JP2003328164A - Method for preventing adhesion of marine organism to titanium ship - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique of preventing adhesion of marine organisms, which technique makes paintless use of a titanium ship possible and reduces the burden on the environment. <P>SOLUTION: The method for preventing the adhesion of the marine organisms to the titanium ship having a structure to electrically insulate screw propellers and their shaft from the hull comprises maintaining reference electrodes for bringing the hull of the titanium ship into contact with seawater at a potential of 1.2 to 1.4 V (based on a saturated KCl Ag/AgCl reference electrode). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention solves the problem caused by marine organisms that grow and multiply by adhering to the surface of the submerged part of a titanium ship that is in contact with seawater. On how to do.

[0002]

2. Description of the Related Art Generally, titanium has high corrosion resistance due to a passive film which is an oxide film on the surface. In addition, due to its light weight and beautiful design, it is used in environments that come into contact with various seawater, such as marine structures located in the ebb and splash zone, power plant condensers, titanium vessels, and so on. For example, a titanium-made ship can be used as a high-speed ship because of the lightness peculiar to titanium, and can be used without painting because of its high corrosion resistance and by utilizing the beautiful design of titanium. In addition, coating of organotin-based paints such as tributyltin has been used to prevent adhesion of marine organisms. Organotin-based paints are widely used for preventing marine organisms from adhering to ships because they are highly toxic and repellent to marine organisms.

Further, in recent years, in place of the organic tin-based paint,
Silicone antifouling paints and zinc thermal spray coatings have been proposed as methods for preventing marine organisms from adhering to ships. In addition, a method has been proposed in which the surface of a ship is coated with a conductive paint containing carbon, graphite, etc., and the paint film is used as an anode to generate electricity to generate hypochlorite ions and chlorine to prevent biofouling of the surface. There is. In addition, an electrocatalyst film made of a platinum group metal, an alloy based on these metals, or an oxide of these metals is formed on the surface of titanium in contact with seawater, and seawater is electrolyzed using this as an anode to generate oxygen. The method of generating and preventing the adhesion of marine organisms is Japanese Patent Publication 1-465.
It is introduced in Japanese Patent Publication No. 95. In addition to the method of directly removing the marine organisms that have been physically attached using a sponge ball, etc., the method of killing and removing the attached marine organisms using chemicals such as hydrogen peroxide and sodium hypochlorite. And so on.

[0004]

As described above, when a titanium ship is used in the ocean, there are various problems caused by marine organisms adhering to titanium. When a titanium ship is used without painting, marine life (barnacles, mussels,
Sea anemones, seaweed, etc.) are attached, increasing the resistance of the titanium ship hull in contact with seawater, which is an obstacle to high-speed navigation, which is a feature of titanium ships. In addition, organotin-based paints such as tributyltin, which have been most widely used to prevent the adhesion of marine organisms, are feared to have an adverse effect on the environment, and thus their use tends to be withheld. If silicone coating is applied to the entire submerged part of the ship, it will be a significant cost factor, and there are many unclear points such as the life of the coating. Applying zinc spray coating to the entire submerged part of the ship also causes a great cost factor, and the environmental load of the eluted zinc ions is unknown.

Regarding the method of coating the surface of a ship with a conductive paint containing carbon, graphite, etc., and using the paint film as an anode to generate electricity to generate hypochlorite ions and chlorine to prevent biofouling, conductive coating is used. There are many problems in terms of construction, such as cost generation and the need to insulate between the coating film and the hull, and there are many problems to be solved for practical use. An electrocatalyst coating consisting of a platinum group metal, an alloy based on these metals, or an oxide of these metals is formed on the surface of titanium in contact with seawater, and this is used as an anode to electrolyze seawater to generate oxygen. As for the method of preventing the adhesion of marine organisms, the cost of the electrode material and the on-site construction man-hour are higher than the expectation of long-term effect, and the construction cost may be higher than other methods. The coating and coating of the hull not only increases the weight of titanium vessels, but also loses the smoothness of titanium materials, which may cause hull resistance and adversely affect the high-speed navigation characteristic of titanium vessels. There is also.

In addition to the method of directly removing the marine organisms which are physically attached using a sponge ball or the like, the attached marine organisms are killed by using a chemical agent such as hydrogen peroxide or sodium hypochlorite. There is also a huge maintenance cost for the method of removal. In addition, when chemicals are used, there is concern about the environmental load associated with their disposal in seawater.

