JPH0796716B2 - Anticorrosion device on the inner surface of oil tank - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anticorrosion device for the inner surface of an oil tank, and more particularly to a device for anticorrosion of a welded portion on the inner surface of an oil tank for a long period of time.

[Problems to be Solved by Conventional Techniques and Inventions] Conventionally, as a method for preventing corrosion of the inner surface of a tank such as an oil tank, coating mainly composed of vinyl ester-based, polyester-based or epoxy-based resin, glass flake or glass fiber There is a method of applying a resin lining containing.

However, if the entire inner surface of the oil tank is painted or lined, it is necessary to peel off the paint etc. of the welded part at the time of non-destructive inspection that is regularly carried out based on the Fire Service Law and then apply the paint again after the inspection. Occurs. Therefore, the conventional method described above has a drawback in that a great deal of time and effort is required for nondestructive inspection.

In addition, there is a method using cathodic protection as another method for preventing corrosion on the inner surface of the tank. Method (Japanese Utility Model Publication No. 60-9244) or a method of applying a base potential metal foil to the welded portion of a steel plate storage tank to prevent internal pitting corrosion (Japanese Patent Laid-Open No. 59-
50185).

However, all of the above-mentioned cathodic protection methods are anticorrosion methods at the time of tank water filling test, and the former cathodic protection method is completely anticorrosive in some cases when the amount of water accumulated at the bottom is irregular like oil tanks. There was a risk that the tank could not be obtained, and it was unsuitable except during the water filling test of the tank. Further, in the latter method of cathodic protection, the base potential metal foil is liable to be locally consumed due to the non-uniformity of the electrolyte state, and thus long-term anticorrosion is impossible. Further, in the conventional cathodic protection method, an electrolytic scale such as calcium carbonate produced by electrolysis of an electrolyte solution covers the surface to be corroded (electro coating), and peeling is required at the time of destructive inspection, which is troublesome. There was a drawback.

The present invention has been made to solve the above-mentioned conventional problems, and can completely and reliably protect the inner surface of an oil tank, particularly a welded portion, for a long period of time, and facilitates the non-corrosive surface during nondestructive inspection. It is an object of the present invention to provide an anticorrosion device that can be exposed to water.

MEANS FOR SOLVING THE PROBLEMS The present invention is directed to a water-absorbing member that is in close contact with the inner surface of an oil tank, a container that covers the water-absorbing member, and a galvanic element that is arranged on a portion of the water-absorbing member opposite to the inner surface of the tank. An anticorrosion device for an inner surface of an oil tank, comprising: an anode, a short-circuit means for short-circuiting the galvanic anode and the tank body at at least one point, and a fixing means for fixing the container to the inner surface of the tank. .

The container is excellent in oil resistance, corrosion resistance, seawater resistance, heat resistance,
Further, a material made of a material having excellent workability, for example, a synthetic resin, FRP or a corrosion resistant metal is preferable. Corrosion resistant metals include titanium, tantalum, niobium, stainless steel,
Copper etc. are mentioned. When the container is made of a corrosion resistant metal, it is preferable to electrically insulate the container and galvanic anode.

Further, the above-mentioned container may be formed by integrally molding the above-mentioned material, or other materials such as synthetic rubber such as silicone rubber having excellent oil resistance, seawater resistance, heat resistance, and flexibility and elasticity. It may be a combination of the above materials.

The shape of the container is not particularly limited, and a shape capable of covering the following water-absorbing member when the container is installed on the inner surface of the oil tank, that is, a desired water-absorbing member or the like is filled between the container and the inner surface of the oil tank. Any shape may be used as long as it forms the space. As a preferable shape of the above-mentioned container, one having a substantially U-shaped cross section can be mentioned. The container according to the present invention does not need to completely shut off the water absorbing member and the contents of the tank.

The water-absorbing member used in the present invention described above serves as an electrolyte that holds a low-resistance electrolyte solution and forms a cell between the galvanic anode and the inner surface of the oil tank, which will be described later. It must be excellent. As such a water-absorbing member, one made of a granular or sheet-shaped highly water-absorbing polymer material is preferable, and a combination of a highly water-absorbing polymer material and highly water-absorbent pulp or water-absorbent paper is also exemplified. It Further, the water absorbent member according to the present invention is preferably an oleophobic member, and specifically, a polyacrylic acid-based polymer which is a highly water absorbent polymer material is preferably used.

