JPH06299377A - Electrolytic corrosion and rust inhibiting method of marine engine and device therefor - Google Patents

Abstract

PURPOSE:To attain a long life of the engine by adopting an external power source system for prevention of electrolytic corrosion of a marine engine, preventing not only electrolytic corrosion, but also generation of rust with a corrosion inhibiting electric current, also removing the rust being already present on and achieving a plating work. CONSTITUTION:An electrolytic corrosion inhibiting device 3 in which a low potential metallic body being capable of allowing sea water to flow is stored is installed in a cooling pipe conduit of the marine engine 1 and a terminal 4 led out from the low potential metallic body is connected to a plus side terminal of the external power source 10 via a resistor 5, and a minus side terminal of the external power source 10 is connected to each member of the engine and other body 2 to be inhibited corrosion to allow a corrosion inhibiting current to flow and to prevent electrolytic corrosion. Dissolved low potential metal is deposited within a cooling pipe conduit of the marine engine 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for preventing galvanic corrosion and rust in a marine engine, and more particularly, to prevent galvanic corrosion of various parts of the engine by seawater, in the vicinity of the intake port of a cooling pipe of the engine. Interposing a low-potential metal body such as zinc,
The low-potential metal body is electrically connected to the positive pole of the power source such as a battery installed outside, and the negative pole of the power source and each part of the engine, which is a body against corrosion and rust prevention, and the steering member are electrically connected. By making a positive connection, a corrosion-preventing current is generated in the body to be electrolyzed and rusted to prevent galvanic corrosion.On the other hand, galvanized zinc etc. adheres to the inner surface of the cooling pipe by plating, causing rust inside and outside the pipe. In addition to removing the film, it is coated to protect it.

[0002]

2. Description of the Related Art Generally, as a means for preventing metal from rusting, a method of coating a surface of the metal to shield it from air, water and moisture is often used. Marine engines, including engines that use seawater as cooling water, are often unusable due to corrosion due to electrolytic corrosion rather than the life of the engine itself, due to electrolytic corrosion caused by seawater.

The electrolytic corrosion means a phenomenon in which, when two kinds of metals are immersed in an electrolyte solution, a battery is formed due to a difference in electrode potential between the two metals, and the metal on the anode side is eluted as ions. Taking the case of a ship as an example, the hull is made of steel, whereas the components that make up the engine, the propeller and the steering member are brass or aluminum bronze, so they are made of a metal with a high ionization tendency. Each engine member, steering member, etc. are in a state where corrosion due to electrolytic corrosion is likely to proceed.

In order to deal with the above-mentioned galvanic corrosion, there is a means known as galvanic protection. In other words, it is a method of canceling the corrosion current by continuously flowing an anticorrosion current that overcomes the current flowing from the metal surface in the opposite direction.

The galvanic protection method includes a galvanic anode method and an external power source method. In the galvanic anode method, a metal to be corroded and a lower potential metal such as aluminum is used for iron. This is a method in which an anode made of magnesium, zinc, or the like is connected to an electric wire, and the current generated by the local battery action of both metals is used as a corrosion protection current. On the other hand, the external power supply method generally installs an electrode in a corrosive liquid or soil and connects it to the positive terminal of the external DC power supply and the corrosion-resistant terminal to the negative terminal to protect the electrode from corrosion. This is a method in which an anticorrosion current is made to flow toward the metal to be processed.

In the case of marine engines, the galvanic anode method is often used, and galvanized zinc is attached to the outer surface of the engine to prevent galvanic corrosion. In particular, by using high-purity zinc with a low content of impurities, it is possible to maintain an anode potential within -1.0 V throughout the period of use, which is approximately 0.25 V with respect to the corrosion protection potential of steel.
Therefore, it becomes possible to generate a sufficient corrosion protection current in the sea.

[0007]

However, in the case of the galvanic anode method as described above, even if a bolt-shaped or plate-shaped zinc is partially attached to the marine engine, the total amount of the zinc itself is too small. Since there is no zinc, the zinc disappears in about 5 to 8 months, and zinc must be frequently replenished. In reality, this replenishment is often forgotten, and there is a problem that the anticorrosion effect cannot be sufficiently obtained. It was

Further, since zinc is partially attached to the marine engine, only local prevention of galvanic corrosion is achieved, and conventional low potential metal bodies such as zinc attached to the outer surface of the engine are electrically charged. The present situation is that only corrosion is prevented, and there is no action of removing rust from each part of the engine or preventing the formation of rust, and the dissolved zinc is released to the outside as it is.

