JPS62259832A - Method of corrosion-proofing steel material - Google Patents

Abstract

PURPOSE:To obtain heat resistant, corrosion-proofed steel material without employing special heating device by a method wherein the surface of the steel material is coated with undercoating consisting of two-part cold-setting epoxy resin and, after that, lap-wound by a specified thermosetting tape. CONSTITUTION:Because the undercoating to be applied onto the surface of steel material contains epoxy resin and/or modified epoxy resin, hardening agent to harden said resins under normal temperatures and various addition agent, when necessary and completely hardens after the period of time which is several times the drying time required to dry to touch from its application, no intrusion of corrosive substance between the surface of a steel pipe and the bonding interface of the undercoating and the hardened epoxy resin fully shows corrosion resisting performance. In addition, because the corrosion- resistant tape is wound immediately after the application of the undercoating, the wetting between the undercoating and the tap is satisfactory and enough adhesion is produced between the undercoating and the tape after the hardening of the adhesive layer of the corrosion-resistant tape so as to fully show corrosion resisting performance even at elevated temperatures.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing corrosion of steel materials, and more particularly to a method for preventing corrosion of steel materials by coating the surface of the steel material with an anti-corrosion tape.

[Prior art]

One of the methods for transporting fluids such as oil and gas is to install a pipeline using four pipes.

One problem with such methods is that the sh tubes corrode.

Various methods have been used to prevent corrosion of steel pipes.

One method is to protect the surface of the steel pipe with bituminous material. However, this method has the problem that the bituminous material layer is easily damaged by external impacts.

In recent years, as a method to solve the problems of such methods, a method has been adopted in which the surface of the steel pipe is coated with plastics such as polyethylene and polyvinyl chloride.

The following three methods are generally known for coating the surface of steel pipes with plastics.

1) A method of heating a steel pipe, applying an undercoat composition to the surface, coating the surface with molten plastic, and cooling.

2) A method in which plastics are processed into a cylindrical heat-shrinkable pipe in advance, this is attached to a steel pipe coated with a surface undercoating composition, and the pipe is heated to shrink and coat the pipe.

3.Preliminarily form a plastic into a tape shape and form an adhesive layer on one surface of the tape, and wrap this in a spiral shape, overlapping some parts, on the surface of a steel pipe whose surface has been coated with an undercoat composition. The so-called anti-corrosion tape coating method.

The ffE steel pipes protected with plastics in this way have remarkable effects in terms of corrosion protection and service life, as compared to the above-mentioned coated steel pipes protected with bituminous materials.

However, the primer or adhesive layer used in these methods is either a thermoplastic resin or rubber-based material, and at high temperatures the coating layer softens and becomes vulnerable to physical impact, causing it to break. Also, the adhesion with metal is lost, causing defects such as displacement or peeling of the coating layer. The problem is that water and oxygen enter through such defective parts, causing corrosion and progressing, that is, the corrosion resistance deteriorates.

Furthermore, in pipelines for transporting fluids such as petroleum and heavy oil, the fluid is usually pressurized and heated to reduce its viscosity and improve transport efficiency. When applying a plastic coating with poor quality, there was also a drawback that there was a limit to the operating temperature. In order to solve these drawbacks of plastic coatings, various countermeasures have been considered in the past, and the following attempts have also been made in anticorrosion tape construction methods. For example, in the anticorrosion tape construction method, a plastic sheet with a higher softening point is used as the support for the anticorrosion tape used, and in some cases, attempts are being made to attach a heat-resistant release base material to the plastic sheet. is also being carried out. This attempt is excellent in improving the heat resistance of the support for anticorrosive tapes.

However, if the adhesive layer is made of rubber or thermoplastic resin that does not easily soften at high temperatures, it will not exhibit adhesive properties at room temperature, the temperature at which the tape is applied, and the steel pipe will be heated. Construction must be carried out at the same time. This greatly impairs the workability and simplicity that are the advantages of the tape method.

Therefore, attempts have been made to use B-stage thermosetting resin compositions in the adhesive layer of anticorrosive tapes.

