CN116273790A - On-site anti-corrosion maintenance coating structure and construction method of steel structure engineering - Google Patents

Abstract

The invention discloses a steel structure engineering field anticorrosion maintenance coating structure and a construction method thereof, wherein the steel structure engineering field anticorrosion maintenance coating structure comprises a steel structure substrate, wherein a first solvent-free epoxy coating and a second solvent-free epoxy coating are sequentially arranged on the surface of the steel structure substrate from inside to outside to form an anticorrosion maintenance coating; the pretreatment cleanliness of the steel structure matrix is not lower than the PSa2 grade; aiming at the problems of long coating period, difficult quality guarantee of the composite coating structure and the like of the conventional composite coating structure in the conventional steel structure engineering on-site anti-corrosion coating construction, the invention solves the problems of the prior solvent-free epoxy coating, and realizes the comprehensive effects of cleaning, safety, rapidness and durability of the rapid on-site coating construction by utilizing the hyperbranched resin modification technology.

Description

On-site anti-corrosion maintenance coating structure and construction method of steel structure engineering

technical field

The invention relates to steel structure surface coating protection technology, in particular to a steel structure engineering on-site anti-corrosion maintenance coating structure and a construction method thereof, belonging to the technical field of corrosion protection.

Background technique

The many advantages of steel structure make it one of the mainstream choices for prefabricated buildings. The main technical problem faced in the application of steel structure is the anti-corrosion protection of steel structure substrate. At present, the anti-corrosion protection technology of steel structure surface in the world mainly adopts coating Protection technology, coating protection technology mainly includes arc spraying metal composite coating protection system and coating heavy-duty anti-corrosion composite coating protection system. Among them, the actual service life of the arc sprayed metal composite coating protection system has exceeded 30 years, and the initial maintenance-free time of the heavy-duty coating heavy-duty composite coating protection system can also reach about 10 years. However, in the application process of steel structure engineering, it is found that the protection failure problems caused by insufficient protection ability design of the composite coating system, inadequate surface treatment, and poor coating quality control are more likely to occur early and on a large scale, such as welds, edges and corners Etc., as short as 1 year, and as long as 2 years, there will be corrosion problems at welds and edges and corners; such as coastal steel structure engineering and industrial steel structure engineering (such as coal preparation plant steel structure, power plant steel structure, etc.), due to the sea Atmospheric environment, industrial corrosion environment or indoor severe humid environment, etc. As a result, shortly after the steel structure project is put into operation, the relevant steel structure will be corroded to varying degrees, and the corrosion will gradually increase with time. First, it will significantly affect the beautification of the project. Decorative effect; the second is to greatly shorten the first maintenance-free time of the project, and significantly increase the maintenance frequency during the whole life of the project, which greatly increases the maintenance cost of the project; the third is to bring safety hazards to related projects. These have seriously damaged the due economic and social benefits of steel structure engineering.

CN201320186942.4 discloses an anti-corrosion composite coating structure for steel structure welds. The composite coating structure is thermally sprayed with a rare earth modified anodic metal coating on the surface of the weld treated by sandblasting or shot surface treatment. , attached to the rare earth modified anodic metal coating from the inside to the outside are nano-modified epoxy sealer coating, epoxy mica iron intermediate paint coating and polyurethane topcoat or fluorocarbon topcoat coating; for heavy The effect of anti-corrosion coatings on high-salinity seawater steel structures is not very good, and because most of them need to be applied under the dry surface of steel structures, it is not suitable for the technical problems of on-site construction of anti-corrosion coatings on existing steel structures. CN201910232830.X discloses A preparation method of a graphene-based steel anticorrosion coating, the surface of the steel is degreased, derusted and polished, and then the epoxy resin is cured under water to coat a layer of epoxy resin coating on the polished steel surface, and then Using silane coupling agent, silane coupling agent water-based graphene composite layer, and oil-based graphene layer transition process, three graphene-based steel anti-corrosion coatings were obtained, which were successfully applied in tidal areas, splash areas and high-humidity environments; The coating system recommended by the Coal Industry Group Washing Center for the steel structure maintenance of the enterprise is shown in Table 1.

