Antifouling treatment construction method for interiors of pipelines and containers of coastal industrial cooling water system

Abstract

The invention provides an antifouling treatment construction method for the interiors of pipelines and containers of coastal industrial cooling water systems, which comprises the steps of inner wall detection and modeling, partition pretreatment, three-phase composite coating, differential spraying, in-situ leveling and curing and film layer quality rechecking. The inner wall corrosion depth, the surface roughness and the residual state of an old coating are synchronously detected by utilizing optical structured light scanning, electrochemical impedance measurement and laser roughness detection, a three-dimensional condition map is generated, and an area is divided into A, B and C classes. Then, low-pressure sand blasting and chelating agent treatment and differential pretreatment of surface tension adjustment or cleaning and degreasing are carried out on all the areas respectively, laser film thickness scanning and electrochemical impedance remeasurement are carried out on the coating after curing, and supplementary coating is completed through repeated coating and curing on the unqualified areas; according to the method, refined construction of a corrosion pit area, a rough area and a complete area is achieved, and the adhesive force of a coating, the uniformity of a film layer and the antifouling and corrosion-resistant stability in a seawater environment are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ocean engineering, in particular to a method for anti-fouling treatment of the inside of a pipeline and a container of a coastal industrial cooling water system. BACKGROUND

[0002] The coastal industrial cooling water system is widely used in the power, petrochemical, steel, shipbuilding and seawater desalination industries, and its pipeline and container are in contact with high-salinity seawater for a long time. The seawater has high chloride ion content, high hardness and sufficient dissolved oxygen, and is associated with a variety of marine organisms (such as mussels, barnacles, and algal larvae), which can easily lead to accelerated corrosion of the metal substrate, biological attachment fouling, old coating peeling, flow passage blockage, and flow resistance increase under the environment of continuous circulation scouring. With the increase of the running time, the inside of the pipeline and the container often simultaneously appear complex degradation forms such as corrosion pits, local roughening, surface contamination, and uneven residual coating, which significantly increases the maintenance cost and downtime risk in the later period.

[0003] In the existing disclosed technology, the following two types of schemes are mainly used for the anti-fouling treatment of the inside of the coastal cooling water system, but both have obvious defects:

[0004] 1. Traditional epoxy or acrylic coating construction scheme: This scheme generally uses the construction method of overall sandblasting, overall spraying and normal temperature or heating curing, and the coating material is mostly single-phase structure, which lacks the differential reinforcement capability for corrosion pits, roughened areas and residual old coating. Therefore, in the complex aging area, problems such as insufficient pit filling, low local adhesion, uneven film thickness and early failure are prone to occur, which makes it difficult to adapt to the non-uniform degradation form of the inside of the pipeline and the container.

[0005] 2. Biological anti-fouling scheme based on chemical cleaning or single spraying: This technology usually directly sprays ordinary coating after acid pickling, chelation or surface inhibitor treatment, which belongs to an integrated and unified construction mode. This scheme lacks zoned treatment according to the corrosion depth, roughness and residual state of the old coating, so the sandblasting intensity, coating method and curing process cannot be optimized according to the area, and problems such as rapid recovery of biological attachment, early damage of coating, and continued expansion of pitting corrosion are prone to occur in operation, which lacks long-term stability of anti-fouling and corrosion resistance.

[0006] Therefore, a method for anti-fouling treatment of the inside of a pipeline and a container of a coastal industrial cooling water system is proposed. SUMMARY

[0007] Therefore, the present application provides a method for anti-fouling treatment of the inside of a pipeline and a container of a coastal industrial cooling water system to solve or alleviate the technical problems in the prior art, and at least provides a beneficial option.

[0008] The technical scheme of the present application is implemented as follows: a method for preventing fouling in the interior of a pipeline or container of a coastal industrial cooling water system, comprising the following steps:

[0009] S1: inner wall state detection and three-dimensional modeling

[0010] After the system is shut down and emptied, the inner wall of the pipeline or container is detected synchronously using multi-source detection equipment:

[0011] An optical structured light scanning device acquires a three-dimensional topography with a lateral resolution of 0.1 mm-1.0 mm;

[0012] An electrochemical impedance probe detects corrosion pits and coating residues with an impedance scan frequency of 1 Hz-10000 Hz;

[0013] A laser roughness sensor collects the roughness Ra value with a measurement accuracy of 1 μm-5 μm.

[0014] The detection data is fused to generate an inner wall three-dimensional condition map, and the inner wall is regionally divided according to the following standards:

[0015] A zone: corrosion depth ≥ 0.5 mm;

[0016] B zone: surface roughness Ra ≥ 10 μm;

[0017] C zone: surface roughness Ra < 10 μm.

[0018] When partitioning, the average value of each 10-30 cm axial section is calculated, and a 5 cm transition zone is set to avoid the influence of local anomalies on boundary judgment.

[0019] S2: executing a pretreatment process according to the region

[0020] Differentiated pretreatment is performed according to the characteristics of different regions:

[0021] A zone: 0.1 MPa-0.3 MPa low-pressure sandblasting is used to remove corrosion products, and 1wt%-5wt% amino carboxylic acid chelating agent (EDTA or MGDA) is sprayed to further clean the metal ion residues;

[0022] B zone: a modified siloxane surface tension regulator is sprayed to stabilize the wetting angle at 10°-40° within 3-10 min;

[0023] C zone: water flushing and organic solvent degreasing treatment are performed to ensure the cleanliness of the substrate.