This attempt is to cure the adhesive layer using the heat generated during pipeline operation to develop anti-corrosion performance, but the #S curable resin composition used for the adhesive layer usually cannot be stored at room temperature for several months or more. The adhesive layer hardly hardens after the tape is wrapped and until the pipeline is put into operation. Therefore, during this time, corrosive substances such as water enter the adhesive interface with the pipe, resulting in a drawback that the anticorrosion performance after curing becomes insufficient.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is that the present invention exhibits good anti-corrosion performance even against high-temperature materials. Another objective is to develop a corrosion prevention method that does not require a special heating device during its construction.

[Means for solving problems]

This problem is solved by applying an undercoat consisting of a two-component cold-curing epoxy resin composition to the surface of the steel material, and then laminating a thermosetting resin composition to a plastic sheet or rubber sheet as an adhesive layer. This is achieved by wrapping the . The hammered surface of the steel material according to the present invention,
In the corrosion protection method for steel materials, which involves wrapping a thermosetting tape over and over again after applying an undercoat consisting of a two-component cold-curing epoxy resin composition, the nuclear thermosetting tape adheres to both sides of the heat-resistant polyolefin film. The present invention relates to a method for preventing corrosion of steel materials, characterized in that a polyolefin layer is formed, and an adhesive layer made of an epoxy resin composition that is sticky at room temperature is formed on one side of the adhesive polyolefin layer. .

[Function and structure of the invention]

The anticorrosion tape used in the present invention has a heat-resistant polyolefin film as a support that does not soften under the operating temperature environment, and an adhesive layer of an epoxy resin composition whose glass transition temperature after curing is higher than that of the operating temperature environment. The combination of an adhesive polyolefin layer that ensures adhesion between the polyolefin film and the adhesive layer provides excellent anti-corrosion performance even when heated.

In addition, the undercoat agent applied prior to wrapping the anticorrosive tape is composed of a two-component room temperature curing epoxy resin composition,
It dries to the touch within several tens of minutes to several hours after application, and is completely cured after several times that amount of time, so corrosive substances will not enter the adhesive interface between the SVi tube surface and the primer (hardened epoxy Fully exhibits the anti-corrosion properties inherent in resin.

In addition, since the anti-corrosion tape is wrapped immediately after applying the undercoat, the adhesive layer of the undercoat and the anti-corrosion tape is sufficiently wetted, and after the pipeline is in operation, the adhesive layer of the anti-corrosion tape is cured by the heat, and then the undercoat layer is applied. The adhesive layer exhibits sufficient adhesion and exhibits sufficient anticorrosion performance even at high temperatures.

The primer used in the present invention includes epoxy resin and/or
Contains a modified epoxy resin and a curing agent that can cure it at room temperature as essential components, and optionally a curing accelerator, filler, softener, organic solvent, adhesion imparting agent, colorant, and thermoplastic resin. , rubber, anti-aging agents, coupling agents, and other additives.

As the epoxy resin, epoxy resin (preferably M resin) which is liquid at room temperature, but if necessary, an epoxy resin which is solid at room temperature can be dissolved in an organic solvent and used.Epoxy resin that can be used or modified epoxy resin is a glycidyl ether type, glycidyl ester type, or glycidyl amine type epoxy resin such as a bisphenol type or a novolac type, or a rubber-modified epoxy resin modified with a liquid rubber having a carboxyl group or an amine group at both ends,
There are epoxy urethane resins, epoxy ester resins, epoxy alkyd resins, epoxy phenol resins, epoxy alkyd melamine resins, etc., and one type of these resins may be used alone or two or more types may be used in combination.

Examples of curing agents for curing at room temperature for curing this include polyamide polyamines, aliphatic polyamines, aromatic polyamines, alicyclic polyamines, and the like. Of course, other curing agents and curing accelerators can also be used, such as acid anhydrides, polyamides, sulfide resins, phenolic resins, etc.
In addition to initial condensates such as urea resin and melamine resin, dianediamide, tertiary amines used as catalysts, boron trifluoride-amine complexes, etc. can also be used. These curing agents may be used alone or in combination of two or more.

