Rust layer stabilizing treatment method for weather-proof bridge steel

Abstract

The invention relates to the technical field of weather-proof steel surface protection, in particular to a rust layer stabilizing treatment method for weather-proof bridge steel. Through the synergistic effect of laccase catalysis, phytic acid chelation speed control and manganous nitrate crystallization promotion, generation of an alpha-FeOOH stable phase is directionally promoted, the stabilization period is shortened to be within 12 h, and the content of the alpha-FeOOH phase is larger than or equal to 85%.

Description

Technical Field

[0001] This invention relates to the field of weathering steel surface protection technology, specifically to a method for stabilizing the rust layer of weathering bridge steel. It is particularly suitable for rust layer modification of weathering bridge steel in highway, railway bridges and offshore platforms, and can achieve rapid rust layer stabilization in complex service environments. It belongs to the field of green construction and infrastructure protection technology. Background Technology

[0002] Weathering bridge steel is a type of low-alloy steel made by adding trace amounts of alloying elements such as Cu, Cr, Ni, and P. Its core advantage lies in its ability to spontaneously form a dense protective rust layer during service, achieving a self-protective effect of "rust nourishing rust," thus eliminating the need for traditional painting processes and reducing subsequent maintenance costs. Currently, grades of weathering bridge steel such as Q420NH, Q420qNH, and Q500qENH are widely used in various bridge projects, but true paint-free applications have not yet been widely promoted, primarily due to numerous bottlenecks in existing technology.

[0003] First, the stabilization process of weathering steel rust layer in natural environments is slow, requiring 3-10 years to form a stable and dense protective rust layer. The initially formed unstable phases such as γ-FeOOH, Fe3O4, and β-FeOOH are loose and porous, easily leading to rust liquid dripping and spreading, damaging the bridge's appearance and polluting the surrounding environment. Second, in complex environments such as marine atmospheres and acidic industrial atmospheres, Cl... - Problems such as penetration and acidic media corrosion can hinder the formation of protective rust layers, leading to continuous corrosion of the steel substrate. In particular, the corrosion problem is more prominent in critical parts such as welded joints due to uneven structure and stress concentration.

[0004] Existing rust stabilization technologies have significant drawbacks: organic resin-based treatments suffer from VOC emissions, high costs, and easy peeling after long-term use; water-based inorganic salt treatments often contain heavy metals such as chromium and copper, resulting in poor environmental performance and insufficient corrosion resistance in high-salt environments; while silane coupling agent-based treatments offer improved environmental friendliness, high concentrations of silane can reduce the permeability of the film, affecting the long-term transformation of the rust layer. Traditional treatments often use chemical oxidants such as potassium dichromate to promote rust transformation, which releases toxic and harmful substances, posing environmental risks. Furthermore, they have long stabilization cycles (typically over 24-48 hours) and high construction complexity, making it difficult to meet the engineering requirements for environmentally friendly, efficient, and long-lasting protection.

[0005] Therefore, developing a green, non-toxic, efficient, rapid, and environmentally friendly method for stabilizing the rust layer of weathering bridge steel, which can promote the formation of the α-FeOOH stable phase, shorten the stabilization cycle, and improve the corrosion resistance and stability of the rust layer, is key to promoting the application of paint-free weathering steel. Summary of the Invention

[0006] To address the shortcomings of existing technologies, such as long rust stabilization cycles for weather-resistant bridge steel, initial rust flow pollution, poor adaptability to complex environments, toxic and harmful components in treatment agents, and complex construction, the core objective of this invention is to provide a rust stabilization treatment method for weather-resistant bridge steel. This method utilizes a green composite treatment liquid with laccase as its core, synergistically promoting the formation of the α-FeOOH stable phase through the functional interaction of multiple components. The choice of laccase dosage significantly affects the final rust-preventive effect of rust stabilization, achieving the following objectives: 1. It replaces traditional toxic oxidants such as potassium dichromate, achieving a green and non-toxic treatment process; 2. Shorten the rust stabilization cycle to within 12 hours to solve the initial rust flow problem; 3. Improve the corrosion resistance and structural stability of the rust layer in complex environments such as high salt and acidity, ensuring that the α-FeOOH phase content is ≥85%; 4. Simplified construction process, no sandblasting pretreatment required, construction can be carried out at room temperature, reducing project costs.

[0007] To achieve the above technical objectives, the technical solution adopted by the present invention is as follows: A method for stabilizing the rust layer of weathering bridge steel includes four steps: substrate pretreatment, preparation of stabilization solution, coating treatment, and post-treatment, as detailed below: 1. Substrate Pretreatment The surface of the weathering bridge steel substrate is blew with 0.8 MPa high-pressure air to remove loose rust, dust, and other impurities, eliminating the need for sandblasting or acid pickling. This process preserves a 0.05–0.5 mm thick natural rust layer on the substrate surface, resulting in a rusted surface ready for treatment. This pretreatment method avoids the dust pollution and substrate damage associated with traditional sandblasting, reducing construction complexity.

