JP2005113167A - Efficient electrolytic corrosion protection method, corrosion-protected steel, and corrosion-protected structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient electrolytic corrosion protection method with which corrosion protection above the water level less prone to be effective in the electrolytic corrosion protection method is reliably performed, and an electrode for electrolytic corrosion resistance need not be replaced, and corrosion protected steel and a corrosion protected steel structure. <P>SOLUTION: In the efficient electrolytic corrosion protection method, and the corrosion protected steel and the corrosion protected steel structure, an intermediate resin adhesive layer having the volumetric resistivity of ≥ 10<SP>9</SP>Ωcm is covered on a part of a steel surface with the thickness of ≥ 0.1 mm, and a highly corrosion-resistant metal layer is laminated on the adhesive layer. In this corrosion-resistant steel, a highly corrosion-resistant metal lamination part and a non-lamination part are simultaneously in contact with the environment of fresh water or sea water. The corrosion-resistant steel is connected to a DC power supply with the highly corrosion-resistant metal layer as an anode, and the steel as a cathode to perform the electrolytic corrosion protection is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a steel material corrosion prevention method and a corrosion-proof structure that ensures long-term corrosion resistance when the steel structure is exposed to a corrosive environment of fresh water or seawater environment such as a pier or revetment of a harbor or river. .

  Steel pipe piles, steel pipe sheet piles, steel sheet piles, etc. used for jacket structures and other structures used in severe corrosive environments are subject to deterioration due to corrosion, and the anticorrosion method determines the life of the structure. It's not too much to say. In general, coating is performed, and particularly heavy anticorrosion coating having a thickness of several mm is effective. When long-term durability for several decades is required, it is excellent in various anticorrosive properties such as electrical insulation and chemical resistance, and is a heavy-duty anticorrosion using a resin such as polyolefin or polyurethane, which is an inexpensive resin, as a coating material. Coated steel is manufactured. In the heavy anticorrosion coating, long-term adhesion durability is secured by combining the anticorrosion coating with the base treatment and primer treatment of a special steel material as shown in JP-A-3-23527 (Patent Document 1). .

In addition, the anticorrosion method is also frequently used. The electrocorrosion protection method is a very general method, and is described in detail, for example, in “Anti-corrosion Engineering” written by Shigeru Kijima (Nikkan Kogyo Shimbun, 1982) (Non-Patent Document 1). Furthermore, Japanese Patent Application Laid-Open No. 9-143766 (Patent Document 2) describes a method for performing an anticorrosion with high efficiency. In this, a method for efficiently preventing corrosion by combining steel, painting, and further anti-corrosion is described.
JP-A-3-23527 Japanese Patent Laid-Open No. 9-143766 "Anti-corrosion engineering" by Shigeru Kijima (Nikkan Kogyo Shimbun, 1982)

As described above, as a method for preventing corrosion of a steel structure installed in a freshwater or seawater environment, coating corrosion protection and electrocorrosion protection with an organic resin are generally used.
However, in the case of coating with heavy anticorrosion coating or polyolefin resin, corrosion of the steel material cannot be suppressed unless the entire structure is in contact with seawater or fresh water. Is difficult to repair.

  Moreover, in the anticorrosion by the electric anticorrosion, the anticorrosion can be performed in an underwater portion where an electric current flows due to the conduction of ions, but the anticorrosion cannot be performed in a portion above the water surface. In the structure in the sea area, the position of the water surface changes due to the tidal flow, and in the structure in the river area, the height of the water surface changes due to the difference in the amount of water inflow, so there is a part that cannot be protected against corrosion. End up. In addition, in the externally-prevented method of cathodic protection, an insoluble electrode is used. In the galvanic anode method, an anode such as aluminum or zinc is joined to the underwater part of the structure by welding or the like. Furthermore, if the anode deteriorates or wears out over time, it must be replaced. Since this operation is a diving operation performed in an underwater part, it takes time and effort and it is difficult to ensure reliability.

  Therefore, in order to solve the above-described problems of the prior art, the present invention reliably performs corrosion protection on the water surface where the electrocorrosion protection method is not effective, and does not need to replace the electrode for electrocorrosion in the underwater part. An object of the present invention is to provide an efficient cathodic protection method, and a corrosion-resistant steel material and a corrosion-proof structure therefor.