Furthermore, in the present invention, when a substance having an inhibitory effect (inhibitor) is contained in the water absorbent member,
It is preferable because the consumption of the granular electrode anode tends to be further reduced. The inhibitor is preferably a phosphoric acid-based inhibitor, which is relatively less problematic in terms of environmental protection, and more preferably a polymerized phosphoric acid-based or phosphonic acid-based inhibitor. Further, an acrylic acid-based scale inhibitor may be added to the above inhibitor.

The water absorbent member may be impregnated with artificial seawater, tap water or the like in advance as an electrolyte solution.

The galvanic anode may be any metal that can be a sacrificial anode for the oil tank body, such as steel, and may be zinc, zinc alloy, aluminum alloy, magnesium alloy, or the like, and zinc alloy or aluminum alloy is particularly preferable. preferable. When the above-mentioned inhibitor is used, compatibility with it must be taken into consideration, and a zinc alloy, which is expected to have a synergistic anticorrosion effect with the phosphate-based inhibitor, is preferable.

The fixing means in the present invention is not particularly limited, and may be a bolt or the like, but a means that can be easily attached to and detached from the inner surface of the oil tank of the container and that can weld the container to the inner surface of the oil tank, such as having magnetic force and oil resistance, seawater resistance It is preferable to use an elastic material having excellent heat resistance or a combination of this and a bolt.

In the present invention, the short-circuit means for short-circuiting the galvanic anode and the oil tank body at at least one point is not particularly limited. For example, when a bolt is used as the fixing means, it may be used as a stat bolt welded to the oil tank body so as to serve as the fixing means and the short-circuiting means. Further, a lead wire may be provided as the short-circuit means.

Further, in the present invention, instead of installing the galvanic anode separately from the container, a container having a ceiling portion composed of the galvanic anode may be used. The present invention in this case has at least one of a container having a water-absorbing member that is in close contact with the inner surface of the oil tank, a ceiling portion made of a galvanic anode, and covering the water-absorbing member, the galvanic anode and the tank body. And a fixing means for fixing the container to the inner surface of the tank, the anticorrosion device for the inner surface of the oil tank.

Specific examples of the container in this case include the ceiling part and the side wall part made of the synthetic rubber.

When the galvanic anode is used as the ceiling of the container, the surface of the galvanic anode opposite to the water absorbing member may be subjected to anticorrosion treatment by coating, lining, insulating material such as resin sheet, or the like.

[Operation] In the anticorrosion device for the inner surface of the oil tank of the present invention configured as described above, when the electrolyte solution permeates the water-absorbing member, it swells and fills a small gap between the galvanic anode and the inner surface of the oil tank. Therefore, the electrolytic state does not become nonuniform and the anticorrosion effect does not become nonuniform, and stable anticorrosion can be achieved over a long period of time. Further, the anticorrosion device of the present invention is extremely easy to attach and detach, and since oil sludge and the like are not generated on the inner surface of the oil tank, it is possible to easily expose the anticorrosion surface at the time of nondestructive inspection of the welded portion. Further, since the anticorrosion device of the present invention can simply replace only the galvanic anode when the galvanic anode is consumed, the anticorrosion cost can be reduced as a result.

Furthermore, when a water-absorbent member made of a highly water-absorbent polymer material is used, electrocoating does not occur, and the time and effort at the time of nondestructive inspection can be further reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a side sectional view showing a state in which an anticorrosion device according to an embodiment of the present invention is attached to an oil tank inner surface welded portion. In the figure, 1 is a container, 2 is an adhesive, and 3 is a galvanic discharge. Anode (zinc alloy), 4 water absorbing member (polyacrylic acid polymer), 5 magnetized rubber, 6 oil tank body, 7 bolts, 8 lead wires, 9
Indicates a welding line, 10 indicates a nut, and 11 indicates a covering member.

