JP5387356B2 - Corrosion-proof electrodeposition coating method and apparatus for marine steel structures - Google Patents

Description

  The present invention relates to an anticorrosion electrodeposition coating method and apparatus for marine steel structures.

  In general, some steel marine structures such as steel sheet piles provided on the quay for revetment, steel pipe piles provided on bridges and piers, etc., or steel caissons whose concrete structures are covered with steel members It is provided in a state where it is submerged in seawater, and is exposed to an environment where rust is likely to occur.

  Accordingly, in such marine steel structures, rust is generated due to long-term use and the thickness is reduced and the strength is reduced. Therefore, it is necessary to perform reinforcement work or replacement work. Since a great deal of cost is required for construction, it is attempted to extend the life of the marine steel structure by means of anticorrosion, anticorrosion, or a combination thereof.

FIG. 3 is a schematic view showing an example of the conventional electrodeposition film formation on the marine steel structure 1, and the anode 3 is arranged at a predetermined interval with respect to the submerged portion 2 submerged in the seawater of the marine steel structure 1. By providing a DC power source 4 between the anode 3 and the marine steel structure 1 and energizing a DC current, calcium ions (Ca ²⁺ ), magnesium ions (Mg ²⁺ ) and the like dissolved in seawater The cations migrate in the seawater toward the marine steel structure 1 as a cathode, and electrons are obtained in the marine steel structure 1. CaCO ₃ and Mg are formed on the surface of the submerged portion 2 of the marine steel structure 1. An anticorrosion electrodeposition coating 5 (electrocoating layer) mainly composed of (OH) ₂ or the like is formed, and the submerged portion 2 of the marine steel structure 1 is anticorrosion by the anticorrosion electrodeposition coating 5. .

  In the conventional case, a direct current is applied from the direct current power source 4 under an energization condition selected based on the construction area of the marine steel structure 1 and the current density condition.

  For example, Patent Documents 1 and 2 show the general technical level of the anticorrosion method for marine steel structures as described above.

Japanese Patent No. 4146737 Japanese Patent No. 3799679

  However, as described above, when a direct current is applied from the direct current power source 4 under the energization conditions selected based on the construction area of the marine steel structure 1 and the current density condition, the marine steel structure 1 to be electrodeposited and the anode No. 3 corrosion resistance electrodeposition coating with uniform film thickness, such as uneven current density when energized due to slight difference in distance, wiring resistance, etc., and peeling of film due to gas generation at high current density locations It has been difficult to generate 5.

  In Patent Document 2, when the anticorrosion coating is formed, the current flowing from the anode to the structural steel body that performs the anticorrosion coating treatment, the potential difference applied between the reference electrode and the structural steel body, and the temperature of the electrolytic solution are measured. Although it is described that monitoring of whether or not the anticorrosion coating treatment is performed satisfactorily, this is merely monitoring, and there is no particular disclosure regarding specific direct current control.

  In view of such circumstances, the present invention intends to provide an anticorrosion electrodeposition coating method and apparatus for an marine steel structure that can reliably form an anticorrosion electrodeposition coating having a uniform thickness on the surface of the marine steel structure. Is.

The present invention provides an anode with a predetermined interval with respect to a submerged portion of a marine steel structure submerged in seawater, and a direct current is applied by providing a direct current power source between the anode and the marine steel structure. In the method of applying an anticorrosion electrodeposition coating for a marine steel structure that forms an anticorrosion electrodeposition coating on the surface of the submerged portion of the marine steel structure,
Measure the potential on the marine steel structure side with the reference electrode when energized by the DC power supply, and if the potential on the marine steel structure side is within the preset electrodeposition reference potential range, hold the DC current value However, when the potential on the marine steel structure side is equal to or less than a preset electrodeposition reference potential range, the DC current value is decreased while the potential on the marine steel structure side is set to a preset voltage. In the case where it is equal to or higher than the deposition reference potential range, the present invention relates to a method for applying an anticorrosion electrodeposition coating for a marine steel structure, wherein the direct current value is increased.