In the present invention, as a result of earnestly studying a method for eliminating the need to replace the electrode for anticorrosion on the water surface where the anticorrosion is hardly effective and the electrode for anticorrosion in the underwater portion, the following means have been found.
(1) An intermediate resin adhesive layer having a volume resistivity of 10 ⁹ Ω · cm or more is coated on a part of the steel material surface with a thickness of 0.1 mm or more, and a highly corrosion-resistant metal layer is laminated on the adhesive layer. The anticorrosive steel material is electrically anticorrosive by connecting a DC power source with the high corrosion resistant metal layer as the anode and the steel material as the cathode, with the high corrosion resistant metal laminated portion and the non-laminated portion in contact with the freshwater or seawater environment at the same time. An efficient cathodic protection method.

(2) The electric corrosion protection method according to claim 1, wherein the surface potential of the steel material is maintained at -0.8 V or less based on a saturated KCl silver / silver chloride standard electrode standard.
(3) The anticorrosion method according to (1) or (2), wherein all or part of the highly corrosion-resistant metal layer is made of titanium or a titanium alloy.
(4) The cathodic protection method according to (3), wherein the surface of the titanium or titanium alloy is subjected to a low polarization treatment.
(5) Corrosion-resistant steel material laid in freshwater or seawater environment, and an intermediate resin adhesive layer having a volume resistivity of 10 ⁹ Ω · cm or more is 0.1 mm or more on the surface of the steel material located on the water surface when laying A corrosion-resistant steel material comprising: a high-corrosion-resistant metal layer formed thereon; a high-corrosion-resistant metal layer and a steel material having a connection portion with an external power source.

(6) The anticorrosion steel material according to (5), wherein all or part of the highly corrosion-resistant metal layer is made of titanium or a titanium alloy.
(7) The anticorrosion steel material according to (6), wherein the surface of the titanium or titanium alloy is subjected to a low polarization treatment.
(8) An anticorrosion structure obtained by laying at least the anticorrosion steel material according to any one of (5) to (7) in a freshwater or seawater environment, and externally connected through the connection portion of the high corrosion resistance metal layer and the steel material. The anticorrosive structure is connected to a power source.

  The anticorrosion method and the anticorrosive steel material and the anticorrosive structure of the present invention have a specific volume resistivity, an intermediate resin adhesive layer having a thickness, and a highly corrosion-resistant metal layer, and a voltage between the steel material and the highly corrosion-resistant metal layer as a cathode. By applying, it is not necessary to attach an electrode as in the conventional galvanic anode method, or to replace it after deterioration. Furthermore, since the aerial part on the surface of the water, which could not be protected by the conventional cathodic protection method, can be protected by a highly corrosion-resistant metal, efficient corrosion protection is possible.

  The best configuration for carrying out the present invention is shown in FIG. In the present invention, the steel material partially submerged in seawater or fresh water is subjected to corrosion protection. At that time, in the water, the steel material and seawater or fresh water come into contact as they are. However, as shown in FIG. 1, the water surface portion is in contact with a coating material in which a high corrosion-resistant metal layer is laminated via a steel material and an intermediate resin layer. Furthermore, in the state where the highly corrosion-resistant metal laminated portion and the non-laminated portion are simultaneously in contact with fresh water or seawater environment, the steel material is electrically protected by connecting a direct current power source with the high corrosion-resistant metal layer as the anode and the steel material as the cathode.

The anticorrosion steel material in this invention is a steel material for implement | achieving the said anticorrosion method. That is, an anti-corrosion steel material laid in a freshwater or seawater environment, and an intermediate resin adhesive layer having a volume resistivity of 10 ⁹ Ω · cm or more on a surface of the steel material located on the water surface at the time of laying is 0.1 mm or more. The high-corrosion-resistant metal layer is laminated thereon, and the high-corrosion-resistant metal layer and the steel material have a connection portion with an external power source.