The anticorrosion device shown in FIG. 1 has a rod-shaped zinc alloy via an insulating adhesive 2 on the inner surface of the recess (ceiling) of a titanium container 1 having a recess having a U-shaped cross section in the central portion in the longitudinal direction. 3 are arranged in parallel, and the entire concave portion is made of polyacrylic acid-based polymer 4
And the polyacrylic acid-based polymer 4 is impregnated with an electrolyte solution (not shown). Further, a magnetized rubber 5 (a magnetic rubber obtained by mixing barium ferrite powder with chloroprene rubber) is adhered to both ends of the container 1, and further the oil tank body 6 and the zinc are joined through a stat bolt 7 welded to the oil tank body 6. A lead wire 8 is provided to short-circuit the alloy 3.

Then, the anticorrosion device is attached to the welding line 9 of the oil tank body 6 and the inner surface of the periphery (welding part) of the magnetized rubber 5 and the nut 10.
The welded part was well protected by the installation. The inner surface of the oil tank body 6 is covered with a coating member 11 such as coating or resin lining in advance, except for the portion covered by the anticorrosion device of the present invention.

Next, the anticorrosion performance of the above anticorrosion device was evaluated by the following test method.

(Test method) Two steel plates (SS41) each having a width of 4 cm, a length of 20 cm and a thickness of 4.5 cm are connected in parallel by welding, surface-treated with 15% HCl containing 0.5% of an inhibitor for acid treatment, and then with water. Washed. After degreasing the surface with acetone, 5 cm x 12 cm was left as the test surface centering on the welding line on one side of the steel sheet, and the remaining steel sheet surface was insulated and sealed with tar epoxy paint.

The anticorrosion device of Example 1 was installed on this test surface, and the surface condition, the corrosion protection rate, the average corrosion protection current density, and the presence or absence of pitting corrosion of the test surface after 3 months and 6 months were examined. The results are shown in Table 1. It should be noted that artificial seawater was used as the electrolyte solution, and seawater containing about 10% by weight of heavy oil sludge was used as the test solution, and the test was performed at room temperature at a rotation speed of 2 cm / sec. In addition, the corrosion protection rate is the same as that of the test part.
The value was calculated based on the natural immersion piece of 1).

Embodiment 2 FIG. 2 is a side sectional view showing a state in which an anticorrosion device of another embodiment of the present invention is attached to an oil tank inner surface welded portion.
Represents a FRP plate, 1b represents a rod-shaped silicone rubber, and other symbols represent the same as in Example 1, respectively.

The anticorrosion device shown in FIG. 2 is formed by bonding a ceiling portion made of FRP plate 1a and a side wall portion made of rod-shaped silicone rubber 1b to the inner surface of the recessed portion (ceiling portion) of a U-shaped groove-shaped container. A rod-shaped zinc alloy 3 is arranged via an adhesive 2, and the entire concave portion is filled with a polyacrylic acid-based polymer 4 containing sodium hexametaphosphate (500 ppm) as an inhibitor (not shown). The polyacrylic acid-based polymer 4 is impregnated with an electrolyte solution (not shown). A magnetized rubber 5 similar to that used in the first embodiment is adhered to the silicone rubber 1b, and the oil tank body 6 and the zinc alloy 3 are joined together by a stat bolt welded to the oil tank body 6.
A lead wire 8 is provided for short-circuiting and.

Then, by installing the above-mentioned anticorrosion device on the inner surface of the welded portion of the oil tank main body 6 in the same manner as in Example 1, the welded portion was well protected.

Next, the anticorrosion performance of the anticorrosion device was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Embodiments 3 to 4 FIG. 3 is a side sectional view showing a state in which the corrosion preventive device of still another embodiment of the present invention is attached to an oil tank inner surface welded portion. In FIG. The symbols are the same as in Example 1, respectively.

The anticorrosion device of FIG. 3 is a groove type with a U-shaped cross section formed by bonding a ceiling part made of a plate-shaped zinc alloy 3 with anticorrosion coating 12 on one side and a side wall part made of rod-shaped silicone rubber 1b. Fill the entire recess of the container with polyacrylic acid-based polymer 4,
The polyacrylic acid-based polymer 4 is impregnated with an electrolyte solution (not shown). In Example 4, sodium hexamethanephosphate (500 ppm) was contained as an inhibitor (not shown) in the polyacrylic acid polymer 4. A magnetized rubber 5 similar to that used in the first embodiment is adhered to the silicone rubber 1b, and the oil tank body 6 and the zinc alloy 3 are short-circuited via a stat bolt 7 welded to the oil tank body 6. There is.

