Method for repairing damage to anti-corrosion coating layer in metal material

Abstract

Provided is a repair method with which it is possible to repair an anti-corrosion coating layer (2) in a metal material (1) by a simple method, and with which the stability and durability of the repaired portion are excellent. The repair method of the present invention comprises at least: a coating removal part formation step for forming a coating removal part (23) in which a metal material (1) is exposed by removing a damaged part (21) of an anti-corrosion coating layer (2) and a floating part (22) around the damaged part (21); and a filling part forming step in which two or more polyolefin sheets (31A, 32A, 33A) for filling are laminated and bonded to fill the coating removal part (23) in the form of two or more sheet layers (31, 32, 33), thereby forming a filling part having substantially the same height as the anti-corrosion coating layer (2) surrounding the coating removal part (23). Each of the sheet layers is formed by joining two or more polyolefin sheets for filling, so that the sheet layers have seam lines (31B, 32B, 33B), and the seam lines do not overlap between adjacent sheet layers.

Description

Technical Field

[0001] The present invention relates to a method for repairing damage to a corrosion protection coating in a metal material coated with a corrosion protection coating made of polyolefin. Background Art

[0002] Polyolefin is easy to process and has excellent durability against moisture, soil, gas, etc., and thus is widely used for corrosion protection coating of metal materials such as steel pipes.

[0003] Metal materials are subject to various physical impacts during storage, transportation, construction, etc. At this time, the corrosion protection coating of a metal material coated with polyolefin may sometimes be damaged. The damaged part causes a reduction in the corrosion resistance of polyolefin. Therefore, when damage occurs, it is necessary to repair it. Various repair methods have been proposed for the damage.

[0004] For example, several methods of filling a portion where the corrosion protection coating is exposed with a filling material (sealant) are known (Patent Documents 1 to 3).

[0005] Patent Document 1 discloses a repair method in which a sealant showing thermomelting property or adhesiveness and fluidity at normal temperature is filled in a damaged portion formed as a recess in a corrosion protection coating, and after the upper surface thereof becomes flush with the surface of the corrosion protection coating, a repair member formed by disposing an adhesive layer on one side of a crosslinked polyolefin sheet is heat-pressed to the damaged portion of the corrosion protection coating through the adhesive layer so as to also cover the surrounding corrosion protection coating of the damaged portion, and then, a reinforcing heat-fusible polyolefin sheet having a softening point higher than the softening point of the adhesive of the adhesive layer used for the repair member is heat-pressed so as to continuously cover at least the outer peripheral portion of the repair member and the corrosion protection coating close to the outer peripheral portion.

[0006] Patent Document 2 discloses a repair method in which a filling material is filled in a film damaged portion of a polyethylene-coated corrosion protection steel material, a polyethylene sheet is placed thereon so as to cover the filling material, and the polyethylene sheet is ultrasonically welded to the polyethylene coating film on the steel material surface.

[0007] Patent Document 3 discloses a repair method, in which a primer containing a reaction-curable resin showing adhesiveness to polyolefin is applied to at least a sealant contact predetermined surface of a polyolefin anticorrosive coating around the exposed surface of a steel pipe, and then a sealant containing a reaction-curable resin showing adhesiveness to the steel pipe is applied to the sealant contact predetermined surface and the exposed surface of the steel pipe. Then, a heat-shrinkable covering material coated with the primer on one surface is disposed at least on the sealant layer in such a manner that the primer-coated surface faces the sealant layer, and before the curing reaction of the primer ends at the latest, the heat-shrinkable covering material is heated to cause thermal shrinkage thereof and is at least pressed against the sealant layer.

[0008] In addition, a method of repairing a portion where an anticorrosive coating is exposed using a polyolefin sheet is also known (Patent Documents 4 to 5).

[0009] Patent Document 4 discloses a repair method, in which a modified polyethylene sheet is heat-pressed onto a damaged portion of a Milcoat polyethylene coating of a steel material and the coating surface around the damaged portion for coating, and then a double-layer sheet (lower layer: modified polyethylene, upper layer: polyethylene) is heat-pressed onto the modified polyethylene coating for coating.

[0010] Patent Document 5 discloses a repair method, in which a primer containing an organometallic compound is applied to a damaged portion of a polyolefin-coated steel material and the Milcoat polyolefin coating around the damaged portion, and a primer is applied to one surface and the side surface of a repair polyolefin sheet having a shape inserted into the damaged portion. Then, an α-cyanoacrylate resin-based composition is applied to at least one of the primer-coated surfaces of the Milcoat polyolefin coating around the damaged portion and the primer-coated surface of the repair polyolefin sheet, and the primer-coated surfaces are opposed to each other to bond the repair polyolefin sheet to the damaged portion.

[0011] When a metal material repaired by the method using a filler (sealant) in Patent Documents 1 to 3 has a structure in which different materials (filler and polyolefin) are joined, there is a possibility that the repaired portion may be damaged due to different thermal expansion rates in an environment where the temperature around the metal material can rise.