[0008] 2. Preparation of stabilization treatment solution Using deionized water as a solvent, add each component sequentially according to the following concentration range, and stir at 20-35℃ for 30-60 minutes until uniformly dispersed to form a stable water-based treatment solution. The pH of the treatment solution is controlled at 4.5-6.5 (the optimal activity range of laccase). Core catalytic component: Laccase 50~100 U / L (derived from white-rot fungi, enzyme activity determined by ABTS method), replacing traditional chemical oxidants to catalyze the Fe in the rust layer. 2+ Directional oxidation to Fe 3+ It is green and non-toxic; the chelating regulator is phytic acid 0.8~1.5 g / L, which binds to Fe through 6 phosphate groups. 3+ Formation of stable chelates, controlling Fe 3+Hydrolysis rate, avoids the formation of unstable phases, and guides α-FeOOH crystallization; stabilizing phase promoting components: manganese nitrate (Mn(NO3)2·4H2O) 0.1~0.5 g / L, Mn 2+ As a crystallization promoter for α-FeOOH formation, it lowers the activation energy for crystal growth and simultaneously embeds into the α-FeOOH lattice to form a solid solution, enhancing crystal stability; Densification component: γ-aminopropyltriethoxysilane (KH550) 0.3~1.0 vol%, which forms a Si-O-Si network after hydrolysis, filling the pores of the rust layer and enhancing its density and adhesion; pH buffer component: citric acid-sodium citrate buffer pair 0.1~0.3 mol / L (molar ratio 1:1~1:2), maintaining the pH stability of the treatment solution and preventing pH fluctuations from causing a decrease in laccase activity; Dispersion stabilizing component: sodium dodecylbenzenesulfonate (SDBS) 0.05~0.1 g / L, improving the dispersibility of each component and preventing laccase aggregation and stratification of the treatment solution; Moisturizing auxiliary component: glycerol 0.5~1.0 vol%, reducing the surface evaporation rate of the treatment solution and providing sufficient time for the laccase catalytic reaction, suitable for outdoor construction environments.

[0009] 3. Coating treatment Spraying treatment: Using an airless spraying device with a pressure of 0.2~0.5 MPa, the treatment solution is evenly sprayed onto the surface to be treated. The volume of treatment solution used is 100~150 mL / m². 2 Ensure the surface is completely wet; Compared with the prior art, the present invention has the following significant advantages: 1. Excellent green and environmentally friendly performance: The treatment solution uses laccase as the core catalytic component, completely replacing toxic oxidants such as potassium dichromate, and is free of chromium. 6+ It contains heavy metals such as Pb and Hg, and its VOC content meets the requirements of GB / T 23985-2009 standard. It has a weakly acidic pH (4.5~6.5), does not corrode the substrate, and causes no secondary pollution during construction, which is in line with the concept of green engineering. 2. High stabilization efficiency: Through the synergistic effect of laccase catalysis, phytic acid chelation rate control and manganese nitrate crystallization promotion, the formation of α-FeOOH stable phase is promoted in a targeted manner, shortening the stabilization cycle to within 12 hours (the traditional method requires 24~48 hours), and the α-FeOOH phase content is ≥85%, effectively solving the problem of initial rust contamination; 3. Strong corrosion resistance and stability: The dense network formed by silane hydrolysis fills the pores of the rust layer, Mn 2+ Solid solution-enhanced α-FeOOH crystal structure, suitable for complex environments such as marine and high-salt environments; 4. Simple construction and low cost: No complex pretreatment such as sandblasting and acid washing is required. Construction can be carried out at room temperature. Post-treatment only requires natural air drying. No special equipment is required. The raw materials are all conventional industrial products. Laccase can be mass-produced industrially. Phytic acid is derived from grain processing by-products. The treatment cost is reduced by more than 30% compared with treatment solutions containing titanates and precious metals. 5. High versatility: Compatible with mainstream weathering bridge steel grades such as Q420NH, Q420qNH, and Q500qENH. It can be applied by spraying and is suitable for different parts of the bridge base material, welded joints, and components with different curvatures such as curved beams. Detailed Implementation

[0010] The technical solution of the present invention will be described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments described. Example

[0011] 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 70 U / L laccase, 1.0 g / L phytic acid, 0.3 g / L manganese nitrate, 0.6 vol% γ-aminopropyltriethoxysilane, 0.2 mol / L citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L SDBS, and 0.8 vol% glycerol in sequence. Stir at 25℃ for 40 min and adjust the pH to 5.5 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 92% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing. Example