In addition, when selecting an epoxy resin and its curing agent, it is preferable that the cured product has a glass transition temperature higher than the temperature environment in which the anticorrosive construction product is used.

Diluents used in the primer of the present invention include high boiling point solvents such as glycols and esters, plasticizers such as phthalates and phosphates, pine oil, non-reactive diluents such as coal tar, and butyl glycidyl ether. monoepoxy compounds such as, polyepoxy compounds such as diglyndyl ether, vinyl compounds such as styrene, diallyl phthalate, epoxidized vinyl salts such as grindyl methacrylate, triphenyl phosphite, tetrahydrofuran-A, polyols, lactones, etc. There are reactive diluents, etc.

The organic solvent used in the undercoat is one that can dissolve the above-mentioned curing agent and diluent and is compatible with the epoxy resin. For example, select one or more of toluene, xylene, cyclohexanone, methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate, ethyl acetate, methyl ethyl ketone, methyl butyl ketone, dioxane, methylene chloride, acetone, etc., and use a curing agent or diluent. The agent is melted and dispersed and used as a primer solution. The solid content in the undercoat solution is set so that the viscosity is suitable for applying the undercoat solution with a brush, spray, etc., and usually about 10 to 100% is preferable. The amount of the undercoat solution applied is adjusted so that the thickness of the undercoat layer after the organic solvent has evaporated is 0.005 to 0.5 mm, preferably 0.0 to 0.2 mm.

As shown in Figure 1, the thermosetting anticorrosive tape used in the present invention has adhesive polyolefin layers (2) and (2') formed on both sides of a heat-resistant polyolefin film (1). It has a structure in which an adhesive layer (3) made of a Yuboquine resin composition having adhesive properties at room temperature is formed on one layer (2) of the polyolefin layer.

The epoxy resin composition forming the adhesive layer (3) of the thermosetting anticorrosion tape of the present invention contains as essential components an epoxy resin and/or a modified epoxy resin and a curing agent capable of curing this, and optionally curing accelerator, filler, softener,
It contains various additives such as an adhesion promoter, a coloring agent, a thermoplastic resin, a rubber, an anti-aging agent, and a compressing agent.

As an epoxy resin, in order to give it tackiness at room temperature,
It is preferable to use an epoxy resin that is liquid at room temperature and an epoxy resin that is solid at room temperature in combination. Epoxy resins that can be used include glycidyl ether type, glycidyl ester type, glycidyl amine type epoxy resins such as bisphenol type and novolac type. Examples of modified epoxy resins include epoxy urethane resins, epoxy ester resins, epoxy alkyd resins, epoxy phenol resins, epoxy alkyd melamine resins, and rubber-modified epoxy resins. One of these may be used alone or two or more may be used in combination.

As the curing agent for curing these, the curing agent normally used for epoxy resins is applied, but it is preferable to use a curing agent that can be cured at 120°C or less, taking into account the common parts.For example, aromatic curing agents such as diaminodiphenylamine Amine-based curing agents such as diamines, condensates of aliphatic amines and aliphatic dicarboxylic acids, dicyandiamide, imidazoles, etc., fi acid anhydride-based curing agents such as tetrahydrophthalic anhydride, benzophenonetetracarboxylic anhydride, trimellitic anhydride, etc. ,
Examples include phenolic resins and phenolic curing agents such as bisphenol A. These hardening agents are one or two types.
Used by more than one species.

In addition, when selecting an epoxy resin and its curing agent, it is preferable that the cured product has a glass transition temperature higher than the temperature environment in which the anticorrosive construction product is used.

Further, the epoxy resin composition can contain various additives such as those described below, if necessary. For example, for the purpose of adjusting the viscosity of the adhesive layer and improving the strength after curing, calcium carbonate, talc, asbestos, silicic acids, carbon black,
A filler such as colloidal silica is used. The compounding amount is
The amount may normally be about 0 to 300 parts by weight per 100 parts by weight of the epoxy resin. Furthermore, in order to lower the viscosity and improve wettability, reactive diluents such as butyl glycytyl ether and monoglycidyl ethers of long-chain alcohols, phthalic acid plasticizers such as dioctyl phthalate, and phosphoric acids such as triclean diphosphate are used. Can be blended with plasticizers, etc.