The length of the highly corrosion-resistant metal coating layer used in the present invention is not particularly specified, but the lower end must always be covered to a position that is in contact with the water surface even if the sea level or the water level of the river fluctuates. As positions where current can flow, it is desirable to cover 0.5m below the LWL (average low tide surface) in the seawater area and 0.5m below the water level in the dry season in the river area. Although the upper end is not particularly specified, it is preferable that the upper end is higher than the HWL (average high tide surface) in seawater by 0.5 m or more from the average water level in rivers. In addition, the highly corrosion-resistant metal layer is excellent in impact resistance from the inflowing driftwood, pleasure boat, etc., and therefore it is desirable to cover it more widely.
Here, the steel material used in the present invention is not particularly limited, but is used as a member for a structure in a freshwater or seawater environment, a hot-rolled steel plate, a thick plate, a steel pipe, a steel pipe pile, a steel pipe sheet pile, a steel sheet pile, Various shapes, steel bars, wire rods, etc. can be applied.

The intermediate resin adhesive layer used in the present invention needs to have a volume resistivity of 10 ⁹ Ω · cm or more and a thickness of 0.1 mm or more. If the volume resistivity is less than 10 ⁹ Ω · cm, the leakage current cannot be ignored between the upper high-corrosion-resistant metal layer and the steel material. 10 ¹² Ω · cm or more is desirable. The volume resistivity is preferably as high as possible, but a high resistivity material obtained practically is about 10 ¹⁴ Ω · cm. Further, if the thickness is less than 0.1 mm, dielectric breakdown occurs at the time of construction, and a leakage current is likely to be generated. Therefore, a thickness of 0.1 mm or more is necessary. Preferably, it is 0.5 mm or more. As the thickness is increased, the dielectric breakdown can be withstood, but the strength as a structure may be lowered. Therefore, it is practical to set the thickness to 10 mm or less.

  The material of the intermediate resin layer is not particularly limited as long as it satisfies the above volume resistivity and thickness, and a thermoplastic resin, a thermosetting resin, a room temperature curable resin, or the like is used. However, it is necessary to be able to ensure adhesion with a steel material or a highly corrosion-resistant metal layer. Therefore, a method of laminating an adhesive or a pressure-sensitive adhesive material on the intermediate resin layer can be selected as appropriate.

  The material of the highly corrosion-resistant metal layer used in the present invention is not limited as long as it is a metal that does not easily corrode in freshwater or seawater environments. Specifically, stainless steel, titanium or titanium alloy, copper or copper alloy, gold, platinum , Etc. can be suitably used. In the case of using stainless steel, among them, a high Cr system and a high Mo system that hardly cause crevice corrosion in seawater are desirable. In particular, titanium or a titanium alloy is excellent in crevice corrosion resistance, and is suitable for a highly corrosion-resistant metal layer used in the present invention. Further, the surface of titanium or a titanium alloy subjected to low polarization treatment is optimal because a polarization phenomenon due to long-term cathodic protection hardly occurs.

  Here, the low polarization treatment means that if a voltage is continuously applied for a long period of time in the present invention, a film is formed on the surface of the highly corrosion-resistant metal layer that is an anode, and a polarization phenomenon that makes it difficult for current to flow may occur. This is a method for preventing this, and the surface of titanium or titanium alloy is increased in roughness by hydrofluoric acid treatment or blasting to increase the surface area. The surface of titanium or titanium alloy is plated with nickel or platinum. The method of processing by either of these methods or a combination of these two types can be mentioned.

  Further, in the cathodic protection method of the present invention, in a state where the highly corrosion-resistant metal laminated portion and the non-laminated portion are simultaneously in contact with fresh water or seawater environment, the steel material is connected to a DC power source with the high corrosion-resistant metal layer as the anode and the steel material as the cathode. It is essential to have anti-corrosion. By using a highly corrosion-resistant metal for the anode, it can be used permanently without being deteriorated or consumed like anodes such as aluminum and zinc used in the galvanic anode method, and there is no need to replace the anode. It can be.

  Further, it is preferable that the surface potential of the steel material is maintained at −0.8 V or less with respect to a saturated KCl silver / silver chloride standard electrode. If this potential is nobler than -0.8 V, the steel material surface may not be in a state where corrosion can be prevented, and the steel material may be corroded. If it is lower than this, the steel material can be prevented from corrosion, but if the potential is lowered too much, generation of hydrogen starts from the surface of the highly corrosion-resistant metal. Therefore, it is desirable to prevent the generation of hydrogen, and the potential at that time varies slightly depending on the type of the highly corrosion-resistant metal, but can be prevented by setting the surface potential of the steel material to −1.1 V or more.