[0007]

[Means for Solving the Problems] In order to solve the above problems, the present invention has been completed by earnestly studying the development of a method for preventing adhesion of marine organisms to a titanium ship which is inexpensive and has a low environmental load. The means are as follows. (1) A method for preventing marine organisms from adhering to a titanium ship, which has a structure in which a screw propeller and its shaft are electrically insulated from the ship body made of titanium. 1.4V (saturated KCl A
A method for preventing marine organisms from adhering to a titanium ship, which is characterized in that a potential of g / AgCl reference electrode is maintained.

(2) A method for preventing marine organisms from adhering to a titanium ship, wherein the insoluble electrode in contact with seawater is connected as a cathode to the same potential as the reference electrode in (1). (3) A method for preventing marine organisms from adhering to a titanium ship, and a method for preventing corrosion of a screw propeller and a shaft portion, characterized in that the screw propeller and the shaft are connected to the same potential as the reference electrode using the screw propeller as a cathode in the above (1). is there. Therefore, it is an object of the present invention to provide a technique for preventing the adhesion of marine organisms, which has a low environmental load and enables a titanium ship to be used without painting.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In a titanium ship, the marine organisms to be applied to the titanium ship in the unpainted state without surface modification or thermal spraying while maintaining the design and gloss of the titanium material. Preventing the adhesion is also advantageous in terms of cost. Furthermore, the method of preventing the adhesion of marine organisms by using a large amount of chemicals such as sodium hypochlorite and hydrogen peroxide may adversely affect other organisms living in seawater. It is desired to prevent marine organisms from adhering to the hull. Here, a comparison was made between titanium vessels and other metal vessels that have been put into practical use.

As metal vessels other than titanium vessels,
Steel and stainless steel vessels and aluminum vessels are widely used. Steel vessels, stainless steel vessels,
Parts of aluminum vessels that come into contact with seawater are generally painted. This is because steel, stainless steel, and aluminum are highly likely to corrode in seawater, so corrosion by painting is necessary. It is difficult to use unpainted seawater on steel / stainless steel vessels and aluminum vessels.
Further, if the coating film is defective and locally unpainted steel, stainless steel, or aluminum is exposed to seawater, there is a problem that it may cause local corrosion. In order to solve such a corrosion problem, a sacrificial anode made of zinc or aluminum may be used in a steel / stainless steel ship.

On the other hand, titanium vessels can be used without coating in seawater. This is due to the corrosion resistance of the oxide film on the titanium surface. Further, with steel, stainless steel, and aluminum, if the anode potential for seawater electrolysis is set, the anode easily dissolves, and it is not possible to directly prevent the adhesion of marine organisms by seawater electrolysis. On the other hand, titanium is unpainted, and even if the anode potential for seawater electrolysis is set, anodic dissolution of titanium hardly occurs. Therefore,
We thought that it is possible to electrically prevent marine organisms from adhering to titanium vessels without painting while making good use of their design and luster.

Therefore, as a result of investigating the effect of preventing adhesion of marine organisms by immersing an unpainted titanium plate in natural seawater and setting various anode potentials, 1.2 to 1.4 V (saturated KCl
It was confirmed that the effect of preventing the adhesion of marine organisms is remarkable by keeping chlorine (Ag / AgCl reference electrode reference) at a potential at which chlorine is generated, and the applied potential at the seawater submersion part in the titanium ship of the present invention. We have found a method to prevent marine organisms from adhering to titanium vessels by establishing the energization conditions.

The present invention will be described in detail below. In titanium ships, only the screw propeller shaft of the drive unit is often made of stainless steel. this is,
This is due to the fact that it is not easy to make a screw propeller shaft from titanium as compared to stainless steel.
If the stainless steel screw propeller shaft part is not electrically insulated from the titanium ship hull, the stainless steel screw propeller shaft part and the titanium ship hull form a galvanic cell through seawater. Therefore, there is a great possibility that the propeller shaft will be severely corroded. Therefore, by electrically insulating by interposing an insulator between the stainless steel screw propeller shaft part and the titanium ship hull, the titanium and the stainless steel come into contact with each other and come into contact with seawater. It is possible to prevent the stainless steel corrosion of the screw propeller shaft portion due to the formation of galvanic cells.

As described above, by electrically insulating the stainless steel screw propeller shaft portion from the titanium ship hull, the stainless steel screw propeller
It is possible to apply a potential with the titanium hull as the anode while avoiding the melting of the stainless steel in the shaft anode. The present inventors have found that the potential of titanium in seawater is +1.2 to +1.4 V (saturated KCl Ag / A) with respect to the reference electrode immersed in seawater.
It has been found that, by maintaining the gCl standard), chlorine is generated, so that the bactericidal effect of chlorine can prevent the adhesion of marine organisms. Therefore, based on this knowledge, we have established a method for preventing marine organisms from attaching to titanium vessels.