These amounts are usually about 0 to 30 parts by weight based on 11,100 parts by weight of the epoxy tree.

Further, in order to improve the adhesion between the adhesive polyolefin layers (2), (2') and the adhesive layer (3), a resin used for the adhesive polyolefin layer can be blended into the epoxy resin composition. In this case, the blending amount is epoxy resin 100
O~30ffi of adhesive polyolefin based on parts by weight
There are about 1 part and 2 parts.

Next, it is necessary that the heat-resistant polyolefin film (1) forming the support of the anticorrosion tape of the present invention does not soften at the usage environment temperature, and preferably the Vikato softening point (AS
TM-D 1525.1kg load) is made of polypropylene or polyethylene with a temperature of 120℃ or higher, and these IJ
f can be used alone, or two or more kinds can be used in a stacked or mixed manner. Further, the heat-resistant polyolefin layer may contain various additives such as colorants, antioxidants, fillers, etc., if necessary. In addition, the support is usually 5 to 1000 μm, preferably 10 to 60 μm in order to ensure flexibility as a tape.
Make the thickness 0 μm.

In general, many plastic films that have a high softening temperature themselves have poor flexibility, and if the thickness of the support is too thick, the flexibility of the tape will be extremely impaired, and the workability of tape wrapping will decrease. Cheap.

As explained in FIG. 1, in the anticorrosion tape of the present invention, the heat-resistant polyolefin film (1) has an adhesive layer on both sides with adhesive polyolefin layers (2) and (2') interposed therebetween. (3) is formed.

Heat-resistant polyolefin film (1) has very low water permeability and is extremely effective in preventing deterioration of the adhesive layer due to water absorption, but it generally has poor adhesion with epoxy resin due to its low polarity. It is inferior. For this reason, it is necessary to apply an adhesive treatment to the surface of the heat-resistant polyolefin film (1), and one of the typical uses of the tape of the present invention is to wrap it around a pipe, etc. Therefore, it is necessary to form modified polyolefin layers (2) and (2') on both sides of the heat-resistant polyolefin film (1).

The adhesive polyolefin resin used here is a modified polyolefin resin obtained by graft polymerizing an unsaturated carboxylic acid or its anhydride or an unsaturated epoxy monomer to a polyolefin resin as a modifying agent, and the amount of the modifying agent is determined by the modified polyolefin resin. 1 (t.

0.1 to 20 parts by weight, preferably 0.2 to 20 parts by weight
The amount is preferably 15 parts by weight, more preferably 0.5 to 10 parts by weight.

Polyolefin resins serving as the base of the above-mentioned modified polyolefin resin include polyethylene, polypropylene, ethylene-ethyl acrylate copolymer, and ethylene-vinyl acetate copolymer (thermoplastic copolymerized polyester).

In addition, the unsaturated carboxylic acids and their anhydrides used as the above-mentioned modification agents include acrylic acid, methacrylic acid, maleic acid, fumaric acid, maleic anhydride, fumaric anhydride, itaconic acid, etc., and the unsaturated epoxy monomers include Examples include glycidyl acrylate, glycidyl methacrylate, mono-, di- and triglycidyl esters of itaconic acid, acrylic glycidyl ether, 3,4-epoxy-1-butene, etc., preferably acrylic acid, methacrylic acid, maleic acid,
Malesiic anhydride, glycidyl acrylate, glycidyl methacrylate, etc. are used.

The thickness of the adhesive polyolefin layer (2), (2') is about 10 to 80 μm, preferably about 15 to 50 μm. If this thickness is too small, ffN! ,
If the tightness between the heat-resistant polyolefin film (1) and the adhesive layer (3) is insufficient or the thickness is too large, the gap between the heat-resistant polyolefin film (1) and the adhesive layer (3) may be insufficient. Moisture can easily penetrate into the product, which may affect its durability in hot and humid environments.

Further, it is preferable that the adhesive polyolefin resin has a Vicat softening point of 100° C. or higher to ensure adhesive strength at the operating temperature.

