JP2518720B2 - Cathodic protection equipment for ships - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrolytic protection device for preventing electrolytic corrosion (electrochemical corrosion) of an object to be protected including a hull of a ship.

[Conventional technology]

One of the means of cathodic protection for ships is a galvanic anode (sacrificial anode) system.

This is to forcibly apply a predetermined negative potential to a corrosion resistant body such as a hull, a propeller, a propeller shaft, and a rudder by attaching a galvanic anode made of a metal such as zinc, aluminum, or magnesium. is there.

In this case, there is an ideal range for the potential of the corrosion-prevented body against seawater, and that potential is the corrosion-prevention potential of the corrosion-prevented body (this is the potential at which corrosion protection works, for example -785 m in the case of iron).
In the case of V and aluminum, if it is higher than -830 mV) (that is, on the positive side), electrolytic corrosion will occur, and if it is significantly lower than this (that is, on the negative side), it will be over-corrosion and will coat the hull with alkali. Problems such as film peeling occur.

However, the potential of the body to be protected against seawater changes greatly due to changes in the corrosive environment such as the traveling speed of the ship, but the galvanic anode has energy determined by the material and size of the galvanic anode, and the anticorrosion current changes the corrosive environment. Therefore, even if the potential of the body to be protected against corrosion is idealized while the ship is stopped, the potential will be higher than that during traveling and the anticorrosion effect will be lost. There is a problem. On the contrary, if the galvanic anode is increased so that the electric potential during traveling becomes ideal, the weight increases and
When the ship is stopped, there is a problem that the potential of the corrosion-prevented body becomes too low and over-corrosion occurs.

There is an external power supply system that employs automatic control as a solution to such a problem of the galvanic anode system.

This is equipped with an anticorrosion device body including a DC power supply device, an anode, and a reference electrode, and the anticorrosion current supplied from the body of the anticorrosion device so that the reference electrode detects the potential of the anticorrosion object and brings it closer to the set potential. Is automatically controlled.

According to this external power supply method, the potential of the corrosion-protected body can always be kept in an optimum state in response to changes in the corrosive environment, and this is the mainstream.

[Problems to be Solved by the Invention]

However, in the case of the external power supply method, there is a problem in that maintenance of the anticorrosion device is very troublesome because the anticorrosion device must be kept working even when the ship is anchored for a long period of time.

For example, even in the case of an anticorrosion device for a small ship with a total length of about 20 m, an input of 3 to 4 A at DC24V is required even when moored (By the way, an input of more than 10 A is required because a large anticorrosion current is required while traveling become). Since the engine of the ship and the generator connected to it are not running during the berth, this power is normally supplied from the battery, but since it requires a large input as described above, it is necessary to turn the engine from time to time. This battery has to be charged, which is very troublesome. This is not possible if the sailors are out for a long time.

There is also a method of supplying commercial power from land, but the wiring and the like are troublesome, and it may not be possible depending on the anchorage.

In addition, if the anticorrosion device stops working due to the exhaustion of the battery, there is a risk of corroding the ship.

Therefore, the present invention can effectively prevent electrolytic corrosion of the body to be protected including the hull of the ship, whether it is running or stopped, and does not require maintenance and maintenance while moored. The main purpose is to provide a cathodic protection device for ships.

[Means for Solving the Problems] In order to achieve the above object, the cathodic protection device of the present invention includes a body of a device for corrosive protection including a DC power supply device, an anode and a reference electrode, and an anticorrosion device including a hull of a ship. An external power supply type anticorrosion device that controls the anticorrosion current supplied from the anticorrosion device main body so that the potential of the body is detected by the reference electrode and approaches the set potential, and it is outside the ship and the ship is stopped. It is characterized in that it is provided with a galvanic anode which is attached to a position where the inside is immersed in seawater and is exposed above the sea surface while traveling.

In this case, it is preferable that the set potential of the external power source type anticorrosion device is set to be lower than the anticorrosion potential of the anticorrosion target and higher than the potential of the anticorrosion target by the galvanic anode while the ship is stopped.

[Action]

According to the above configuration, since the galvanic anode is submerged in seawater while the ship is stopped, the function of the galvanic anode prevents electrolytic corrosion of the body to be protected including the hull. Moreover, when the ship is stopped, unlike in the case where the vehicle is traveling, the corrosive environment hardly changes, so that electrolytic corrosion can be effectively prevented even in the case of the galvanic anode. Therefore, it is not necessary to operate the external power supply type anticorrosion device, and maintenance and the like thereof becomes very easy.

On the other hand, when the ship is traveling, the external power supply type anticorrosion device can be activated to effectively prevent electrolytic corrosion of the anticorrosion object in response to changes in the corrosive environment. Therefore, in this case, it is not necessary to operate the galvanic anode, and in the present invention, the galvanic anode naturally comes out on the sea surface when the ship is traveling. As a result, the life of the galvanic anode can be significantly extended.