[0012] In addition, in the case of the method using a polyolefin sheet as in Patent Documents 4 to 5, in order to sufficiently ensure the adhesion between the polyolefin sheet and the metal material as a base or the surrounding polyolefin anticorrosive coating, there are difficulties in that heating is required or special materials are required as adhesives and primers.

[0013] Therefore, it is desired to develop a repair method that can repair damage to an anticorrosive coating in a metal material by a simple method and has excellent stability and durability of the repaired portion.

[0014] Prior art documents

[0015] Patent documents

[0016] Patent document 1: Japanese Patent Laid-Open No. 61-170586

[0017] Patent document 2: Japanese Patent Laid-Open No. 2001-129892

[0018] Patent document 3: Japanese Patent Laid-Open No. 61-193832

[0019] Patent document 4: Japanese Patent Laid-Open No. 1-95029

[0020] Patent document 5: Japanese Patent Laid-Open No. 1-275032 Summary of the invention

[0021] Problems to be solved by the invention

[0022] The present invention has been completed in view of the above background art, and its object is to provide a repair method that can repair damage to the anticorrosion coating in a metal material by a simple method (for example, even a non-expert can repair it), and the stability and durability of the repaired portion are excellent.

[0023] Means for solving the problems

[0024] The inventor of the present invention conducted repeated and in-depth studies to solve the above problems, and as a result, found that when repairing the anticorrosion coating by filling a polyolefin sheet, which is the same raw material as the anticorrosion coating, into the coating removal portion, it is easy to bond evenly by laminating and bonding two or more polyolefin sheets, and forming each sheet layer by joining two or more polyolefin sheets.

[0025] In addition, it was found that when each sheet layer is composed of two or more sheets, there is a risk that liquids such as water may enter from the seams between the sheets. By configuring the seam lines between the upper and lower adjacent sheet layers not to coincide, this risk can be reduced, ensuring the stability and durability of the repaired portion, and thus the present invention was completed.

[0026] That is, the present invention provides a repair method, which is a repair method for damage to an anticorrosion coating in a metal material coated with an anticorrosion coating composed of polyolefin, and is characterized by at least having:

[0027] A coating removal portion forming step of forming a coating removal portion where the metal material is exposed by removing the damaged portion of the anticorrosion coating and the raised portion around the damaged portion; and

[0028] The filling part forming step: by laminating and bonding two or more sheets of filling polyolefin sheets and filling them into the coating removal part, a filling part having substantially the same height as the anticorrosion coating layer surrounding the coating removal part is formed.

[0029] Each of these layers is formed by joining two or more filling polyolefin sheets, and thus has a seam line, such that the seam lines do not overlap between adjacent layers.

[0030] In addition, the present invention provides the above-mentioned repair method, which further has a covering part forming step: at the boundary part between the above-mentioned filling part and the anticorrosion coating layer surrounding the filling part, a covering polyolefin sheet is provided by bonding to form a covering part that covers the boundary part from above.

[0031] It should be noted that in this specification, "polyolefin sheet" is sometimes abbreviated as "sheet", "filling polyolefin sheet" is abbreviated as "filling sheet", and "covering polyolefin sheet" is abbreviated as "covering sheet".

[0032] Advantages of the Invention

[0033] According to the present invention, a repair method can be provided, which can repair the damage of the anticorrosion coating layer in a metal material by a simple method, and the stability and durability of the repaired part are excellent.

[0034] In particular, metal materials such as steel pipes to which the present invention is applied are mostly used in places with a lot of moisture and environments exposed to chemicals, and the metal materials repaired by the method of the present invention can also exhibit sufficient durability in such places.

[0035] In the method of the present invention, when pasting the polyolefin sheet on the metal material, heating is not required, so repair can be carried out even in places and situations where fire must be avoided.

[0036] In the method of the present invention, the sheet filled in the coating removal part and the anticorrosion coating layer remaining around the coating removal part are made of the same polyolefin, so their thermal expansion rates are of the same level, and the repaired part is not easily damaged even in an environment where the temperature around the metal material can rise.

[0037] In the method of the present invention, the layer is formed by joining two or more sheets, so the size of each sheet is relatively small. Therefore, compared with the case of repairing by filling with a single polyolefin sheet, the method of the present invention has various advantages.

[0038] First, in the method of the present invention, even for an unskilled operator, it is easy to uniformly apply the primer and the adhesive to the sheet. In addition, in the method of the present invention, it is easy to deal with damages of various shapes. Especially when the metal material is a bent pipe, a tower tank, etc., if damages occur on the curved surfaces such as the bending part and the branch part, it is extremely difficult to uniformly apply the primer and the adhesive to the sheet in the method of filling with a single polyolefin sheet, while the method of the present invention can easily repair such curved surfaces.

[0039] In the method of the present invention, a filling part is formed by laminating two or more sheet layers. Thus, the present invention has various advantages compared with the case of forming a filling part with a single sheet layer.

