between the steel pipes to prepare a pipe for testing. DC power supply is "potentiostat" manufactured by Hokuto Denko
What connected the function generator (7) to (6) was used.
The anode terminal, the cathode terminal, and the reference electrode terminal of the potentiostat (6) were wired with the connection terminal, the electrode material, and the reference electrode (5) provided on each steel pipe with a connection cable. In FIG. 2, (8) is an insulator.

Seawater was passed through this pipe at a flow rate of 0.5 m / sec. A direct current of 40 to 100 mA is applied to each steel pipe, and the potential difference between the conductive coating layer and the reference electrode (SCE) is 1.2 V, 0.9 V, 0.6 per hour.
Antifouling of the pipe was performed while controlling so as to change to V, 0.0V, -0.6V, and 1.2V again.

When the inside of the pipe was examined one year later, the adhesion of marine organisms was hardly seen. For comparison,
The potential difference between the conductive coating layer and the reference electrode (SCE) is set to 0.
Antifouling of the pipe was carried out in the same manner as above except that the control was carried out within the range of 8 to 1.2V. A year later, when the inside of the pipe was examined, scales were formed here and there, and marine organisms adhered to the scales.

[0026]

According to the antifouling method of the present invention, not only the adhesion of marine organisms but also the formation of scales can be prevented. Therefore, in the antifouling technique by energization, there is no problem that a scale is formed on the conductive coating layer and current does not flow to that portion, and marine organisms adhere to the scale. In this way, the effect of preventing the adhesion of marine organisms was improved.

[Brief description of drawings]

FIG. 1 pH of NaCl solution and A in the solution
graph showing the relationship between the zeta potential of the l ₂ O _3.

FIG. 2 is a diagram for explaining an example in which the antifouling method of the present invention is applied to piping.

[Explanation of symbols]

 1 Antifouling Material 3 Conductive Coating Layer 4 Electrode Material 5 Reference Electrode 6 DC Power Supply 8 Insulator 9 Seawater

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kanjo Takahashi 36-1, Arae, Sawara-ku, Fukuoka-shi, Fukuoka

Claims (3)

[Claims] 1. A method for preventing pollution due to adhesion of marine organisms and scales to structures, ships, pipes or nets that come into contact with seawater, which is electrically conductive in a portion of an antifouling object requiring antifouling. A coating layer of material is provided as a working electrode, an electrode material insoluble in seawater is provided as a counter electrode so as not to come into contact with this coating layer, and a counter electrode is arranged to apply a DC voltage between the working electrode and the counter electrode. Then, the electric potential difference between the reference electrode and the working electrode is measured, and a weak current is flown while controlling it so that it changes periodically within the range of 1.2 to -0.6 V (vs. SCE), and marine organisms. And an antifouling method comprising preventing scale from adhering. 2. The antifouling method according to claim 1, wherein the coating layer is a lining layer of a conductive rubber or a conductive resin, or a coating film of a conductive paint. 3. The antifouling method according to claim 1, which is carried out by using a coating layer provided with a power feeding body.