[0024] S3: preparing a three-phase composite coating material

[0025] The following components are mixed uniformly according to the solid mass percentage to prepare a three-phase composite coating material:

[0026] Matrix phase: Solvent-free underwater curing resin, composed of bisphenol A epoxy modified resin and amino-terminated polyamide curing agent in a mass ratio of 2:1–3:1, with a curing temperature of 5℃–30℃ and a curing time of 1–4h;

[0027] Microparticle phase: ceramic microparticles with a particle size of 5 μm–50 μm and a porosity of 10%–40%, which are at least one of alumina, silicon oxide or silicon carbide, and account for 5 wt%–20 wt% of the solid composition;

[0028] Active phase: sustained-release microcapsules with a particle size of 0.5 μm–5 μm, coated with starch-grafted polymer, accounting for 2 wt%–8 wt% of the solid component, with a release rate of 0.01–0.1 mg / (m³) of antifouling active substance. 2 ·day).

[0029] S4: Implement differentiated coating application according to region

[0030] Different coating methods are selected based on the surface characteristics of each area:

[0031] Area A: Cross-spraying is used to effectively sink ceramic particles to the bottom of the corrosion pit;

[0032] Area B: A spraying method with atomized particle size of 20μm–80μm is used to ensure that the material is evenly spread along the low surface tension interface;

[0033] Area C: A continuous coating layer is formed by roller coating or conventional spraying.

[0034] S5: Implement in-situ leveling and curing processes

[0035] A low-frequency vibration device is fixed to the outer wall of a pipe or container, applying vibrations of 10Hz–60Hz and amplitudes of 0.2mm–2mm. This frequency is selected as 20%–80% of the structure's natural frequency, promoting the vertical settling of ceramic particles and deeply filling the micro-pits and troughs in areas A and B.

[0036] Simultaneously, directional hot air at 30℃–60℃ and an inclination angle of 5°–30° is applied, causing the coating curing front to advance along the direction of gravity, thereby achieving in-situ leveling and layer-by-layer curing of the coating.

[0037] S6: Film quality inspection and local touch-up coating

[0038] After the coating has cured, laser film thickness scanning (resolution 10μm–50μm) and multi-frequency impedance spectroscopy re-measurement are performed, and differentiated evaluation is carried out according to the 3D modeling zoning standard:

[0039] Film thickness in region A <300μm–800μm; or

[0040] Film thickness in region B <200μm–500μm; or

[0041] Film thickness in region C < 100 μm–300 μm; or

[0042] If the area of ​​any region in the Nyquist map is less than 20%–40% of the normal area surrounding the same segment, the corresponding area will be automatically triggered to repeat steps S4 and S5.

[0043] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions:

[0044] I. This invention establishes a three-dimensional condition map of the inner wall through multi-source data fusion of optical structured light scanning, electrochemical impedance spectroscopy, and laser roughness measurement. The area is divided into zones A, B, and C according to indicators such as corrosion depth and roughness, enabling accurate identification of corrosion pits, roughened areas, and intact areas. Based on the zoning results, differentiated pretreatment processes are adopted: zone A uses "low-pressure sandblasting + high-concentration chelation" to enhance interface stability; zone B uses "surface tension adjustment" to optimize coating spreadability; and zone C uses "degreasing and cleaning only" to preserve the intact substrate. This makes the pretreatment more targeted and effectively avoids the problems of insufficient local treatment, uneven adhesion, and early failure caused by traditional uniform construction.

[0045] II. This invention utilizes the synergistic effect of three-phase composite coating materials, low-frequency vibration, and directional hot air to cause ceramic microparticles to vertically settle and fill corrosion pits in the uncured coating. Simultaneously, the resin system is cured layer by layer along the direction of gravity, achieving in-situ leveling and directional curing of the coating. This significantly improves the uniformity of coating thickness, surface smoothness, and overall density, resulting in high long-term electrochemical resistance, low pitting corrosion expansion rate, and continuous inhibition of bio-attachment, thereby enhancing the long-term service performance of coastal cooling water system pipelines and containers.

[0046] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is the overall flowchart of the present invention. Detailed Implementation

[0049] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0050] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0051] This invention provides a method for antifouling treatment of pipes and containers in coastal industrial cooling water systems, applicable to structures such as seawater coolers, seawater circulating pump outlet mains, box-type cooling water distribution containers, seawater sedimentation tanks, and condenser pre-pipelines;

[0052] I. This method is applicable to the following working conditions:

[0053] High salinity environment: chloride ion concentration >15000 mg / L;

[0054] High-risk areas for marine organism attachment: including areas where mussels, barnacles, and algal larvae attach;

[0055] Corrosion level: Medium to high: Pitting corrosion, pitting corrosion, and areas of coating peeling are present.

[0056] Mixed arrangement of multiple pipe diameters: DN200–DN2000 pipes, cylindrical containers, etc.

[0057] This implementation method achieves repeatable, controllable, and quantifiable antifouling construction under highly corrosive conditions through a complete process of detection, zoning, pretreatment, three-phase coating preparation, differential coating, in-situ leveling and curing, film thickness / impedance verification, and recoating.

[0058] II. Construction Environment and System Preparation

[0059] (1) System shutdown and purging: The following preparations must be completed before construction:

[0060] Shut down the machine and isolate the inlet and outlet valves;

[0061] Drain the seawater and use compressed air at 0.2–0.3 MPa to dry the remaining water;

[0062] Internal humidity control: Ventilate with a fan for 10–20 minutes to reduce the relative humidity to <70%;

[0063] If it is a sealed container, open the access panel to ensure that the testing equipment can enter smoothly.

[0064] (2) Construction environment requirements

[0065] Construction should be carried out under the following conditions:

[0066] Parameters Requirements Ambient temperature 10℃–40℃ Relative humidity <80％ Internal liquid film residue No visible water beads Grease Should not be present (dependent on S2 degreasing treatment)

[0067] (3) Equipment and material preparation

[0068] Testing equipment:

[0069] Optical structured light scanner (resolution 0.1–1.0 mm); electrochemical impedance spectroscopy analyzer (frequency 1–10000 Hz); laser roughness meter (accuracy 1–5 μm).

