JPS6282021A - Corrosion prevention method for steel material - Google Patents

Abstract

PURPOSE:To provide a corrosion prevention method which displays favorable corrosion prevention properties even to a high-temperature steel material and does not necessitate a heating device at the time of its execution, by making use of an adhesive agent layer composed of a thermosetting resin composite and an undercoating agent containing a curing agent which is capable of curing the thermosetting resin composite at the normal temperature. CONSTITUTION:A corrosion prevention method is constitute basically of application of an undercoating agent and lap winding of a corrosion prevention tape. The undercoating agent to be used contains a curing agent which is capable of curing thermosetting resin composite forming an adhesive agent layer of the corrosion prevention tape at the normal temperature for its indispensable ingredient. The curing agent having compatibility with the adhesive agent layer is especially desirable. For an instance, an ordinary cold-setting curing agent which can cure epoxy resin at the normal temperature is used and a compounding quantity is more than 1wt% of the whole quantity of the undercoating agent. A quantity of coating of an undercoating agent solution is regulated so that the thickness of the undercoating agent layer after volatilization of an inorganic solvent becomes 0.002-0.2mm. The corrosion prevention tape to be used is formed of a supporting material composed of a plastic sheet or rubber sheet and the adhesive agent layer composed of the thermosetting resin composite.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for preventing corrosion of steel materials, and more particularly to a method of preventing corrosion of steel materials using an anticorrosion tape.

[Prior art]

2. Description of the Related Art One method of transporting fluids such as oil and gas is to construct pipelines using steel pipes.

One problem with such methods is that the steel pipes 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) Plastic is formed into a tape shape in advance, and an adhesive layer is formed on one surface of the tape, and this is wrapped spirally around the surface of a steel pipe on which an undercoat composition has been applied, overlapping a portion of the tape. The so-called anti-corrosion tape coating method.

In this way, coated steel pipes protected by plastics are
Protected with the bituminous material f! Compared to steel pipes, it has remarkable effects in terms of corrosion protection and service life.

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 to metals 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 to occur and progress, that is, the corrosion resistance deteriorates.

Furthermore, in pipelines for transporting fluids such as petroleum and oil, the fluid is usually pressurized and heated to lower the viscosity of the fluid and improve transport efficiency. When applying a plastic coating with poor properties, there was also a problem in that there was a limit to the usage limit. 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 anti-corrosion tape construction method, a plastic sheet with a higher softening point is used as the support for the anti-corrosion tape, and in some cases a heat-resistant release base material is attached to the plastic sheet. Attempts are also being made. 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 thermosetting resins for the adhesive layer of anticorrosive tapes, but for example, when using two-component thermosetting resins that harden at room temperature, their pot life, so-called bot life, is extremely short. Furthermore, as the curing progresses, the workability is poor, as it becomes difficult to wind the tape over and over again, and the heat resistance properties are also not satisfactory.

Furthermore, in the case of heat-curable two-component thermosetting resins, the pipe must be heated during construction, which again results in the above-mentioned point y1.

[Problem that the invention seeks to solve]

The problem to be solved by the present invention is to solve the above-mentioned disadvantages of conventional plastic coating, especially the above-mentioned disadvantages of anti-corrosion tape method. The purpose of the present invention is to develop a corrosion prevention method that exhibits good corrosion prevention performance even for four materials and does not require a special heating device during its construction.

[Means for solving problems]

This problem can be solved by using an anti-corrosion tape made of an adhesive layer attached to a plastic or rubber sheet, in which the adhesive layer is made of a thermosetting resin composition, and the thermosetting resin composition is used as an undercoat. This is achieved by using a material containing a hardening agent that can harden the material at room temperature. Pl'
In the present invention, a primer layer is formed on the surface of the steel material,
Next, an anticorrosion tape made of a thermosetting resin composition applied as an adhesive layer is wrapped around a plastic sheet or a rubber sheet, and the primer coats the thermosetting resin composition in a tray. This relates to a method for preventing corrosion of steel+A, characterized in that it contains a hardening agent that can be hardened.