[0040] For example, the anticorrosive coating layer of the metal material has various thicknesses. In the method of the present invention using two or more sheet layers, it is possible to cope with anticorrosive coating layers of various thicknesses.

[0041] In addition, in the method of the present invention using two or more sheet layers, even if something goes wrong in one of the sheet layers, the influence is not easily spread to the metal material as the base.

[0042] Furthermore, in an environment where the temperature around the metal material can rise, due to the different thermal expansion rates of the metal material and the polyolefin sheet, the adhesive layer between the metal material and the polyolefin sheet is likely to deteriorate. However, in the case of laminating two or more sheet layers as in the present invention, there is no difference in the thermal expansion rates between the sheet layers, so the adhesive layer between the sheet layers is not easily deteriorated.

[0043] As described above, in the method of the present invention, since two or more sheet layers are used and each sheet layer is composed of joining two or more sheets, the repair is extremely easy, and the stability and durability of the repaired part can be made excellent. Description of the Drawings

[0044] Figure 1 is a schematic cross-sectional view of the metal material.

[0045] Figure 2 is a schematic cross-sectional view near the damaged part of the anticorrosive coating layer of the metal material.

[0046] Figure 3 is a schematic cross-sectional view of the metal material after the formation process of the coating removal part.

[0047] Figure 4 is a top view of the metal material after the formation process of the coating removal part.

[0048] Figure 5 is a top view of the metal material after the formation process of the coating removal part.

[0049] Figure 6 It is a schematic cross-sectional view of a metal material after the filling portion forming process.

[0050] Figure 7 It is a schematic cross-sectional view showing the process of the filling portion forming process. (a) The state of the layer where the first layer is formed; (b) The state of the layer where the second layer is formed; (c) The state of the layer where the third layer is formed.

[0051] Figure 8 It is a top view showing the process of the filling portion forming process. (a) The state of the layer where the first layer is formed; (b) The state of the layer where the second layer is formed; (c) The state of the layer where the third layer is formed.

[0052] Figure 9 It is a top view showing the process of the filling portion forming process. (a) The state of the layer where the first layer is formed; (b) The state of the layer where the second layer is formed; (c) The state of the layer where the third layer is formed.

[0053] Figure 10 It is a schematic cross-sectional view of a metal material after the covering portion forming process.

[0054] Figure 11 It is a top view of a metal material after the covering portion forming process.

[0055] Figure 12 It is a schematic cross-sectional view of a metal material after the covering portion forming process.

[0056] Figure 13 It is a top view of a metal material after the covering portion forming process.

[0057] Figure 14 It is a schematic cross-sectional view showing the processes of the filling portion forming process and the covering portion forming process (in the filling portion forming process, the case where a partially covered removal portion is formed). (a) The state of the layer where the first layer is formed; (a’) The state where a partially covered removal portion is formed after the layer of the first layer is formed; (b) The state of the layer where the second layer is formed.

[0058] Figure 15 It is Figure 14 A continuation of the figure. (b’) The state where a partially covered removal portion is formed after the layer of the second layer is formed; (c) The state of the layer where the third layer is formed; (d) The state after the covering portion forming process. Detailed implementation mode

[0059] Hereinafter, the present invention will be described, but the present invention is not limited to the following embodiments and can be implemented with arbitrary deformations.

[0060] The present invention relates to a method for repairing damage to the corrosion - resistant coating 2 on a metal material 1 coated with a corrosion - resistant coating 2 made of polyolefin. A schematic cross - sectional view of the metal material 1 before repair in the present invention is shown in Figure 1 . The metal material 1 is coated with a corrosion - resistant coating 2 made of polyolefin.

[0061] There is no particular limitation on the type of metal constituting the metal material 1, and examples thereof include iron, aluminum, copper, zinc, steel, etc.

[0062] There is also no particular limitation on the shape of the metal material 1, and examples thereof include metal plates, metal pipes, metal rods, metal containers such as cans, etc.

[0063] When the metal material 1 is a metal pipe, the metal pipe may have the corrosion - resistant coating 2 on its inner surface, may have the corrosion - resistant coating 2 on its outer surface, or may have the metal layer on both the inner surface and the outer surface. The repair method of the present invention can also be applied to the corrosion - resistant coating 2 on either the inner surface or the outer surface.

[0064] In addition, when the metal material 1 is a metal pipe, the metal pipe may be a straight pipe, or may be a bent pipe (a metal pipe with a bent portion), a branched pipe, a tapered pipe, etc.

[0065] When the metal material 1 is a metal pipe, its inner diameter is not particularly limited. The inner diameter of the metal pipe is, for example, 20 cm or more, 40 cm or more, or 50 cm or more, and is 10 m or less, 5 m or less, or 3 m or less.