[0070] Coating preparation materials:

[0071] Bisphenol A type epoxy modified resin; amino-terminated polyamide curing agent; ceramic microparticles (alumina / silicon carbide / silicon micropowder); antifouling slow-release microcapsules (coated with starch grafted polymer).

[0072] Construction equipment:

[0073] Pneumatic sandblasting gun (0.1–0.3MPa); atomizing sprayer (particle size 20–80μm); roller coater; low-frequency vibrator (10–60Hz); hot air curing system (30–60℃, 5–30° angle adjustable).

[0074] Example 1: Construction of the interior of the main pipe of the seawater cooler

[0075] like Figure 1 As shown, this embodiment uses the interior of a DN1200 cooling water main in a seawater cooling circulation system of a coastal power plant as a typical application example. This system is located in a seawater environment with a salinity of 20,000–28,000 mg / L, and contains a high density of marine organisms, including mussels, barnacles, and algal larvae. After three years of operation, the pipeline exhibits varying degrees of corrosion pitting, surface roughening, peeling of the old coating, and residue of marine organism shells. The construction method provided by this invention can restore the internal coating, enhance antifouling properties, and extend the pipeline's lifespan without replacing the pipeline itself. This embodiment is described in the order of steps S1-S6.

[0076] S1: Inner wall condition detection and 3D modeling

[0077] Before construction, shut down the cooling water system and close the inlet and outlet valves connected to the main pipe. Then open the drain valve to drain the seawater in the pipe and blow dry the residual liquid inside with compressed air.

[0078] Afterwards, the construction team carried an optical structured light scanner, an electrochemical impedance probe, and a laser roughness sensor into the main pipe to conduct a full-coverage inspection along the axial and circumferential directions in the 30m long pipeline.

[0079] The structured light scanner uses a lateral resolution of 0.1–1.0 mm to acquire three-dimensional geometric shapes by projecting structured light stripes, and combines them with a high frame rate real-time reconstruction algorithm to generate a million-level point cloud model.

[0080] An electrochemical impedance spectroscopy probe detects the location of corrosion pits, corrosion products, and residual electrochemical activity in a multi-frequency scanning mode of 1 Hz–10000 Hz. The resulting impedance Nyquist plot is used to determine the degree of metal exposure in the corrosion area and the remaining protective performance of the old coating. A laser roughness sensor continuously records the Ra value of the inner wall with a measurement accuracy of 1–5 μm.

[0081] During the testing process, the adhesion of the old coating was simultaneously determined using the pull-off method.

[0082] If the adhesion is ≥3MPa, it is marked as "Compatibility Retention Zone"; if the adhesion is 1-3MPa, it is marked as "Partial Removal Zone"; if the adhesion is <1MPa, it is marked as "Complete Removal Zone".

[0083] This result will directly guide the S2 pretreatment process;

[0084] After the inspection is completed, all data is imported into the pipeline 3D analysis software. A high-precision 3D surface model is generated by point cloud fitting. Then, the corrosion depth map, roughness distribution map and impedance spectrum results are fused with the 3D model to generate a complete 3D condition map of the inner wall.

[0085] Using an automatic identification algorithm, the A zone (severely corroded section) is defined based on a corrosion depth ≥ 0.5 mm, the B zone (roughened section) is defined based on Ra ≥ 10 μm, and the remaining areas are defined as the C zone (basically intact section).

[0086] To avoid fragmenting the region due to local anomalies, each analysis segment is defined as 10–30 cm, with a 5 cm transition segment at the boundary of each segment to ensure a natural transition between region boundaries. The resulting 3D partition map is shown below.

[0087] Zone A accounts for approximately 12%, mainly concentrated in the low-velocity area near the bottom; Zone B accounts for 35%, mainly in the bends of the pipe and areas where wall erosion is restricted; Zone C accounts for 53%.

[0088] S2: Perform pre-processing procedures by region

[0089] After the regions are divided, different preprocessing methods are performed based on the differences between the three types of regions:

[0090] For area A (corrosion depth ≥ 0.5 mm), surface cleaning is performed using low-pressure sandblasting at 0.1–0.3 MPa, with 80–120 mesh quartz sand as the abrasive. The spray gun is kept 20–30 cm away from the inner wall, and sandblasting is performed in a crisscross pattern until all corrosion products and loose metal are removed. At the same time, the surface roughness after sandblasting is ensured to be in the range of 10–30 μm to facilitate the mechanical bonding of the coating. Immediately after sandblasting, a 1–5 wt% aminocarboxylic acid chelating solution (EDTA or MGDA) is sprayed to further chelate and remove residual metal ions, oxide film, and difficult-to-remove corrosion active sites, forming a metal surface with lower chemical activity and improving the adhesion of subsequent coatings.

[0091] For zone B (roughened section with Ra≥10μm), sandblasting is not required; instead, a modified siloxane surface tension modifier is applied. Within 3–10 minutes after application, the modifier forms a chemical adsorption with the micro-unevenness of the surface, reducing the wetting angle of this area from 60–80° to 10–40°. This significantly improves the spreadability of subsequent coating materials, allowing the atomized coating layer to naturally fill in shallow micro-textures and improve interlayer density.

[0092] For Zone C (lightly contaminated areas with Ra < 10 μm), only water rinsing and organic solvent degreasing are required to remove oil, microbial film, and residual salt. The water rinsing pressure should be controlled at 0.1–0.15 MPa. Then, the surface should be thoroughly degreased by wiping with ethanol or acetone to ensure that the subsequent coating can form a good interface with the substrate.

[0093] S3: Preparation of three-phase composite coating materials

[0094] According to the present invention, the coating material is composed of a three-phase composite system consisting of a matrix phase, a particulate phase, and an active phase, and the three phases are controlled according to the following solid mass percentages: particulate phase 5–20 wt%, active phase 2–8 wt%, and matrix phase accounting for the remainder;

[0095] In the specific preparation process, the solvent-free underwater curing resin and the amino-terminated polyamide curing agent are first mixed at a mass ratio of 2:1–3:1, so that the resin system has an operable time of 1–4 hours under the condition of 5–30℃. In the initial stirring stage, the resin is stirred at a rate of 300 rpm for 5 minutes to allow the resin and curing agent to fully react and form a uniform matrix.

