JPH0158278B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrodeposition device, and in particular, the present invention relates to an electrodeposition device for electrodepositing a hard electrodeposit mainly composed of calcium carbonate from seawater onto the surface of a cathode body of electrodes placed opposite each other in the sea. This relates to a device for

[Conventional technology]

Approximately 400 ppm of calcium ions and 1,200 ppm of magnesium ions are dissolved in seawater, and methods for precipitating these ions as CaCO ₃ and Mg(OH) ₂ are known.

As shown in FIG. 3, this type of conventional electrodeposition technology involves placing an anode 2 and a cathode 4 facing each other in seawater, and connecting both electrodes to a DC power source 6 and energizing the cathode 4. Electrodeposit 8 containing CaCO ₃ as a main component is formed on the surface.

[Problem to be solved by the invention]

However, in the conventional electrodeposition method, as shown in Figure 3, there is a large water level difference between water level A at high tide and water level B at low tide due to the ebb and flow of the tide, and the water level of the cathode 4 is close to the water level A at high tide. Because the period of immersion in seawater is so short, the electrodeposit is thin and there is a problem in that it is not possible to obtain an electrodeposit with a uniform thickness in the direction of the water level. Also
When trying to form a hard electrodeposit containing CaCO ₃ as the main component, it is desirable to set the current density on the cathode side to around 0.2 mA/cm ² , but conventionally, current is applied so that the current value on the cathode side is constant. Therefore, at low water level during low tide, the current density increases and Mg(OH) ₂
The amount of electrodeposit with a high composition ratio increases,
Another problem was that the imbalance in the thickness of the electrodeposit in the direction of the water level was further increased. In addition to the area 4A near water level A at high tide, the spray zone area 4 exposed to waves
B is also a region that is susceptible to corrosion, but since this splash zone region is not immersed in seawater, there is no conventional means of forming electrodeposit in this region, and a corrosion prevention means by electrodeposition of this splash zone region 4B is desired. It had been.

The present invention was devised in view of the problems of the prior art, and its object is to provide an electrodeposition apparatus capable of forming electrodeposit over the entire region of a steel marine structure exposed to seawater.

[Means for Solving the Problems] As a means for solving the problems described above, the electrodeposition apparatus according to the present invention includes a structure in which a portion of a steel structure exposed to seawater is used as a cathode body, and the part of the steel structure exposed to seawater is made to face the cathode body. This is an electrodeposition device in which an anode body is arranged at The first anode body is arranged so that the distance between the electrodes becomes small, and a cylindrical container is installed to keep the splash zone part of the cathode body immersed in seawater. Anode bodies are arranged, and the first anode body and the second anode body are connected in parallel to a power source.

[Effect]

Since the present invention is configured as described above, the water level in the splash zone region is kept constant, the cathode current density is constant in the direction of the water level, and the composition ratio and thickness of the electrodeposit attached to the surface of the structure are controlled. The water level remains constant in the direction.

According to the present invention, the distance between the anode body and the cathode body becomes smaller as the water level approaches the water level at high tide, so the current distribution in the cathode body at high tide is as shown in FIG. The current value near water level A at high tide is the largest. Therefore, even if there is a period when the water level falls during low tide and no electrodeposit is formed in the low tide zone area 14B, a large amount of electrodeposit is formed during high tide, so that in the long term, the thickness is approximately uniform in the vertical direction. Electrodeposits will be formed. In FIG. 2, reference numeral 14 indicates the leg of the steel structure which is the cathode body, reference numeral 12 indicates the anode member,
Symbol B indicates the water level at low tide.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.
In this figure, a steel leg 14 of a steel offshore structure is shown.
is fixed to the seabed 10, and the anode member 12 is arranged opposite to a portion 14B of the leg portion 14 located between the high tide water level position A and the low tide water level position B (hereinafter referred to as the low tide zone area). The leg portions 14 and the anode member 12 are connected to a DC power source 16, and when energized, electrodeposit is deposited on the surface of the low tide region which becomes the cathode body. The anode member 12 is arranged in an inclined state so that the inter-electrode distance d decreases from the low tide water level position B to the high tide water level position A, and the current distribution on the cathode side at high tide is shown in Fig. 2. The situation is now as shown. In other words, the cathode current flowing through a portion that is immersed in seawater for a shorter period of time due to the ebb and flow of the tide is greater, and the rate of electrodeposit deposition per unit time is correspondingly faster. Therefore, if the current is continued for a long period of several months, the period of immersion in seawater is short in the low tide zone region 14B, but the rate at which electrodeposit is formed is faster near the high tide water level position A. It is possible to form an electrodeposit with a substantially uniform thickness. The electrodeposit is mainly
Composed of CaCO ₃ and Mg(OH) ₂ , cathode current density is 0.1
A coating layer of electrodeposit that is difficult to peel off can be formed within the range of ~0.5 mA/cm ² , and within this predetermined current density range, the inclination angle θ of the anode member 12 and the leg portion 1
It is desirable to set the distance from 4.

A substantially cylindrical container 22 in which an anode member 24 is disposed is installed around the splash zone region 14A above the high tide water level A of the leg portion 14 that receives sea spray. It is constantly filled with seawater supplied by the The anode member 24 is connected to the anode side of the DC power supply 16. That is, the anode member 12 and the anode member 24 are connected in parallel. Since the seawater in the container 22 overflows from the upper opening of the container, the level of the seawater in the container 22 is always maintained constant. Therefore, the magnitude of the cathode current in the splash zone region 14A, which is the cathode body, is constant in the water depth direction, and
The thickness of the electrodeposit formed on the surface is also constant in the water depth direction.

Thus, in the embodiment shown in FIG.
Electrodeposit 18 having a uniform thickness in the longitudinal direction can be formed in the splash zone region 14A and the low tide zone region 14B.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to form electrodeposit over the entire area of a steel structure exposed to seawater and to make the thickness of the electrodeposit uniform.
This has the effect of increasing corrosion resistance and extending the life of steel structures.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a cathode current distribution state of the invention, and FIG. 3 is an overall configuration diagram of a conventional electrodeposition apparatus. DESCRIPTION OF SYMBOLS 12, 24... Anode member, 14... Leg of steel marine structure, 14A... Splash zone area, 14B... Low tide zone area, 16... DC power supply, 18... Electrodeposit, 22... Cylindrical container, 26... Pump.

Claims (1)

[Claims] 1 The part of the steel structure exposed to seawater is used as a cathode body, and the anode body is placed opposite to this cathode body,
An electrodeposition device that applies electricity between electrodes to form an electrodeposit mainly composed of calcium carbonate on the surface of the cathode body, which is placed facing the tidal zone of the cathode body, and the distance between the electrodes becomes smaller as the water level approaches the high tide. In addition to arranging the first anode body as shown in FIG.
An electrodeposition apparatus characterized in that a second anode body is disposed within the cylindrical container, and the first anode body and the second anode body are connected in parallel to a power source.