[0066] When the metal material 1 is a steel pipe whose inner surface and / or outer surface is coated with the above - mentioned corrosion - resistant coating, especially when the steel pipe is a steel pipe for transporting liquids (such as water, chemicals, etc.), the chance of damage is high, and the steel pipe is widely used. Therefore, the advantages of the present invention can be easily exerted: a repair part with excellent stability and durability can be formed by a simple method.

[0067] When the metal material 1 is a steel pipe, more specifically, examples include electric - welded steel pipes, forged steel pipes, coated steel pipes, seamless steel pipes, spiral steel pipes, UOE steel pipes, etc., but are not limited to these.

[0068] The corrosion - resistant coating 2 is made of polyolefin and serves to protect the metal material 1 from corrosion and impact.

[0069] There is no particular limitation on the polyolefin as the raw material of the corrosion - resistant coating 2, and examples thereof include low - density polyethylene, medium - density polyethylene, high - density polyethylene, polypropylene, polybutene, copolymers thereof, etc.

[0070] They can be used individually, one type at a time, to form the anticorrosive coating 2, or two or more types can be used in combination to form the anticorrosive coating 2.

[0071] The thickness of the anticorrosive coating 2 (hereinafter, when referred to as "thickness" in this specification, it means the average thickness unless otherwise specified) is preferably 0.5 mm or more, more preferably 1 mm or more, particularly preferably 1.2 mm or more, and most preferably 1.5 mm or more. Further, it is preferably 5 mm or less, more preferably 4.5 mm or less, and particularly preferably 4 mm or less.

[0072] If the thickness is above the above lower limit, the anticorrosive property and impact resistance are excellent. In addition, if the thickness is below the above upper limit, it is advantageous in terms of cost.

[0073] In the repair method of the present invention, first, a coating removal part forming step is performed. In the coating removal part forming step, by removing the damaged part 21 of the anticorrosive coating 2 and the raised part 22 around the damaged part 21, a coating removal part 23 where the metal material 1 is exposed is formed.

[0074] Figure 2 is a schematic cross-sectional view near the damaged part 21 of the anticorrosive coating 2 of the metal material 1. Due to contact with other materials during storage and transportation, and contact with tools during maintenance, etc., a damaged part 21 is generated in the anticorrosive coating 2. It can be visually confirmed that the periphery of the damaged part 21 is in a state of being raised above the surface of the surrounding anticorrosive coating 2 (becoming the raised part 22) (it should be noted that, Figure 2 in, the damaged part 21 and the raised part 22 are exaggeratedly depicted).

[0075] In the coating removal part forming step, the damaged part 21 and the raised part 22 around the damaged part 21 are removed.

[0076] The removal of the raised part 22 can be carried out by a known method using a cutter, scissors, power tools, etc.

[0077] The schematic cross-sectional view of the metal material 1 after the coating removal part forming step is shown in Figure 3 , and the top view is shown in Figure 4 . The part where the damaged part 21 and the raised part 22 are removed becomes a state where the anticorrosive coating 2 is removed and the metal material 1 is exposed (becoming the coating removal part 23).

[0078] In the coating removal part forming step, at least the anticorrosive coating 2 of the damaged part 21 and the raised part 22 (that is, the part that can be visually confirmed to be in a state of being more raised than the surface of the surrounding anticorrosive coating 2) is removed, but a certain margin (more) of the anticorrosive coating 2 outside the raised part 22 can also be removed.

[0079] In addition, when the shape of the coating removal portion 23 is Figure 4 the random shape shown, in the subsequent filling portion forming step, it is necessary to cut the shaped polyolefin sheet to match the shape of the coating removal portion 23. In order to reduce the labor of such cutting, the anti-corrosion coating layer 2 including the anti-corrosion coating layer 2 outside the floating portion 22 may also be removed to form, for example, Figure 5 the rectangular coating removal portion 23 shown.

[0080] The area of the coating removal portion 23 is preferably 50 cm 2 or more, more preferably 75 cm 2 or more, particularly preferably 100 cm 2 or more. In addition, it is preferably 500 cm 2 or less, more preferably 400 cm 2 or less, particularly preferably 300 cm 2 or less.

[0081] In the repair method of the present invention, after the coating removal portion forming step, a filling portion forming step is performed. In the filling portion forming step, the filling polyolefin sheets (31A, 32A, 33A) are laminated and bonded in two or more layers (31, 32, 33) and filled in the coating removal portion 23 to form a filling portion 3 having substantially the same height as the anti-corrosion coating layer 2 surrounding the coating removal portion 23.

[0082] Figure 6 FIG. shows a schematic cross-sectional view of the metal material 1 after the filling portion forming step is performed. By performing the filling portion forming step, a state is obtained in which the polyolefin sheet is filled in the portion that was originally the coating removal portion 23 formed by removing the damaged portion 21 and the floating portion 22 around the damaged portion 21.