Further, the present invention provides an anode provided at a predetermined interval with respect to a submerged portion submerged in seawater of a marine steel structure,
A direct current power source for forming a corrosion-proof electrodeposition coating on the surface of the submerged portion of the marine steel structure by passing a direct current between the anode and the marine steel structure;
A reference electrode for measuring the potential of the marine steel structure when energized by the DC power supply;
When the potential on the marine steel structure side measured with the reference electrode is in the preset electrodeposition reference potential range, the DC current value is retained, and the marine steel structure side measured with the reference electrode Is less than a preset electrodeposition reference potential range, the DC current value is reduced, while the marine steel structure side potential measured by the reference electrode is set in advance. And a control device for outputting a control signal for increasing the direct current value to the direct current power source when the potential range is exceeded. It is.

  According to the above means, the following operation can be obtained.

  When energized by the DC power source, the potential of the marine steel structure side is measured by the reference electrode, and the potential of the marine steel structure side measured by the reference electrode is within a preset electrodeposition reference potential range The control signal holding the DC current value is output from the control device to the DC power supply, but the potential on the marine steel structure side measured by the verification electrode is below a preset electrodeposition reference potential range In this case, a control signal for decreasing the DC current value is output from the control device to the DC power supply, while the marine steel structure side potential measured by the reference electrode is equal to or greater than a predetermined electrodeposition reference potential range. In this case, a control signal for increasing the DC current value is output from the control device to the DC power source.

  As a result, unlike the conventional case where the DC current is simply supplied from the DC power source under the current-carrying conditions selected based on the construction area and current density conditions of the marine steel structure, the marine steel structure subject to electrodeposition If there is unevenness in the current density during energization due to slight differences in the distance between the anode and the anode, differences in wiring resistance, etc., the direct current value is corrected so that the unevenness in the current density is eliminated, Since energization can be performed with a uniform current density, it is possible to avoid film peeling due to gas generation at a location with a high current density, and it is possible to generate an anticorrosive electrodeposition film with a uniform film thickness.

  According to the anticorrosion electrodeposition coating method and apparatus for marine steel structures of the present invention, it is possible to achieve an excellent effect that an anticorrosion electrodeposition film having a uniform thickness can be reliably formed on the surface of the marine steel structure.

It is a block diagram which shows the apparatus structure in the Example of this invention. It is a flowchart which shows the flow of control in the Example of this invention. It is the schematic which shows an example of the electrodeposition film formation to the conventional marine steel structure.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 and 2 show an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 denote the same components, and the basic configuration is the same as that of the conventional one shown in FIG. However, the feature of this embodiment is that, as shown in FIGS. 1 and 2, a reference electrode 6 for measuring the potential on the marine steel structure 1 side when energized by the DC power supply 4 is disposed, and When the potential on the marine steel structure 1 side measured by the verification electrode 6 is in a preset electrodeposition reference potential range, the DC current value is held, and the marine steel structure measured by the verification electrode 6 When the potential 6a on the object 1 side is equal to or less than the predetermined electrodeposition reference potential range, the direct current value is decreased, while the potential 6a on the marine steel structure 1 side measured by the verification electrode 6 is reduced. If it is above the preset electrodeposition reference potential range, increase the DC current value. Certain control signal 4a to the point of providing the control unit 7 to be output to the DC power supply 4.

In the case of the present example, provisional energization was performed using a test piece as a cathode assumed as the marine steel structure 1 to obtain a current density-potential relationship. ² ] is set to the minimum value of the electrodeposition reference potential, and the cathode current density is 3 [A / m ² ] in the temporary energization (for the complex shape such as a steel sheet pile, 2 [A / M ² ]) is set as the maximum value of the electrodeposition reference potential, and the range from the minimum value to the maximum value is preset as the electrodeposition reference potential range. Incidentally, when the reference electrode 6 is, for example, a silver-silver chloride electrode, the electrodeposition reference potential range in a still water environment such as a harbor is −1.3 to −1.1 [V].

  In FIG. 1, for convenience, two DC power supplies 4, two anodes connected to the DC power supply 4 (four in total), and two reference electrodes 6 corresponding to the DC power supply 4 are shown. However, it goes without saying that the number of each is appropriately selected according to the scale of the marine steel structure 1 to be subjected to electrodeposition coating.

  Next, the operation of the above embodiment will be described.

  First, as shown in the flowchart of FIG. 2, energization by the DC power source 4 is performed with an initial set DC current value (see step S <b> 1 in FIG. 2). The potential measurement on the object 1 side is performed (see step S2 in FIG. 2).

