JP2020026558A - Structure corrosion prevention method and device - Google Patents

Abstract

To provide a corrosion prevention method that can prevent a top coat on a conductive coating from deteriorating, and has high reliability for a long time.SOLUTION: On a structure 1, an insulation coating 2 is formed. On the insulation coating 2, a conductive coating 3 is formed. To the conductive coating 3, a first anode 4 is electrically connected. On the conductive coating 3, a top coat 5 is formed. On the top coat 5, a second anode 6 is installed. To the first anode 4, a DC voltage is applied, and to the second anode 6, a DC voltage is applied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method and an apparatus for preventing corrosion of a structure exposed to the atmosphere.

Structures such as walls, stairs, gantry, bridges, and tanks of industrial plants that are exposed to the atmosphere are often made of steel. Steel contains impurities such as carbon, and the surface of the steel is an aggregate of countless micro batteries (having an anode and a cathode). When the steel surface comes into contact with atmospheric moisture or rainwater, cations (corrosives Fe ²⁺ ) move from the anode side to the cathode side via atmospheric moisture or rainwater, and the cations exchange with oxygen and the like on the cathode side. Reacts and generates rust.

  In order to prevent the generation of rust, an anticorrosion method by coating a structure exposed to the atmosphere with a weather-resistant paint is widely used. However, if a part of the structure is exposed due to a coating defect such as uneven coating, physical damage, deterioration of the paint, or the like, the exposed part of the structure is corroded. For this reason, repair or repainting is repeated periodically, especially in a salt-affected area near the coast, in a short period of time.

  In order to extend the period until re-coating, heavy-duty anti-corrosion coating consisting of undercoating, intermediate coating, and topcoating has been established as a general coating technique. However, heavy-duty anticorrosion coating not only complicates construction but also causes a large cost increase.

  In order to solve the above-mentioned problems of heavy corrosion protection coating, a galvanic anode method using zinc or the like or an external power supply method has been proposed. The galvanic anode system is used for underground structures and ships, but has a fundamental problem of exhaustion of the anode, and its use is limited. Many proposals have been made for the external power supply type of anti-corrosion technology, but the water film formed on the painted surface often has unevenness. There is a problem in controlling the amount of current that does not cause the problem, and there are many unsolved problems in economy and simplicity.

  In the external power supply type of cathodic protection technology, an insulating coating is formed on a structure, and a conductive coating is formed on the insulating coating with the aim of securing the flow path of the anticorrosion current described above. An anticorrosion method is disclosed in which an anode is electrically connected to a conductive film, an overcoat film is formed on the conductive film, and a voltage is applied to the conductive film (see Patent Document 1).

  According to the invention of Patent Literature 1, since a DC voltage is applied to the conductive coating film, an anticorrosion current can flow between the conductive coating film and the structure in a direction opposite to the corrosion current, and the structure can be corroded. Can be suppressed. Further, since the anticorrosion current flows through the conductive coating film, a flow path of the anticorrosion current can be secured.

JP-A-11-314309

  However, in the invention of Patent Document 1, when a DC voltage is applied to the conductive coating, there is a problem that the glossiness of the overcoat on the conductive coating is reduced, and the overcoat is deteriorated. . Deterioration of the overcoat film adversely affects the underlying conductive coating film and the underlying insulating coating film.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an anticorrosion method and apparatus which can prevent deterioration of an overcoat film on a conductive coating film and have high reliability over a long period of time. And

  In order to solve the above problem, one embodiment of the present invention is to form an insulating coating on a structure, form a conductive coating on the insulating coating, and form a first coating on the conductive coating. An anode is electrically connected, an overcoat film is formed on the conductive coating film, a second anode is provided on the overcoat film, a DC voltage is applied to the first anode, and a DC voltage is applied to the second anode. This is a method of preventing corrosion of a structure to which a voltage is applied.

  Another aspect of the present invention provides a structure in which an insulating coating is formed, a conductive coating is formed on the insulating coating, and a topcoat is formed on the conductive coating. A first anode electrically connected to the conductive coating, a second anode provided on the overcoat of the structure, and a DC voltage applied to the first anode, and a DC voltage applied to the second anode. And a power supply device for applying a voltage.

  According to the present invention, the second anode is installed on the overcoat film formed on the conductive coating film, and a DC voltage is applied to the overcoat film, so that the overcoat film is electrolytically protected and the glossiness of the overcoat film is deteriorated. Is suppressed. For this reason, the life of the entire painted surface can be extended, and highly reliable cathodic protection can be performed over a long period of time.

