KR102536406B1 - Composition of repair layer for protecting welding part - Google Patents

Abstract

A repair layer composition for protecting welded areas that has good workability, sufficient hardness and tensile shear adhesive strength, and improves corrosion resistance, abrasion resistance, and adhesive strength is proposed. The composition is applied to cover the welded area, and is composed of a mixture of a main agent and a hardener. The main agent is 25 to 40% by weight of polymer resin, 1 to 8% by weight of diluent, 5 to 15% by weight of ceramic powder, 5 to 10% by weight of alumina, 5 to 15% by weight of anticorrosive pigment, 5 to 15% by weight of silicon carbide, 5 to 15% by weight of tungsten carbide, 5 to 15% by weight of boron carbide, 1 to 5% by weight of thixotropic agent and other additives The curing agent includes 50 to 70% by weight of cured resin, 20 to 30% by weight of ceramic powder, 5 to 15% by weight of thixotropic agent and other additives, and based on the total weight of the subject, tungsten carbide is based on tungsten and carbon Boron carbide is a compound based on boron and carbon.

Description

Repair layer composition for protecting welding part {Composition of repair layer for protecting welding part}

The present invention relates to a repair layer composition, and more particularly, to a repair layer composition for protecting a region where a metal material is welded.

Fusion welding heats and melts a metal material at a junction to rearrange and combine atomic bonds of different metal materials. Welding methods include arc welding, gas welding, and thermite welding. The welding is used in various ways such as ships, water supply steel pipes, oil tanks, gas pipes, concrete structures, piers, and various docking facilities. On the other hand, defects such as insufficient penetration, poor fusion, cracks, slag intervention, and blowholes may exist in the welded portion. If the above defect exists, the welding strength is lowered and the durability period is reduced. In addition, even if the above defects do not exist, the welding strength and durability period are lowered due to corrosion or the like. In order not to reduce the welding strength and durability, the welded portion is protected by a repair layer, such as in Korean Patent Registration No. 10-0383445.

On the other hand, in order to increase the welding strength and durability of the repair layer, physical properties such as corrosion resistance, abrasion resistance, and adhesive strength are required along with sufficient hardness and tensile shear adhesive strength. In addition, stable workability in the process of manufacturing the repair layer is required. Even if workability, hardness, and tensile shear adhesive strength are sufficiently secured, if corrosion resistance, abrasion resistance, and adhesive strength are not satisfied, the welding strength and durability of the repair layer drop rapidly. However, conventionally, the physical properties of the repair layer are not satisfied.

The problem to be solved by the present invention is to provide a repair layer composition for protecting a welded area that has good workability, sufficiently secured hardness and tensile shear adhesive strength, and improves corrosion resistance, wear resistance and adhesion strength.

In order to solve the problem of the present invention, the repair layer composition for protecting the welded portion is applied to cover the welded portion, and is made by mixing the main agent and the curing agent, and the subject is composed of 25 to 40% by weight of the polymer resin and a diluent based on the total weight. 1 to 8% by weight, 5 to 15% by weight of ceramic powder, 5 to 10% by weight of alumina, 5 to 15% by weight of anticorrosive pigment, 5 to 15% by weight of silicon carbide, 5 to 15% by weight of tungsten carbide, 5 to 15% by weight of boron carbide The curing agent includes 50 to 70 wt% of cured resin, 20 to 30 wt% of ceramic powder, 5 to 15 wt% of thixotropic agent and other additives. At this time, with respect to the total weight of the subject matter, the tungsten carbide is a compound based on tungsten and carbon, and the boron carbide is a compound based on boron and carbon.

In the composition of the present invention, the thickness of the repair layer is 1 to 5 mm, and the repair layer has an extended width extending to both sides of the welded portion, and the extended width may be 20 to 50 mm. The tungsten carbide may replace a part of the tungsten with cobalt. The polymer resin of the above subject may be a bisphenol F-type epoxy resin having an epoxy equivalent of 190 to 220 g/eq and a viscosity of about 9,000 to 15,000 cps.