[Structure and operation of the invention]

The anticorrosive tape used in the present invention has a support made of a plastic sheet or a rubber sheet that does not soften under the usage limit environment, and a thermosetting resin composition whose glass transition temperature after curing is higher than the usage temperature environment as an adhesive layer. By doing so, it exhibits excellent anti-corrosion performance even when hot.

Furthermore, after applying an undercoat containing a curing agent that can cure the above-mentioned thermosetting resin at room temperature to the surface of the steel pipe, wrapping the above-mentioned anti-corrosion tape improves the wetting between the adhesive layer and the steel pipe. The adhesive layer can be cured at least in the vicinity of the steel pipe in a short time using the hardening agent. As a result, the anticorrosion performance is exhibited immediately after the anticorrosion tape is wrapped, and when the temperature of the steel pipe rises, the thermosetting resin composition progresses in curing due to the heat, and the anticorrosion performance at high temperatures is exhibited.

The anticorrosion method of the present invention basically consists of applying an undercoat and wrapping an anticorrosive tape in layers.

The undercoat used in the present invention contains as an essential component a curing agent capable of curing the thermosetting resin composition forming the adhesive layer of the anticorrosion tape at room temperature, and also contains a curing accelerator as necessary. , diluent, organic solvent, filler, softener,
Those containing adhesion imparting agents, coloring agents, antioxidants, flow control agents, etc. are used.

In this case, a wide variety of curing agents can be used that act as a curing agent for the adhesive layer of the anticorrosive tape used, and those that are compatible with the adhesive layer are particularly preferred. Specifically, for example, when the thermosetting resin composition is an epoxy-based thermosetting resin composition, the curing agent used is a normal curing agent for curing at low temperatures that can cure the epoxy resin at room temperature. , polyamide polyamine, aliphatic polyamine, aromatic polyamine, alicyclic polyamine and the like. It is of course possible to use other curing agents and curing accelerators, such as acid anhydrides, polyamides, sulfide resins, phenol resins, urea resins, initial condensates of melamine resins, dicyandiamide, etc. Tertiary amines, boron trifluoride-amine complexes, etc. can also be used.

These curing agents may be used alone or in combinations of 2 pi or more.

In addition, in the case of a phenolic resin thermosetting resin composition,
Various organic peroxides and the like can be used for unsaturated polyester resin compositions such as triethylamine and pyridine. Furthermore, for resins other than these, a curing agent that can be cured at room temperature may be similarly selected and used as appropriate.

The amount of curing agent blended is 1% by weight or more, preferably 2% by weight or more of the total amount of the undercoat. If the blending amount does not reach 1% by weight, wetting between the steel pipe and the adhesive layer of the anticorrosion tape may be insufficient, resulting in a decrease in adhesive properties.

Diluents used in the primer of the present invention include high boiling point solvents such as glycols and esters, plasticizers such as phthalate esters and phosphate esters, non-reactive diluents such as pine oil and coal tar, butyl glycidyl ether, etc. monoepoxy compounds, polyepoxy compounds such as diglycidyl ether, vinyl compounds such as styrene and diallylphthalate,
Epoxidized vinyl septamers such as glycidyl methacrylate, triphenylfusphite, tetrahydrofuran
A, polyols, lactones, and other reactive diluents are used.

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. Dissolve and disperse the agent and use it as a primer solution. The solid content in the undercoat solution is set so as to have a viscosity suitable for applying the undercoat solution with a brush, spray, etc., and is usually preferably about 10 to 50%. The amount of the undercoat solution applied is adjusted so that the thickness of the undercoat layer after the organic solvent has evaporated is 0.002 to 0.2 mm, preferably 0.005 to 0.1 mm.

The anticorrosion tape used in the present invention is formed from a support made of a plastic sheet or a rubber sheet and an adhesive layer made of a thermosetting resin composition.