Then, by installing the above-mentioned anticorrosion device on the inner surface of the welded portion of the oil tank main body 6 in the same manner as in Example 1, the welded portion was well protected.

Next, the anticorrosion performance of the anticorrosion device was evaluated in the same manner as in Example 1. The results are shown in Table 1.

As is clear from the results shown in Table 1, when the anticorrosion device of the present invention was used, the anticorrosion rate of 90% or more was obtained for both the test period of 3 months and 6 months, and in particular, in Examples 2 and 4, 100% was obtained. A corrosion protection rate of% could be obtained.

Further, in any of the examples, no pitting corrosion was generated in the weld line and its vicinity, and neither electrocoating nor heavy oil sludge was generated.

Fifth Embodiment FIG. 4 is a side sectional view showing a state in which a corrosion preventive device of still another embodiment of the present invention is attached to an inner surface of a welded portion around an oil tank, and symbols in the figure are the same as those in the fourth embodiment. Are shown respectively.

The anticorrosion device of FIG. 4 is configured in the same manner as in Example 4 except that a plate-shaped zinc alloy 3 bent at a right angle in the center is used.

Then, by installing the above-mentioned anticorrosion device on the inner surface of the welded portion around the oil tank body 6 in the same manner as in Example 4, the welding was well protected against corrosion.

[Effects of the Invention] As described above, according to the present invention, the inner surface of the oil tank, particularly the welded portion, can be completely and reliably protected from corrosion for a long period of time, and the surface to be protected can be easily protected during nondestructive inspection. Can be exposed.

Further, by using the anticorrosion device of the present invention, the cost of anticorrosion on the inner surface of the oil tank can be reduced.

Furthermore, when a water-absorbent member made of a highly water-absorbent polymer material is used, electrocoating does not occur, and the time and effort at the time of destructive inspection can be further reduced.

[Brief description of drawings]

1 to 4 are side cross-sectional views showing a state in which the anticorrosion device of one embodiment of the present invention is attached to an oil tank inner surface welded portion. 1: container, 1a: FRP plate, 1b: rod-shaped silicone rubber, 2: adhesive, 3: galvanic anode, 4: water-absorbing member, 5: magnetized rubber, 6: oil tank body, 7: bolt, 8: Lead wire, 9: Weld wire, 10: Nut, 11: Cover material, 12: Anticorrosion paint.

Claims (8)

[Claims] 1. A water-absorbing member that is in close contact with the inner surface of an oil tank, a container that covers the water-absorbing member, a galvanic anode that is disposed on a portion of the water-absorbing member opposite to the inner surface of the tank, and the galvanic anode and the tank. An anticorrosion device for an inner surface of an oil tank, comprising: a short-circuit means for short-circuiting the main body at at least one point; and a fixing means for fixing the container to the inner surface of the tank. 2. The anticorrosion device for the inner surface of the oil tank according to claim 1, wherein the container is made of synthetic resin or FRP. 3. The anticorrosion device for the inner surface of the oil tank according to claim 1, wherein the container is made of a corrosion-resistant metal, and electrically insulates the container and the galvanic anode. 4. A container having a water-absorbing member that is in close contact with the inner surface of the oil tank, a ceiling portion made of a galvanic anode and covering the water-absorbing member, and a short-circuit between the galvanic anode and the tank body at at least one point. And a fixing means for fixing the container to the inner surface of the tank. 5. The anticorrosion device for the inner surface of the oil tank according to claim 4, wherein the container is composed of the ceiling portion and a side wall portion made of synthetic rubber. 6. The water-absorbent member is made of a granular or sheet-shaped superabsorbent polymer material.
5. The anticorrosion device for the inner surface of the oil tank according to any one of 5 above. 7. The anticorrosion device for the inner surface of the oil tank according to claim 1, wherein the water absorbing member further contains a substance having an inhibitory effect. 8. The anticorrosion device for the inner surface of the oil tank according to claim 1, wherein the fixing means is made of an elastic material having a magnetic force.