[0096] Subsequently, ceramic microparticles with a particle size of 5–50 μm and a porosity of 10–40% are gradually added. The ceramic microparticles can be at least one of alumina, silicon oxide, or silicon carbide. The mixture is stirred at 500 rpm for 10 minutes using a spiral blade mixer to ensure that the microparticles are uniformly suspended in the system and that the microparticles are uniformly dispersed without agglomeration.

[0097] Finally, the active phase, namely sustained-release microcapsules with a particle size of 0.5–5 μm and coated with starch-grafted polymer, is added, with a designed release rate controlled at 0.01–0.1 mg / (m³). 2 •day), can continuously release antifouling active substances during pipeline operation to inhibit marine organism attachment. After adding, stir gently at 200 rpm for 3 minutes to ensure even distribution, in order to avoid shearing and damage of the microcapsules;

[0098] In this embodiment, the mixing order of the three-phase materials (resin → ceramic microparticles → microcapsules) is not arbitrarily set: the resin and ceramic microparticles are mixed first, and the microparticles are uniformly dispersed to form a "skeleton structure" by high-speed stirring at 500 rpm. This structure can improve the mechanical properties of the coating. The microcapsules are then added at a low speed of 200 rpm to avoid shear damage to the coating layer. At the same time, the microcapsules are attached to the surface of the microparticles to form a "slow-release point-skeleton" synergy, which ensures the long-term stable release of the antifouling agent and solves the problem that traditional coatings cannot achieve both antifouling and reinforcement.

[0099] Final testing showed that the viscosity of the coating material was controlled at 2000–3500 mPa·s, which is conducive to spraying and also meets the requirements for wall adhesion.

[0100] S4: Implement differentiated coating application according to region

[0101] Based on the partitioning results, different coating strategies are selected;

[0102] Due to the presence of deep corrosion pits in Area A, a cross-spraying method was used for construction.

[0103] First, spray the first coat along the axial direction of the pipe, with a spray width of 25–30 cm and a spray gun pressure controlled at 0.15–0.25 MPa. Then, spray the second coat in a transverse direction at 60–90° to the first coat. This allows the ceramic particles in the coating material to effectively enter the bottom of the pit under the action of spraying kinetic energy and leveling, achieving "deep pit filling". This ensures that the particles can form a directional skeleton structure in the uncured resin system, improving the coating's wear resistance and erosion resistance.

[0104] Area B employs an atomized spraying method, with the spray particle size controlled within the range of 20–80 μm. This allows the coating material to spread rapidly on the metal surface after the surface tension is reduced, filling in shallow rough textures. During spraying, the material flow rate is controlled at 300–600 mL / min, and the spray gun movement speed is 0.2–0.4 m / s to ensure the formation of a uniform coating and avoid localized accumulation.

[0105] The surface of area C is relatively intact, so roller coating or conventional spraying can be used. Use a roller with a pile length of 10–15 mm and coat evenly at a speed of 0.3–0.5 m / s to keep the film thickness in the range of 50–100 μm and ensure full coverage.

[0106] S5: Implement in-situ leveling and curing processes

[0107] Immediately after coating, in-situ leveling and curing with low-frequency vibration and directional hot air is performed. The low-frequency vibrator is fixed to the outer wall of the pipe using magnetic attraction or clamps. The vibration frequency is selected as 10–60Hz, which corresponds to 20–80% of the natural frequency of the pipe, and the amplitude is controlled at 0.2–2mm. Vibration continues for 5–15 minutes, causing the ceramic particles inside the coating material to settle vertically under the combined action of gravity and vibration, and preferentially depositing in the pits or valleys of areas A and B, thereby improving the mechanical uniformity of the coating.

[0108] Simultaneously activate the hot air curing system, blowing hot air at a temperature of 30–60℃ and an angle of 5–30° onto the coating surface. This causes the uncured material to form a curing front along the direction of gravity, promoting the coating to cure layer by layer from the inside out. The hot air flow rate is controlled at 3–6 m³ / h. 3 / min, and continue for 10–30 min / m 2 This is to ensure that the resin system undergoes stable curing within a suitable temperature range;

[0109] The combined effect of this step can improve the smoothness of the coating, and control the surface height difference after construction within the range of ±0.1–0.15mm;

[0110] If the ambient water temperature is <5℃, increase the hot air temperature to 50-60℃ and extend the resin curing time to 4-5 hours to ensure full curing.

[0111] S6: Film quality inspection and local touch-up coating

[0112] After the coating has fully cured, a laser film thickness scanner is used to perform a full scan along the inner wall of the pipe. The scanning resolution is 10–50 μm, and a cross-scanning route of circumferential and axial directions is used to obtain a film thickness contour map of the entire pipe section. According to the film thickness standards of different regions, if the film thickness in region A is less than 300–800 μm, or in region B less than 200–500 μm, or in region C less than 100–300 μm, it is determined to be insufficient film thickness.

[0113] Simultaneously, electrochemical impedance spectroscopy was performed, with multi-frequency scanning in the range of 1–10000 Hz, and Nyquist plots were generated. If the Nyquist plot area of ​​a certain region is less than 20–40% of the surrounding normal area, it indicates that the coating density in that region is insufficient or there are potential defects.

[0114] When any of the recoating trigger conditions are met, the S4 and S5 processes are repeated on the corresponding area to achieve closed-loop autonomous quality assurance. Under normal circumstances, 1-2 recoatings are sufficient to complete all defect repairs.

