Bridge steel surface anti-corrosion treatment process

Abstract

The invention relates to the technical field of steel surface anti-corrosion treatment, in particular to a bridge steel surface anti-corrosion treatment process. The method comprises the following steps: S1, pretreating a base material by adopting a plasma activation and sand blasting process; s2, the Zn-Al-based quaternary alloy is sprayed to the surface of the base material through a spraying deposition technology, and an inner coating for sacrificial anode protection is formed; an inverted-cone-shaped micropore is machined in the surface of the inner coating through femtosecond laser; and S3, electrostatic spraying of a fluorocarbon resin composite coating is conducted, specifically, spraying is conducted twice, the micropores are filled with the fluorocarbon resin composite coating, and a compact barrier layer is formed. Through the special micropore technology of the inner coating and the secondary spraying technology of the outer coating, micropore interlocking lifting mechanical combination is formed, meanwhile, a sacrificial anode of the inner coating continuously provides cathode protection, and damage is repaired in real time through the self-repairing function of the outer coating; and the graphene oxide and the fluorocarbon resin of the outer coating form a compact impervious layer. And secondly, the micropores are filled with gradient curing resin, so that the interface residual stress is reduced, and crack propagation caused by dynamic load is effectively inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of steel surface anti-corrosion treatment, and in particular to a bridge steel surface anti-corrosion treatment process. Background Art

[0002] Steel structures are the core bearing systems of major projects such as bridges, offshore platforms, and chemical storage tanks. Their long-term protection is directly related to the safety and economy of the structure. Most of the losses caused by metal corrosion are related to coating failure.

[0003] At present, in the technology for steel structure coating, the penetration defects (porosity> 0.3%) of a single coating are allowed to be Cl - Low resistance diffusion path (diffusion rate up to 5×10 -6 cm 2 / s), and lacks a blocking mechanism for the corrosion products that have already invaded. Secondly, conventional technology uses a double coating combination, but the traditional inner coating (such as zinc-rich primer) and the outer coating (such as fluorocarbon topcoat) are only combined by intermolecular forces and are easy to peel off under dynamic loads (ASTM D4541 test adhesion <6MPa). The interface between the inner and outer coatings is prone to form a permeation channel (SEM shows that the interface porosity is >3%), Cl - The diffusion rate along the interface is 2×10 -7 cm 2 / s, which easily creates the risk of corrosive media penetration. Secondly, when the outer coating is partially damaged, the traditional inner coating usually lacks the ability to respond quickly and repair, and the corrosion rate of the exposed area of ​​the substrate suddenly increases to 0.5mm / a. Summary of the invention

[0004] The purpose of the present invention is to provide a surface anti-corrosion treatment process for bridge steel, which forms a three-dimensional interlocking structure through micropore filling, combines the active protection of the inner coating with the passive barrier of the outer coating, and achieves a multi-level protection effect of mechanical anchoring on the interface and self-repair of the failure area, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above objectives, according to Figure 1 As shown, the present invention provides a bridge steel surface anti-corrosion treatment process, comprising the following steps: S1. Pre-treat the substrate by plasma activation (argon flow rate 20L / min, power 800W) combined with controllable sandblasting process (alumina sand particle size 40-60μm, sandblasting pressure 0.5-0.8MPa) to form an active interface layer with a roughness Ra=8-12μm on the steel surface (surface energy increased to 58-65mN / m).

[0006] S2. Preparation of microstructured inner coating, including inner coating spraying and laser micro-hole processing. Specifically: Deposit a Zn-Al-based quaternary alloy coating by supersonic arc spraying process, with the coating thickness of 80 - 120 μm, to form an inner coating for sacrificial anode protection (open circuit potential -1.05V vs SCE).

[0007] Use femtosecond laser (wavelength 1030nm, pulse width 300fs) to process inverted conical micropores (pore diameter 200 - 300μm, ratio of pore bottom diameter to surface aperture 0.5 - 0.7) on the surface of the inner coating, with a density of 400 - 600 pores / cm 2 (porosity 15 - 20%) to form a mechanical anchoring structure, and the pore wall has a gradient heterogeneous interface (EDS shows that the Al / Zn ratio gradually changes from 1:4 at the pore bottom to 1:1 at the pore mouth).