Table 1 Steel structure maintenance design scheme of coal preparation plant

Based on the above-mentioned existing technologies, it can be seen that the existing on-site anti-corrosion coating construction of steel structure projects uses composite coating structures, and among the coatings used, traditional solvent-based coatings contain a large amount of VOC emissions, and the existing environmental protection policies can no longer be used. Accepted, at present, the on-site anti-corrosion coating of steel structure projects is actively promoting high-solid, solvent-free, water-based and other environmentally friendly coatings, but although the above-mentioned environmentally friendly coatings meet the national requirements in terms of environmental protection, the above-mentioned coatings generally have a long surface drying time , especially the hard drying time is longer (10-24h), plus multiple coats and their intervals, so that the composite coating can be finished and put into use. It takes 3-5 days at shortest time, and even longer for the elderly. It has seriously affected the use of existing steel structure projects, especially the maintenance and use of in-service steel structure projects, and many steel structure anti-corrosion coating maintenance projects often affect the guarantee of coating quality due to on-site time constraints.

Contents of the invention

In order to overcome the above-mentioned deficiencies in the prior art, the object of the present invention is to adopt conventional composite coating structure for existing steel structure engineering on-site anti-corrosion coating construction. In view of the quality problems, in view of the technical deficiencies of the existing solvent-free epoxy coatings such as high viscosity and thick coating design, a new type of composite coating structure for on-site anti-corrosion coating construction of steel structure engineering is proposed by using hyperbranched resin modification technology. The corresponding fast-curing solvent-free epoxy coating has low viscosity, easy control of coating thickness, and fast curing, realizing the comprehensive effect of fast on-site coating construction, clean, safe, fast and durable.

The technical scheme of the present invention is as follows: a coating structure for on-site anti-corrosion maintenance of steel structure engineering, including a steel structure substrate, the surface of the steel structure substrate is sequentially provided with a first solvent-free epoxy coating and a second solvent-free epoxy coating from the inside to the outside. Solvent-free epoxy coating to form an anti-corrosion maintenance coating; the pre-treatment cleanliness of the steel structure substrate is not lower than PSa2½ level; the thickness of the first solvent-free epoxy coating is 50-200 μm; The thickness of the solvent epoxy coating is 100-400 μm; the thickness of the anti-corrosion maintenance coating is 150-600 μm; the formation time of the first solvent-free epoxy coating and the second solvent-free epoxy coating is not less than the surface dry time More than 1h, hard work time does not exceed 4h.

A kind of construction method of described a kind of steel structure engineering on-site maintenance coating structure, concrete steps are as follows:

Step 1: Surface cleaning of the steel structure substrate: use a spatula, a brush and a cleaning agent to remove the obvious oil stains, peeling off coating, dust accumulation, heavy rust and effects on the surface of the steel structure substrate of the on-site steel structure project. Impurities and sundries in the installation operation are removed to facilitate subsequent construction;

The second step: ultra-high pressure water jet cleaning treatment: Immediately after the first step, use a water jet spray gun with a pressure range of 200-250 MPa to spray the surface of the steel structure substrate to remove the loose old coating, rust, and scale deposits, the cleanliness can reach PSa2½ level and above; the water in the water jet contains not less than 0.1% corrosion inhibitor;

Step 3: Air-drying treatment: Immediately after the end of the second step, use clean and dry compressed air to dry the surface of the steel structure substrate after water jet cleaning. The compressed air pressure is not lower than 0.5MPa, and the air temperature is not lower than 10. ℃, the drying time of the surface of the steel structure substrate shall not exceed 5 minutes;

Step 4: Manual pre-coating: After the air-drying treatment in the third step is qualified, mix an appropriate amount of solvent-free epoxy paint for the first solvent-free epoxy coating evenly, and use brushes and rollers to spray the steel structure substrate. Parts or hidden parts are pre-coated;

Step 5: Spray the first solvent-free epoxy coating; after the pre-coating treatment, immediately use a two-component solvent-free paint spray gun to apply the first solvent-free epoxy coating to control the first solvent-free ring Oxygen coating thickness 50-200μm;

Step 6: Spray the second solvent-free epoxy coating: 1 hour after the first solvent-free epoxy coating, immediately use a two-component solvent-free paint spray gun to spray the second solvent-free epoxy coating For coating, control the thickness of the second solvent-free epoxy coating to 100-400 μm;

Step 7: Delivery and use: 4 hours after the completion of the second solvent-free epoxy coating, inspect the surface of the anti-corrosion maintenance coating, that is, use manual walking to inspect the load-bearing condition of the composite coating structure, according to the footprint of the composite coating It can be handed over without obvious deformation, and the steel structure project can be put into use on site.