[0115] Example 2: Construction Method for Anti-fouling Treatment of the Interior of Cooling Water Distribution Box (Container Structure)

[0116] This embodiment uses a square seawater distribution box (internal volume approximately 36m³) in a seawater cooling system of a coastal power plant. 3 The object is a container structure with dimensions of approximately 6m × 3m × 2m. Unlike long-distance pipelines, this container structure has a larger internal surface area, more dead corners, and different fluid distribution in multiple regions. The biofouling mode changes from "axial attachment" to "area attachment + corner accumulation". Therefore, the antifouling treatment must be re-adapted according to the regional characteristics.

[0117] This embodiment adopts the corresponding S1–S6 steps and incorporates a construction supplement strategy specific to the container.

[0118] S1: Container Inner Wall Condition Detection and 3D Modeling

[0119] After shutdown and emptying, open the manhole on top of the distribution box and set up a temporary lighting system to maintain sufficient brightness inside the box. Due to the large internal height of the container, a structured light scanner is mounted on a fixed tripod and used in conjunction with a handheld scanning aid to perform a full-range scan of the inner wall. The scanner's lateral resolution is set to 0.3mm, and a face-by-face scanning mode is used.

[0120] First, scan the bottom plane, then scan the two end walls and the two side walls, and finally scan the top structure. During the process, use a calibration plate to correct the position and ensure that the splicing error between the multi-face scans is less than 1mm.

[0121] The electrochemical impedance probe uses a magnetic probe head that can be adsorbed onto the wall surface, enabling it to perform multi-frequency impedance scanning on non-horizontal surfaces such as vertical walls. The scanning frequency is set from 1Hz to 10000Hz. Impedance sampling is performed on the inner wall of the chamber using a grid method of 50cm×50cm to form an impedance attenuation matrix, which is used to identify coating defects and corrosion hotspots.

[0122] The laser roughness sensor uses a triaxial positioning platform, and Ra is measured manually by moving it along the wall. The measurement accuracy is 1–5 μm. In the bottom area of ​​the container, due to insufficient scouring and sediment accumulation, the Ra value is generally higher than 12 μm; while in the middle area of ​​the wall, the Ra value is about 6–9 μm; and in the top area, due to strong fluid scouring, Ra is often lower than 5 μm.

[0123] The above test results are imported into 3D modeling software to generate a complete 3D structural model of the container's interior, including the bottom sedimentation zone, corner zone, main scour zone, and top recirculation zone.

[0124] On the model, zone A is defined as corrosion depth ≥ 0.5 mm, zone B as Ra ≥ 10 μm, and zone C as Ra < 10 μm;

[0125] The container is divided into 6 large faces by partitioning. Each face is processed into an average of 10-30cm grid segments, and a 5cm transition zone is set at the joints between the blocks. The final partitioning result is shown below:

[0126] Area A is mainly distributed at the bottom and on the lower side of the wall near the entrance;

[0127] Zone B is concentrated at the corners of the two ends of the wall where the flow velocity is uneven;

[0128] Zone C is distributed across most of the top and middle areas.

[0129] S2: Perform pre-processing steps according to the container area.

[0130] The container has a large internal space that can accommodate 2-3 construction workers at the same time, so the pretreatment process is carried out in groups and zones.

[0131] First, low-pressure sandblasting at 0.1–0.3 MPa is applied to the designated area A. Workers use long-handled telescopic sandblasting guns, employing staggered approaches to treat pits and corroded areas, ensuring thorough removal of corrosion products and achieving a uniform roughness. Because sand easily accumulates at the bottom of the container, a mobile sand suction device is installed during sandblasting. This device involves adding a suction port next to the sandblasting gun to simultaneously remove sand and loose impurities, preventing secondary contamination.

[0132] Immediately after sandblasting, spray with a 1–5 wt% EDTA or MGDA solution, controlling the spraying rate at 80–150 g / m². 2 This allows residual metal ions on the wall surface to be chelated and removed, enhancing the interfacial stability of subsequent coatings.

[0133] For area B, a modified siloxane surface tension modifier was sprayed using a low-pressure, high-atomization spray gun at a pressure of 0.1–0.15 MPa. The modifier was sprayed evenly along the wall surface, reducing the wetting angle to 10–40° within 3–10 minutes. This significantly improved the spreadability and uniformity of the coating material in subsequent atomized spraying.

[0134] For Zone C, a mobile high-pressure washer was used for rinsing with clean water at a pressure of 0.1–0.15 MPa. Then, oil stains and deposited microbial films were wiped off manually with a solvent cloth until the surface was clean and free of oil and film.

[0135] S3: Mass Production of Three-Phase Composite Coating Materials

[0136] Due to the large internal surface area of ​​the distribution box, approximately 70–80 m² 2， Approximately 40–60 kg of three-phase composite coating material needs to be prepared in advance;

[0137] According to the formulation ratio in the claims, bisphenol A epoxy modified resin and amino-terminated polyamide curing agent are first mixed at a mass ratio of 2:1–3:1 and stirred at 300 rpm for 5–7 minutes to form a matrix phase. Then, alumina / silicon carbide ceramic microparticles with a particle size of 5–50 μm and a porosity of 10–40% are added, and the stirring speed is increased to 500 rpm for 10 minutes to ensure that the microparticles are uniformly suspended in the system without agglomeration.

[0138] Finally, sustained-release microcapsules with a particle size of 0.5–5 μm and a release rate of 0.01–0.1 mg / (m³) are added. 2 • day), control the stirring speed at 200 rpm and stir for 3 minutes to avoid emulsification;

[0139] If the system seawater salinity is >30000mg / L, increase the amount of microcapsules added to 6-8wt% to ensure stable antifouling effect. The viscosity of the final composite system is maintained at 2200–3000mPa·s, so that the coating has both good wall adhesion performance and is suitable for large-area construction by spraying equipment.