Here, if the potential of titanium in seawater is less than +1.2 V with respect to the reference electrode immersed in seawater, chlorine is not generated in an amount sufficient to obtain a sufficient bactericidal effect, which is not preferable. Also, when the potential of titanium in seawater exceeds +1.4 V with respect to the reference electrode immersed in seawater, discoloration of titanium occurs and the dead body of marine microorganisms is adsorbed.
Not preferable.

Next, the case where an insoluble electrode is used in the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram of a method for preventing adhesion of marine organisms to a titanium hull by suspending an external power source and an insoluble cathode in seawater. In the present invention, the part of the titanium ship hull that contacts seawater is unpainted. In order to prevent marine organisms from attaching to the parts of the hull that come into contact with seawater,
The hull is made an anode by an external power supply method. It is desirable to use a battery capable of continuously supplying current for a long time as an external power source used for applying a potential. The positive electrode of the power supply is connected to the hull of a titanium ship. The negative electrode is connected to the insoluble electrode 3 suspended in seawater as a cathode. The material of the insoluble electrode is preferably platinum-plated titanium, platinum or the like.

In this system, the insoluble cathode 3 suspended in seawater is connected to the negative electrode of the external power source, but in order to prevent the conductive wire up to the insoluble cathode 3 from being short-circuited with the hull connected to the anode, the conductive wire is connected. Insulating resin arm 1 in which is covered with an insulating coating
Through the inside, and by covering this arm with a cushion material, the hull is prevented from being damaged due to a mechanical collision with the hull. Further, the negative electrode of the external power source is connected to the reference electrode 4 which is in contact with seawater. As a reference electrode, saturated KC
An Ag / AgCl electrode, a saturated sweet koh electrode or the like can be used.

As described above, by connecting the external power source and the hull, and the insoluble electrode and the reference electrode, it becomes possible to conduct electricity through seawater. +1. For the reference electrode in seawater.
By keeping the potential of 2 to +1.4 V (saturated KCl Ag / AgCl standard), the adhesion of marine organisms can be prevented. Reference numeral 2 in FIG. 1 denotes an engine insulated from the hull, and 5 denotes a screw propeller and a shaft insulated from the hull.

Further, another embodiment of the present invention will be described with reference to FIG. FIG. 2 is an explanatory view of a method capable of simultaneously adhering marine organisms to a titanium ship hull and preventing corrosion of a screw propeller and a shaft portion electrically insulated from the hull by an external power supply method. In the present invention, the part of the titanium ship hull that contacts seawater is unpainted. In order to prevent marine organisms from adhering to the parts of the hull that come into contact with seawater, the hull is made an anode by an external power supply method. It is desirable to use a battery capable of continuously supplying current for a long time as an external power source used for applying a potential. The positive electrode of the power supply is connected to the hull of a titanium ship. The negative electrode is connected to a stainless steel screw propeller and shaft. Also,
The negative electrode of the external power source is connected to the reference electrode 4 which is in contact with seawater.
As a reference electrode, a saturated KCl Ag / AgCl electrode,
For example, a saturated sweet ko electrode can be used.

As described above, by connecting the external power source and the hull, the screw propeller electrically insulated from the hull, the shaft portion 5 and the reference electrode 4, it becomes possible to conduct electricity through seawater. Hull the vessel to the reference electrode 4 in seawater +1.
By keeping the potential of 2 to +1.4 V (saturated KClAg / AgCl standard), it is possible to prevent the adhesion of marine organisms to the hull and at the same time anticorrosive effect of the screw propeller and the shaft can be expected. Although it is desirable to continue the energization period as much as possible, for example, in winter when large marine organisms do not become a problem, in the spring, when the marine life begins to become violent in early spring You may energize together. Therefore, it is possible to appropriately set the energization period while observing the cost generated by energization and the state of organism attachment to the hull.