Therefore, the present invention solves the problems of the conventional method and apparatus for preventing galvanic corrosion in a marine engine, and in particular, by adopting the external power supply system, it is only necessary to prevent galvanic corrosion. Instead, the corrosion-preventing current prevents the generation of rust due to electrolytic corrosion and removes the existing rust.
Moreover, it is an object of the present invention to provide an electrolytic corrosion / rust preventing method and apparatus capable of extending the life of an marine engine by performing a plating operation.

[0010]

In order to achieve the above object, the present invention provides a cooling pipe of an marine engine with an electrolytic corrosion prevention device in which a low-potential metal body through which seawater can flow is housed. The terminal derived from the potential metal body is connected to the positive side terminal of the external power source via a resistor, and the negative side terminal of the external power source is connected to each member constituting the engine or other corrosion-resistant body to prevent corrosion current. The present invention provides a method for preventing galvanic corrosion and rust in a marine engine, in which the galvanic current is applied to prevent galvanic corrosion of various parts of the engine or other corroded objects by this galvanic protection current. Further, the melted low-potential metal adheres to the inside of the cooling pipe.

The above-mentioned electrolytic corrosion preventing device is provided with a predetermined casing, a low potential metal body housed in the casing and having a hole penetrating along the longitudinal direction thereof, and a conductive material derived from the low potential metal body. A semi-cylindrical casing having an electrically conductive terminal and a resistor attached to the electrically conductive terminal, the upper half of which is opened, and the casing is housed inside the casing.
A cylindrical low-potential metal body in which a hole penetrating along the longitudinal direction is formed, a lid member that covers the opening portion of the casing, and a conductive terminal that is led from the low-potential metal body onto the lid member. A resistor attached to the conductive terminal. This resistor is provided with an indicator lamp that lights up when energized.

A plurality of grooves extending in the longitudinal direction are formed on the inner wall of the low-potential metal body, and an iron plate is embedded along the longitudinal direction inside the low-potential metal body. A mesh wire mesh is fixed to the outer peripheral surface of the iron plate. The outer peripheral portion of the low-potential metal body is covered with an insulating film. Further, a check valve for preventing backflow of seawater when the ship is stopped is provided in the connection pipe on the seawater input side of the electrolytic corrosion prevention device.

A container into which seawater is injected is provided separately from the external power source, a low potential metal body is immersed in the container, and the low potential metal body is connected to the positive side terminal of the external power source. The other electric equipment mounted on the hull and the low-potential metal body are connected by a ground wire.

[0014]

According to the present invention having the above-described structure, according to the electrolytic corrosion / rust prevention method and the apparatus thereof, when the cooling water pump is driven along with the start of the marine engine, the seawater taken in as the cooling water is removed. When entering the electrolytic corrosion prevention device and flowing through the holes of the low-potential metal body, the battery action using seawater as an electrolyte solution causes the parts of the engine, which are the metal on the anode side, to become ions and become easily eluted. , The current flowing from the low-potential metal body due to the difference in the electrode potential flows to the positive side terminal of the external power source through the resistor, and the battery action is performed from the negative side terminal of the external power source to each part of the engine and other corrosion-protected objects. Corrosion-preventing current, which is sufficient to overcome this, is continuously supplied from a direction opposite to the direction of the current based on. This corrosion-prevention current prevents electrolytic corrosion of each part of the engine and other corrosion-protected objects, and the partially dissolved low-potential metal body adheres to the inside of the cooling water pipe by plating and removes rust inside and outside the pipe. It has the effect of coating and protecting. Further, it also has a function of preventing adhesion of oysters and shellfish to the outside of the hull.

Further, the iron plate embedded inside the low-potential metal body and the mesh wire mesh fixed to the outer peripheral surface of the iron plate promotes the melting of the low-potential metal body and insulates the outer peripheral portion of the low-potential metal body. The low potential metal body is sequentially melted from the inner side to the outer side by being coated with the conductive film. Further, the resistor attached to the conductive terminal has a function of keeping the current flowing to the external power supply constant, and at the time of energizing the resistor, the indicator lamp is turned on to confirm the presence or absence of energization.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment of a method for preventing galvanic corrosion and rust in a marine engine and an apparatus therefor according to the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram for generally explaining the basic concept of the present invention. Reference numeral 1 is a marine engine as a corrosion-resistant body, and 2 is another corrosion-resistant body. This corrosion resistant body 2
Examples include steering members and propellers.