[0140] S4: Differentiated Coating Application Inside Containers

[0141] Area A of the container is concentrated at the bottom and corners. To ensure the coating penetrates deep into the corrosion pits, a cross-spraying method is used. The spray gun nozzle diameter is 1.0–1.3 mm. The operator sprays one coat axially and one coat laterally, and adds 1–2 extra coats to the corners to avoid insufficient film thickness in dead areas. The spray gun pressure is controlled at 0.15–0.25 MPa to allow the ceramic particles to penetrate deeper into the pits under the action of kinetic energy.

[0142] For area B, a high-atomization spraying method with atomized particle size of 20–80 μm is used to ensure that the coating material can be evenly spread along the adjusted low surface tension interface. The construction personnel use a backpack-style high-position spray bar to maintain a suitable spraying distance of 30–40 cm between the spray gun and the wall surface to cover the high area of ​​the container. By controlling the atomized particle size, spraying speed and spraying coverage, a flat and stable medium-thickness film layer is formed in area B.

[0143] For area C, roller coating or low-pressure spraying is used. Since area C has a large area and a relatively flat surface, the construction speed can be increased to 0.4–0.6 m / s. The film thickness of each coat is maintained at 50–100 μm to ensure the formation of a continuous covering layer for overall antifouling.

[0144] For container dead zones with a depth of ≥50cm, use a spraying device with a flexible extension rod to perform the S4 process. The length of the extension rod is adjusted to 0.8-1.2m according to the depth of the dead zone to ensure that there are no blind spots in the spraying.

[0145] S5: In-situ leveling and curing process inside the container

[0146] The container structure necessitates adaptation of the vibrator installation method. In this embodiment, four sets of low-frequency vibrators are installed in four directions on the outer wall of the container, with a frequency set at 10–60 Hz and an amplitude of 0.2–2 mm. Since the container has a plate-like structure, its natural frequency is lower than that of the pipe; therefore, the vibration frequency is generally selected as 30–60% of the natural frequency. The vibration is applied for approximately 8–15 minutes, which promotes the vertical settling of ceramic particles under the combined action of gravity and vibration, forming a deeper filling layer in areas such as pits, weld grooves, and corners.

[0147] Simultaneously, a mobile hot air curing system is activated, blowing hot air along the wall at 30–60° and 5–30° angles. Depending on the container structure, a top-down curing method can be used, allowing the coating material to form a curing front along the direction of gravity. The hot air flow rate is 4–8 m³ / h. 3 / min, construction time 10–25min / m 2 This allows the coating to cure layer by layer at a suitable temperature, reducing sagging and improving the density of the film.

[0148] S6: Quality inspection and localized touch-up coating of the inner wall membrane of the container

[0149] After the coating has cured, laser film thickness scanning and impedance remeasurement are performed on the entire inner wall of the container. The laser film thickness scanner scans horizontally and vertically along the four walls of the container with a resolution of 10–50 μm. The measurement results form an intuitive film thickness cloud map in the three-dimensional model.

[0150] If the film thickness in area A is found to be less than 300–800 μm, in area B less than 200–500 μm, or in area C less than 100–300 μm, it should be marked immediately and the recoating process should begin.

[0151] Subsequently, multi-frequency impedance spectroscopy scans were performed in the range of 1–10000 Hz, and the compactness and integrity of the film were determined by comparing the changes in the Nyquist plot area.

[0152] If the Nyquist map area of ​​a certain region is 20-40% lower than that of the surrounding normal area, it is considered that the coating density is insufficient or there are microcracks. It needs to be recoated immediately. The recoating method is the same as the first construction. S4 and S5 processes are repeated according to the block until the film quality meets the requirements.

[0153] Example 3: Construction Plan Adapted to Extreme Working Conditions

[0154] This embodiment addresses the extreme operating environments that may occur in coastal industrial cooling water systems, such as high salinity, low temperature, sharp bends in pipes, and deep corners of containers. It adapts the S1–S6 construction process of the aforementioned Embodiments 1 and 2 to ensure that the present invention can still stably achieve the expected antifouling and anti-corrosion performance under complex working conditions. This embodiment is applicable to supplementary optimization of construction parameters, material ratios, and process paths without changing the scope of the claims.

[0155] I. Suitable for high salinity conditions (salinity > 30000 mg / L)

[0156] Under high salinity conditions, marine organisms reproduce more rapidly, and the resin curing process is easily affected by salt ions, leading to incomplete cross-linking and thus affecting the long-term density of the film. In this embodiment, the following adaptations are made in processes S3 and S5:

[0157] Adjusting the amount of sustained-release microcapsules to 6–8 wt% will give the antifouling agent a higher initial release strength in a high-salt environment, thereby enhancing its inhibitory effect on barnacles and mussel larvae.

[0158] In S2, the concentration of the chelating agent in area A is fixed at the upper limit of 5 wt% to quickly passivate the exposed metal surface and reduce the secondary active sites formed by salt spray corrosion.

[0159] The curing process in S5 is extended to 3–4 hours to ensure sufficient resin crosslinking reaction under high salt conditions and avoid the formation of potential pores.

[0160] Verified by a 180-day seawater immersion test, under conditions with a salinity as high as 35000 mg / L, the electrochemical impedance of the coating of this invention remained at 10. 6 Ω·cm 2 Magnitude.

[0161] II. Adaptability to low-temperature operating conditions (water temperature < 5℃)

[0162] Low temperatures weaken the fluidity, wettability, and curing rate of coating materials. This embodiment mainly focuses on process compensation for S3, S4, and S5:

[0163] Increase the temperature of the directional hot air to 50–60°C to provide sufficient heat to activate the curing reaction.

[0164] The resin curing time is extended to 4–5 hours to avoid incomplete curing under low temperature conditions.

[0165] In S3, the final system viscosity is adjusted to 3000–3500 mPa·s to improve wall adhesion and prevent the coating from sagging or shrinking at low temperatures.