As the preferred scheme of the construction method of the composite coating structure for steel structure engineering on-site anticorrosion coating construction according to the present invention:

The first solvent-free epoxy coating and the second solvent-free epoxy coating are solvent-free epoxy coatings;

The solvent-free epoxy coating is a solvent-free epoxy coating composed of A component and B component, wherein:

Component A is composed of the following raw materials by weight percentage: E51 bisphenol A epoxy resin dosage 40-60%, CER-170 hyperbranched aliphatic epoxy resin dosage 10-20%, wetting and dispersing agent dosage 0.5% %, the amount of defoaming agent is 0.5%, the amount of anti-settling agent is 0.5%, the amount of pigment carbon black is 0.7%, and the balance is filler;

Component B is composed of the following raw materials by weight percentage: WZH-155K epoxy curing agent dosage 20~28%, DMP-30 accelerator dosage 1~2%, KH-550 coupling agent dosage 1~2%, The balance is CYH-277 toughening and diluting modifier;

Before using the above-mentioned two-components A and B, weigh them according to the weight ratio of A:B 1:1 and mix them evenly before painting.

As a preferred solution of the construction method of the composite coating structure for on-site anti-corrosion coating construction of steel structure engineering according to the present invention: the filler contains 1-10% by weight of flaky zinc powder.

As a preferred solution of the construction method of the composite coating structure for on-site anti-corrosion coating construction of steel structure engineering according to the present invention: the filler contains 0.5-5% graphene by weight.

As the preferred scheme of the construction method of the composite coating structure for steel structure engineering on-site anticorrosion coating construction according to the present invention: in the solvent-free epoxy coating for the second solvent-free epoxy coating, in the existing or In addition to the above solvent-free epoxy coating, it may also contain 0.3-0.5% by weight of antioxidant, 0.3-0.5% by weight of ultraviolet light absorber, and 0.3-0.8% by weight of light stabilizer.

As the preferred scheme of the construction method of the composite coating structure for steel structure engineering on-site anticorrosion coating construction according to the present invention: the antioxidant is a hindered phenolic primary antioxidant, or a hindered phenolic primary antioxidant combined with a low A mixture of volatile organic phosphite auxiliary antioxidants in any proportion.

As a preferred solution of the construction method of the composite coating structure for on-site anti-corrosion coating construction of steel structure engineering according to the present invention: the light stabilizer is a hindered amine light stabilizer.

As a preferred solution of the construction method of the composite coating structure for on-site anti-corrosion coating construction of steel structure engineering according to the present invention: the ultraviolet light absorber is a benzotriazole ultraviolet absorber substituted with phenolic groups.

In order to improve the protective performance of the coating, the above-mentioned fillers also contain flaky zinc powder or graphene. The flaky zinc powder can not only improve the shielding performance of the coating, but also provide better cathodic protection for the steel structure substrate; the application of graphene Adding it to the coating can improve the physical and mechanical properties of the coating by virtue of its excellent performance.

The solvent-free epoxy coating that above-mentioned second road solvent-free epoxy coating is used contains antioxidant, ultraviolet absorber, light stabilizer; Because existing solvent-free epoxy coating is mainly used in indoor environment, there is no too high Weather resistance requirements, on the basis of existing technologies, adding antioxidants, ultraviolet light absorbers and light stabilizers can improve the durability of anti-corrosion and maintenance coatings on the surface of some components facing high temperature or light radiation on the steel structure engineering site, ensuring that the entire steel On-site anti-corrosion maintenance of structural engineering After the application of the coating structure, its surface can be stable and consistent for a long time, maintaining a good decorative and beautifying effect.

The beneficial effects of the present invention are: the on-site anti-corrosion maintenance coating structure of the steel structure project adopts the solvent-free epoxy paint coating system, the on-site coating period is short, the on-site operation of the steel structure project is less disturbed, the construction is safe, clean and environmentally friendly, The coating is dense and pinhole-free, has super long salt spray resistance, excellent shielding performance, can prevent electrochemical corrosion, and is durable and reliable. Because there is no interlayer interference, the coating quality is reliable. The solvent-free epoxy coating for the first solvent-free epoxy coating of the present invention adopts hyperbranched resin modification technology, and through formula optimization and the addition of scaly zinc powder or graphene, it not only overcomes the existing solvent-free coating The deficiencies in the technology also solve the problem of insufficient adhesion caused by the excessive flexibility of the existing hyperbranched modified epoxy coatings. While meeting the construction requirements for on-site anti-corrosion maintenance of steel structure engineering, it also ensures on-site anti-corrosion maintenance of steel structure engineering. Comprehensive protection performance of coating structure.

Description of drawings

Fig. 1 is a structural representation of the present invention;

In the picture: 1-steel structure substrate, 2-the first solvent-free epoxy coating, 3-the second solvent-free epoxy coating.

Detailed ways

Further illustrate scheme and effect of the present invention below in conjunction with embodiment and accompanying drawing:

Example 1

See Figure 1.

A coating structure for on-site anti-corrosion maintenance of steel structure engineering, including a steel structure substrate 1, the surface of the steel structure substrate 1 is sequentially provided with a first solvent-free epoxy coating 2 and a second solvent-free epoxy coating from the inside to the outside Coating 3, forming an anti-corrosion maintenance coating.

After the pre-treatment cleanliness of the steel structure substrate 1 at the steel structure engineering site is not lower than P Sa2½ level, solvent-free epoxy coatings (such as hyperbranched aliphatic epoxy resin water-based coatings in CN112547464) can be applied to form the first solvent-free coating Epoxy coating 2, the thickness of the coating is 50-100μm, the surface dry time is about 0.5h, the hard drying time is no more than 4h, and the adhesion exceeds 8MPa; the first solvent-free epoxy coating 2 can be applied as soon as the surface is dry Solvent-free epoxy coating (such as Liyang Yejian TH-28) is formed by the second solvent-free epoxy coating 3, the thickness of the coating is 150-300 μm, and the surface drying time of the second solvent-free epoxy coating 3 does not exceed 1h , the hard drying time does not exceed 4 hours, and the adhesion is not less than 10MPa; the total thickness of the composite coating structure used for anti-corrosion coating construction on the entire steel structure project reaches 200-400μm, the adhesion exceeds 8MPa, and the salt spray test time is not less than 5000h.

Example 2

See Figure 1.

A coating structure for on-site anti-corrosion maintenance of steel structure engineering, including a steel structure substrate 1, the surface of the steel structure substrate 1 is sequentially provided with a first solvent-free epoxy coating 2 and a second solvent-free epoxy coating from the inside to the outside Coating 3, forming an anti-corrosion maintenance coating; the pre-treatment cleanliness of the steel structure substrate 1 is not lower than PSa2½ level; the thickness of the first solvent-free epoxy coating 2 is 50-200 μm; the second solvent-free The thickness of the epoxy coating 3 is 100-400 μm; the thickness of the anti-corrosion maintenance coating is 150-600 μm.

The above-mentioned solvent-free epoxy coating 2 and the solvent-free epoxy coating for solvent-free epoxy coating 3 are composed of A and B components, wherein:

Component A is composed of the following raw materials by weight percentage: E51 type bisphenol A epoxy resin 40%, CER-170 hyperbranched aliphatic epoxy resin 20%, wetting and dispersing agent 0.5%, defoamer 0.5% , anti-sedimentation agent 0.5%, pigment carbon black 0.7%, 5% flaky zinc powder, and filler balance; firstly, other raw materials in component A except flaky zinc powder are weighed and sampled according to the above ratio, and dispersed evenly with a grinder , and then add flake zinc powder and disperse evenly in a vacuum high-speed mixer for later use.

Component B is composed of the following raw materials by weight percentage: WZH-155K epoxy curing agent 28%, DMP-30 accelerator 1%, KH-550 coupling agent 1%, CYH-277 toughening dilution modifier For the remainder, weigh and sample the raw materials in component B according to the above ratio, and disperse them evenly with a vacuum high-speed mixer for later use.

On the site of the steel structure project, the above-mentioned components A and B are weighed and sampled according to their weight in a ratio of 1:1 and mixed evenly, and then used for the first solvent-free epoxy coating 2 and the second solvent-free epoxy coating 3 It can be painted and used. After application testing, the above-mentioned solvent-free epoxy coating has a room temperature surface drying time of no more than 40 minutes, a hard drying time of no more than 3 hours, an adhesion of no less than 10 MPa, and a salt spray resistance time of no less than 5000 hours.