In a preferred composition of the present invention, the subject polymer resin may be a phenol novolac type epoxy resin mixed with the bisphenol F type epoxy resin. The diluent may be a non-reactive diluent. The rust-preventive raw material may include barium metaborate monohydrate. The curing resin of the curing agent may be an amine-based polymer. The curing resin of the curing agent may be a polyamide amine-based resin having a total amine value of about 280 to 340 mgKOH/g. As the cured resin, an aliphatic amine-based resin may be mixed with the polyamide amine-based resin.

According to the repair layer composition for protecting welded parts of the present invention, by using a property improving agent such as rust-preventive pigment, tungsten carbide, boron carbide, etc., workability is good, hardness and tensile shear adhesive strength are sufficiently secured, and corrosion resistance, wear resistance and Improve adhesion strength.

1 shows cases in which a repair layer according to the present invention is applied.
2 is a planar view of a case in which a repair layer is applied.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below may be modified in many different forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. In the drawings, it is exaggeratedly expressed for convenience of explanation. Meanwhile, in the drawings, the thicknesses of films (layers, patterns) and regions may be exaggerated for clarity. Further, when it is said that a film (layer, pattern) is on, above, below, or on one side of another film (layer, pattern), it may be directly formed on the other film (layer, pattern) or other films (layer, pattern) may be formed therebetween. A film (layer, pattern) may be interposed.

In the embodiment of the present invention, by utilizing a property improving agent such as anti-rust pigment, tungsten carbide, boron carbide, etc., workability is good, hardness and tensile shear adhesive strength are sufficiently secured, and corrosion resistance, abrasion resistance, and adhesion strength are improved to improve welding parts. A repair layer composition for protection is presented. To this end, the physical property improving agent will be examined in detail, and the physical property improving effect by the physical property improving agent will be described in detail. The repair layer of the present invention is applied to a welded portion to increase welding strength and durability, thereby protecting the welded portion. The repair layer is used in various ways such as ships, water supply steel pipes, oil tanks, gas pipes, concrete structures, piers, and various docking facilities.

FIG. 1 shows cases to which the repair layer 10 according to an embodiment of the present invention is applied, and FIG. 2 is a planar view of a case to which the repair layer 10 is applied. However, it is not a drawing in a strict sense, and there may be components not shown in the drawing for convenience of description.

Referring to FIGS. 1 and 2, the repair layer 10 is formed on a welded portion WD at a portion (a) and a flat portion (b) where a metal structure (MS) made of a metal material, for example, steel, meets at an angle. exist. The repair layer 10 satisfies various physical properties, but particularly has stable workability and sufficiently secures general physical properties including hardness and tensile shear adhesive strength and welding properties including corrosion resistance, abrasion resistance, and adhesive strength. The general physical properties and weldable properties are classified for convenience of description, and may be classified differently according to circumstances. In particular, the welding properties have a great influence on the welding strength and durability of the welded portion WD. The repair layer 10 covers the welded portion WD and has a thickness t and an extension width W within a range that sufficiently secures the general and welded properties. For example, the thickness t of the repair layer 10 is about 1 to 5 mm, and the width W extended to both sides of the welding region WD is about 20 to 50 mm.

The repair layer 10 is divided into a main agent and a curing agent, and the main agent includes a polymer resin such as epoxy resin, a non-reactive diluent, ceramic powder, alumina, a thixotropic agent and other additives. In particular, the subject in the embodiment of the present invention contains anti-rust pigments, silicon carbide, tungsten carbide and boron carbide. The rust-preventive pigment, silicon carbide, tungsten carbide, and boron carbide may be referred to as water improvement agents for improving physical properties of the repair layer 10 . At this time, the ceramic powder includes titanium dioxide, calcium carbonate, silica, mica, and the like. The curing agent includes cured resin, ceramic powder, thixotropic agent and other additives. The ceramic powder of the curing agent includes titanium dioxide, calcium carbonate, silica, mica, and the like, as in the case of the main agent.