Also, if the set potential of the external power supply type anticorrosion device is set as above, the potential of the anticorrosion target falls below the set potential due to the action of the galvanic anode while the ship is stopped, so the anticorrosion current is automatically supplied from the anticorrosion device. Then, the action of the galvanic anode disappears during running, and the potential of the body to be protected is about to rise above the set potential, so that the supply of the protection current from the protection device automatically starts.

〔Example〕

FIG. 1 is a schematic view showing a cathodic protection device for a ship according to an embodiment of the present invention. FIG. 2 is a schematic view of the ship of FIG. 1 viewed from the stern side.

The cathodic protection device according to this embodiment includes an external power supply type anticorrosion device 3 and several galvanic anodes 4.

The anticorrosion device 3 is attached to the anticorrosion device main body 31 including a variable-power DC power supply device 32 and a control circuit 33 for controlling it, and electrically insulated from the hull 21 in the seawater 1 outside the hull 21 of the ship 20. A positive electrode 34 and a reference electrode 35 are provided, and a positive potential is relatively applied from the body 31 of the anticorrosion device to the anode 34. In this example of the ship 20, the hull 21, propeller shaft 22, propeller 23 and rudder are provided.
By applying a relatively negative potential to the body to be protected 2 including 24,
An anticorrosion current is supplied from the anode 34 to the anticorrosion body 2 through the seawater 1.

Moreover, the reference electrode 35 detects the potential of the body 2 to be protected against the seawater 1 (more specifically, the hull 21 occupying most of it), and the control circuit 33 directs the direct current so that it approaches the set potential E. The anticorrosion current output from the power supply device 32 is automatically controlled.

The anode 34 is, for example, a titanium surface plated with platinum, and the reference electrode 35 is, for example, a silver chloride electrode. Also,
Reference numeral 36 in the figure is a brush for electrically connecting the anticorrosion device body 31 and the propeller shaft 22.

On the other hand, in this embodiment, as an example of a preferable position outside the stern 20 and submerged in the seawater 1 when the ship is stopped and above the sea surface while traveling, the water line outside the stern skin 25 and when the ship is stopped 11
Below, more specifically along the ship's bottom near the ship's bottom, as shown in FIG. 2, there are several (not limited to five galvanic anodes as shown) galvanic anodes. 4 is attached.

The galvanic anode 4 is made of, for example, a metal such as zinc, aluminum, or magnesium, and the material, size, number, and the like may be appropriately selected according to environmental conditions, anticorrosion specifications, and the like.

According to the above configuration, since the galvanic anode 4 is submerged in the seawater 1 while the ship 20 is stopped, its function, that is, the galvanic anode 4 supplies the anticorrosion current to the body 2 to be protected through the seawater 1 As a result, electrolytic corrosion of the body 2 to be protected is prevented. Moreover, when the ship is stopped, the corrosive environment hardly changes unlike when the vehicle is running, so that electrolytic corrosion can be effectively prevented even in the case of the galvanic anode 4.

Therefore, it is not necessary to operate the external power supply type anticorrosion device 3 while the ship is stopped, and the maintenance and the like thereof becomes very easy.
For example, when the ship 20 is in a long berth, the corrosion protection device main body 31 may be switched off so that it is not necessary to supply input power from a battery or the like. Therefore, even when the seafarer is absent for a long time or when the commercial power supply cannot be supplied from the land, it can be dealt with without any problem.

On the other hand, when the ship 20 is traveling, by operating the anticorrosion device 3 of the external power supply system, it is possible to effectively prevent electrolytic corrosion of the corrosion-prevented body 2 in response to changes in the corrosive environment. it can. Therefore, in this case, since it is not necessary to operate the galvanic anode 4, in the present invention, the galvanic anode 4 naturally comes out on the sea surface by the mounting position as described above.

This will be described with reference to FIGS. 2 and 3. When the boat 20 is traveling in the direction of arrow A in FIG. 3, the seawater 1 behind the stern skin 25 is removed by the hull. But,
Since the speed at which the ship 20 travels is faster than the speed at which the seawater 1 enters there, a triangular recessed region 13 is formed behind the stern skin 25 as shown in FIG. The size of this area 13 depends on the traveling speed of the ship 20. Therefore, as indicated by the thick solid line in FIG. 2, the water level line 12 at the portion of the stern outer plate 25 that is running is lowered to near the bottom of the ship, and the galvanic anode 4 naturally appears above the sea surface.

If the galvanic anode 4 is installed in a conventional manner so that the galvanic anode 4 is always immersed in the seawater 1 even while the ship 20 is traveling, the galvanic anode 4 releases energy for corrosion protection even though it is not necessary. The galvanic anode 4 continues to be worn out. For example, conventionally, it was necessary to replace the galvanic anode about once a year.