It is a schematic diagram of the anticorrosion device of one Embodiment of this invention. It is a figure showing an example of an interval of the 1st anode and an interval of the 2nd anode. FIG. 3 is a circuit diagram of a constant voltage control unit of the power supply device according to the embodiment. It is a circuit diagram of a constant current control unit of the power supply device of the present embodiment.

Hereinafter, a method and an apparatus for preventing corrosion of a structure according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the structure anticorrosion method and apparatus of the present invention can be embodied in various forms, and are not limited to the embodiments described in this specification. This embodiment is provided with the intent to make the disclosure of the specification sufficient so that those skilled in the art can fully understand the scope of the invention.
(Configuration of anticorrosion device)

  FIG. 1 is a schematic diagram of an anticorrosion device according to one embodiment of the present invention. Reference numeral 1 denotes a structure, 4 denotes a first anode, 6 denotes a second anode, and 7 denotes a power supply device. First, the structure 1 will be described.

  The structure 1 is made of steel or the like. An insulating coating film 2 is formed on the entire surface of the structure 1. The paint constituting the insulating coating film 2 is an organic resin, epoxy, urethane, acrylic, or the like, which has been used as a material for the paint.

  On the insulating coating film 2, a conductive coating film 3 that can conduct electricity is formed. The paint constituting the conductive coating film 3 is made of an organic resin such as epoxy, urethane, or acryl, which has been used as a material for the paint, and is mixed with conductive particles or powder such as carbon particles. This is a conductive paint adjusted to. If necessary, a carbon powder may be used in combination with a metal powder such as nickel, aluminum, and zinc. The conductivity of the conductive coating film 3 is preferably 10 Ω / cm to 10,000 Ω / cm, preferably 20 Ω / cm to 1,000 Ω / cm, more preferably 20 Ω / cm to 500 Ω / cm in an air environment. is there.

  The conductive coating 3 is formed on a portion 100 of the insulating coating 2. Rust is likely to occur in the discontinuous portion of the structure 1, that is, the non-planar portion 1a, in the short term. The conductive coating 3 is formed on a portion 100 of the insulating coating 2 including the non-planar portion 1a.

  The first anode 4 is electrically connected to the conductive coating 3. The first anode 4 supplies electric power to the conductive coating 3. The first anode 4 is made of a thin plate of stainless steel or copper. A DC voltage of, for example, 3 to 4 V is applied to the first anode 4, and a current of, for example, 0.01 to 0.1 mA flows.

  The first anode 4 attaches the first anode 4 on the insulating coating 2, and then forms the conductive coating 3 on the insulating coating 2, so that the conductive coating 3 is electrically connected. The first anode 4 may be attached on the conductive coating 3 to be electrically connected to the conductive coating 3.

  A weather-resistant or insulating overcoat film 5 is formed on the remaining portion 200 of the conductive coating film 3 and the insulating coating film 2 (the portion where the conductive coating film 3 is not formed). As the paint constituting the overcoat film 5, a paint which has been used as a paint for the outer surface of the structure 1 is used. For example, an insulating paint such as a vinyl-modified epoxy resin paint obtained by increasing the molecular weight of an epoxy resin using a modifier, or a hydrophobic paint such as an aqueous self-crosslinking acrylic emulsion paint can be used.

  The second anode 6 is provided on the overcoat 5 so as to be exposed to the atmosphere. The second anode 6 supplies power to the overcoat film 5. The second anode 6 is made of, for example, aluminum. A DC voltage of, for example, 20 to 50 V is applied to the second anode 6, and a current of, for example, 0.05 to 1.00 mA flows.

  The first anode 4 is connected to a terminal 8b of the power supply device 7. The second anode 6 is connected to a terminal 8a of the power supply device 7. The terminal 8 c of the power supply 7 is grounded by the ground 10. The structure 1 is grounded by a ground 9. Note that the terminal 8c of the power supply device 7 can be connected to the structure 1.

  The power supply device 7 applies an independent voltage and current to each of the first anode 4 and the second anode 6. Maximum output voltage of DC applied by power supply device 7 to second anode 6: The maximum output voltage of DC applied by power supply device 7 to first anode 4 is 3 to 17: 1. The configuration of the power supply device 7 will be described later.

  As described above, a relatively high voltage is applied to the second anode 6 using the water film on the surface of the overcoat film 5 as a conductive medium, thereby achieving a wide range of corrosion protection. Also, since the effective current is lower than the output current, a relatively high current value is set to increase the accuracy of anticorrosion. Since the first anode 4 using the conductive coating film 3 as a conductive medium is not greatly affected by the atmospheric environment, a relatively low voltage and current can be set in consideration of excessive corrosion prevention. The detailed configuration of the power supply device 7 will be described later.

As shown in FIG. 2, the number of the first anodes 4 and the second anodes 6 is determined by the shape and area of the structure 1 to be covered, and is usually plural. The effective range of the first anode 4 is, for example, a radius of 7 m of the portion of the conductive coating 3 centered on the first anode 4. The effective range of the second anode 6 is, for example, a radius of 2.5 m to 3.0 m of the portion of the overcoat film 5 centered on the second anode 6. An interval P1 between adjacent first anodes 4 (P1 = 7 m × 2) is longer than an interval P2 between adjacent second anodes 6 (P2 = 2.5 m to 3.0 m × 2).
(Effect of anticorrosion device)

  According to the anticorrosion device of the present embodiment, the following effects can be obtained.

  Since a DC voltage is applied to the first anode 4, an anticorrosion current can flow between the conductive coating 3 and the structure 1 in a direction opposite to the corrosion current, and the corrosion of the structure 1 can be suppressed. .

  When a DC voltage is applied to the first anode 4, the glossiness of the overcoat 5 on the conductive coating film 3 is reduced, and the overcoat 5 is deteriorated. However, since the second anode 6 is provided on the overcoat film 5 and a DC voltage is applied to the second anode 6, the overcoat film 5 is electrically eroded and the deterioration of the glossiness of the overcoat film 5 is suppressed. For this reason, the life of the entire painted surface can be extended, and highly reliable cathodic protection can be performed over a long period of time.

  Since an independent anti-corrosion current is supplied to the first anode 4 and the second anode 6 independently, each of the anti-corrosion using the water film on the overcoat film 5 as a conductive medium and the anti-corrosion using the conductive coating 3 as a conductive medium. Function is improved. It is easy to optimize the conductivity of the conductive coating film 3, and in addition to reducing the cost of the coating material, the deterioration and deterioration of the coating film are improved.

Since the conductive coating 3 is formed on a portion 100 of the insulating coating 2, that is, on the portion 100 including the discontinuous non-planar portion 1 a in which rust easily occurs in a short period of time, the conductive coating 3 is formed. 3 can be reduced, and the economy can be secured. On the other hand, when the conductive coating film 3 is formed on the entire surface of the insulating coating film 2 as in the conventional case, the cost of the paint and the painting work is relatively high, and there is a problem in economy.
(Configuration of power supply device)

  The power supply device 7 of the present embodiment includes a constant voltage control unit 41 (see FIG. 3) and a constant current control unit 42 (see FIG. 4). The constant voltage control unit 41 includes one for the first anode 4 and one for the second anode 6. The configuration of the constant voltage control unit 41 for the first anode 4 and the configuration of the constant voltage control unit 41 for the second anode 6 are substantially the same. The constant current control unit 42 may be arranged in the case of the power supply device 7 or may be built in the first anode 4 and the second anode 6.

  FIG. 3 is an example of a circuit diagram of the constant voltage control unit 41. The power supply plug 11 is connected to a commonly used AC power supply of 100 to 200 V, the input AC voltage is stepped down by the transformer 14, and is converted to DC by the rectifier circuit 15. Here, the fuse 12 and / or the varistor 13 may be inserted into the primary side of the transformer 14 in order to prevent the destruction of the constant voltage control unit 41 due to the excessive voltage or the excessive current. The output voltage on the secondary side of the transformer 14 is set to 3 to 4 V (for the first anode 4) or 20 to 50 V (for the second anode 6). The regulator 18 finely adjusts the output voltage to make the output voltage of the constant voltage control unit 41 constant. The capacitors 16, 17, 19 and 20 before and after the regulator 18 suppress and absorb voltage fluctuations and / or disturbance noise, and assist in stabilizing the output voltage. Furthermore, the light emitting diode 21 and the resistor 22 are inserted in parallel between the anode and the cathode of the output part of the constant voltage control unit 41, and the operation of the constant voltage control unit 41 is visually displayed by the light emission of the light emitting diode 21. I do.