Reference numeral 3 denotes an electrolytic corrosion prevention device which is a characteristic structure of the present invention. Terminals 4 are provided on the outer peripheral surface of the electrolytic corrosion prevention device 3.
Is attached. Reference numeral 5 is a resistor attached to the terminal 4. The specific structure of the electrolytic corrosion prevention device 3 is shown in FIG.
It will be described later with reference to FIG.

The marine engine 1 and the electrolytic corrosion prevention device 3 are connected by a connecting pipe 6. Reference numeral 7 is an inlet for seawater, and 8 is an outlet for the same. Further, a check valve 9 is arranged between the seawater inlet 7 and the electrolytic corrosion prevention device 3.

Reference numeral 10 denotes an external power source composed of a battery. A positive side terminal of the external power source 10 and the resistor 5 are connected by a wiring 11, and a negative side terminal of the external power source 10 and the marine engine 1 and other objects. The anticorrosion body 2 is connected by wirings 12 and 13, respectively. Further, seawater 15 is poured into a separately provided container 14, and the low-potential metal body 16 is immersed in this seawater 15. Reference numeral 17 denotes another electric device mounted inside the hull, and the electric device 17 and the low-potential metal body 16 are connected by a ground wire 18.

Next, the structure of the electrolytic corrosion preventing device 3 will be described with reference to FIGS. Reference numeral 21 in the drawing denotes a semi-cylindrical casing having an open upper half, and the casing 21 is fixed to a pedestal 22 in a horizontal position. Reference numeral 23 denotes a lid member for covering the opening portion, and the flange portion 2 of the casing 21.
1a and the flange portion 23a of the lid member 23 are tightening bolts 2
It is fixed by 4, 24. FIG. 4 shows the lid member 23.
It shows a state in which the opening is exposed by detaching.

Inside the casing 21, a low potential metal body 25 is housed. This low-potential metal body 25 has a hole 2 penetrating along the longitudinal direction as shown in FIGS.
6 has a cylindrical shape, and a plurality of grooves 27 extending in the longitudinal direction are formed on the inner wall portion thereof. Further, a hole portion 28 for inserting a bolt as a terminal is opened on the upper surface of the low potential metal body 25.

Further, as shown in FIGS. 2 and 6, an iron plate 29 is embedded along the longitudinal direction inside the low potential metal body 25, and the mesh wire mesh 3 is provided on the outer peripheral surface of the iron plate 29.
0 is fixed. The outer peripheral portion of the low-potential metal body 25 is covered with an insulating film 35. The iron plate 29 may be embedded not only over the entire inner periphery of the low-potential metal body 25 as shown, but also partially.

At both ends of the casing 21, lids 31,
32 is detachably attached. This lid 31, 32
Are connected to connection pipes 33 and 34, respectively, and the check valve 9 is provided in one of the connection pipes 33.

A terminal 4 for wiring connection is inserted and fixed from the upper surface of the lid member 23. The terminal 4 is formed of a conductive metal body such as a bolt, and the tip of the terminal 4 penetrates the low-potential metal body 25 and projects into the inner hollow portion. The resistor 5 attached to the terminal 4 is provided with a display lamp 5a that lights up when energized.

As the low-potential metal body 25, for example, zinc node (ZINNOD) made of high-purity zinc or zinc alloy is used.
E) and the like are suitable, but it is also possible to employ a metal such as magnesium or aluminum. The connection pipe 33 serves as an inlet for seawater, and the connection pipe 34 serves as an outlet for allowing seawater to flow through the hole 26 of the low-potential metal body 25.

A mode of using the electrolytic corrosion prevention device 3 will be described below. FIG. 7 shows the first embodiment, and the electrolytic corrosion prevention device 3 is provided in the cooling pipe line near the water intake of the marine engine 1. That is, the connecting pipe 33 is connected to the Kingston valve 36 side, and the connecting pipe 34 is connected to the cooling water pump 37 side.
Are connected.

It is required that the electrolytic corrosion prevention device 3 and the cooling pipe connecting the engine parts are insulated. Therefore, although there is no problem when the cooling pipe is a rubber hose, when adopting a pipe using a flange or the like, it is necessary to dispose the flange portion at a position at least 1 to 2 m away from the electrolytic corrosion prevention device 3.