[0166] After adaptation, a continuous and dense film layer can still be obtained when applied at temperatures below 5°C, and the adhesion can be stably maintained above 7.0 MPa after curing.

[0167] III. Adaptation for sharp bend pipe sections (bending radius ≤ 10cm)

[0168] In sharp bends, the attenuation of spraying kinetic energy leads to a thinner coating, and vibration may trigger local resonance. This embodiment makes the following adjustments in S4 and S5:

[0169] Increase the spraying pressure by 0.05–0.1 MPa to allow the coating material to fully penetrate the curved concave area.

[0170] The vibration frequency is reduced by 10–20% compared to the straight pipe section to avoid vibration damage caused by insufficient local plate thickness in the curved section.

[0171] Apply an additional 1-2 coats of spray to the curved outer arc area to ensure the film thickness meets the standards for Zone C or Zone B.

[0172] This adaptation scheme allows the film thickness at sharp bends to be controlled within 150–300 μm, with no obvious sagging or film peeling.

[0173] IV. Adaptation for deep corner working conditions of containers (dead corner depth ≥ 50cm)

[0174] Container-type structures have blind spots in the coating process, which can easily lead to areas with insufficient film thickness if not handled properly. This embodiment mainly supplements the adaptation in S4:

[0175] The use of a flexible or curved extension spray bar of 0.8–1.2m allows the spray gun to reach deep corners.

[0176] Apply 1-2 additional coats of spray to the corner areas to ensure the film thickness meets the standards for Zone B or Zone C.

[0177] The S5's hot air and vibration parameters remain consistent with normal conditions, requiring no additional adjustments.

[0178] Construction verification shows that this solution can effectively avoid the formation of low impedance points or film thickness defects in dead zones.

[0179] V. Summary Table of Extreme Operating Condition Parameter Adaptation

[0180] The table below presents the parameterized representation of the above adaptation scheme, which can be directly used as the basis for construction operations. If there are complex working conditions such as "low temperature + high salt", the "parameter superposition" principle can be adopted.

[0181]

[0182]

[0183] Test Example 1: Long-term performance verification test

[0184] To verify the stability, antifouling ability, and anticorrosion ability of the three-phase composite coating system and in-situ leveling and curing process proposed in this invention under long-term service conditions of coastal industrial cooling water, a 180-day seawater immersion comparative test was conducted. The test was carried out in a natural seawater environment simulating the water quality of the intake of a coastal power plant, with the temperature maintained within a periodic fluctuation range of 18–26℃. The COD, salinity, hardness, and dissolved oxygen of the water were all controlled according to the typical seawater indicators in the "Seawater Cooling Water Discharge Standard (GB / T39361-2020)".

[0185] The experiment was set up with three groups of control samples:

[0186] Sample 1: The three-phase composite coating sample of the present invention (prepared using the entire process of steps S1-S6);

[0187] Sample 2: A control sample of commercially available ordinary epoxy anti-corrosion coating (conventional 2-coat spraying, no particulate phase, no active phase, no leveling and curing process);

[0188] Sample 3: Commercially available advanced self-polishing anti-fouling coating sample (applied according to the manufacturer's recommended process).

[0189] After the 180-day period, the surface adhesion, corrosion propagation, coating adhesion, and electrochemical impedance of the samples were tested. The test data are shown in the table below:

[0190] Item The present invention Commercially available ordinary epoxy coating Commercially available advanced self-polishing coating Adhesion (MPa) 7.5-9.0 3.0-5.0 4.2-6.0 Electrochemical impedance (Ω·cm 2 )]]> ≥ 1.2 x 10 6 ]] ≤ 3 x 10 5 ]] 5.0 x 10 5 -8.0 x 10 5 ]]> Bioattachment number (cells / cm 2 )]]> <5 ＞85 18-25 Pitting propagation rate <1％ 15％—22％ 6％—10％ Coating lifetime estimation (years) 5-8 1-2 3-4

[0191] As can be seen from the long-term performance data above:

[0192] 1. Superior Coating Adhesion: The microparticle filling, low-frequency vibration settling, and directional hot air curing employed in this invention enable ceramic microparticles to form a three-dimensional support skeleton in the coating system. This allows the coating to maintain a steady-state adhesion of 7.5-9.0 MPa even after long-term immersion in seawater, which is not only 1.8-2.5 times that of ordinary epoxy systems, but also superior to the 4.2-6.0 MPa of self-polishing coatings.

[0193] 2. Significant advantages in electrochemical impedance: The coating impedance of this invention can be maintained at 10. 6 Ω·cm 2 The coating density is about 4 times higher than that of ordinary epoxy and 1.5-2.4 times higher than that of self-polishing coatings, indicating that the coating system still has high density and low water permeability after 180 days, significantly reducing the diffusion of seawater media to the substrate.

[0194] 3. Outstanding biofouling inhibition effect: Under natural seawater conditions, the number of biofouling organisms on the coating surface of this invention is less than 5 per cm. 2 It is less than 1 / 15 of that of ordinary epoxy systems, and far lower than the 18-25 particles / cm of self-polishing coatings. 2This is mainly due to the sustained inhibitory effect produced by the trace amount of antifouling agent released by the slow-release microcapsules in the active phase, which combines with the highly dense surface structure.

[0195] 4. Pitting corrosion expansion is basically suppressed: The pitting corrosion expansion rate of the coating of this invention is <1% after 180 days, which is far lower than the 15%-22% of ordinary epoxy and the 6%-10% of self-polishing coating. This indicates that the particle filling effect and curing directionality of the three-phase composite system can block the corrosion of the substrate at the source and extend the service life of containers and pipelines.

[0196] In summary, the coating system of this invention exhibits excellent antifouling, anticorrosion, and long-term stable curing performance under long-term seawater conditions, and its performance is superior to that of existing ordinary epoxy anticorrosion systems.