An example of a method for manufacturing the thermosetting tape of the present invention having such a configuration is as follows. First, as for the manufacturing method for the support layer of the tape, (a) #JI thermal polyolefin resin is made into a film having a structure of one or more layers without defects such as pinholes by calendering or extrusion molding, and then by inflation molding etc. A method of laminating the produced adhesive polyolefin film, (b) forming a multilayer structure film having adhesive polyolefin layers on both sides of the heat resistant polyolefin layer by multilayer extrusion molding of the heat resistant polyolefin resin and the adhesive polyolefin resin. There are various methods, and the support layer of the tape can be created using these methods.

Next, the thermosetting tape of the present invention is obtained by laminating the evoquino resin composition sheet formed into a sheet by extrusion molding, calendering, etc. to the tape support layer.

In either case, the thickness of the adhesive layer is preferably 20 μm or more in order to obtain good adhesive strength. If it is difficult to unwind the tape when used as a tape, it is preferable to attach a release film to the adhesive layer in advance and then wrap the tape around the piping while releasing the release film during use.

For convenience, the method of carrying out the method of the present invention will be explained below using a steel pipe. First, remove rust and surface condition the outer surface of the steel pipe to be constructed using plastic or sandpaper as necessary.Next, apply the above primer using an appropriate means such as a spatula, brush, or spray to reduce the thickness after the organic solvent has evaporated. o, o
o s~0.5a+m preferably 0.01~0.2mm
Cloth i so that If the amount of undercoat applied is too small, adhesion at the interface between the steel pipe and the adhesive layer of the tape will decrease after 1 degree of wetting, which is not preferable. In addition, if too much primer is applied, the primer will sag after application, the thickness of the coating will be uneven due to the sag, and if the tape is wrapped, a large amount of the primer will ooze out, which is undesirable for construction work. .

Next, before the laminated solvent of the undercoat agent evaporates, the anticorrosion tape is quickly wrapped in a spiral shape in overlapping layers. It is preferable to temporarily secure the beginning and end of the winding with heat-resistant tape such as fluorine resin tape.

Furthermore, in cases where a large force is applied from the outside, such as when buried underground, a more complete anti-corrosion performance can be ensured by further wrapping a protective tape around the outside of the tape.

In this case, the support of the protective tape is preferably a plastic sheet or a rubber sheet with a high elastic modulus within the range that can be handled as a tape, and the adhesive layer is an adhesive mainly composed of non-polar rubber. Compounds are preferred. The protective tape has the effect of protecting the tape from external forces such as earth pressure and stones, and preventing the tape from shifting and wrinkles, at least until the adhesive layer of the anticorrosion tape of the present invention hardens.

〔Example〕

The present invention will be explained below with reference to Examples. However, the following parts refer to parts by weight. Example 1 Main agent: 0 bisphenol A type epoxy resin (epoxy equivalent: 190) 100 parts 0 Tetrapropylene glycol・・・・・・・・・ 30M diglycidyl ether 0 carbon black・・・・・・・・・・・・・・・・
・・3 parts 0 fine powder silica・・・・・・・・・・・・
・・・・・・・・・・・・ 1 part Curing agent: 02-ethyl-4-methyl・・・・・・・・・・・・1
00 parts Imidazole O fine powder talc・・・・・・・・・・・・・・・・・・
...100f? I+0 slightly undressed silica...
・・・・・・・・・・・・・・・ 5 parts 0 Methyl ethyl ketone ・・・・・・・・・・・・・ 200 parts Heat-resistant polyolefin layer : Vicat softening point 155℃,
Polypropylene with melt flow index 0.5g/10min, thickness 300. cam.

0 Adhesive polyolefin layer: Modified polypropylene obtained by grafting maleic anhydride onto the above polypropylene (additional amount of maleic anhydride 2 to 100 parts by weight of polyprolene)
．． 0 parts, Vikaft softening point 140°C, melt flow index 0.8 g/10 minutes), thickness 30 parts m.

Formed on both sides of heat-resistant polyolefin layer.