Reference numeral 10 denotes an external power source, and the resistor 5 attached to the terminal 4 and the positive side terminal of the external power source 10 are connected by a wiring 11. The negative side terminal of the external power source 10 is connected via a resistor box 38. The cooling water pump 37,
The wirings 12a and 1 are respectively connected to the cooling water tank 39 and the exhaust pipe 40.
They are connected using 2b and 12c. In the figure, 41 is a screw, 42 is a steering member, and 43 is a shoe piece, and these members and the marine engine 1 are connected using a wiring 12d.

The operation of the first embodiment having such a configuration will be described below. First, when the marine engine 1 is started and the cooling water pump 37 is driven, the seawater taken in from the Kingston valve 36 enters the electrolytic corrosion prevention device 3 through the connecting pipe 33 and is stored in the electrolytic corrosion prevention device 3. When flowing through the hole 26 of the low-potential metal body 25, the low-potential metal body 25 comes into contact with the low-potential metal body 25, further reaches from the connection pipe 34 to the cooling water pump 37 to the cooling water tank 39, and is composed of fresh water by the indirect cooling action. After cooling the cooling water, it enters the exhaust pipe 40, where it takes heat and is discharged to the outside together with smoke.

At this time, due to the battery action using seawater as the electrolyte solution, corrosion of the engine portion, which is the metal on the anode side, is likely to proceed due to electrolytic corrosion that is eluted as ions, but in this example, the difference in electrode potential is caused. Causes the current flowing from the low-potential metal body 25 to flow through the resistor 5 and the wiring 11 to the positive side terminal of the external power source 10, and from the negative side terminal of the external power source 10 to the cooling water pump 37 and the cooling water as the corrosion-resistant body. Corrosion-preventing current, which is sufficient to overcome this, continuously flows into the tank 39 and the exhaust pipe 40 from the direction opposite to the direction of the current based on the cell action. This corrosion-prevention current prevents electrolytic corrosion of each part of the engine and the steering member, and the partially melted low-potential metal body 25 adheres to the inside of the cooling water pipe by plating to remove rust inside and outside the pipe, After that, it has a function of coating and protecting.

During such an operation, the low-potential metal body 25 gradually dissolves from the plurality of grooves 27, 27 formed in the inner wall portion, and gradually disappears even after many years of use without blocking the seawater flow passage. . Further, the iron plate 29 embedded in the low-potential metal body 25 and the mesh wire net 30 fixed to the outer peripheral surface of the iron plate 29 enhance the conductivity of the low-potential metal body 25 and promote the melting thereof. Low potential metal body 25
By covering the outer peripheral portion of the with the insulating film 35, the low-potential metal body 25 is sequentially melted from the inside to the outside.

The resistor 5 attached to the terminal 4 has the function of keeping the current flowing through the external power source 10 constant.
In this embodiment, a constant current of 0.02 to 0.03 amperes is set to always flow. When the resistor 5 is energized, the display lamp 5a is turned on, so that the presence or absence of energization can be confirmed.

FIG. 8 shows a second embodiment, which has the same basic configuration as that of the first embodiment and is designated by the same reference numeral. In this embodiment, the resistor 5 attached to the terminal 4 and the positive side terminal of the external power source 10 are connected by the wiring 11, and the negative side terminal of the external power source 10 is directly connected to the steering member 42 and the steering member 42 via the wiring 12e. Shoe piece 43
It is connected to the.

According to the second embodiment, in the same operation mode as that of the first embodiment, an anticorrosion current flows from the negative side terminal of the external power source 10 to the steering member 42 side, and the electrolytic corrosion of the steering member is caused. Of the cooling water pump 37, the cooling water tank 39, the exhaust pipe 40, etc., through the wiring 12d toward the marine engine 1 side, and the anticorrosion current that overcomes the current based on the battery action continuously flows. Electrolytic corrosion of each part of the engine and the steering member is prevented.

In the case of a small boat of 380 horsepower or less,
Since it is customary to electrically connect the minus side of the external power source and the starter motor part of the engine, in the case of such a small boat, the external power source 10 and each part of the engine are electrically connected as in the first embodiment. You don't have to make a physical connection. Further, in the case of a large ship in which the negative side of the external power source 10 is not electrically connected to each engine part, it is necessary to wire as in the first embodiment described above. Even in the case of a small ship, the external power source 10 and each engine part may be electrically overlapped and connected.