[0083] In the filling portion forming step, the filling polyolefin sheets (31A, 32A, 33A) are laminated on the coating removal portion 23 in two or more layers (31, 32, 33). Each layer (31, 32, 33) is formed by joining two or more filling polyolefin sheets (31A, 32A, 33A), and thus has a seam line, so that the seam lines (31B, 32B, 33B) do not coincide between adjacent layers.

[0084] In Figure 7 , Figure 8 , Figure 9 , taking the case where the number of layers laminated on the coating removal portion 23 is three as an example, a specific example of the process of the filling portion forming step is shown.

[0085] First, a polyolefin sheet 31A for filling is bonded to the metal material 1 exposed in the coating removal portion 23, thereby forming the first-layer sheet layer 31 ( Figure 7 of (a), Figure 8 of (a), Figure 9 of (a)).

[0086] As Figure 8 of (a), Figure 9 of (a) shows, the first-layer sheet layer 31 is formed by joining two or more polyolefin sheets 31A for filling, and a seam line 31B is formed between the sheets 31A and 31A.

[0087] The sheet 31A is used by cutting a shaped (e.g., rectangular) polyolefin sheet commercially available or the like according to the shape of the coating removal portion 23. In the coating removal portion forming process, when the shape of the coating removal portion 23 is formed into, for example, Figure 5 the rectangular shape shown in Figure 9 of (a), the first-layer sheet layer 31 also becomes rectangular as shown in

[0088] of (a), and the labor of cutting the sheet in the filling portion forming process can be reduced. Figure 7 of (b), Figure 8 of (b), Figure 9 of (b)).

[0089] As Figure 8 of (b), Figure 9 of (b) shows, the second-layer sheet layer 32 is also formed by joining two or more polyolefin sheets 32A for filling, and a seam line 32B is formed between the sheets 32A and 32A.

[0090] Here, the seam line 32B in the second-layer sheet layer 32 is formed so as not to coincide with the seam line 31B in the first-layer sheet layer 31 (adjacent sheet layer) (it should be noted that in Figure 8 of (b), Figure 9 of (b), the seam line 31B in the first-layer sheet layer 31 is indicated by a one-dot chain line).

[0091] By making the seam lines not coincide between the upper and lower adjacent sheet layers, when the filling portion 3 comes into contact with a liquid such as water, it is difficult for the liquid to enter the lower-layer sheet and further difficult to enter the metal material 1, and the stability and durability of the trapping portion are improved.

[0092] In order to more easily prevent the entry of a liquid such as water, the positions of the seam lines (seam line 32B and seam line 31B) of the upper and lower adjacent sheet layers are preferably as far apart as possible. For example, as Figure 8 of (b),Figure 9 As shown in FIG. (b), preferably, the seam line 32B is formed at a position near the middle of the two seam lines 31B.

[0093] After forming the sheet layer 32 of the second layer, a polyolefin sheet 33A for filling is bonded thereto, thereby forming the sheet layer 33 of the third layer ( Figure 7 FIG. (c), Figure 8 FIG. (c), Figure 9 FIG. (c)).

[0094] As Figure 8 FIG. (c), Figure 9 FIG. (c) shows, the sheet layer 33 of the third layer is also formed by joining two or more polyolefin sheets 33A for filling, and a seam line 33B is formed between the sheets 33A and 33A.

[0095] Similar to the case of the sheet layer 32 of the second layer, in the sheet layer 33 of the third layer, the seam line 33B is also formed so as not to coincide with the seam line 32B in the sheet layer 32 (adjacent sheet layer) of the second layer (it should be noted that in Figure 8 FIG. (c), Figure 9 FIG. (c), the seam line 32B in the sheet layer 32 of the second layer is indicated by a one-dot chain line).

[0096] In order to more easily prevent the entry of liquids such as water, the positions of the seam line 33B and the seam line 32B are preferably as far apart as possible. For example, as Figure 8 FIG. (c), Figure 9 FIG. (c) shows, preferably, the seam line 33B is formed at a position near the middle of the two seam lines 32B. That is, the position of the seam line 33B of the sheet layer 33 of the third layer can be substantially the same as the position of the seam line 31B of the sheet layer 31 of the first layer.

[0097] In the case where the number of sheet layers is three, by forming the sheet layer 33 of the third layer, a state is formed in which the filling portion 3 is formed in the portion that was originally the damaged portion 21 and its periphery of the anticorrosion coating 2 of the metal material 1 ( Figure 6 ).

[0098] The anticorrosion coating 2 is made of polyolefin, and the filling portion 3 is formed by bonding a polyolefin sheet for filling. Therefore, the thermal expansion rate of the filling portion 3 and the anticorrosion coating 2 around it is of the same degree, and even in an environment where the temperature around the metal material 1 can rise, the repaired portion of the metal material repaired by the method of the present invention is not easily damaged.