  The above-described anti-corrosion steel material and the electro-corrosion method using the same make sure that the anti-corrosion method does not work effectively on the surface of the water, so that it is possible to eliminate the need to replace the electrode for electro-corrosion in the water. An anticorrosion method can be provided. Furthermore, the anticorrosion structure of the present invention is an anticorrosion structure in which at least the above-mentioned anticorrosion steel material is laid in a freshwater or seawater environment, and the high corrosion resistance metal layer is used as an anode and the steel material is used as a cathode through each connection portion. The anticorrosion structure is connected to an external power source.

  Here, the anticorrosion structure is a steel structure installed in a freshwater or seawater environment using the anticorrosion steel material of the present invention. Specifically, a steel sheet pile, a quay wall using a steel pipe sheet pile, and a retaining wall Examples include piers, foundation structures such as piers and piers using steel pipe piles, and floating structures using steel materials. In the anticorrosion structure, the anticorrosion structure of the present invention is essential in a normal cathodic protection structure. There is no need to install an electrode for anticorrosion after construction, and no installation work is required when the electrode is consumed, so that the total cost can be minimized.

(Example 1)
A steel plate of 9 mm thickness x 100 mm width x 200 mm length is subjected to grid blasting treatment, scales, etc. are removed, and then an intermediate resin layer and a high corrosion resistant metal layer of the level shown in Table 1 are exposed to an iron surface on one side to 100 mm. It coat | covered with the area of * 100mm, and was set as the test material. Test Nos. A to D are two-component cured urethane elastomers that are spray-coated with a urethane resin primer of 15 to 50 μm in thickness and mixed with a commercially available polyol resin and an isocyanate curing agent. Were mixed with a mixer and spray-coated to the desired film thickness. On top of that, a two-component curable urethane resin adhesive was applied in an amount of 100 μm to 500 μm, and a high corrosion-resistant metal was adhered while being pressed by a roll.

  Test number E was the same as described above up to the urethane elastomer, and the total film thickness was 2.5 mm. In test number F, a commercially available thermosetting powder epoxy resin was applied to 100 μm, the steel surface was heated to 180 ° C., a maleic acid-modified polyethylene layer was attached to 400 μm, and a low-density polyethylene layer was attached to 2 mm. On top of that, a 2 mm thick sheet coated with an adhesive on the surface of butyl rubber was pasted, and a high corrosion resistant metal plate was pasted. A pure titanium plate of test number F is previously immersed in a 5% hydrofluoric acid + 20% nitric acid solution at room temperature for 10 minutes, and then Pt is counter electroded in 10% hydrochloric acid + 2% chloroplatinic acid solution. went.

  Further, in test numbers G to K, a mixture of a block isocyanate curing agent, an epoxy resin, and xylene was applied as an adhesive to a predetermined film thickness, and after the highly corrosion-resistant metal layer was laminated, it was polymerized and cured by heating to 200 ° C. The material was used as a test material. G, H, J, and K contain 30% by mass of talc as extender pigments, but I contains 70% by mass of Zn powder instead. In addition, K does not laminate | stack the highly corrosion-resistant metal layer as a comparison.

  The back and side surfaces of this test piece were coated with a tar epoxy paint at 300 μm and sealed. Lead wires were attached to the high corrosion-resistant metal surface and the steel material surface of the test material, respectively, and immersed in artificial seawater at 25 ° C. Table 2 shows changes in the surface of the steel material after a voltage was applied to the lead wire installed between the immersed steel material and the highly corrosion-resistant metal and left for one week. Application of the voltage is no. For 1 to 8, the potential of the steel surface is measured with a saturated KCl silver / silver chloride electrode, the potential is set to -0.85 V, the potential is measured every day, and if there is a fluctuation, the interelectrode voltage is Changed. In other tests, the potential was initially set and the experiment was continued as it was. The potentials shown in Table 2 are values after one week.

No. Reference numerals 6, 9, and 10 are examples in which the potential of the sample number F was changed and the experiment was performed. No. No. 12 is a comparative example in which the test material of sample number A was inverted for the anode and cathode, No. 12; Reference numeral 13 is a comparative example in which a high corrosion resistant metal and a steel material are short-circuited.
In the present invention example, the steel material surface is covered with a white film called electrocoating, and no corrosion occurs. This is evidence that the cathodic protection is effective. In the comparative examples, all are corroded and may be corroded severely. With respect to the surface potential of the steel material, a more preferable condition of −0.8 V or less as defined in the present invention was satisfactory with no occurrence of corrosion. In particular, Sample No. F obtained by subjecting the titanium surface to a low polarization treatment does not change the applied voltage over the course of one week, and good anticorrosive properties are obtained.