In the description of the first and second embodiments described above, when seawater in the engine cooling pipe above the water line is drained from the inflow port 7 in FIG. 1 when the ship is stopped, oxidation will occur inside the cooling pipe. Since there is a risk that corrosion will progress, in this embodiment, as shown in the conceptual diagram of FIG. 1, a check valve 9 is provided between the seawater inlet 7 and the electrolytic corrosion prevention device 3. This eliminates the backflow of seawater from the cooling pipe to the inlet 7 side,
Even when the ship is stopped, the inside of the cooling pipe is always filled with seawater, and a corrosion protection current flows and at the same time corrosion due to oxidation can be prevented.

On the other hand, various electric devices such as a communication device and a fish finder are loaded on the hull, and it is customary to ground these electric devices to the marine engine 1. However, when the electrolytic corrosion preventing device using the external power supply system as in the present embodiment is used, the current flowing from the ground has an adverse effect on preventing the electrolytic corrosion of each part of the engine.
As shown in FIG. 2, a separately prepared low-potential metal body 16 is immersed in the seawater 15 injected into the container 14 to connect the low-potential metal body 16 and the positive side terminal of the external power source 10, while Since the electric device 17 and the low-potential metal body 16 are connected by the ground wire 18, the adverse effect of the ground current can be eliminated and the effect of removing noise can be obtained.

[0038]

According to the present invention described above, when the seawater used as the cooling water for the marine engine flows through the holes of the low potential metal body in the electrolytic corrosion prevention device, the low potential is caused by the difference in the electrode potential. The current flowing from the metal body flows through the resistor to the positive side terminal of the external power source, and from the negative side terminal of the external power source toward each part of the engine and other corrosion-resistant body, the direction of the current based on the battery action is opposite. Corrosion-preventing current, which is sufficient to overcome this, continuously flows in from the direction, and this corrosion-preventing current can effectively prevent galvanic corrosion of various parts of the engine and other corroded objects. Further, it also has a function of preventing adhesion of oysters and shellfish to the outside of the hull.

According to the present invention, the large low-potential metal body is housed in the casing, so that a sufficient and sufficient amount of low-potential metal body is provided on the hull to prevent galvanic corrosion over a long period of several years. Therefore, it is possible to obtain an effect that the low potential metal body does not need to be replaced frequently and the maintenance is easy.

Further, the resistor attached to the conductive terminal makes the current flowing to the external power source constant, and the indicator lamp lights up when the resistor is energized to confirm the presence or absence of energization. Further, the dissolution of the low potential metal body is promoted by the iron plate embedded inside the low potential metal body and the mesh wire mesh fixed to the outer peripheral surface of the iron plate, and the outer peripheral portion of the low potential metal body is made of an insulating film. By coating,
The low-potential metal body is melted in order from the inner side to the outer side, and the effect of not wasting materials or the like is exerted.

In particular, in the present invention, by adopting the external power supply system, not only the electrolytic corrosion is prevented, but also the partially dissolved low-potential metal body adheres to the inside of the cooling water pipe by the plating action and the inside and outside of the pipe. Since the rust is removed and the subsequent coating is protected, the life of the marine engine can be extended.

[Brief description of drawings]

FIG. 1 is a conceptual diagram for generally explaining the basic concept of the present invention.

FIG. 2 is a cross-sectional view of an essential part for explaining the configuration of an electrolytic corrosion prevention device adopted in the present invention.

3 is a perspective view of the electrolytic corrosion prevention device of FIG.

4 is a perspective view showing a state in which a lid member of the electrolytic corrosion prevention device of FIG. 2 is removed.

FIG. 5 is a perspective view showing a structural example of a low-potential metal body used in this example.

6 is a cross-sectional view of a main part of the low-potential metal body in FIG.

FIG. 7 is a schematic diagram generally showing a first embodiment of the present invention.

FIG. 8 is a schematic diagram generally showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Marine engine 2 ... Corrosion preventive body 3 ... Electrolytic corrosion prevention device 4 ... Terminal 5 ... Resistor 6 ... Connection pipe 7 ... Inflow port 8 ... Discharge port 9 ... Check valve 10 ... External power supply 14 ... Container 16 ... Low potential Metal body 17 ... Other electric equipment 18 ... Ground wire 21 ... Casing 22 ... Pedestal 23 ... Lid member 25 ... Low-potential metal body 26 ... Hole 27 ... Groove 28 ... Hole part 29 ... Iron plate 30 ... Mesh wire mesh 31, 32 ... Lid Body 33, 34 ... Connection pipe 35 ... (Insulating) film 36 ... Kingston valve 37 ... Cooling water pump 38 ... Resistance box 39 ... Cooling water tank 40 ... Exhaust pipe 41 ... Screw 42 ... Steering member 43 ... Shoe piece