[0197] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for the antifouling treatment of the interior of pipes and vessels of coastal industrial cooling water systems, characterized in that Comprising the following steps: S1, inner wall state detection and three-dimensional modeling After the system is shut down and emptied, the optical structured light scanning device is used to obtain the three-dimensional topography data of the inner wall of the pipeline or container, the electrochemical impedance probe is used to detect the inner wall corrosion pit and coating residual state, and the laser roughness sensor is used to collect the inner wall surface roughness parameters. A complete data source is formed through multi-device synchronous detection, and the inner wall three-dimensional condition map is generated based on the data source. The inner wall is divided into regions according to the following standards: A area: corrosion depth≥0.5mm; B area: surface roughness Ra≥10μm; C area: surface roughness Ra<10μm. S2, execute pretreatment process according to region A area uses low pressure sand blasting treatment of 0.1MPa-0.3MPa, and sprays 1wt%-5wt% of amino carboxylic acid chelating solution; B area sprays modified siloxane surface tension regulator to adjust the surface wetting angle to 10°-40°; C area uses water flushing and organic solvent degreasing treatment. S3, prepare three-phase composite coating material Mix the matrix phase, particulate phase and active phase uniformly according to the following proportions to form the coating material: (1) Matrix phase: solvent-free underwater curing resin, curing temperature 5℃-30℃, curing time 1h—4h; (2) Particulate phase: ceramic microparticles with particle size 5μm-50μm and porosity 10%—40%, which account for 5wt%-20wt% of the total solid components of the coating material; (3) Active phase: slow-release microcapsules coated with starch grafted polymers with particle size 0.5μm-5μm, which account for 2wt%-8wt% of the total solid components of the coating material. S4: implement differential coating construction according to region A area uses cross spraying to make ceramic microparticles enter the corrosion pit bottom; B area uses atomizing spraying to make the material evenly spread along the reduced surface tension; C area uses rolling or conventional spraying to form a continuous cover layer. S5, implement in-situ leveling and curing process Fix the low-frequency vibration device on the outer wall of the pipeline or container, apply 10Hz—60Hz vibration and 0.2mm—2mm amplitude to the coated area, make the ceramic microparticles vertically settle in the uncured coating to fill the corrosion pit; At the same time, apply 30℃-60℃ directional hot air to promote the resin to gradually cure vertically during the microparticle settlement and setting stage, forming a uniform film layer with smooth surface. S6, film layer quality detection and local re-coating Perform laser film thickness scanning and electrochemical impedance re-measurement on the cured coating, if the film thickness of A area is less than 300μm-800μm, the film thickness of B area is less than 200μm-500μm, the film thickness of C area is less than 100μm-300μm, or the impedance value of any region is less than 20% of the surrounding normal region, then repeat S4 and S5 for the corresponding region.

2. A method of applying an antifouling treatment to the interior of a pipe or vessel of a marine industrial cooling water system according to claim 1, characterised in that: The lateral resolution of the optical structured light scanning device is 0.1mm—1.0mm, the impedance scanning frequency of the electrochemical impedance probe is 1Hz—10000Hz, and the measurement accuracy of the laser roughness sensor is 1μm-5μm.

3. The antifouling treatment construction method for the inside of a pipe or a container of a coastal industrial cooling water system according to claim 1, characterized by: The division of the A / B / C zones is based on the average value of the inner wall section within 10-30 cm along the pipeline axis direction, and a 5 cm transition section is used at the region boundary to avoid misjudgment caused by local abnormal points.

4. The antifouling treatment construction method for the inside of a pipe or a container of a coastal industrial cooling water system according to claim 1, characterized by: The aminocarboxylic chelating solution is selected from ethylenediaminetetraacetic acid (EDTA), methylglycinediacetic acid (MGDA), or a salt thereof, and the use concentration is 1wt%-5wt%.

5. The antifouling treatment construction method for the inside of a pipe or a container of a coastal industrial cooling water system according to claim 1, characterized by: The modified siloxane surface tension regulator can stabilize the B zone surface wetting angle to 10-40° within 3-10 minutes after spraying.

6. The antifouling treatment construction method for the inside of a pipe or a container of a coastal industrial cooling water system according to claim 1, characterized by: The solvent-free underwater curing resin is composed of bisphenol A epoxy modified resin and amino-terminated polyamide curing agent with a mass ratio of 2:1-3:1, the ceramic microparticles are at least one of alumina, silicon oxide or silicon carbide, and the release rate of the antifouling active substance of the slow-release microcapsule is 0.01-0.1 mg / (m 2 ·day).

7. The antifouling treatment construction method for the inside of a pipe or a container of a coastal industrial cooling water system according to claim 1, characterized by: The atomized spray particle size of the B zone in S4 is controlled within 20-80 μm.

8. The antifouling treatment construction method for the inside of a pipe or a vessel of a coastal industrial cooling water system according to claim 1, characterized by: The vibration frequency of 10-60 Hz is selected as 20%-80% of the inherent frequency of the pipeline or container.

9. The method for the antifouling treatment construction of the coastal industrial cooling water system pipe, the container inside according to claim 1, its characterized in that: The directional hot air is blown at an inclination angle of 5-30° to the pipeline axis towards the gravity direction, so that the coating material forms a solidification front in the settlement stage and advances along the gravity direction.

10. The method for the antifouling treatment of the inside of a pipe or a vessel of a coastal industrial cooling water system according to claim 1, characterized in that: When S6 is executed, the scanning resolution of the laser film thickness scanner is 10-50 μm, and the electrochemical impedance retest adopts multi-frequency impedance spectrum analysis, and by detecting that the Nyquist plot area of each region is lower than 20%-40% of the normal area around the same section as one of the re-coating judgment basis, whether to enter the re-coating logic of repeating S4 and S5 is determined.

Images