0 Adhesive layer: 200 μm thick Bisphenol A type epoxy resin 100 parts (
Epoxy equivalent: 190) 0 Phenoxy resin・・・・・・・・・・・・・・・・・・
... 20 parts (molecular weight 40,000) 0 Butyl diglycidyl ether 10
Part 0 Fine powder talc・・・・・・・・・・・・・・・・・・
...50 parts 0 vinylon short fibers...
・・・・・・・・・・・・101 (thickness 20μm, average length 20mm) 0 Carbon short fibers・・・・・・・・・・・・・・・・・・
... 50 parts (thickness 10 μm, average length 20 mm) 0 gamma-glycidoxypropylmethyl ... 1 part jetoxysilane 0 dicyandiamide ......
... 5 parts O2 undecyl imidazole...
... 1s After polishing the surface of a steel pipe with an outer diameter of 50 mm with sandpaper (#240), the undercoat prepared according to the above composition was mixed at a weight ratio of main agent: hardening agent - 100:20. Immediately apply the undercoat with a brush so that the thickness of the undercoat after the methyl ethyl ketone has evaporated is 0.11, then wrap a tape with a width of 50 VW with the above structure in a half-wrap, and wrap the end of the wrap with fluororesin tape. I stopped it temporarily.

Example 2 In Example 1, the structure of the anticorrosive tape and the composition of the adhesive layer were as shown below, and the other conditions were the same as in Example 1.

Elbow nib sole Q heat-resistant polyolefin layer: Vikant softening point 128℃1
High-density polyethylene with a melt flow index of 0.5 g/lo, thickness 300 μm.

0 Adhesive Polyolefin Layer 2 Modified polyethylene obtained by grafting methacrylic acid onto the above polyethylene (methacrylic acid addition amount: 3.0 parts per 100 parts by weight of polyethylene, Vikaft softening point: 120°C, melt flow index: 0.
8g/10min), thickness 30ttm, formed on both sides of the heat-resistant polyolefin layer.

0 Adhesive rr1: 300 μm thick layer of A co-O bisphenol A type epoxy resin...70 parts (
Epoxy equivalent: 190) 0 bisphenol A type epoxy resin... 30 parts (
Epoxy equivalent weight: 1700) 0 Having carboxyl groups at both ends... 20 parts acrylonitrile butadiene copolymer (average molecular weight: 4000) 0 Crystalline silica powder......
・・100 parts (average particle size 20μm) 0 short glass fibers・・・・・・・・・・・・・・・・・・・
...100 parts (thickness 10 μm, average length 20 mm) 0 gamma-7 minopropyl trimethoxy ... 1 part silane 0 adipic acid hydrazide ...
Part 5 02 Methylimidazole・・・・・・・・・
... 1 part Example 3 In Example 1, the structure of the anticorrosion tape and the composition of the adhesive layer were as shown below, and the other treatments were carried out in the same manner as in Example 1.

Heat-resistant polyolefin layer: Vicat softening point 150℃,
A mixture of polypropylene with a melt flow index of 0.7 g/10 min and high-density polyethylene with a Vikatsu softening point of 128°C and a melt flow index of 0.5 g/10 min in an IT ratio of 1:1. Thickness: 300μm.

0-adhesive polyolefin layer: modified 1-part resin made by grafting glycidyl meccrylate onto ethylene ethyl acrylate (5.0 parts by weight of glycidyl meccrylate added to 1 part of 100ii ethylene ethyl acrylate, Vikatsu softening point 110°C, melt flow index) 1.
0 g/10 min), 20 μm thick, and a heat-resistant polyolefin layer was formed on both αII.

0 adhesive layer: J! 40 bisphenol A type epoxy resin...40 parts (
Epoxy equivalent: 190) 0 bisphenol A type epoxy resin... 30 parts (
Epoxy equivalent: 1700) Zero engineering poxy urethane 4M resin...
・ 30 parts (epoxy equivalent: 600) O crystalline silica powder・・・・・・・・・・・・・・・
・・80 parts (average particle size 20 μm) O glass short #3 + fiber・・・・・・・・・・・・・・・・
...100 copies (thickness 10μm, average length 20mm
) OT-aminopropyltrimethoxy... 1 part silane 0 dianediamide...
・・Part 302-Undecylimidazole・・・・
... 2 parts Example 4 In Example 1, the undercoat was mixed as follows, and the mixing ratio of the undercoat was 1, and the base resin: curing agent = 100:40. The rest was treated in the same manner as in Example 1.