The plastic sheet or rubber sheet used in the anticorrosion tape of the present invention uses polyethylene,
Polypropylene, modified polyolefin, polyamide, polyester, aromatic polyamide, polyether sulfone, polyvinylidene fluoride, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, phenoxy resin, butadiene-acrylonitrile rubber, butyl rubber, polyisobutylene rubber , styrene-butadiene rubber,
Ethylene-propylene rubber etc. can be used.

It is necessary that the raw material used for the above-mentioned support does not soften under the temperature environment in which it is used. Furthermore, in addition to the above raw materials, various additives such as colorants, antioxidants, fillers, etc. can be blended as necessary. The support is a tape and has a thickness of usually 5 to 1000 .mu.m, preferably 10 to 600 .mu.m in order to ensure flexibility.

In general, plastic films with a high softening salt content often have poor flexibility, and if the thickness of the support is made too thick, the flexibility of the tape becomes extremely low.
Wrapping with tape tends to reduce workability.

Note that the support layer may include glass cloth, glass nonwoven fabric, or synthetic fiber cloth or nonwoven fabric with excellent heat resistance. Further, if necessary, the support layer can have a multilayer structure.

Next, the thermosetting resin composition that forms the adhesive layer of the anticorrosive tape contains a thermosetting resin and a curing agent as essential components, and optionally a curing accelerator, filler, softener, and adhesion imparting agent. , colorants, thermoplastic resins, rubber, anti-aging materials, and other additives. Examples of the thermosetting resin include epoxy resin, unsaturated polyester resin, phenol resin, acrylic resin, silicone resin, urea resin, etc., and usually one or two of these thermosetting resins are used. Use the above in combination.

As the curing agent for the thermosetting resin, a wide variety of commonly known curing agents can be used, and those that are active in the temperature environment in which they are used, and those that can be cured in the temperature range of usually 50 to 150°C, are preferred. Examples of the curing agent include dicyandiamide, 4,4'-diaminodiphenylsulfone, imidazole derivatives such as 2-n-heptadecyl imidazole, isophthalic acid hydrazide,
N.

There are N-dialkyl urea derivatives and the like.

Further, the thermosetting resin composition can contain various additives as described below, if necessary. For example, fillers such as calcium carbonate, talc, asbestos, IJI, carbon blank, and colloidal silica are used to adjust the viscosity of the adhesive layer and improve its strength after curing. The blending amount may be generally about 0 to 300 parts by weight per 100 parts by weight of the thermosetting resin. Furthermore, for the purpose of lowering viscosity and improving wettability, reactive diluents such as butyl glycidyl ether and monoglycidyl ether of long-chain alcohols, phthalic acid plasticizers such as dioctyl phthalate, and phosphoric acid-based plasticizers such as triclean diphosphate are used. Plasticizers etc. can be added. These amounts are preferably about 0 to 3 parts by weight per 100 parts by weight of the thermosetting resin.

In addition, in order to improve the adhesion between the support of the anticorrosive tape and the adhesive layer, the main raw material of the support can be blended into the thermosetting (nonfatty fat composition).In this case, the amount of thermosetting It is preferable that the main raw material of the support is about 0 to 30 parts by weight based on 100 parts by weight of the resin.

In addition, by incorporating glass cloth, glass nonwoven fabric, or synthetic fiber cloth or nonwoven fabric with excellent heat resistance into the adhesive layer, it is possible to use thermosetting resin after wrapping the anticorrosion tape and before the adhesive layer hardens. It is effective in preventing the composition from extruding and the tape from slipping.

For convenience, the method of carrying out the method of the present invention will be explained below using a steel pipe. First, the outer surface of the steel pipe to be constructed is cleaned by blasting, sandpaper, etc. as necessary to remove rust and smooth the surface. Next, apply the above-mentioned undercoat by brushing, spraying, or other appropriate means until the thickness of the organic solvent after volatilization is 0.002~0.
Coat to a thickness of 2 mm, preferably 0.005 to 0.1 mm. If the amount of undercoat applied is too small, it is not preferable because it causes a decrease in wetting and a decrease in adhesion at the interface between the steel pipe and the adhesive layer of the tape. In addition, if the amount of primer coated is too large, unreacted curing agent will remain at the interface between the steel pipe and the adhesive layer, resulting in poor adhesion, no matter how well the curing agent is compatible with the thermosetting resin. do not have.