[0099] Specific examples of the polyolefin resin as the raw material of the anticorrosive coating layer 2 are as described above. Preferably, the polyolefin constituting the anticorrosive coating layer 2 is chemically the same as the polyolefin constituting the polyolefin sheets for filling (31A, 32A, 33A). That is, it is preferable to select a polyolefin sheet that is chemically the same as the polyolefin of the anticorrosive coating layer 2 of the metal material 1 to which the method of the present invention is applied and use it as the polyolefin sheet for filling (31A, 32A, 33A).

[0100] Thereby, it is easier to prevent breakage of the repaired portion in an environment where the temperature around the metal material 1 can rise.

[0101] In the filling portion forming step, the polyolefin sheets for filling are laminated in two or more layers.

[0102] The number of layers is preferably 2, 3, or 4 layers. When the number of layers is 5 or more, the working time increases and the number of bonding portions increases, and thus the stability and durability of the repaired portion may sometimes decrease.

[0103] In the filling portion forming step, a commercially available shaped (e.g., rectangular) polyolefin sheet is cut as needed and used.

[0104] The thickness of the shaped polyolefin sheet is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more. In addition, it is preferably 5 mm or less, more preferably 4 mm or less, and particularly preferably 3 mm or less.

[0105] If the thickness is within the above range, it is easy to make the number of layers within the above preferred range.

[0106] The area of each shaped polyolefin sheet is preferably 50 cm 2 or more, more preferably 75 cm 2 or more, and particularly preferably 100 cm 2 or more. In addition, it is preferably 500 cm 2 or less, more preferably 400 cm 2 or less, and particularly preferably 300 cm 2 or less.

[0107] If the area is above the above lower limit, the workability (working time) is easily improved. If the area is below the above upper limit, the adhesive and the primer can be uniformly coated on the sheet, and peeling of the sheet is less likely to occur.

[0108] The shaped polyolefin sheet is cut according to the shape of the coating removal portion 23 and used. Especially when the shape of the coating removal portion 23 is Figure 4 the random shape shown, the area of the cut sheet may sometimes be below the above lower limit, but there is no particular problem.

[0109] In the filling part forming process, bonding is preferably carried out by coating a primer on the polyolefin sheet for filling, drying the primer, and then coating an adhesive on the polyolefin sheet for filling.

[0110] The first layer of the sheet layer 31 is formed by bonding the sheet 31A to the metal material 1 exposed in the coating removal part 23. Compared with coating a primer and an adhesive on the metal material 1, coating a primer and an adhesive on the sheet 31A can be evenly coated, and the adhesiveness is easily improved.

[0111] The sheet layers after the second layer are formed by bonding polyolefin sheets to each other. In this case, the primer and the adhesive can be coated on the polyolefin sheet constituting the already provided sheet layer, or can be coated on the newly provided polyolefin sheet, or can be coated on two polyolefin sheets.

[0112] From the aspect of improving adhesiveness, it is preferable to coat a primer and an adhesive on two polyolefin sheets.

[0113] By coating a primer before coating an adhesive on the bonding surface such as a polyolefin sheet, the adhesiveness between the adhesive and the bonding surface becomes good.

[0114] As a specific example of the primer used in the filling part forming process, amine-based primers, synthetic rubber-based primers, acrylic-based primers, polyurethane-based primers, epoxy-based primers, etc. can be exemplified.

[0115] These primers can be used alone as one kind, or two or more kinds can be used in combination. From the aspect of working efficiency, it is preferable to use one kind alone.

[0116] The coating amount of the primer used in the filling part forming process is preferably 0.1 g / m 2 or more, more preferably 0.5 g / m 2 or more, particularly preferably 1.0 g / m 2 or more. In addition, it is preferably 6.0 g / m 2 or less, more preferably 3.0 g / m 2 or less, particularly preferably 2.0 g / m 2 or less.

[0117] If the coating amount is above the above lower limit, the workability (working time) is easily improved, and it is advantageous in terms of cost. If the area is below the above upper limit, the adhesiveness is easily improved.

[0118] After applying the primer, an adhesive is applied over the primer. Regarding the timing of applying the adhesive, the time interval from the completion of applying the primer to the start of applying the adhesive is preferably 0.5 minutes or more, more preferably 1 minute or more, and particularly preferably 2 minutes or more. Further, it is preferably 10 minutes or less, more preferably 7 minutes or less, and particularly preferably 5 minutes or less.

[0119] Specific examples of the adhesive used in the filling portion forming step include polyvinyl acetate adhesives, cyanoacrylate adhesives, cellulose adhesives, polyester adhesives, polyether adhesives, polyamide adhesives, polyimide adhesives, epoxy adhesives, polyurethane adhesives, rubber adhesives, silicone adhesives, and the like.

[0120] These adhesives may be used singly or in combination of two or more. From the viewpoint of working efficiency, it is preferable to use one kind alone.

[0121] The coating amount of the adhesive used in the filling portion forming step is preferably 20 g / m 2 or more, more preferably 30 g / m 2 or more, and particularly preferably 40 g / m 2 or more. Further, it is preferably 70 g / m 2 or less, more preferably 60 g / m 2 or less, and particularly preferably 50 g / m 2 or less.