[0008] S3. Apply fluorocarbon resin composite coating by electrostatic spraying (voltage 50kV, atomization pressure 0.3MPa) [Binder: FEVE fluorocarbon resin; Filler: flaky graphene oxide (15wt%) + cerium oxide (CeO 2 ) nanoparticles (5wt%)], and spray it in two times: The first spraying: The coating penetrates into the conical micropores and fills the anchoring area through capillary action to form an inverted hook-shaped cured structure inside the micropores (SEM shows that the pore filling rate > 92%); The second spraying: Spray for surface leveling to a total thickness of 200 - 250μm to form a continuous and dense barrier layer (the gas permeability measured by helium mass spectrometry < 5×10 -14 Pa·m 3 / s).

[0009] In the present invention, through the morphological matching of the inverted conical micropores and the outer coating filler (the contact area increases by 180%), the bonding strength ≥ 34MPa (ASTM D3164 standard) is achieved to form mechanical interlocking; Chemical bonding: The gradient Al / Zn ratio on the pore wall of the inner coating promotes the Lewis acid-base interaction between the C-F bond in the FEVE resin of the outer coating and the metal oxide (FTIR shows the generation of a characteristic peak at 1220cm -1 ).

[0010] When the outer coating is intact, nano CeO 2 inhibits the initiation of local corrosion through redox reaction (Ce 3+ ⇔Ce 4+ ); When the outer coating is damaged, the Zn-Al alloy of the inner coating preferentially dissolves to provide cathodic protection current (polarization resistance Rp > 1×10 6 Ω·cm 2 ). The graphene oxide sheets form a tortuous barrier around the micropores (Cl -The diffusion path is extended by 5 times). At the same time, the corrosion inhibitor (benzotriazole) adsorbed between the sheets is released when the external pH is greater than 8 to repair the microcracks (the self-repair efficiency reaches 78% after 480 hours of salt spray test) and realize the self-healing function.

[0011] As a further optimization of this solution, the fluorocarbon resin composite coating adopts a gradient curing process (pre-curing at 80°C for 10 minutes → final curing at 150°C for 30 minutes) to eliminate the interface stress (residual stress is reduced from 30MPa to 8MPa).

[0012] Compared with the prior art, the present invention has the following beneficial effects: Through the characteristic microporous process of the inner coating and the secondary spraying process of the outer coating, microporous interlocking is formed to enhance the mechanical bonding. At the same time, the sacrificial anode of the inner coating continuously provides cathodic protection, and the self-repair function of the outer coating repairs damage in real time; the graphene oxide and fluorocarbon resin of the outer coating form a dense impermeability layer. Secondly, through laser processing to control the pore size, inverted cone ratio and distribution density, match the diffusion path of different corrosive media, and for Cl - , H + , freeze-thaw stress and other specific failure factors, dynamically optimize the corrosion inhibitor and nano-reinforcement phase. Through the mechanical interlocking of the inverted cone micropores, the bonding strength between the outer coating and the inner coating is ≥34MPa (conventional process <6MPa) (see Table 1), and the micropores are filled with gradient curing resin to reduce the interface residual stress (from 30MPa to 8MPa), effectively inhibiting the crack propagation caused by dynamic loads (see Table 5).

[0013] In addition, the process of the present invention can also be expanded to oil pipelines, offshore wind power towers and other scenarios by adjusting the coating components (such as replacing the type of corrosion inhibitor). - Concentration-sensitive repair agent that enables in-situ sensing and response to coating damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flowchart of the overall process of the present invention. DETAILED DESCRIPTION

[0015] The following will be combined with the accompanying drawings in the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0016] Embodiment 1: This embodiment provides a process for anti-corrosion treatment of bridge steel in a marine environment, comprising the following steps: S1. Sandblasting activation pretreatment of substrate surface: Q345qD bridge steel (size 2000m×500mm×20mm) was used; alumina sand (particle size 50μm, pressure 0.6MPa) was used for sandblasting, and the surface roughness after sandblasting was Ra=10.2μm; plasma activation parameters were: argon flow rate 20L / min, power 800W, treatment time 5min; surface energy was increased to 67.3mN / m.

[0017] S2. Preparation of inner coating and micropore construction on substrate surface: The inner coating material was sprayed onto the substrate surface by supersonic arc spraying (HVAS) process; supersonic arc spraying parameters: voltage 32V, current 200A, spraying distance 150mm; inner coating material: Zn-Al based quaternary alloy coating (Al: 15%, Mg: 3%, Si: 1%, Zn: 81%), coating thickness 110±5μm, porosity <1%; The inverted cone micropores were processed on the inner coating surface by femtosecond laser processing (wavelength 1030nm, pulse width 300fs, energy density 1.8J / cm²), with a pore diameter of 250μm, a pore depth of 120μm, an inverted cone ratio (hole bottom diameter / surface diameter ratio) of 0.5-0.7, and a density of 480 pores / cm 2 , the Zn / Al atomic ratio at the hole bottom is 3.8:1.

[0018] S3. Double spraying of outer coating: select outer coating material (80wt% FEVE fluorocarbon resin, 15wt% graphene oxide, 5wt% cerium oxide nanoparticles, viscosity 120mPa·s at 25℃); the first spraying adopts electrostatic spraying (voltage 50kV), and the outer coating material penetrates into the conical micropores (filling rate 93%), and pre-cures at 80℃ for 10min to form a barb structure with a hook curvature radius of R=18±3μm and a hook depth of h=25±5μm, forming a mechanical locking effect; the second spraying covers the entire inner coating with a total thickness of 220μm, and finally cures at 150℃ for 30min. The surface hydrophobic angle is 152°, and it is continuous and defect-free.

[0019] The bridge steel obtained by the process of this embodiment was tested according to ASTM B117 for 4000h, and the inner coating had no red rust, the outer coating had no blistering, and the corrosion area was 0.5%. The bonding strength between the coating and the substrate was 34.5MPa (ASTM D4541), which was 475% higher than that of the traditional process (6MPa).

[0020] Example 2: This example provides a steel surface anti-corrosion treatment process for protecting bridge piers in a cold region deicing salt corrosion environment. Compared with Example 1, this example is different in that: (1) Inner coating: The inner coating material is a Zn-Al-Mg-Re quaternary alloy coating (Re: 0.5%, Al: 15%, Mg: 3.5%, Zn: 81%), which enhances the anode activity at low temperatures (-40℃ polarization resistance 8.3×10 5 Ω·cm 2 ); The micropore characteristics of the inner coating are a pore diameter of 200 μm, a pore bottom diameter of 120 μm (inverted cone ratio of 0.6), and a gradient pore depth (80 μm in the edge area → 150 μm in the center area) to adapt to the freeze-thaw stress distribution.

[0021] (2) External coating: In the outer coating material, pH-responsive microcapsules (shell material: polyurethane; corrosion inhibitor: benzotriazole) are loaded between the graphene oxide layers. When the outer coating cracks during a freeze-thaw cycle at -30°C, the microcapsules rupture and release the corrosion inhibitor (repair efficiency 82%).

[0022] Except for the above differences, the other processes of this embodiment are the same as those of embodiment 1, and will not be described in detail in this embodiment. The steel treated by the process of this embodiment has a coating adhesion retention rate of 89% after 50 freeze-thaw cycles (-40°C → 25°C); the cathode peeling radius is 1.2mm (ISO 15711), which is 75% lower than the traditional process (4.8mm).

[0023] Example 3: This example provides an anti-corrosion treatment process for high-humidity steel structures in industrial pollution areas. Compared with Example 1, this example is different in that: (1) Inner coating: The inner coating material is Zn-Al-Ti-B quaternary alloy coating (Ti: 2%, B: 0.1%, Al: 15.8%, Zn: 82.1%). 2 Dispersion strengthening improves wear resistance; The microporous structure of the inner coating is a honeycomb hexagonal array (pore spacing 350 μm), and the pore wall forms a nanocrystalline structure (grain size 85 nm) after laser processing.

[0024] (2) External coating: The flake graphene oxide used in the outer coating material is modified to have edge carboxylation (XPS shows a COOH content of 12.6%) to enhance the interfacial bonding with the resin; secondly, the outer coating is cured using a gradient temperature increase (80°C / 20min→120°C / 40min→150°C / 30min) to eliminate thermal stress cracks.

[0025] Except for the above differences, the other processes of this embodiment are the same as those of embodiment 1, and will not be described in detail in this embodiment. 2 SO 4 +NaCl mixed solution (Cl- The concentration was 1M) and the spraying cycle was 2000 hours; the results showed that the corrosion rate was 0.003mm / a (traditional coating was 0.12mm / a), and the protection efficiency was increased by 40 times.