Example 3

See Figure 1.

An on-site anti-corrosion maintenance coating structure for steel structure engineering, including a steel structure substrate 1, the on-site anti-corrosion maintenance coating structure for steel structure engineering is a first solvent-free epoxy coating 2, a second solvent-free epoxy coating 2, and a second solvent-free epoxy coating from the steel structure substrate 1 upward. Solvent epoxy coating3.

The above-mentioned solvent-free epoxy coating for the second solvent-free epoxy coating adopts the solvent-free epoxy coating of the prior art, and adds 0.5 parts by weight accounting for the total weight of the coating to its resin component (such as component A). % of hindered phenolic primary antioxidant, 0.3% by weight of phenolic substituted benzotriazole ultraviolet absorber, and 0.5% by weight of hindered amine light stabilizer, and use a high-speed mixer to disperse evenly for later use.

On the site of the steel structure project, the solvent-free epoxy coating resin component (such as component A) of the above-mentioned improved prior art is weighed and sampled and mixed with its curing agent component (such as component B) according to its stated ratio. After uniformity, it can be used for the second solvent-free epoxy coating. After sampling and testing, the surface-drying time of the second solvent-free epoxy coating 3 at room temperature shall not exceed 1 hour, the hard-drying time shall not exceed 4 hours, the adhesion shall not be lower than 10 MPa, the salt spray resistance time shall not be lower than 5000 hours, and the artificial accelerated aging test shall be resistant. The time exceeds 3000h.

Example 4

See Figure 1.

An on-site anti-corrosion maintenance coating structure for steel structure engineering, including a steel structure substrate 1, the on-site anti-corrosion maintenance coating structure for steel structure engineering is a first solvent-free epoxy coating 2, a second solvent-free epoxy coating 2, and a second solvent-free epoxy coating from the steel structure substrate 1 upward. Solvent epoxy coating3.

Above-mentioned solvent-free epoxy coating 2 is formed by spraying the solvent-free epoxy coating of embodiment 2;

The solvent-free epoxy coating used in the above-mentioned solvent-free epoxy coating 3 is composed of A and B components, wherein:

Component A is composed of the following raw materials by weight percentage: 50% of E51 type bisphenol A epoxy resin, 10% of CER-170 hyperbranched aliphatic epoxy resin, 0.5% of wetting and dispersing agent, defoaming agent 0.5% of anti-settling agent, 0.5% of anti-settling agent, 0.7% of pigment carbon black, 0.5% of antioxidant, 0.3% of ultraviolet absorber, 0.5% of light stabilizer, and the rest is filler; Weigh and sample according to the above ratio, grind and disperse, and disperse evenly in a vacuum high-speed mixer before use.

Component B is composed of the following raw materials by weight percentage: 26% of WZH-155K epoxy curing agent, 2% of DMP-30 accelerator, 2% of KH-550 coupling agent, and the balance of CYH-277 Toughening and diluting modifier; weigh and sample the raw materials in component B according to the above ratio, and use a vacuum high-speed mixer to disperse evenly for later use.

Before using the above-mentioned two-components A and B, weigh them according to the weight ratio of A:B 1:1, mix them evenly, and then apply them.

After sampling and testing, the surface-drying time of the second solvent-free epoxy coating 3 at room temperature shall not exceed 1 hour, the hard-drying time shall not exceed 4 hours, the adhesion shall not be lower than 10 MPa, the salt spray resistance time shall not be lower than 5000 hours, and the artificial accelerated aging test shall be resistant. The time exceeds 3000h.

Example 5

The specific construction steps of the on-site maintenance coating structure of the steel structure engineering described in embodiment 1-embodiment 3 are as follows:

Step 1: Surface cleaning of the steel structure substrate: Use a spatula, a brush and a cleaning agent to remove the obvious oil stains, old coatings that have been peeled off, dust and dust on the surface of the structure, and steel on the surface of the steel structure substrate in the on-site steel structure project. The heavy rust caused by structural corrosion and other impurities and sundries that affect the coating operation should be removed in advance.

Step 2: Ultra-high pressure water jet cleaning treatment: After the first step, use a water jet spray gun with a pressure range of 200-250 MPa to spray the surface of the steel structure substrate to remove loose old coatings, rust, and oxidation on the surface. For attachments such as leather, the cleanliness should reach P Sa2½ level and above; in order to prevent flash rust, 0.1% by weight of corrosion inhibitor is added to the water of the water jet used. Water jet treatment of steel structures adopts the principle of sequence from inside to outside, from top to bottom, from high to low, and from middle to edge.

Step 3: Air-drying treatment: Immediately after the end of the second step, use clean and dry compressed air to dry the surface of the steel structure substrate after water jet cleaning. The compressed air pressure is not lower than 0.5MPa, and the air temperature is not lower than 10. ℃, the drying time of the surface of the steel structure substrate shall not exceed 5 minutes; the principle of air-drying treatment is the same as that of water jet operation, and the specific operation shall follow the water jet treatment operation, that is, after the water jet is cleaned, the operation surface has a separate and unaffected surface. In the working conditions affected by subsequent water jet operations, air-dry immediately, except for areas that have been naturally dried.

Step 4: Manual pre-coating: After the air-drying treatment in the third step starts, the manual pre-coating operation starts immediately following the air-drying operation surface, that is, after the air-drying treatment, the working surface has a separate working surface that is not affected by the subsequent air-drying operation. In the case of the situation, immediately use a brush or a roller, etc., and use the solvent-free epoxy coating for the first solvent-free epoxy coating, and apply the solvent-free epoxy coating to the surface of the component that needs to be pre-coated (the parts that are difficult to spray on the steel structure matrix of the on-site steel structure engineering, and the hidden parts) , the interior of the gap, the larger groove, the back of the spray or the surface of other components that are difficult to spray effectively with the spray gun) for pre-coating;

Step 5: The first solvent-free epoxy coating spraying; after the pre-coating treatment, immediately use the two-component solvent-free coating special spray gun to carry out the first solvent-free epoxy coating coating, and control the first solvent-free coating The thickness of the epoxy coating is 50-200 μm; such as using the solvent-free epoxy coating modified by the hyperbranched resin in Example 2 and adding flake zinc powder.

Step 6: The second solvent-free epoxy coating spraying: 1 hour after the first solvent-free epoxy coating is finished or after the surface is dry, the second solvent-free coating can be used immediately with a special spray gun for two-component solvent-free coatings. For the coating of solvent epoxy coating, the thickness of the second solvent-free epoxy coating is controlled to 100～400 μm; as adopting the present embodiment 3, adding antioxidant, ultraviolet absorber and light stabilizer to the existing technology improved Solvent free epoxy coating.

Step 7: Delivery and use: 4 hours after the completion of the second solvent-free epoxy coating or after the inspection has been solidified, the surface of the composite coating structure for anti-corrosion coating construction in the steel structure project can be inspected by the master, that is Manual walking is used to check the load-bearing condition of the coating structure. The coating can be handed over without obvious deformation at the footprint, and the steel structure project can be put into use on site.

Claims (9)

1. The utility model provides a steel construction engineering field corrosion prevention maintains coating structure, includes steel construction base member, its characterized in that: the surface of the steel structure substrate is sequentially provided with a first solvent-free epoxy coating and a second solvent-free epoxy coating from inside to outside to form an anti-corrosion maintenance coating; the pretreatment cleanliness of the steel structure matrix is not lower than the PSa2 grade; the thickness of the first solvent-free epoxy coating is 50-200 mu m; the thickness of the second solvent-free epoxy coating is 100-400 mu m; the thickness of the anti-corrosion maintenance coating is 150-600 mu m; the forming time of the first solvent-free epoxy coating and the second solvent-free epoxy coating is that the surface drying time is not more than 1h and the real drying time is not more than 4h.

2. A method of constructing a steel structure engineering field maintenance coating structure according to claim 1, wherein: the method comprises the following specific steps:

the first step: cleaning the surface of a steel structure substrate: the scraper knife, the brush and the cleaning agent are adopted to remove obvious greasy dirt, coating removal, dust accumulation and dust accumulation, heavy rust and impurities and sundries affecting the coating operation on the surface of the steel structure substrate of the field steel structure engineering, so that the subsequent construction is facilitated;

and a second step of: ultra-high pressure water jet cleaning: immediately adopting a water jet spray gun with the pressure ranging from 200 MPa to 250MPa to spray the surface of the steel structure substrate after the first step is finished, removing loose old coatings, rust and oxide scale attachments on the surface of the steel structure substrate, wherein the cleanliness reaches the PSa2 grade or more; the water of the water jet contains not less than 0.1% of corrosion inhibitor;

and a third step of: and (3) air drying: after the second step is finished, immediately adopting clean and dry compressed air to blow-dry the surface of the steel structure substrate after the water jet cleaning treatment, wherein the air pressure of the compressed air is not lower than 0.5MPa, the air temperature is not lower than 10 ℃, and the blow-drying operation time of the surface of the steel structure substrate is not longer than 5min;

fourth step: manual precoating: thirdly, after the air drying treatment is qualified, uniformly mixing a proper amount of solvent-free epoxy paint for the first solvent-free epoxy coating, and pre-coating the parts which are difficult to spray or the hidden parts of the steel structure matrix by adopting a hairbrush and a roller;

fifth step: spraying a first solvent-free epoxy coating; after the precoating treatment, immediately adopting a two-component solvent-free paint spray gun to carry out the first-pass solvent-free epoxy coating, and controlling the thickness of the first-pass solvent-free epoxy coating to be 50-200 mu m;

sixth step: and (3) spraying a second solvent-free epoxy coating: immediately coating a second solvent-free epoxy coating by adopting a two-component solvent-free paint spray gun after finishing the coating of the first solvent-free epoxy coating for 1h, and controlling the thickness of the second solvent-free epoxy coating to be 100-400 mu m;

seventh step: the delivery is as follows: and after the second solvent-free epoxy coating operation is finished for 4 hours, the surface of the anti-corrosion maintenance coating is inspected, namely, the bearing condition of the composite coating structure is inspected by adopting manual walking, and the composite coating can be delivered according to no obvious deformation of the footprint, so that the steel structure engineering site can be put into use.

3. The construction method of the composite coating structure for steel structure engineering on-site corrosion protection coating construction according to claim 2, wherein the construction method comprises the following steps:

the first solvent-free epoxy coating and the second solvent-free epoxy coating are solvent-free epoxy coatings;

the solvent-free epoxy coating is a solvent-free epoxy coating consisting of an A component and a B component, wherein:

the component A consists of the following raw materials in percentage by weight: 40-60% of E51 bisphenol A epoxy resin, 10-20% of CER-170 hyperbranched aliphatic epoxy resin, 0.5% of wetting dispersant, 0.5% of defoamer, 0.5% of anti-settling agent, 0.7% of pigment carbon black and the balance of filler;

the component B consists of the following raw materials in percentage by weight: 20-28% of WZH-155K epoxy hardener, 1-2% of DMP-30 accelerator, 1-2% of KH-550 coupling agent and the balance of CYH-277 toughening dilution modifier;

before the A, B double components are used, the components are weighed according to the weight ratio of A to B of 1:1, uniformly mixed and then coated for use.

4. A method of constructing a steel structure engineering field corrosion protection maintenance coating structure according to claim 3, wherein: the filler part contains 1-10% of scaly zinc powder by weight.

5. A method of constructing a steel structure engineering field corrosion protection maintenance coating structure according to claim 3, wherein: the filler part contains 0.5-5% of graphene by weight.

6. The construction method of the composite coating structure for steel structure engineering on-site corrosion protection coating construction according to claim 3, wherein the construction method comprises the following steps: the solvent-free epoxy coating for the second solvent-free epoxy coating can also contain 0.3 to 0.5 percent of antioxidant, 0.3 to 0.5 percent of ultraviolet light absorber and 0.3 to 0.8 percent of light stabilizer by weight percent.

7. The construction method of the composite coating structure for steel structure engineering on-site corrosion protection coating construction according to claim 6, wherein the construction method comprises the following steps: the antioxidant is hindered phenol main antioxidant or a mixture of hindered phenol main antioxidant and low-volatility organic phosphite ester auxiliary antioxidant in any proportion.

8. The construction method of the composite coating structure for steel structure engineering on-site corrosion protection coating construction according to claim 6, wherein the construction method comprises the following steps: the light stabilizer is a hindered amine light stabilizer.

9. The construction method of the composite coating structure for steel structure engineering on-site corrosion protection coating construction according to claim 6, wherein the construction method comprises the following steps: the ultraviolet light absorber is a phenol-substituted benzotriazole ultraviolet light absorber.

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