[0021]

EXAMPLES The present invention will be described below based on examples. (Example 1) Effect of application of electric potential on adhesion of marine organisms to unpainted titanium immersed in seawater, emery # 400 polished unpainted titanium test piece (seawater-immersed portion is 50 mm x 3)
0 mm rectangle) was prepared. Saturated KCl Ag / AgC obtained by immersing this test piece in seawater and also immersing it in seawater
0 electrode as a reference electrode, and a platinum plate (seawater immersion part is 50 mm × 30 mm rectangle) as an insoluble cathode 0
V, + 0.2V, + 0.4V, + 0.6V, +0.8
V, + 1.0V, + 1.2V, + 1.4V, + 1.6V
Was applied to each potential. After soaking in seawater for 3 months in summer,
The state of adhesion of marine organisms on the surface was observed. After the test, the marine organisms having a maximum major axis length of 2 mm or more were found to have adhesion, and the results are shown in Table 1. Further, in Table 1, Table 1 shows x when the discoloration of titanium occurred in this test, and ◯ when it did not occur.

[0022]

[Table 1]

At a set potential of 0 V to +1.0 V, the attachment of marine organisms was remarkable. Further, even at +1.6 V, although it was effective in preventing biological attachment itself, it was found that the titanium discolored violently and turned into a reddish brown color, impairing the design and glossiness peculiar to titanium. +1.2
At V and +1.4 V, good results were obtained for preventing the adhesion of marine organisms.

(Example 2) The effect of potential application on the adhesion of marine microorganisms to unpainted titanium immersed in seawater, and the adhesion of large marine organisms such as barnacles and mussels is hardly observed in winter seawater due to the low temperature. However, even in winter, microorganisms living in seawater adhere to the titanium surface. Larger marine organisms are considered to attach to these microorganisms as they predate. Therefore, in winter seawater, a test was conducted for the effect of preventing microbial adhesion. As in Example 1, an unpainted titanium test piece immersed in seawater was used as an anode, a saturated KCl Ag / AgCl electrode was used as a reference electrode, and a platinum plate was used as an insoluble cathode.
+ 0.4V, + 0.6V, + 0.8V, + 1.0V, +
Electric potentials of 1.2V, + 1.4V and + 1.6V were applied.
After being soaked in seawater for 2 weeks in winter, the microorganisms adhering to the surface were visualized by staining the DNA of the microorganism with the fluorescent dye DAPI. By observing the microorganisms adhering to the surface of the titanium test piece with a fluorescence microscope,
% Or more, DAPI dyeing has no effect of preventing microbial adhesion, and D is less than 10% of surface area.
In the case where API staining was not carried out, it is shown in Table 2 as ⊚ as having a preventive effect against microbial adhesion.

[0025]

[Table 2]

At a set potential of 0 V to +1.0 V, the attachment of marine organisms was remarkable. At +1.6 V, carcasses such as marine microorganisms were remarkably adsorbed on the surface. Therefore, the amount of microorganism-derived DNA detected on the titanium surface was remarkably large. At +1.2 V and +1.4 V, good results were obtained for preventing the adhesion of marine microorganisms.

[0027]

As described above, it is possible to prevent marine organisms from adhering to titanium vessels under the potential application conditions defined in the present invention. Further, the screw propeller and the shaft portion of a titanium ship can also be protected against corrosion at the same time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of preventing adhesion of marine organisms to a titanium hull by suspending an external power source and an insoluble cathode in seawater.

FIG. 2 is an explanatory view of a method capable of simultaneously adhering marine organisms to a ship made of titanium and preventing corrosion of a screw propeller and a shaft portion electrically insulated from the ship by an external power supply method.

[Explanation of symbols]

1 Insulating resin arm 2 Engine insulated from the hull 3 Insoluble cathode 4 reference electrode 5 Screw propellers and shafts insulated from the hull

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Osamu Miki             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division (72) Inventor Hiroshi Kihira             20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel shares             Company Technology Development Division F-term (reference) 4K060 AA03 BA02 BA39 CA04 CA15                       DA07 EA02 EB02 EB06 FA03

Claims (3)

[Claims] 1. A method for preventing marine organisms from adhering to a titanium ship, which has a structure in which a screw propeller and its shaft are electrically insulated from a titanium ship body, wherein: 1. 2 to 1.4V (saturated K
A method for preventing marine organisms from adhering to a titanium ship, which is characterized by holding the potential of Cl 2 Ag / AgCl reference electrode). 2. The method for preventing adhesion of marine organisms on a titanium ship according to claim 1, wherein an insoluble electrode in contact with seawater is used as a cathode and connected to the same potential as the reference electrode. 3. The method according to claim 1, wherein the screw propeller and the shaft are connected as a cathode to a potential equal to that of the reference electrode, and a method for preventing adhesion of marine organisms on a titanium ship, a screw propeller, and a shaft portion. Corrosion prevention method.