In the above subject matter, known polymeric resins can be suitably employed, and epoxy resins are preferred. The epoxy resin is preferably a bisphenol F-type epoxy resin, and a resin having an epoxy equivalent of about 190 to 220 g/eq is used. In some cases, a bisphenol F-type epoxy resin having an epoxy equivalent of 190 to 220 g/eq and a viscosity of about 9,000 to 15,000 cps is preferred to adjust the viscosity of the repair layer 10. The epoxy resin contains 25 to 40% by weight of the total weight of the subject. If the content of the epoxy resin is less than 25% by weight, it cannot serve as a binder as a support (matrix), and thus the adhesive strength is lowered and the crosslinking density is lowered in crosslinking with the curing agent. In this case, physical properties such as acid resistance and alkali resistance of the repair layer 10 as well as the general physical properties and welding properties are deteriorated. If the content of the epoxy resin exceeds 40% by weight, the adhesion may be partially increased, but the flowability is lowered and the content of other components is insufficient, resulting in poor physical properties and workability.

In the above subject matter, the polymer resin may be a bisphenol F type epoxy resin mixed with a phenol novolac type epoxy resin. At this time, the phenolovolac-type epoxy resin is referred to as epoxy resin-1, and the bisphenol F-type epoxy resin is referred to as epoxy resin-2. Phenol novolak-type epoxy resin has functions such as chemical resistance and abrasion resistance, and bisphenol F-type resin has excellent adhesive properties and is environmentally friendly, so Epoxy Resin-1 and Epoxy Resin-2 can be appropriately selected. When combined, they exhibit excellent physical properties.

In the above subject matter, the diluent is a reactive glycidyl ester such as butyl glycidyl ether, phenyl glycidyl ether, aliphatic glycidyl ether (C ₁₂ to C ₁₄ ), 2,3-epoxypropylneodecanate. Diluents may be used. In addition, aromatic hydrocarbons such as toluene and xylene, esters such as normal butyl acetate and ethylene glycol ethyl ether acetate, ketones such as methyl isobutyl ketone and methyl normal amyl ketone, alcohols such as isopropanol, normal butanol, and isobutanol; And non-reactive diluents such as glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether may be used.

On the other hand, when a reactive diluent is used, the hardness is increased, and when a solvent-type diluent is used, it is volatilized into the atmosphere and becomes an environmental problem. Accordingly, the diluent in the water retention layer 10 according to the embodiment of the present invention is preferably a non-reactive diluent. The diluent contains 1 to 8% by weight of the total weight of the subject. If the content of the diluent is less than 1% by weight, the dilution effect is lowered and the viscosity is high, resulting in poor workability. The flow resistance is lowered.

In the above subject, the ceramic powder is any one selected from titanium dioxide, calcium carbonate, mica, and silica having an average particle diameter of 0.2 to 50 μm, and is mixed at 5 to 15% by weight based on the total weight of the subject, improving durability. , reinforcing mechanical strength, improving workability and adjusting gloss. If the amount of the ceramic powder is less than 5% by weight, mechanical strength may decrease, and if it exceeds 15% by weight, the volume concentration of the critical pigment may be exceeded, making it difficult to manufacture the repair layer 10 and the physical properties of the repair layer 10 may rapidly deteriorate. can

The alumina in the above subject is in the form of a powder, and the alumina powder having an average particle diameter of 10 to 50 μm is used, and has high hardness and excellent strength and corrosion resistance. The alumina powder contains 5 to 10% by weight of the total weight of the main agent. If the alumina is less than 5% by weight, the abrasion resistance may not be exhibited, and if it exceeds 10% by weight, the viscosity of the main material may excessively increase, resulting in poor workability and increased specific gravity, resulting in poor flow resistance. In the above subject matter, the thixotropic agent may be a layered silicate. The thixotropic agent is contained in an amount of 1 to 5% by weight of the total weight of the main agent. If the thixotropic agent is less than 1% by weight, flow resistance and rheological properties are not improved, and if it exceeds 5% by weight, the viscosity of the main material is excessively increased, adversely affecting the surface roughness and workability of the repair layer 10.

In the above subject matter, the rust-preventive pigment is a pigment component in the repair layer 10 and exhibits an anticorrosive effect of protecting the welded portion WD from corrosion, and imparts color and hiding power. The anti-corrosion pigment is selected from among zinc, zinc oxide, zinc phosphate, zinc flake, zinc potassium chromate, strontium chromate, barium metaborate monohydrate, Kwangmyeongdan, molybdate, phosphate, silicate, and zinc phosphate having an average particle diameter in the range of 0.1 to 12 μm. any one or a mixture thereof. The anti-corrosive pigment contains 5 to 15% by weight based on the total weight of the subject. If the amount of the rust-preventive pigment is less than 5% by weight, the color and hiding power may be deteriorated, and the anti-corrosion effect may also be deteriorated. If it exceeds 15% by weight, the color, hiding power, and anti-corrosion effect are improved, but there is a concern about the cost increase of raw materials, and the smooth appearance of the surface of the repair layer 10 may be deteriorated. In particular, the rust-preventive raw material containing barium metaborate monohydrate has excellent rust-preventive properties, and is classified as rust-preventive raw material-2.

In the above subject, the silicon carbide (SiC) uses a powder having an average particle diameter of 5 to 500 μm, and has excellent chemical stability and corrosion resistance at high temperatures and high hardness. The silicon carbide contains 5 to 15% by weight of the total weight of the main subject. If the amount of silicon carbide is less than 5% by weight, chemical resistance and wear resistance are deteriorated, and if it exceeds 15% by weight, the viscosity of the subject greatly increases, resulting in poor workability, and the hardness of the repair layer 10 is excessively increased to cause brittle fracture. .

In the above subject matter, the tungsten carbide uses powder having an average particle diameter of 1 to 10 μm, which has excellent hardness, high strength, and physical properties, particularly corrosion stability. Tungsten carbide includes WC and W ₂ C. The tungsten carbide refers to all compounds based on tungsten and carbon. In the tungsten carbide of the present invention, in addition to the WC and W ₂ C, in order to improve corrosion resistance, a part of tungsten (W) may be replaced with cobalt (Co). The tungsten carbide (WC) further improves weld properties such as corrosion resistance, wear resistance, and adhesion strength of the repair layer 10 . The tungsten carbide contains 5 to 15% by weight of the total weight of the main material. If the tungsten carbide is less than 5% by weight, the corrosion resistance and wear resistance are poor, and if it exceeds 15% by weight, the viscosity of the subject greatly increases, resulting in poor workability, and the hardness of the repair layer 10 is excessively increased to cause brittle fracture. .

In the above subject matter, the boron carbide is represented by B ₄ C, has the third highest hardness after diamond and cubic boron nitride, and has excellent wear resistance and corrosion resistance due to high covalent bonding and high bonding strength. The boron carbide refers to all compounds based on boron and carbon. The boron carbide further improves weld properties such as corrosion resistance, abrasion resistance, and adhesive strength of the repair layer 10 . The boron carbide contains 5 to 15% by weight of the total weight of the main subject. If the boron carbide is less than 5% by weight, the corrosion resistance and wear resistance are poor, and if it exceeds 15% by weight, the viscosity of the subject greatly increases, resulting in poor workability, and the hardness of the repair layer 10 is excessively increased to cause brittle fracture. .

In the above subject, it is included in the composition to form the repair layer 10, improve physical properties and workability of the repair layer 10, and other additives such as a known coupling agent, dispersant, and antifoaming agent may be mixed therein. . Coupling agents, dispersing agents, antifoaming agents, etc. are collectively referred to as other additives. The content of other additives in the subject may be appropriately adjusted and added in consideration of the type and content of the subject within the scope of the present invention. For example, the other additives are mixed in an amount of 2 to 5% by weight, preferably 1 to 5% by weight, based on the total weight of the main agent. If the amount is less than the above range, problems may occur in the workability of the repair layer 10, and if it exceeds the above range, repelling or deterioration may occur in the repair layer 10.

As the curing agent, a known curing resin may be appropriately employed, and in the embodiment of the present invention, a polyamide amine-based resin having a total amine value of about 280 to 340 mgKOH/g, which is an amine-based polymer, was used as the curing resin. In some cases, aliphatic amine resins having a total amine value of 450 to 500 mgKOH/g and a viscosity of about 500 to 4,000 cps may be used to adjust the viscosity of the repair layer 10. The polyamide amine-based resin contains 20 to 60% by weight of the total weight of the curing agent. If the curing agent resin is less than 50% by weight, the working time is good but the drying time is slow, and if it exceeds 70% by weight, the drying time is shortened but the working time is short and the workability is poor. The curing accelerator for curing the curing resin uses, for example, tertiary amine (amine value: 630 mgKOH/g, trade name: Ancamine K-54), and contains 1 to 8% by weight of the total weight of the curing agent.

In the curing agent, the main component of the curing resin may be a polyamide amine-based resin mixed with an aliphatic amine-based resin as a main component. At this time, the aliphatic amine-based resin cured resin is referred to as cured resin-1, and the polyamide amine-based resin is referred to as cured resin-2. The cured resin-1, aliphatic amine-based resin, has excellent curing time and wet surface adhesion, and the cured resin-2, polyamideamine-based resin, has excellent adhesiveness.

In the curing agent, the ceramic powder of the subject may be equally applied to the curing agent in an amount of 20 to 30% by weight based on the total weight of the curing agent, and the content of the thixotropic agent and the antifoaming agent of the subject may be changed to the curing agent. can be applied In particular, the thixotropic agent of the curing agent is preferably 5 to 15% by weight to satisfy the physical properties of the curing agent. Other additives in the curing agent may be appropriately adjusted and applied in consideration of the type and content of the curing agent within the scope of the present invention.

The repair layer 10 is first formed after treating the surface of the welded portion WD. The surface treatment removes mill scale, rust, paint, and other foreign substances using, for example, #80 to 400 sandpaper, a grinder, and the like. Thereafter, the repair layer 10 is formed by molding and repairing the repair agent to a thickness (t) of 1 to 5 mm. At this time, the water retention agent and the curing agent are mixed and mixed in a weight ratio of 3: 1 to 7: 1, and a pot life of 30 minutes or less is applied.

Hereinafter, the present invention will be described in more detail through examples, and the present examples are intended to explain the present invention in more detail through the most preferred embodiments, and the scope of the present invention is not limited to the examples. At this time, the abrasion resistance is a method of measuring the weight (mg) loss when a specimen manufactured according to the Taber-type abrasion test method of ASTM D4060 is subjected to a load of 1 kg using CS-17 WHEEL and cycled 1,000. The weight before and after the test is measured. compared. Hardness was measured according to ASTM D2240, corrosion resistance was measured according to KS D9502, adhesion strength was measured according to ASTM D4541, and tensile shear adhesive strength was measured according to the test method of ASTM D1002.

Table 1 shows the composition constituting the repair layer 10 according to Examples and Comparative Examples of the present invention.

According to Table 1, Epoxy Resin-1 is a phenol novolak-type epoxy resin, and Epoxy Resin-2 is a bisphenol F-type epoxy resin. Phenol novolak-type epoxy resin has excellent chemical resistance and abrasion resistance, and bisphenol F-type resin has excellent adhesive properties and is eco-friendly, so when epoxy resin-1 and epoxy resin-2 are properly combined, excellent physical properties are exhibited. do. Anticorrosive pigment-1 is a known anticorrosive pigment, and anticorrosive pigment 2 contains barium metaborate monohydrate. When rust-preventive pigment-1 and rust-preventive pigment-2 are mixed, the rust-preventive effect can be further enhanced. The cured resin-1, aliphatic amine-based resin, has excellent curing time and wet surface adhesion, and the cured resin-2, polyamideamine-based resin, has excellent adhesiveness. When cured resin-1 and cured resin-2 are properly mixed and applied, it is helpful to secure excellent adhesiveness and rust prevention.

The above subject is epoxy resin-1 (Kukdo Chemical, YDPN-631), epoxy resin-2 (Kukdo Chemical, KSR-177), diluent (Kolon Industries, HIRENOL PL-500), titanium dioxide, calcium carbonate, silica, mica Properly mixed ceramic powder, anticorrosive pigment-1 (Hanchang, #330, UMP), anticorrosive pigment-2 (Buckman Busan, 11M1) with a particle size of 0.1 to 6.5㎛, silicon carbide with a particle size of 5 to 500㎛ (Showa Denko, k.k.), tungsten carbide with a particle size of 1 to 10㎛ (HiMC, WC4.0), boron carbide with a particle size of 10 to 100㎛ (Hanbo World, boron carbide), alumina (Hanbo World, fused alumina), thixotropic agent ( BYK, BYK Garamite 1958), coupling agent (Dow Corning, OFS-6020), dispersing agent (BASF, EFKA FA4609AN), and antifoaming agent (BYK, BYK-054, 066N) were used.

As the curing agent, curing resin-1 (Kukdo Chemical, KH-500) and curing resin-2 (Kukdo Chemical, G-0331) were used, and ceramic powder, thixotropic agent, and antifoaming agent were the same products as those of the above subject. As the curing agent, a ceramic powder properly mixed with titanium dioxide, calcium carbonate, silica, and mica, a thixotropic agent (BYK, Garamite 1958), and a defoaming agent (BYK, BYK-054) were used.

<Example 1>

The subject of Table 1 and the curing agent were mixed in a weight ratio of 5: 1, coated/molded to a thickness of about 3 mm on a 3.2T iron plate using an applicator, spatula, etc., and cured at room temperature for 24 hours. Specimens for the durability (corrosion resistance) test were pretreated with a grinder on cold-rolled steel sheets, then coated using an applicator, spatula, spatula, etc. to a thickness of about 3mm, at a temperature of 22ㅁ2℃ and relative humidity of 50ㅁ After drying in a 3% constant temperature and humidity oven for 7 days, the physical properties of the repair layer were measured.

<Comparative Example 1>

A repair layer was prepared in the same manner as in Example 1, and physical properties were measured, except that 10% by weight of rust-preventive pigment-1 and 21% by weight of silicon carbide were contained, and the rust-preventive pigment-2 was not mixed.

<Comparative Example 2>

A repair layer was prepared in the same manner as in Example 1, except that 10% by weight of anticorrosive pigment-2 and 31% by weight of silicon carbide were contained, and the anticorrosive pigment-1, tungsten carbide and boron carbide were not mixed, and the physical properties were measured. .

Table 2 shows the physical properties of Example 1 and Comparative Examples 1 and 2 of the present invention. At this time, the workability was expressed as 10 mm molding conditions, hardness as Shore D, corrosion resistance after 300 hours, abrasion resistance as Taber, CS17, 1,000 g conditions, and adhesion strength and tensile shear adhesion strength as N/mm2.

Properties Example 1 Comparative Example 1 Comparative Example 2 Workability (10mm molding) Great Good Good Hardness (Shore D) 87 86 85 Corrosion resistance (300 hours) Great commonly commonly Abrasion resistance (Taber, CS17, 1,000g) 28 43 56 Adhesion strength (N/㎟) 11 8 7 Tensile shear adhesion strength (N/㎟) 15 13 12

According to Table 2, Comparative Example 2 had almost the same or slightly better corrosion resistance and adhesion strength than Comparative Example 1, but had lower hardness, wear resistance and tensile shear bonding strength. In particular, the abrasion resistance was remarkably low. That is, in Comparative Example 2, although the content of silicon carbide was increased, tungsten carbide and boron carbide having high hardness did not exist, so it was found that the wear resistance was very low. In addition, Comparative Example 2 did not have anticorrosive pigment-1, and thus the distribution of particles was non-uniform, resulting in poor tensile shear bonding strength. Accordingly, Comparative Example 2 was unsuitable for the repair layer 10 .

Example 1 was superior to Comparative Example 1 in workability, hardness, corrosion resistance, abrasion resistance, adhesion strength, and tensile shear adhesion strength. Example 1 significantly increased wear resistance compared to Comparative Example 1. That is, in Comparative Example 1, although the content of silicon carbide was increased, the content of tungsten carbide and boron carbide having high hardness was reduced, so it was found that the wear resistance was very low. In addition, Comparative Example 2 did not contain the anticorrosive pigment-1, so the distribution of the particles was non-uniform, resulting in low tensile shear adhesive strength, and particularly low adhesive strength. Accordingly, in order to increase the adhesion strength, mixing of the anticorrosive pigment-1 and the anticorrosive pigment-2 was required.

In the above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. possible.

10; conservative
t; thickness W of the repair layer; expansion width
MS; metal structure

Claims (10)

It is applied to cover the welded area, and is composed of a mixture of a main agent and a curing agent, and the main agent is composed of 25 to 40% by weight of polymer resin, 1 to 8% by weight of diluent, 5 to 15% by weight of ceramic powder, and alumina 5 with respect to the total weight. 10% by weight, 5 to 15% by weight of anticorrosive pigment, 5 to 15% by weight of silicon carbide, 5 to 15% by weight of tungsten carbide, 5 to 15% by weight of boron carbide, 1 to 5% by weight of thixotropic agent and other additives , The curing agent includes 50 to 70% by weight of cured resin, 20 to 30% by weight of ceramic powder, 5 to 15% by weight of thixotropic agent and other additives,
With respect to the total weight of the subject matter, the tungsten carbide is a compound based on tungsten and carbon, the boron carbide is a compound based on boron and carbon,
The polymer resin is an epoxy-based resin, the curing resin is an amine-based resin, and the ceramic powder is any one selected from titanium dioxide, calcium carbonate, mica, and silica. The repair layer composition according to claim 1, wherein the repair layer has a thickness of 1 to 5 mm. The repair layer composition according to claim 1, wherein the repair layer has an extended width extending to both sides of the welded region, and the extended width ranges from 20 to 50 mm. The repair layer composition for protecting a welded area according to claim 1, wherein the tungsten carbide replaces a part of the tungsten with cobalt. According to claim 1, wherein the polymer resin of the main material is a bisphenol F-type epoxy resin having an epoxy equivalent of 190 to 220 g/eq and a viscosity of about 9,000 to 15,000 cps. [Claim 6] The repair layer composition according to claim 5, wherein the subject polymer resin is a mixture of the bisphenol F-type epoxy resin and the phenol novolak-type epoxy resin. The repair layer composition according to claim 1, wherein the diluent is a non-reactive diluent. The repair layer composition according to claim 1, wherein the rust-preventive pigment comprises barium metaborate monohydrate. The repair layer composition according to claim 1, wherein the cured resin of the curing agent is a polyamide amine-based resin having a total amine value of about 280 to 340 mgKOH/g. 10. The repair layer composition according to claim 9, wherein the cured resin is a polyamide amine resin mixed with an aliphatic amine resin.

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