(Example 2)
As an example when applied to a steel pipe, a commercially available isocyanate-terminated prepolymer is used as a primer after grid blasting is applied to the upper end 3 m of the outer surface of the steel pipe having an outer diameter of 600 mm, a thickness of 9 mm, and a length of 9 m to remove scales and the like. The moisture-curing urethane resin coating was spray-coated to a thickness of 15-60 μm and cured. Next, a two-component cured urethane elastomer containing fine powder of kaolin clay on the surface is mixed with a mixer and spray-coated, wrapped around the entire circumference while being crimped with a roll with a width of 2.4 m, and the lower end of the titanium plate The metal heavy-duty anti-corrosion-coated steel pipe of the present invention, which was subjected to low polarization treatment by hydrofluoric acid treatment + Pt plating over a width of 50 cm, was produced. On the other hand, a steel pipe of only urethane coating having the same size and not wrapped with a titanium plate was used as a comparison.

  Two steel pipes were built in the sea part of Tokyo Bay, and titanium-coated steel pipes were applied with a constant voltage power source with the titanium side as the anode and the steel material as the cathode side. The portion subjected to the low polarization treatment at that time was positioned at a depth of -0.5 m from the average low tide surface. The set voltage was set to −0.85 V with respect to the silver / silver chloride electrode, and the voltage was reset every week. The voltage change occurred during the first month, but after that, the voltage across the electrodes was constant at 2.8V. One year later, the underwater part was inspected by a diver. In the comparative steel pipe, the steel material was corroded under the attached organism, and the rust was deposited thickly. In the present invention example, a white electrocoating was formed. The occurrence of rust was not observed, and the effect of the present invention was recognized.

It is a figure which shows the structural example of this invention.

Explanation of symbols

1 Steel 2 Intermediate resin layer 3 High corrosion resistance metal 4 Water surface 5 Anode 6 Cathode 7 Constant voltage power supply

Attorney Attorney Shiina and others 1

Claims (8)

An anticorrosion steel material in which an intermediate resin adhesive layer having a volume resistivity of 10 ⁹ Ω · cm or more is coated on a part of the steel material surface with a thickness of 0.1 mm or more, and a highly corrosion-resistant metal layer is laminated on the adhesive layer. Efficient corrosion-proofing of steel materials by connecting a DC power source with a high-corrosion-resistant metal layer as an anode and a steel material as a cathode, while the high-corrosion-resistant metal laminated portion and non-laminated portion are simultaneously in contact with freshwater or seawater environments Safe anti-corrosion method. 2. The cathodic protection method according to claim 1, wherein the surface potential of the steel material is maintained at -0.8 V or less with respect to a saturated KCl silver / silver chloride standard electrode. The cathodic protection method according to claim 1 or 2, wherein all or part of the highly corrosion-resistant metal layer is made of titanium or a titanium alloy. The cathodic protection method according to claim 3, wherein the surface of the titanium or titanium alloy is subjected to a low polarization treatment. A corrosion-resistant steel material laid in a freshwater or seawater environment, and an intermediate resin adhesive layer having a volume resistivity of 10 ⁹ Ω · cm or more is coated to a thickness of 0.1 mm or more on the surface of the steel material located on the surface of the water when laid And a corrosion-resistant steel material comprising a high-corrosion-resistant metal layer laminated thereon, and the high-corrosion-resistant metal layer and the steel material having a connection portion with an external power source. 6. The anticorrosion steel material according to claim 5, wherein all or part of the high corrosion resistance metal layer is made of titanium or a titanium alloy. The anticorrosion steel material according to claim 6, wherein the surface of the titanium or the titanium alloy is subjected to a low polarization treatment. It is a corrosion-proof structure formed by laying at least the corrosion-resistant steel material according to any one of claims 5 to 7 in a freshwater or seawater environment, with the high corrosion-resistant metal layer as an anode and the steel material as a cathode, through each connection portion. An anticorrosion structure connected to an external power supply.

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