On the other hand, if the galvanic anode 4 is exposed above the sea surface while the ship 20 is traveling as in the present invention, it is possible to prevent the galvanic anode 4 from being consumed during traveling. The life of the ship 20 can be extended, and the docking cycle for replacing the galvanic anode 4 of the ship 20 can be greatly extended. This is very advantageous when, for example, the ship 20 is sailing in the ocean, or when sailing in an area where there is no facility for mounting the large ship 20.

The location of the galvanic anode 4 is not necessarily limited to the part of the stern skin 25, but the stern skin 25 has the largest water level fluctuation between when the ship is stopped and when it is running. When the electric anode 4 is attached, it is possible to surely switch whether the galvanic anode 4 is submerged in seawater or exposed to the surface of the sea, and unlike the case where the galvanic anode 4 is attached to the ship side, the galvanic anode 4 has resistance to water flow. It will never happen.

Further, the set potential of the external power supply type anticorrosion device 3, that is, the set potential E of the anticorrosion device main body 31, is set to the anticorrosion potential of the body 2 to be protected (more specifically, the hull 21 occupying most of it) (for example, the hull 21 Is less than -785 mV in the case of iron) and higher than the potential (for example, about -990 mV to -950 mV) of the body 2 to be protected by the galvanic anode 4 when the ship 20 is stopped, for example, -900 mV. When the vessel 20 is stopped, the galvanic anode 4 causes the potential of the corrosion-prevented body 2 to fall below the set potential E, so that the supply of the corrosion-prevention current from the anticorrosion device main body 31 is automatically stopped. During the traveling, the action of the galvanic anode 4 disappears and the potential of the body 2 to be protected is about to exceed the set potential E, so that the supply of the corrosion protection current from the body 31 of the corrosion protection device automatically starts.

Therefore, when the set potential E is set as described above, the anticorrosion action of the external power source type anticorrosion device 3 and the anticorrosion action of the galvanic anode 4 can be completely achieved without any switch operation or addition of other switching means. You will be able to automatically switch to.

Moreover, when the supply of the anticorrosion current from the anticorrosion device main body 31 is stopped while the ship is stopped, the anticorrosion device main body 31 is in a state where only the control circuit 33 is operating, but the power consumption at this time is extremely small. Complete. For example, it is about 175 mA at 24 VDC, which is one digit or more smaller than the case where the anticorrosion current is supplied from the DC power supply device 32. Therefore, since the electric power can be sufficiently supplied from the battery even when the vehicle is berthed for a long period of time, maintenance and the like are not troublesome.

〔The invention's effect〕

As described above, according to the present invention, since the external power supply type anticorrosion device and the galvanic anode attached to the position where the ship is submerged in seawater while the ship is stopped and running on the sea surface, It is possible to effectively prevent electrolytic corrosion of the body to be protected including the hull of the vessel, whether the vessel is running or stopped.

In addition, since it is not necessary to operate the external power supply type anticorrosion device while the ship is stopped, maintenance and the like becomes very easy. In addition, since the galvanic anode naturally comes out above the sea surface during running to prevent its consumption, the life of the galvanic anode can be significantly extended.

Further, if the set potential of the external power supply type anticorrosion device is lower than the anticorrosion potential of the anticorrosion target and higher than the potential of the anticorrosion target by the galvanic anode while the ship is stopped, switch operation or It becomes possible to completely and automatically switch between the anticorrosion action by the external power source type anticorrosion device and the anticorrosion action by the galvanic anode without adding any other switching means.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cathodic protection device for a ship according to an embodiment of the present invention. FIG. 2 is a schematic view of the ship of FIG. 1 viewed from the stern side. FIG. 3 is a schematic plan view showing the vicinity of the stern while the ship of FIG. 1 is traveling. 1 ... Seawater, 2 ... Corrosion-protected object, 3 ... External power supply type corrosion protection device, 4 ... Galvanic anode, 20 ... Ship, 21 ... Ship, 22
...... Propeller shaft, 23 …… Propeller, 24 …… Rudder, 25 …… Stern outer panel, 31 …… Corrosion protection device main body, 32 …… DC power supply unit, 33
...... Control circuit, 34 …… Anode, 35 …… Reference electrode.

Claims (2)

(57) [Claims] 1. An anticorrosion device main body including a DC power supply device, an anode, and a reference electrode, wherein the reference electrode detects the potential of an object to be protected including the hull of a ship so that it approaches a set potential. An external power supply type anticorrosion device that controls the anticorrosion current supplied from the main body of the anticorrosion device, and is attached to a position outside the ship, which is submerged in seawater when the ship is stopped and exposed to the sea surface while traveling. A galvanic protection device for a ship, comprising: a galvanic anode. 2. The set potential of the external power source type anticorrosion device is set to be lower than the anticorrosion potential of the anticorrosion target and higher than the potential of the anticorrosion target by the galvanic anode while the ship is stopped. The cathodic protection device for a ship according to claim 1, wherein: