Marine vessel

Abstract

To provide a marine vessel that can suppress corrosion of a hull due to a counter current method.SOLUTION: A marine vessel comprises: a metal hull including an underwater part immersed in sea water; an underwater electric field reduction device which includes an anode and a cathode provided on the underwater part, and flows a counter electric current toward the cathode from the anode through sea water, thereby reducing an underwater electric field around the hull; and a hull protective member near the anode that is positioned near the anode in the underwater part and is formed from a bare metal with a non-coated surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to marine vessels. [Background technology]

[0002] The following Patent Document 1 discloses a method for reducing the underwater electric potential (UEP) of a ship, which reduces the underwater electric potential (UEP) around the hull by passing an electric current between first and second electrodes arranged in a part of the hull that is immersed in seawater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-88542 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the UEP reduction method described in Patent Document 1 (hereinafter, the "counter current method"), it is assumed that the current flowing between the first and second electrodes (hereinafter, the "counter current") passes through seawater. However, research by the inventors has shown that when the hull is made of metal, part of the counter current flowing between the first and second electrodes becomes a stray current and passes through the hull, which has low electrical resistance. It has also been shown that on the hull surface near the anode where the counter current flows from seawater into the hull, paint peeling and hydrogen embrittlement occur due to a hydrogen generation reaction, and that on the hull surface near the cathode where the counter current flows out from the hull into the seawater, corrosion thinning occurs.

[0005] Therefore, an object of the present disclosure is to provide a ship that can suppress harmful electrochemical reactions (one or both of hydrogen generation reaction and corrosion thinning) on ​​the hull surface caused by the counter current method. [Means for solving the problem]

[0006] A ship according to one embodiment of the present disclosure comprises a metal hull including an underwater portion that is immersed in seawater, an underwater electric field reduction device that includes an anode and a cathode provided in the underwater portion and reduces the underwater electric field around the hull by passing a counter current from the anode through the seawater to the cathode, and an anode-proximal hull protection member located near the anode in the underwater portion and formed of bare metal with an unpainted surface. Effect of the Invention

[0007] This configuration makes it possible to suppress harmful electrochemical reactions on the hull surface caused by the counter current method. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side view of a vessel. [Diagram 2] FIG. 2 is a schematic bottom view of the vessel. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described. Fig. 1 is a schematic side view of a ship 100 according to this embodiment, and Fig. 2 is a schematic bottom view of the ship 100 according to this embodiment. The ship 100 may be a surface vehicle that travels on seawater with only the bottom of the ship submerged in seawater, or an underwater vehicle that travels in seawater with the entire hull submerged in seawater.

[0010] 1, a ship 100 according to this embodiment includes a hull 10, an underwater electric field reduction device 20, an anode vicinity hull protection member 30, and a cathode vicinity hull protection member 40. Below, these components will be described in order.

[0011] <Hull> The hull 10 includes an underwater section 11 that is immersed in seawater. When the ship 100 is a surface vehicle, only the bottom portion of the hull 10 is the underwater section 11, and when the ship 100 is an underwater vehicle, the entire hull 10 is the underwater section 11. The hull 10 of this embodiment is made of metal. Specifically, the hull 10 is formed of carbon steel with a painted surface. However, the hull 10 may be formed of a material other than carbon steel. The metal hull 10 is a hull 10 that is substantially formed of metal, and also includes a hull 10 that uses FRP or rubber in part.

[0012] In addition, an underwater electric field is generated in the seawater around the hull 10 of this embodiment. There are various causes for the generation of the underwater electric field, but there are underwater electric fields caused by hull magnetism and anticorrosion currents. Those caused by hull magnetism include magnetization of the hull 10 due to welding during manufacturing and magnetism of equipment. On the other hand, those caused by anticorrosion currents include those caused by cathodic protection, which is a measure to prevent corrosion of the hull 10.

[0013] <Underwater electric field reduction device> The underwater electric field reduction device 20 is a device for reducing the underwater electric field around the above-mentioned hull 10 by the counter current method. By reducing the underwater electric field around the hull 10, for example, when the ship 100 passes through a dangerous sea area, it is possible to avoid attacks by mines or the like that react to the underwater electric field. The underwater electric field reduction device 20 of this embodiment includes an anode 21 and a cathode 22 provided in the underwater part 11 of the hull 10.

[0014] Both the anode 21 and the cathode 22 are electrically insulated from the hull 10. The underwater electric field reduction device 20 passes a counter current from the anode 21 through the seawater to the cathode 22 so as to generate an underwater electric field in the opposite direction to the underwater electric field around the hull 10. This generates a new underwater electric field, making it possible to reduce the underwater electric field around the hull 10.

[0015] However, when the counter current method is implemented, there is a risk of harmful electrochemical reactions occurring on the surface of the hull 10. In the counter current method, most of the counter current flows from the anode 21 through the water toward the cathode 22, as shown by the dashed-dotted line in Figure 1. However, part of the counter current becomes a stray current, as shown by the dashed-dotted line in Figure 1, and flows from the anode 21 into the water, and then flows into the hull 10 near the anode 21. The stray current that has flowed into the hull 10 then passes through the hull 10, flows out of the hull 10 into the water near the cathode 22, and flows toward the cathode 22.

[0016] In the portion of the hull 10 where the stray current flows in, i.e., the surface of the hull 10 near the anode 21, there is a risk of paint peeling and hydrogen embrittlement due to a hydrogen generation reaction. In addition, in the portion of the hull 10 where the stray current flows out, i.e., the surface of the hull 10 near the cathode 22, there is a risk of corrosion and thinning. In order to suppress such harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method, the ship 100 according to this embodiment is provided with an anode vicinity hull protection member 30 and a cathode vicinity hull protection member 40, which will be described below, on the hull 10.

[0017] <Hull protection material near the anode> The anode vicinity hull protection member 30 is a member that protects the hull 10 around the anode 21 of the hull 10. The anode vicinity hull protection member 30 is located near the anode 21 in the underwater section 11. The anode vicinity hull protection member 30 may be provided in the underwater section 11 instead of a part of the underwater section 11, or may be electrically connected to the surface of the underwater section 11. The electrical connection may be made by bolting, welding, or the like.

[0018] The anode vicinity hull protection member 30 of this embodiment is formed of bare metal with an unpainted surface. Here, bare metal has a lower electrical resistance than painted metal, and current flows more easily through bare metal. Therefore, the stray current generated by the underwater electric field reduction device 20 generating a counter current flows into the hull 10 through the anode vicinity hull protection member 30 as an inlet. As a result, stray current is less likely to flow into the hull 10 other than the anode vicinity hull protection member 30 around the anode 21, and hydrogen generation reaction is less likely to occur. Furthermore, bare metal has the characteristic that hydrogen generation reaction is less likely to occur compared to painted metal. Therefore, the anode vicinity hull protection member 30 itself is less likely to suffer from hydrogen embrittlement. Therefore, according to this embodiment, harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method can be suppressed.

[0019] In this embodiment, the anode nearby hull protection members 30 are arranged at four locations so as to surround the anode 21. By surrounding the anode 21 with the anode nearby hull protection members 30, the electrode potential around the anode 21 can be efficiently increased. However, the anode nearby hull protection members 30 do not have to be arranged so as to surround the anode 21, and the number of anode nearby hull protection members 30 is not limited. For example, the anode nearby hull protection member 30 may be arranged at only one location so as to be adjacent to the anode 21. In addition, the distance between the anode nearby hull protection member 30 and the anode 21, i.e., the gap dimension between the anode nearby hull protection member 30 and the anode 21, is preferably small, and may be, for example, within 200 mm.

[0020] <Hull protection material near the cathode> The cathode vicinity hull protection member 40 is a member that protects the hull 10 around the cathode 22. The cathode vicinity hull protection member 40 is located near the cathode 22 in the underwater section 11. The cathode vicinity hull protection member 40 may be provided in the underwater section 11 instead of a part of the underwater section 11, or may be electrically connected to the surface of the underwater section 11. The electrical connection may be made by bolting, welding, or the like.

[0021] The near-cathode hull protection member 40 of this embodiment is made of zinc with an unpainted surface. As described above, the hull 10 of this embodiment is made of carbon steel with a painted surface, but zinc with an unpainted surface has a lower corrosion potential in seawater than carbon steel with a painted surface. In other words, in this embodiment, the near-cathode hull protection member 40 made of a material with a lower corrosion potential in seawater than the material of the hull 10 is disposed near the cathode 22.

[0022] With this configuration, when the underwater electric field reduction device 20 generates a counter current, the electrode potential of the hull 10 around the cathode 22 is higher than when the cathode vicinity hull protection member 40 is not disposed near the cathode 22. This makes it possible to suppress the occurrence of corrosion thinning of the hull 10 around the cathode 22. In other words, it is possible to suppress harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method.