  FIG. 4 is an example of a circuit diagram of the constant current control unit 42. 27 is a load resistance. The power controlled to a constant voltage by the constant voltage control unit 41 is applied to the transistor 24. The transistor 24, the resistor 23, the Zener diode 25, and the resistor 26 supply electric power to the load 27 by controlling the current not to exceed a predetermined value. LED 29 indicates the input of power. The resistor 28 keeps the current flowing through the LED to a minimum.

  The external power supply of the power supply device 7 is not limited to a commercial power supply. In order to secure long-term corrosion protection for a tower in a depopulated area where commercial power cannot be obtained, a solar battery or a wireless power supply device can be used in addition to the commercial power. The wireless power supply device converts a current into an electromagnetic wave on a power transmission side, receives an electromagnetic wave from an antenna on a power receiving side, and converts the electromagnetic wave into a current with a rectifier circuit.

  As the first anode 4, a copper plate of 20 mm × 50 mm × t2 mm was used. After forming the insulating coating film 2 on the structure 1, the first anode 4 was attached to the insulating coating film 2 with a double-sided tape. The distance between the first anodes 4 was set to 14 m. Thereafter, a conductive coating 3 was formed on a portion 100 of the insulating coating 2 so as to be electrically connected to the first anode 4.

  An overcoat film 5 was formed on the remaining portion 200 of the insulating coating film 2 where the conductive coating film 3 was not formed, and on the conductive coating film 3. As the second anode 6, a 50 mm × 50 mm × 15 mm aluminum rectangular parallelepiped was used. The second anode 6 was stuck on the top coat 5 with a double-sided tape. The interval between the second anodes 6 was set to 5 m.

  As an external power supply of the power supply device 7, a commercial power supply of 100V was used. The maximum output of the power supply device 7 is 4 V DC, 10 mA for the first anode 4 (corresponding to the first anode 4 of 20 ch), and 50 V DC, 200 mA for the second anode 6 (corresponds to the second anode 6 of 20 ch). Possible). As the power supply device 7, a device that automatically shuts off by a surge current and automatically recovers was used. A DC voltage of 3 V was applied to the first anode 4 and a DC voltage of 50 V was applied to the second anode 6.

  It was confirmed by an exposure test and other verification experiments that the glossiness of the overcoat film 5 was maintained for a long period of time. The deterioration of the surface of the overcoat film 5 due to ultraviolet rays was significantly suppressed as compared with the case where the first anode 4 was used alone. Highly reliable anticorrosion, which cannot be achieved by conventional anticorrosion methods, has become possible. Further, the use of the conventional anticorrosion method has been extremely limited in terms of cost, but it has been found that the present invention is applicable to a wide variety of structures 1 in terms of cost.

DESCRIPTION OF SYMBOLS 1 ... Structure 2 ... Insulating coating film 3 ... Conducting coating film 4 ... First anode 5 ... Overcoat film 6 ... Second anode 7 ... Power supply device 100 ... Part of insulating coating film 200 ... Insulating coating film Remaining portion P1: interval between first anodes P2: interval between second anodes

Claims (6)

  Forming an insulating coating on the structure; forming a conductive coating on the insulating coating; electrically connecting a first anode to the conductive coating; A method for preventing corrosion of a structure wherein a top coat is formed on the first coat, a second anode is provided on the top coat, a DC voltage is applied to the first anode, and a DC voltage is applied to the second anode.   The structure according to claim 1, wherein the conductive coating is formed on a portion of the insulating coating, and the overcoat is formed on a remaining portion of the insulating coating. Anticorrosion method.   2. The method according to claim 1, wherein a maximum DC output voltage applied to the second anode: a maximum DC output voltage applied to the first anode is 3 to 17: 1. 3. .   3. The method according to claim 1, wherein an interval between the adjacent first anodes is longer than an interval between the adjacent second anodes. 4.   3. The method according to claim 1, wherein the DC voltage power supply includes at least one of a commercial power supply, a solar battery, and a wireless power supply device. 4. An insulating coating film is formed, a conductive coating film is formed on the insulating coating film, and an electrical coating is formed on the conductive coating film of a structure in which an overcoat film is formed on the conductive coating film. A first anode connected to
A second anode installed on the topcoat of the structure;
A power supply device for applying a DC voltage to the first anode and applying a DC voltage to the second anode.

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