Main agent: 0 bisphenol A type epoxy resin...100 parts (
Epoxy equivalent weight 190) 0 having carboxyl groups at both ends... 10 parts acrylonitrile-butadiene copolymer (average molecular weight 35
00) 0 Tetrapropylene glycol jig... 30 parts Lycidyl ether 0 Carbon blank...
・・3-part curing agent: 0 amine-based curing agent・・・・・・・・・・・・・・・・・・
...100 parts (mixture of aromatic amine and aliphatic amine, active hydrogen equivalent: 40) 0 Finely powdered talc ......
...100 parts 0 fine powder silica...
・・・・・・・・・・・・ 10 parts 0 Methyl ethyl ketone ・・・・・・・・・・・・・・ 200 parts Comparative example 1 Example 1 without using a primer I wrapped the tape around it. The rest was treated in the same manner as in Example 1.

Comparative Example 2 The same tape as in Example 1 was wound without forming an adhesive polyolefin layer. The rest was treated in the same manner as in Example 1.

Comparative Example 3 The tape in which the adhesive polyolefin layer was formed only on one side of the heat-resistant polyolefin layer (only on the adhesive layer side) in Example 1 was wound. The rest was treated in the same manner as in Example 1.

Comparative Example 4 In Example 1, a tape without an adhesive layer was wound. The rest was treated in the same manner as in Example 1.

The NS'R tubes of the above examples and comparative examples were heated at 10°C.
After being left for 20 hours, the following tests were conducted and the results shown in Table 1 were obtained.

(1) Hot water test: After the coated steel pipe was immersed in 100'C water for 20 days, the occurrence of blistering in the coating was observed, and the occurrence of pinholes was confirmed using ACIOKV using a pinhole tester.

(2) Burial test: Heat-resistant and pressure-resistant hoses were attached to both ends of the steel pipe to allow heat medium oil to flow into the coated steel pipe, and after burying the pipe 1 m underground, heat medium oil at 100°C was poured at a rate of 1000 ml/sin. After continuing to flow at the same flow rate for 20 days, the coated steel pipe was taken out and returned to room temperature, and changes in appearance such as swelling and wrinkles of the coating were observed.

Table 1 [Effects of the Invention] As is clear from the above examples, according to the anticorrosion method of the present invention, anticorrosion-treated steel materials having excellent heat resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a thermosetting anticorrosive tape used in the method of the present invention. (1)...Heat-resistant polyolefin film (2) (2')...Adhesive polyolefin layer (3)......From epoxy resin composition Consists of adhesive layer (or more)

Claims (3)

[Claims] (1) In a steel material corrosion prevention method in which a primer consisting of a two-component room-temperature curing epoxy resin composition is applied to the surface of the steel material, a thermosetting tape is repeatedly wrapped around the surface of the steel material, and the thermosetting tape is heat-resistant. An adhesive polyolefin layer is formed on both sides of a polyolefin film, and an adhesive layer made of an epoxy resin composition that is sticky at room temperature is formed on one side of the adhesive polyolefin layer. Corrosion prevention method. (2) The heat-resistant polyolefin film is made of polypropylene and/or polyethylene having a Vicat softening point of 120°C or higher, and the adhesive polyolefin layer has a Vicat softening point of 120°C or higher.
An epoxy resin composition that has a Vicat softening point of 120°C or higher and is sticky at room temperature contains an epoxy resin and/or a modified epoxy resin and a curing agent as essential components, and can be cured at a temperature of 120°C or lower. 2. A method for preventing corrosion of steel according to claim 1, characterized in that: (3) Corrosion prevention according to claim 1 or 2, characterized in that the thickness of the undercoat layer after the organic solvent contained in the undercoat has volatilized is 0.005 to 0.5 mm. Method.