[0023] Moreover, the cathode vicinity hull protection member 40 is formed of bare metal with an unpainted surface. As described above, bare metal has a lower electrical resistance than painted metal, and current flows more easily through bare metal. Therefore, the stray current generated by the underwater electric field reduction device 20 generating a counter current flows out of the hull 10 through the cathode vicinity hull protection member 40 as an outlet. As a result, stray current is less likely to flow out of the hull 10 other than the cathode vicinity hull protection member 40 around the cathode 22, and corrosion thinning is less likely to occur. Therefore, according to this embodiment, harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method can be further suppressed. In addition, since corrosion thinning occurs in the cathode vicinity hull protection member 40, the cathode vicinity hull protection member 40 is replaced periodically.

[0024] The cathode vicinity hull protection member 40 of this embodiment may be formed of a material other than zinc whose surface is unpainted. For example, the cathode vicinity hull protection member 40 may be formed of aluminum whose surface is unpainted, or may be formed of magnesium whose surface is unpainted. In this way, the cathode vicinity hull protection member 40 is formed of a material whose corrosion potential is lower than that of the material of the hull 10. The order of corrosion potential is as follows: magnesium alloy < aluminum alloy < zinc < carbon steel < copper alloy. The material of the cathode vicinity hull protection member 40 has an unpainted surface, but may have a painted surface.

[0025] In this embodiment, the cathode near hull protection members 40 are arranged at four locations so as to surround the cathode 22. Therefore, the electrode potential of the hull 10 around the cathode 22 can be efficiently lowered. However, the cathode near hull protection members 40 do not have to be arranged so as to surround the cathode 22, and the number of the cathode near hull protection members 40 is not limited. For example, the cathode near hull protection member 40 may be arranged at only one location so as to be adjacent to the cathode 22. In addition, the distance between the cathode near hull protection member 40 and the cathode 22, i.e., the gap dimension between the cathode near hull protection member 40 and the cathode 22, is preferably small, and may be, for example, within 200 mm.

[0026] Furthermore, in this embodiment, the cathode vicinity hull protection member 40 is arranged so that when the underwater electric field reduction device 20 generates a counter current, the electrode potential of the hull 10 near the cathode 22 of the underwater section 11 is lower than the upper limit electrode potential. The above-mentioned "upper limit electrode potential" varies depending on the material of the hull 10. For example, when the hull 10 is formed of carbon steel, alloy steel, or aluminum alloy, the "upper limit electrode potential" is minus 0.80 V vs. Ag / AgCl seawater (Ag / AgCl seawater is used as the reference electrode in this embodiment). For example, when the hull 10 is formed of austenitic stainless steel with a PREN of less than 40, nickel-based alloy, duplex stainless steel, or martensitic stainless steel with a PREN of less than 40, the "upper limit electrode potential" is minus 0.50 V vs. Ag / AgCl seawater. It should be noted that PREN (pitting corrosion index) = Cr (chromium content) + 3.3Mo (molybdenum content) + 16N (nitrogen content). For example, if the hull 10 is made of a copper alloy, the "upper electrode potential limit" is minus 0.45 V vs. Ag / AgCl seawater. For example, if the hull 10 is made of an austenitic stainless steel with a PREN of 40 or more, or a nickel-based alloy with a PREN of 40 or more, the "upper electrode potential limit" is minus 0.30 V vs. Ag / AgCl seawater.

[0027] In this way, by arranging the cathode vicinity hull protection member 40 so that the electrode potential of the hull 10 is lower than the upper limit electrode potential, it is possible to suppress the occurrence of corrosion thinning of the hull 10 around the cathode 22 and to suppress harmful electrochemical reactions on the surface of the hull 10 caused by the counter current method. Note that the electrode potential at each position on the hull 10 when the underwater electric field reduction device 20 generates a counter current may be actually measured or may be calculated by simulation.

[0028] Furthermore, although the ship 100 according to this embodiment is equipped with both the anode vicinity hull protection member 30 and the cathode vicinity hull protection member 40, it may be equipped with only one of the anode vicinity hull protection member 30 and the cathode vicinity hull protection member 40. In other words, only one of the anode vicinity hull protection member 30 and the cathode vicinity hull protection member 40 may be provided on the hull 10.

[0029] (summary) The first item disclosed in this specification is a ship comprising a metal hull including an underwater portion that is immersed in seawater, an underwater electric field reduction device that includes an anode and a cathode provided in the underwater portion and reduces the underwater electric field around the hull by passing a counter current from the anode through the seawater to the cathode, and an anode vicinity hull protection member located near the anode in the underwater portion and formed of bare metal with an unpainted surface.

[0030] This configuration makes it possible to suppress harmful electrochemical reactions on the hull surface caused by the counter current method.

[0031] A second item disclosed in the present specification is the vessel according to the first item, wherein the anode vicinity hull protection member is arranged to surround the anode.

[0032] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be efficiently suppressed.