[0122] If the coating amount is at least the above lower limit, workability (working time) is easily improved and it is advantageous in terms of cost. If the area is at most the above upper limit, adhesiveness is easily improved.

[0123] In the filling portion forming step, on the surface of the metal material 1 exposed in the covering removal portion 23, before setting the polyolefin sheet, in order to improve adhesiveness, it is preferable to roughen the surface using sandpaper or the like. Further, the surface of the metal material 1 after surface roughening is preferably cleaned using a solvent such as acetone and waste cloth or the like to remove rust and foreign matters in advance.

[0124] In addition, for the polyolefin sheet provided in the covering removal portion 23 in the filling portion forming step, it is also preferable to perform surface roughening and cleaning using the same method. From the viewpoints of working efficiency and adhesiveness, it is particularly preferable to perform surface roughening and cleaning on both sides of the polyolefin sheet before setting in advance.

[0125] In the repair method of the present invention, a covering portion forming step may also be performed after the filling portion forming step.

[0126] In the covering part forming process, on the boundary part 34 between the filling part 3 and the anticorrosive coating layer 2 surrounding the filling part 3, a covering polyolefin sheet 41 is adhesively provided to form a covering part 4 that covers the boundary part 34 from above ( Figure 10 , Figure 12 ).

[0127] In the filling part 3 of the metal material 1 ( Figure 6 ) after the filling part forming process, by making the seam lines between the upper and lower adjacent sheet layers not coincide, it is possible to make it difficult for liquids such as water to enter the lower layer side sheet layer and further difficult to enter the metal material 1. However, sometimes liquids such as water enter the metal material 1 via the boundary part 34 between the filling part 3 and the anticorrosive coating layer 2 surrounding the filling part 3.

[0128] By performing the covering part forming process and covering the boundary part 34 from above, it is easier to prevent the entry of liquids such as water.

[0129] In the covering part forming process, on the boundary part 34 between the filling part 3 and the anticorrosive coating layer 2, a covering polyolefin sheet 41 is adhesively provided.

[0130] In the covering part forming process, as shown in Figure 10 , Figure 11 , the covering part 4 can be formed in such a way that one covering polyolefin sheet 41 covers the filling part 3 (the uppermost sheet layer) and the boundary part 34, or as shown in Figure 12 , Figure 13 , two or more covering polyolefin sheets can be used to cover only the part required to cover the boundary part 34 without covering a part of the filling part 3 (the uppermost sheet layer).

[0131] In addition, as long as the boundary part 34 can be covered, the shape of the covering polyolefin sheet 41 does not need to be the Figure 11 , Figure 13 -shown rectangle, and can also be a random shape or the like.

[0132] The thickness of the covering polyolefin sheet 41 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more. In addition, it is preferably 5 mm or less, more preferably 4 mm or less, and particularly preferably 3 mm or less.

[0133] As shown in Figure 10 , Figure 11 , when using one covering polyolefin sheet 41, the area of the covering polyolefin sheet 41 is preferably 100 cm 2 or more, more preferably 150 cm 2 or more, and particularly preferably 200 cm 2 or more. In addition, it is preferably 1000 cm 2Hereinafter, more preferably 800 cm 2 Hereinafter, particularly preferably 600 cm 2 Hereinafter.

[0134] As Figure 12 , Figure 13 shown, when using two or more polyolefin sheets 41 for covering, the area of each polyolefin sheet 41 for covering is preferably 50 cm 2 or more, more preferably 75 cm 2 or more, particularly preferably 100 cm 2 or more. In addition, it is preferably 500 cm 2 or less, more preferably 400 cm 2 or less, particularly preferably 300 cm 2 or less.

[0135] The adhesion in the covering portion forming step is also preferably carried out by applying a primer on the polyolefin sheet 41 for covering, drying the primer, and then applying an adhesive on the polyolefin sheet 41 for covering.

[0136] In the adhesion in the covering portion forming step, the primer and the adhesive can be applied to the outermost polyolefin sheet for filling of the filling portion 3 ( Figure 7 , Figure 8 , Figure 9 in the example shown in (a) is 33A), or can be applied to the polyolefin sheet 41 for covering, or can also be applied to both polyolefin sheets.

[0137] From the aspect of improving adhesion, it is preferable to apply the primer and the adhesive on both polyolefin sheets.

[0138] Specific examples of the primer and the adhesive used in the adhesion in the covering portion forming step, their preferred coating amounts, and the time interval from the completion of the application of the primer to the start of the application of the adhesive are the same as those described in the above filling portion forming step.

[0139] The polyolefin sheet 41 for covering used in the covering portion forming step is preferably surface roughened only on one side, and the surface-roughened side is used as the bonding surface with the filling portion 3 and the anticorrosion coating layer 2 (even if the non-bonding surface of the polyolefin sheet 41 for covering is surface roughened, it is meaningless).

