JPH06344978A - Electric anti-corrosion method in ship - Google Patents

Abstract

PURPOSE:To enable anti-corrosion without a possibility of degrading propelling performance in preventing the corrosion of the contact part of an aluminum alloy hull with a steel made hydrofoil and a propelling pipe by applying anti-corrosive potential lower than pitting potential of the aluminum alloy between both. CONSTITUTION:Stainless steel made hydrofoils 2, 3 are mounted on the front and rear positions of the bottom in a hull 1 of a twin-fuselage hydrofoil made of a corrosion resisting aluminum alloy, and the hull 1 is provided on the rear parts of the respective fuselages 1a with steel made propelling pipes 4 for ejecting rearward water sucked from the bottom. Then, alpha power supply device 7 having a DC power source added by a battery 6 is mounted so that a positive electrode terminal at the power supply device 7 side is connected to the hydrofoils 2, 3 and propelling pipe 4 and negative electrode terminal is connected to the hull 1 respectively. Voltage providing potential lower than the anti-corrosive potential of the corrosion resisting aluminum alloy is applied across both electrode terminals to send corrosion protective current to prevent the hull 1 side in the contact parts of both terminals from corrosion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cathodic protection of a ship, such as a ship, such as a high-speed ship whose hull is made of an aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, there are a galvanic anode method and an external power source method by automatic control as a method for cathodic protection of the hull of a ship.

In the former method, a hull made of steel, which is an object to be corroded, is provided with a base metal (for example, an aluminum alloy,
Zinc alloy anode, etc.) is connected, and the anti-corrosion current is made to flow by utilizing the potential difference generated between this metal and the hull.

In the latter method, the reference electrode is attached to the hull which is the object to be protected, the potential difference generated between the reference electrode and the hull is amplified, and the amplified potential difference is input to the power supply device to make it appropriate. This is a method of using a rectifier with an automatic control function that is designed to supply an anticorrosion current.

[0005]

By the way, when the galvanic anode method is applied to a high-speed ship, it is necessary to attach a large number of galvanic anodes having a large size to the hull which is the corrosion-preventing body, on the outer plate of the hull. There is a problem that the propulsive performance is deteriorated and it becomes a source of generation of cavitation, so that coating film damage and erosion damage due to cavitation occur.

On the other hand, in the external power supply method by automatic control, the reference potential changes due to repeated occurrence and disappearance of bubbles due to high-speed flow in the water contact portion of the verification electrode, causing an abnormal anticorrosive current to flow and prevent corrosion. However, in the case of this external power supply system, there is a problem in that power cannot be supplied when the generator onboard the ship is stopped, and thus the anticorrosion function does not work while the ship is moored.

[0007] Therefore, an object of the present invention is to provide a method of cathodic protection in a ship which can solve the above problems.

[0008]

In order to solve the above problems, a method of cathodic protection in a ship according to the present invention is to use a hull made of an aluminum alloy and a steel hydrofoil and / or propulsion pipe attached to the hull. Is a method for preventing corrosion of the contact part of the contact between the hydrofoil and / or the propulsion pipe and the hull by a direct current power supply device having a storage battery, and a potential lower than the pitting potential of the aluminum alloy. As described above, the anticorrosion method is to apply an anticorrosion potential.

[0009]

According to the above structure, the hull, hydrofoil and / or
Or, since a DC power supply is connected between the propulsion pipe and the anti-corrosion potential is applied between the two, unlike the case where galvanic electrodes are attached to the outer plate of the hull, there is no need to worry about propulsion performance deterioration. There is no need to worry about the occurrence of cavitation, etc. and the resulting erosion.

Further, the power supply device for applying the anticorrosion potential is
Since the storage battery is provided and therefore the voltage is applied from the storage battery even when the ship is moored, the anticorrosion function does not stop.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a hull of a catamaran hydrofoil whose hull is made of a corrosion-resistant aluminum alloy. Stainless steel hydrofoils 2, 3 are provided at the front and rear positions of the bottom of the hull 1. At the rear of each body 1a of the hull 1 mounted, steel propelling pipes 4 for sucking in and discharging the water jet rearward are respectively arranged.

In order to prevent contact corrosion due to the contact between the hull 1 and the hydrofoils 2, 3 and the propulsion pipe 4, a corrosive protection current is constantly applied between them. That is, the DC power source 5 is provided with a power supply device 7 with a storage battery 6 added, and the anode terminals on the power supply device 7 side are connected to the hydrofoils 2, 3 and the propulsion pipe 4, which are steel members, respectively. In addition, the cathode terminal is connected to the hull 1 made of corrosion-resistant aluminum alloy, and between these electrode terminals, a voltage (for example, a base voltage lower than the pitting potential of the corrosion-resistant aluminum alloy) is provided. 2 ± 0.
1 V) is applied. That is, since an anticorrosion current is passed between the hydrofoil 2, 3 and the propulsion pipe 4 and the hull 1,
Corrosion on the side of the hull 1 made of corrosion-resistant aluminum alloy is prevented at the contact portion between the two.

FIG. 3 is a graph showing the relationship between the applied voltage and the anticorrosion rate of the corrosion-resistant aluminum alloy. The corrosion protection rate is represented by the following formula.

Corrosion prevention rate (%) = [(A−B) / A] × 100, where A: corrosion amount without cathodic protection B: corrosion amount with cathodic protection As described above, by setting the applied voltage to 2 ± 0.1 V, it is possible to completely prevent contact corrosion due to contact between the corrosion-resistant aluminum alloy and steel.

The power supply device 7 in the above embodiment is
Since the anticorrosion current can always be supplied from the storage battery 5 stored at the time of its operation, even when the ship is moored,
Can perform cathodic protection.

By the way, in the above-mentioned embodiment, it is explained that the hull and the hydrofoil and the propulsion pipe are protected against corrosion. For example, between the hull and either the hydrofoil or the propulsion pipe. It can also be applied only.

[0017]

As described above, according to the cathodic protection method of the present invention, between the hull and the hydrofoil and / or the propulsion pipe,
Since a DC power supply is connected and an anticorrosion potential is applied between the two, unlike the conventional case where galvanic electrodes are attached to the outer plate of the hull, there is no fear of lowering propulsion performance and cavitation etc. There is no concern about the occurrence of erosion and the resulting erosion.

Further, the power supply device for applying the anticorrosion potential is
Since the storage battery is provided and therefore the voltage is applied from the storage battery even when the ship is moored, the anticorrosion function does not stop.

[Brief description of drawings]

FIG. 1 is a side view of a ship for explaining a cathodic protection method according to an embodiment of the present invention.

FIG. 2 is a partially cutaway front view of the ship according to the embodiment.

FIG. 3 is a graph showing the anticorrosion effect in the same example.

[Explanation of symbols]

 1 Hull 2, 3 Hydrofoil 4 Propulsion tube 5 Storage battery 6 DC power supply 7 Power supply device

Claims (1)

[Claims] 1. A galvanic protection method for preventing corrosion of a contact portion between an aluminum alloy hull and a steel hydrofoil and / or a propulsion pipe attached to the hull, the hydrofoil and / or A cathodic protection method for a ship, in which a DC power supply device having a storage battery is applied between the propulsion pipe and the hull so that the anticorrosion potential is applied so that the electric potential is lower than the pitting potential of the aluminum alloy.