[0026] Comparative Example 1: This comparative example adopts the traditional double coating process, specifically: The inner coating uses epoxy zinc-rich primer (Zn content 80%) with a thickness of 80μm; the outer coating uses polyurethane topcoat with a thickness of 200μm; it has no microporous structure and only relies on physical adsorption and bonding.

[0027] Test Example 1: Comparison of coating bonding strength The purpose of this test example is to verify the effect of the interface micro-anchoring structure of the present invention on improving the bonding strength. The test method is as follows: (1) Sample groups: Test group 1 uses the coating sample prepared in Example 1; control group 1 uses the coating sample prepared in Comparative Example 1.

[0028] (2) Test standard: ASTM D4541 (pull-off method for testing bonding strength); Equipment: PosiTest AT-A automatic adhesion tester.

[0029] Table 1 As shown in Table 1, the inverted tapered micropores of the present invention significantly improve the bonding strength through mechanical interlocking, and the failure mode is transformed from interface peeling to material self-fracture, achieving a three-dimensional anchoring effect.

[0030] Test Example 2: Salt spray corrosion accelerated test The purpose of this test example is to compare the Cl resistance of the present invention with that of the traditional process in a harsh marine environment. - Penetration energy, the test method is as follows: (1) Sample groups: 5 groups each for test group 1 (Example 1) and control group 1 (Comparative Example 1); (2) Test standard: ASTM B117 neutral salt spray test, 5% NaCl solution, 35°C, 4000 h; evaluation indicators include corrosion area (ImageJ software analysis), red rust appearance time, and external coating blistering level.

[0031] Table 2 As shown in Table 2, the graphene oxide barrier of the outer coating of the present invention works synergistically with the sacrificial anode of the inner coating to convert Cl - The diffusion rate is reduced to 1 / 60 (calculated value) of the traditional process, significantly prolonging the corrosion initiation time.

[0032] Test Example 3: Freeze-thaw cycle aging test The purpose of this test example is to verify the protective ability of the self-repairing microcapsules in Example 2 under freeze-thaw conditions in cold regions. The test method is as follows: (1) Sample groups: test group 2 (using the coating pattern prepared in Example 2) and control groups 1 and 2 (using the inner coating of Example 2 with a uniform pore depth of 100 μm).

[0033] (2) Test standard: GB / T 9268 standard, cycle program (-40℃×4h→immersion in 25℃ water for 4h), repeated 50 times; test items include adhesion retention rate and cathodic disbonding radius (ISO 15711).

[0034] Table 3 As shown in Table 3, the benzotriazole released by the microcapsules in Example 2 of the present invention can effectively inhibit the corrosion of the substrate at the freeze-thaw cracking site, and the cathode peeling radius is reduced by 66% compared with the prior art. Secondly, the gradient hole depth design adopted in Example 2 has a further effect compared with the uniform hole depth.

[0035] Test Example 4: Acidic Industrial Precipitation Simulation Test The purpose of this test example is to verify the anti-permeability performance of carboxylated graphene oxide in an acidic environment in Example 3. The test method is as follows: (1) Sample groups: test group 3 (coating pattern prepared using Example 3) and control group 3 (similar coating pattern with ordinary graphene filler).

[0036] (2) Test standard: pH=3 2 SO 4 +1M NaCl mixed solution, cyclic spraying (10min / h) at 40℃; evaluation indicators include electrochemical impedance spectroscopy (EIS) test polarization resistance (Rp) and corrosion rate (Tafel fitting).

[0037] Table 4 As shown in Table 4, the carboxylated graphene provided in the coating of Example 3 of the present invention enhances the chemical bonding between the sheets, making the coating resistant to H + and SO 3 2- The barrier efficiency is increased by about 40 times.

[0038] Test Example 5: Dynamic Load Fatigue Test The purpose of this test example is to evaluate the coating's ability to resist peeling under high-frequency vibration. The test method is as follows: (1) Sample groups: experimental group 1 and control group 1.

[0039] (2) Test conditions: Three-point bending fatigue test (stress amplitude Δσ = 150 MPa, frequency 5 Hz, number of cycles 1 × 10 6 times); observation indicators include interface crack extension length (SEM measurement).

[0040] Table 5 As shown in Table 5, the mechanical anchoring structure of the present invention completely suppresses crack initiation under dynamic load, while the conventional coating fails rapidly due to weak interface bonding.