[0140] In the filling portion forming step of the present invention, it is also possible to form a partially removed portion 24 obtained by removing the anticorrosion coating layer 2 around the lower layer so as to have substantially the same height as the "lower layer" before forming the layer after the second layer.

[0141] A specific example of this process is shown in Figure 14 andFigure 15 inside

[0142] Regarding the formation of the sheet 31 of the first layer, it is the same as the case shown in (a) of Figure 7 (the (a) of Figure 14 ).

[0143] After forming the sheet 31 of the first layer, the anticorrosion coating 2 around the sheet 31 is removed to form a partially coated removal part 24 ( Figure 14 (a’) of

[0144] ). At this time, the anticorrosion coating 2 is removed in such a way that the height of the anticorrosion coating 2 below the partially coated removal part 24 is approximately the same as the height of the sheet 31 of the first layer. Figure 14 After forming the partially coated removal part 24, a sheet 32 of the second layer is formed on the sheet 31 of the first layer (

[0145] (b) of Figure 7 ). When forming the sheet 32 of the second layer, the filling polyolefin sheet 32A is filled in a way that includes the partially coated removal part 24.

[0146] The case where the seam line 32B in the sheet 32 of the second layer does not coincide with the seam line 31B in the sheet 31 of the first layer is the same as the case shown in (b) of Figure 15 ). After forming the sheet 32 of the second layer, similarly, the anticorrosion coating 2 around the sheet 32 is removed to form a partially coated removal part 24 ( Figure 15 (b’) of

[0147] ), and then, the filling polyolefin sheet 33A is filled in a way that includes the partially coated removal part 24 to form a sheet 33 of the third layer ( Figure 15 (c) of

[0148] ). It is also possible to perform the covering part forming process after forming the sheet 33 of the third layer (that is, after the filling part forming process is completed) ( Figure 15 (d) of Figure 15 ). In the filling part forming process, by forming the partially coated removal part 24 before forming the sheets after the second layer, as shown in (c) of

[0149] and (d) of

[0150] Industrial Applicability

[0151] The repair method of the present invention can provide a repair method capable of repairing damage to the corrosion protection coating in a metal material in a simple manner, and the repaired part has excellent stability and durability. Therefore, the metal material repaired by the repair method of the present invention is widely used for repairing steel pipes such as water pipes for conveying water for water supply and drainage, agricultural water, industrial water, etc.; pipes for chemical agents and cooling water in workshops, factories, etc.; pipes for conveying gas, electricity, petroleum, etc.

[0152] Symbol Explanation

[0153] 1 Metal material

[0154] 2 Corrosion protection coating

[0155] 3 Filling part

[0156] 4 Covering part

[0157] 21 Damage part

[0158] 22 Lifting part

[0159] 23 Coating removal part

[0160] 24 Partial coating removal part

[0161] 31 Lamina (first layer)

[0162] 31A Polyolefin sheet for filling (first layer)

[0163] 31B Seam line (first layer)

[0164] 32 Lamina (second layer)

[0165] 32A Polyolefin sheet for filling (second layer)

[0166] 32B Seam line (second layer)

[0167] 33 Lamina (third layer)

[0168] 33A Polyolefin sheet for filling (third layer)

[0169] 33B Seam line (third layer)

[0170] 34 Boundary part

[0171] 41 Polyolefin sheet for covering

Claims

1. A repair method for repairing damage to an anti-corrosion coating on a metal material coated with an anti-corrosion coating made of polyolefin, characterized in that it has at least: a coating removal part forming step of forming a coating removal part where the metal material is exposed by removing the damaged part of the anti-corrosion coating and the raised parts around the damaged part; and a filling part forming step of forming a filling part having substantially the same height as the anti-corrosion coating surrounding the coating removal part by laminating and bonding two or more filling polyolefin sheets to fill the coating removal part, each of the layers is composed of two or more joined filling polyolefin sheets, thereby having seam lines, and the seam lines do not overlap between adjacent layers.

2. The repair method according to claim 1, further having a covering part forming step: on the boundary part between the filling part and the anti-corrosion coating surrounding the filling part, a covering polyolefin sheet is provided by bonding to form a covering part that covers the boundary part from above.

3. The repair method according to claim 1 or 2, wherein the bonding in the filling part forming step is performed by applying a primer to the filling polyolefin sheet, drying the primer, and then applying an adhesive to the filling polyolefin sheet.

4. The repair method according to claim 1 or 2, wherein the polyolefin constituting the anti-corrosion coating is chemically the same as the polyolefin constituting the filling polyolefin sheet.

5. The repair method according to claim 1 or 2, wherein the thickness of the anti-corrosion coating is 0.5 mm or more and 5 mm or less.

6. The repair method according to claim 1 or 2, wherein the metal material is a steel pipe whose inner surface and / or outer surface is coated with the anti-corrosion coating.

7. The repair method according to claim 7, wherein the steel pipe is a steel pipe for transporting liquid.

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