  Subsequently, it is determined whether or not the potential 6a on the marine steel structure 1 side measured by the verification electrode 6 is in a preset electrodeposition reference potential range (for example, −1.3 to −1.1 [V]). When the control device 7 (see step S3 in FIG. 2) is within the electrodeposition reference potential range, a control signal 4a for holding the DC current value (see step S4 in FIG. 2) is sent from the control device 7 Output to DC power supply 4.

  When the potential 6a on the marine steel structure 1 side measured by the reference electrode 6 is not within the preset electrodeposition reference potential range, it is determined whether or not the potential 6a is below the electrodeposition reference potential range. 7 (see step S5 in FIG. 2), the potential 6a on the marine steel structure 1 side measured by the reference electrode 6 is below a preset electrodeposition reference potential range (for example, −1.3 [V] or less) ), A control signal 4a for decreasing the DC current value (see step S6 in FIG. 2) is output from the control device 7 to the DC power supply 4.

  On the other hand, if the potential 6a on the marine steel structure 1 side measured by the verification electrode 6 is not less than or equal to the predetermined electrodeposition reference potential range, that is, if it is determined as “NO” in step S5, Since the potential 6a on the marine steel structure 1 side measured by the reference electrode 6 is inevitably higher than a predetermined electrodeposition reference potential range (for example, −1.1 [V] or higher), in this case, A control signal 4a for increasing the DC current value (see step S7 in FIG. 2) is output from the control device 7 to the DC power source 4.

  The control of the direct current value is repeated until a preset energization period (for example, 3 to 7 days) expires (see step S8 in FIG. 2).

  As a result, unlike the conventional case where the direct current is simply supplied from the direct current power source 4 under the current supply conditions selected based on the construction area and the current density condition of the offshore steel structure 1, the marine steel to be electrodeposited is used. If the current density is uneven when energized due to a slight difference in the distance between the structure 1 and the anode, a difference in wiring resistance, etc., the direct current value is corrected so as to eliminate the current density unevenness. Since it can be energized at a uniform current density, it is possible to avoid film peeling due to gas generation at high current density locations, and to produce a corrosion-resistant electrodeposition coating with a uniform film thickness. Become.

  In this way, an anticorrosion electrodeposition film having a uniform thickness can be reliably formed on the surface of the marine steel structure 1.

  The anticorrosion electrodeposition coating method and apparatus for marine steel structures of the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. Of course.

DESCRIPTION OF SYMBOLS 1 Marine steel structure 2 Submerged part 3 Anode 4 DC power supply 4a Control signal 5 Corrosion-proof electrodeposition coating 6 Reference electrode 6a Electric potential 7 Controller

Claims (2)

A marine steel structure is provided by providing a positive electrode with a predetermined interval with respect to the submerged portion of the marine steel structure submerged in seawater, and providing a DC power supply between the anode and the marine steel structure. In the anticorrosion electrodeposition coating method for marine steel structures, which forms an anticorrosion electrodeposition coating on the surface of the submerged part
Measure the potential on the marine steel structure side with the reference electrode when energized by the DC power supply, and if the potential on the marine steel structure side is within the preset electrodeposition reference potential range, hold the DC current value However, when the potential on the marine steel structure side is equal to or less than a preset electrodeposition reference potential range, the DC current value is decreased while the potential on the marine steel structure side is set to a preset voltage. An anticorrosion electrodeposition coating method for marine steel structures, wherein the direct current value is increased when the electrodeposition reference potential range is exceeded. An anode provided at a predetermined interval with respect to a submerged part submerged in seawater of a marine steel structure;
A direct current power source for forming a corrosion-proof electrodeposition coating on the surface of the submerged portion of the marine steel structure by passing a direct current between the anode and the marine steel structure;
A reference electrode for measuring the potential of the marine steel structure when energized by the DC power supply;
When the potential on the marine steel structure side measured with the reference electrode is in the preset electrodeposition reference potential range, the DC current value is retained, and the marine steel structure side measured with the reference electrode Is less than a preset electrodeposition reference potential range, the DC current value is reduced, while the marine steel structure side potential measured by the reference electrode is set in advance. An anticorrosion electrodeposition coating apparatus for a marine steel structure, comprising: a control device that outputs a control signal for increasing the direct current value to the direct current power source when the electric potential range is exceeded.

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