Claims (13)

[Claims] 1. A marine engine cooling pipe is provided with an electrolytic corrosion prevention device containing a low-potential metal body through which seawater can flow.
The terminal derived from the low-potential metal body is connected to the positive side terminal of the external power source through a resistor, and the negative side terminal of the external power source is connected to each member constituting the engine or another corrosion-resistant body. A method for preventing galvanic corrosion and rust in a marine engine, characterized in that a galvanic protection current is applied to prevent galvanic corrosion of various parts of the engine or other corroded objects by the galvanic protection current. 2. The corrosion preventing current prevents electrolytic corrosion of various parts of the engine or other objects to be protected, and the melted low-potential metal adheres to the inside of the cooling pipe. Method for Preventing Electrolytic Corrosion and Rust in Marine Engines of Japan 3. A low-potential metal body having a predetermined casing in the middle of a cooling pipe line of the marine engine and a hole housed inside the casing and penetrating along the longitudinal direction thereof.
An electrolytic corrosion and rust preventive device for a marine engine, characterized in that an electrolytic corrosion preventive device including a conductive terminal led out from a low-potential metal body and a resistor attached to the conductive terminal is provided. 4. A cylindrical shape in which a half-cylindrical casing having an upper half opened and a hole which is housed inside the casing and which penetrates in the longitudinal direction are formed in the middle of a cooling pipe line of the marine engine. Of the low potential metal body, a lid member for covering the opening of the casing, a conductive terminal led out from the low potential metal body onto the lid member, and a resistor attached to the conductive terminal. An anti-corrosion / rust prevention device for marine engines, which is equipped with an anti-corrosion device. 5. The inner wall portion of the low-potential metal body is formed with a plurality of grooves extending in the longitudinal direction.
Electrolytic corrosion and rust prevention device for the marine engine described. 6. The galvanic corrosion / rust prevention device for a marine engine according to claim 3, 4, or 5, wherein a hole for inserting a bolt as a terminal is opened on the upper surface of the low-potential metal body. 7. The anti-corrosion / rust prevention device for a marine engine according to claim 3, 4, 5, or 6, wherein an iron plate is embedded along the longitudinal direction inside the low-potential metal body. 8. The electrolytic corrosion and rust preventive device for a marine engine according to claim 7, wherein a mesh wire net is fixed to the outer peripheral surface of the iron plate. 9. The electrolytic corrosion / rust prevention device for a marine engine according to claim 3, 4, 5, 6, 7, or 8, wherein an outer peripheral portion of the low-potential metal body is covered with an insulating film. 10. A check valve for preventing backflow of seawater when the ship is stopped is provided in a connection pipe on the seawater input side of the electrolytic corrosion prevention device. Electrolytic corrosion and rust prevention device for the marine engine described. 11. A resistor provided on the conductive terminal is provided with an indicator lamp that lights up when energized.
Electrolytic corrosion and rust prevention device for marine engine according to 4, 5, 6, 7, 8, 9, 10. 12. A low-potential metal body having a predetermined casing, a low-potential metal body housed inside the casing and having a hole penetrating along the longitudinal direction formed in the middle of a cooling pipe line of the marine engine, and a low-potential metal body. A conductive terminal derived from the above, and an electrolytic corrosion prevention device comprising a resistor attached to the conductive terminal is provided, and a container into which seawater is injected is provided separately from the external power source, A low-potential metal body is immersed in a container, the low-potential metal body is connected to the positive side terminal of the external power source, and other electrical equipment mounted on the hull is connected to the low-potential metal body by a ground wire. The electrolytic corrosion and rust prevention device in the marine engine characterized by the above. 13. A cylindrical shape in which a half-cylindrical casing having an upper half opened and a hole which is housed inside the casing and which penetrates in the longitudinal direction are formed in the middle of a cooling pipe line of a marine engine. Of the low potential metal body, a lid member for covering the opening of the casing, a conductive terminal led out from the low potential metal body onto the lid member, and a resistor attached to the conductive terminal. An anticorrosion device is provided, a container into which seawater is injected is provided separately from the external power source, a low potential metal body is immersed in the container, and the low potential metal body and the positive side terminal of the external power source. An electrical corrosion and rust preventive device for a marine engine, which is characterized in that the low potential metal body is connected to another electric device equipped on a hull with a ground wire.