[0041] In summary, the surface corrosion treatment process for bridge steel provided by the present invention, with the help of the mechanical anchoring effect of the inverted cone micropores, the coating bonding strength reaches 34.5MPa (6.2MPa in the traditional process), the interface failure mode changes from "substrate peeling" to "coating body fracture", and the three-dimensional interlocking design has a fundamental improvement on the interface stability. In terms of environmental tolerance, the corrosion area after 4000h salt spray test is only 0.5% (34.8% in the traditional process), Cl - The penetration rate was reduced by 98%. After 50 freeze-thaw cycles, the adhesion retention rate was 89%. The self-healing microcapsules reduced the cathode peeling radius by 66% (1.2mm vs 3.5mm). The dense barrier of carboxylated graphene filler reduced the corrosion rate to 0.003mm / a (0.12mm / a in traditional process), and the polarization resistance was increased by 26 times. 1×10 6 There is no crack extension in the coating under the secondary cyclic load (the crack extension of the traditional coating reaches 850μm), which proves that the microporous structure effectively disperses the stress. Therefore, it can be seen that the process of the present invention solves the three major technical problems of weak interface bonding, poor environmental adaptability, and dynamic failure of traditional anti-corrosion coatings through special structural design and material modification, providing further optimization for the longevity of steel in harsh corrosive environments.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A bridge steel surface anti-corrosion treatment process, characterized in that: The following steps are involved: S1. Pre-treating the substrate by plasma activation and sandblasting; S2. Spraying a Zn-Al based quaternary alloy onto the surface of the substrate by a spray deposition process to form an inner coating for sacrificial anode protection; processing inverted cone-shaped micropores on the surface of the inner coating by a femtosecond laser, with the pore wall presenting a gradient heterogeneous interface; S3, electrostatically spray fluorocarbon resin composite coating to the inner coating in two steps: The first spraying of the fluorocarbon resin composite coating penetrates into the inverted cone-shaped micropores to form a barbed hook-shaped solidified structure in the micropores; The second surface leveling spraying is carried out to form a continuous and dense barrier layer.

2. The bridge steel surface anti-corrosion treatment process according to claim 1 is characterized in that: The Zn-Al based quaternary alloy coating includes, in addition to Zn-Al, one of Mg-Si, Mg-Re and Ti-B.

3. The bridge steel surface anti-corrosion treatment process according to claim 1 is characterized in that: The inverted cone micropores have a pore diameter of 200-300 μm, a pore bottom diameter / surface diameter ratio of 0.5-0.7, and a density of 400-600 pores / cm 3 .

4. The bridge steel surface anti-corrosion treatment process according to claim 1 is characterized in that: In the S2, the thickness of the inner coating is 80-12 μm.

5. The bridge steel surface anti-corrosion treatment process according to claim 1 is characterized in that: The fluorocarbon resin composite coating comprises: Base material: 80wt% fluorocarbon resin; Filler: 15wt% of flaky graphene oxide or one of pH-responsive microcapsules loaded between graphene oxide layers, and 5wt% of cerium oxide nanoparticles.

6. The bridge steel surface anti-corrosion treatment process according to claim 5 is characterized in that: The shell material of the pH-responsive microcapsules loaded between graphene oxide layers is polyurethane, and the corrosion inhibitor is benzotriazole. When the outer coating is cracked in a freeze-thaw cycle at -30°C, the pH-responsive microcapsules loaded between graphene oxide layers are broken to release the corrosion inhibitor.

7. The bridge steel surface anti-corrosion treatment process according to claim 1, characterized in that: In S3, the surface is leveled and sprayed to a total thickness of 200-250 μm.

8. The bridge steel surface anti-corrosion treatment process according to claim 1, characterized in that: In S3, the fluorocarbon resin composite coating adopts a gradient curing process to eliminate interface stress.

9. The bridge steel surface anti-corrosion treatment process according to claim 8, characterized in that: The gradient curing process is: pre-curing at 80° C. for 10 min→final curing at 150° C. for 30 min.

10. The bridge steel surface anti-corrosion treatment process according to claim 1, characterized in that: In S3, the fluorocarbon resin composite coating penetrates into the interior of the conical micropores, fills the anchoring area by capillary action, and forms a barb-shaped solidified structure in the micropores.

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