[0033] The third item disclosed in this specification is a ship comprising a metal hull including an underwater portion that is immersed in seawater, an underwater electric field reduction device that includes an anode and a cathode provided in the underwater portion and reduces the underwater electric field around the hull by passing a counter current from the anode through seawater to the cathode, and a cathode vicinity hull protection member that is located near the cathode in the underwater portion and is formed of a material that has a lower corrosion potential in seawater than the material of the hull.

[0034] This configuration makes it possible to suppress harmful electrochemical reactions on the hull surface caused by the counter current method.

[0035] A fourth item disclosed in the present specification is the vessel described in the third item, wherein the cathode vicinity hull protection member is formed of bare metal with no painted surface.

[0036] With this configuration, stray currents are less likely to flow out in areas around the cathode where the cathode near-hull protection member is not located, thereby further suppressing harmful electrochemical reactions on the hull surface caused by the counter current method.

[0037] The fifth item disclosed in this specification is a method for reducing the electrode potential of a hull near the cathode in the underwater portion by a counter current, the cathode vicinity hull protection member being arranged so that the electrode potential of the hull near the cathode in the underwater portion is lower than an upper limit electrode potential, the upper limit electrode potential being minus 0.80 V vs. Ag / AgCl seawater when the hull is made of carbon steel, alloy steel, or aluminum alloy, the upper limit electrode potential being minus 0.50 V vs. Ag / AgCl seawater when the hull is made of austenitic stainless steel having a PREN of less than 40, nickel-based alloy, duplex stainless steel, or martensitic stainless steel having a PREN of less than 40, the upper limit electrode potential being minus 0.45 V vs. Ag / AgCl seawater when the hull is made of copper alloy, and the upper limit electrode potential being minus 0.30 V vs. Ag / AgCl seawater when the hull is made of austenitic stainless steel having a PREN of 40 or more, or nickel-based alloy having a PREN of 40 or more. 2. A vessel as described in paragraph 3 or 4 above that is seawater.

[0038] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be effectively suppressed.

[0039] A sixth item disclosed in this specification is the ship according to any one of the third to fifth items, wherein the cathode vicinity hull protection member is arranged to surround the cathode.

[0040] According to this configuration, harmful electrochemical reactions on the hull surface caused by the counter current method can be efficiently suppressed. [Explanation of symbols]

[0041] 10. Hull 11 Underwater part 20 Underwater electric field reduction device 21 Anode 22 Cathode 30. Hull protection member near anode 40 Cathode-proximal hull protection member 100 ships

Claims

1. A metal hull including a submersible portion that is immersed in seawater; an underwater electric field reduction device including an anode and a cathode provided in the underwater portion, and reducing the underwater electric field around the hull by passing a counter current from the anode through seawater to the cathode; a vessel having an anode vicinity hull protection member located in the underwater portion in the vicinity of the anode and having an unpainted surface made of bare metal.

2. The vessel according to claim 1 , wherein the anode vicinity hull protection member is disposed so as to surround the anode.

3. A metal hull including a submersible portion that is immersed in seawater; an underwater electric field reduction device including an anode and a cathode provided in the underwater portion, and reducing the underwater electric field around the hull by passing a counter current from the anode through seawater to the cathode; a cathode vicinity hull protection member located in the underwater portion in the vicinity of the cathode and formed of a material having a lower corrosion potential in seawater than a material of the hull.

4. 4. The vessel according to claim 3, wherein the near-cathode hull protection member is formed of bare metal with no painted surface.

5. the cathode vicinity hull protection member is disposed so that an electrode potential of the hull in the vicinity of the cathode in the underwater portion becomes lower than an upper limit electrode potential when the underwater electric field reduction device generates a counter current, When the hull is made of carbon steel, alloy steel, or aluminum alloy, the upper limit electrode potential is minus 0.80 V vs. Ag / AgCl seawater; When the hull is made of an austenitic stainless steel having a PREN of less than 40, a nickel-based alloy having a PREN of less than 40, a duplex stainless steel, or a martensitic stainless steel, the upper limit electrode potential is minus 0.50 V vs. Ag / AgCl seawater; When the hull is made of a copper alloy, the upper limit electrode potential is minus 0.45 V vs. Ag / AgCl seawater; 4. The ship according to claim 3, wherein when the hull is formed of an austenitic stainless steel having a PREN of 40 or more, or a nickel-based alloy having a PREN of 40 or more, the upper limit electrode potential is minus 0.30 V vs. Ag / AgCl seawater.

6. The vessel according to claim 3 , wherein the cathode vicinity hull protection member is disposed so as to surround the cathode.

Images