Next, before the organic solvent of the undercoat agent evaporates, the tape is immediately wound in a spiral shape in an overlapping manner. It is preferable to temporarily secure the beginning and end of the winding with heat-resistant tape such as fluororesin 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, parts refer to parts by weight.

Example 1 2-ethyl-4-methylimidazole...10 parts G-n-butyl fucrate......
30 parts toluene・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・6(1-B) Bisphenol A type epoxy resin (epoxy equivalent: 190)・・・・・・・・・50 parts Bisphenol A type epoxy resin (epoxy equivalent: 450)・......50 parts Silica powder (average particle size 20 μm)...120 parts Asbestos...
...IO! Dicyandiamide・・・・・・・・・
・・・・・・・・・・・・・・・ 5 parts 2 undecyl imidazur 0.2 parts outer diameter 50
After polishing the surface of the steel pipe (#240) with sandpaper (#240), the undercoat prepared in the above formulation was applied with a brush so that the thickness of the undercoat after toluene volatilized was 0.02 mm. The support has a two-layer structure including a polyethylene terephthalate film with a thickness of 0.1 am as an outer layer and a thermoplastic copolymerized polyester film with a thickness of 0.05 mm as an inner layer. Sa0.2
It was prepared by forming an adhesive layer on an interior support with mo+. Immediately after applying the anti-corrosion tape with a brush, wrap it around a half lamp to cover F! Made of steel pipe.

Example 2 A steel pipe polished and coated with a primer in the same manner as in Example 1,
Polyester cloth (thickness: 0.07 mm, number of vertical/horizontal fibers: 20 each) was added to the adhesive layer composition of Example 1.
Thickness 0.2m with 25゛ pieces/inch)
An anticorrosion tape consisting of an adhesive layer of m thickness and a support of 0.1 mm thick ethylene-vinyl acetate copolymer (softening temperature 105°C) was wrapped half-wrap m times, and then a 0.1 mm thick anticorrosion tape was wound on top of this tape with a thickness of 0. A protective tape consisting of a support of .2a+m polyethylene (melt index 2.0) and an adhesive layer of 0.10111 thickness and an adhesive layer mainly composed of chill rubber was wound to form a covered steel pipe.

Comparative Example 1 A coated steel pipe was obtained in Example 1 without using an undercoat.

Comparative Example 2 In Example 2, the protective tape was wrapped in layers without using the anticorrosion tape of the present invention.

The R-R steel pipes of the above examples and comparative examples were heated at 40°C for 2 hours.
After standing for 0 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 boiling water at 100°C for 20 days, the occurrence of blistering in the coating was observed, and the occurrence of pinholes was confirmed using a pinhole tester at 10 KV AC.

(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 meter underground, heat medium oil at 100°C was poured at a rate of 1000 ml/min. 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 As is clear from the above examples, the anti-corrosion method of the present invention provides anti-corrosion treated steel materials having excellent heat resistance.

(that's all)

Claims (4)

[Claims] (1) A method in which an undercoat layer is formed on the surface of a steel material, and then an anticorrosion tape made by applying a thermosetting resin composition as an adhesive layer to a plastic or rubber sheet is wrapped in layers, and the undercoat is A method for preventing corrosion of steel materials, characterized in that the agent contains a curing agent capable of curing the thermosetting resin composition at room temperature. (2) The corrosion prevention method according to claim 1, wherein the undercoat contains 1.0% by weight or more of a curing agent. (3) The thickness of the undercoat after the organic solvent etc. has evaporated is 0.
0.002 to 0.2 mm, the corrosion prevention method according to claim 1. (4) The corrosion prevention method according to claim 1, wherein the adhesive layer contains a thermosetting resin and a curing agent thereof.