[0012] 1. Substrate pretreatment: Select Q500qENH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.3 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 90 U / L of laccase, 1.3 g / L of phytic acid, 0.4 g / L of manganese nitrate, 0.8 vol% of γ-aminopropyltriethoxysilane, 0.25 mol / L of citrate-sodium citrate buffer (molar ratio 1:2), 0.09 g / L of SDBS, and 0.9 vol% of glycerol in sequence. Stir at 30℃ for 50 min and adjust the pH to 6.0 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 89% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing. Example

[0013] 1. Substrate pretreatment: Select Q420qNH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.15 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 60 U / L laccase, 0.9 g / L phytic acid, 0.2 g / L manganese nitrate, 0.5 vol% γ-aminopropyltriethoxysilane, 0.15 mol / L citrate-sodium citrate buffer (molar ratio 1:1), 0.07 g / L SDBS, and 0.7 vol% glycerol in sequence. Stir at 22℃ for 35 min and adjust the pH to 5.0 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.4 MPa and a treatment solution volume of 130 mL / m². 2 The coating is completed at room temperature (22℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 92% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing.

[0014] Comparative Example 1 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water, and add 70 U / L laccase, 1.0 g / L phytic acid, 0.6 vol% γ-aminopropyltriethoxysilane, 0.2 mol / L citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L SDBS, and 0.8 vol% glycerol in sequence. Stir at 25℃ for 40 min, and adjust the pH to 5.5 to obtain a stable treatment solution; 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 73% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing.

[0015] Comparative Example 2 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water, and add 70 U / L laccase, 0.3 g / L manganese nitrate, 0.6 vol% γ-aminopropyltriethoxysilane, 0.2 mol / L citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L SDBS, and 0.8 vol% glycerol in sequence. Stir at 25℃ for 40 min, and adjust the pH to 5.5 to obtain a stable treatment solution; 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 76% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing.

[0016] Comparative Example 3 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water, and add 1.0 g / L of phytic acid, 0.3 g / L of manganese nitrate, 0.6 vol% of γ-aminopropyltriethoxysilane, 0.2 mol / L of citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L of SDBS, and 0.8 vol% of glycerol in sequence. Stir at 25℃ for 40 min, and adjust the pH to 5.5 to obtain a stable treatment solution; 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 71% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing.

[0017] Comparative Example 4 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 70 U / L laccase, 1.0 g / L phytic acid, 0.3 g / L nitric acid, 0.6 vol% γ-aminopropyltriethoxysilane, 0.2 mol / L citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L SDBS, and 0.8 vol% glycerol in sequence. Stir at 25℃ for 40 min and adjust the pH to 5.5 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 83% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing.

[0018] Comparative Example 5 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 110 U / L of laccase, 1.0 g / L of phytic acid, 0.3 g / L of manganese nitrate, 0.6 vol% of γ-aminopropyltriethoxysilane, 0.2 mol / L of citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L of SDBS, and 0.8 vol% of glycerol in sequence. Stir at 25℃ for 40 min and adjust the pH to 5.5 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing that the α-FeOOH phase content in the rust layer was 95%. Subsequently, a neutral salt spray test (NSS, ASTM B117) was conducted. Evaluation metrics included: time to red rust appearance (hours): recording the time at which red rust caused by matrix corrosion first appeared on the sample surface; and the scratch corrosion propagation width (mm) after 1000 hours of salt spray testing.

[0019] Comparative Example 6 1. Substrate pretreatment: Select Q420NH weathering bridge steel specimens (100mm×150mm×8mm) with a natural rust layer thickness of 0.2 mm. Use 0.8 MPa high-pressure air to blow away the surface rust and dust, and set aside for later use; 2. Preparation of treatment solution: Take 1L of deionized water and add 40 U / L laccase, 1.0 g / L phytic acid, 0.3 g / L manganese nitrate, 0.6 vol% γ-aminopropyltriethoxysilane, 0.2 mol / L citrate-sodium citrate buffer (molar ratio 1:1.5), 0.08 g / L SDBS, and 0.8 vol% glycerol in sequence. Stir at 25℃ for 40 min and adjust the pH to 5.5 to obtain a stable treatment solution. 3. Coating treatment: A spraying method is used, with a spraying pressure of 0.3 MPa and a treatment solution volume of 120 mL / m². 2 The coating is completed at room temperature (25℃); Twelve hours after treatment, X-ray diffraction analysis was performed on the samples, revealing an α-FeOOH phase content of 87% in the rust layer. A neutral salt spray test (NSS, ASTM B117) was then conducted, with the following evaluation metrics: Time to red rust appearance (hours): Recording the time when red rust caused by matrix corrosion first appeared on the sample surface. Scratch corrosion extension width (mm) after 1000 hours of salt spray testing. The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements that can be made by those skilled in the art without departing from the core ideas of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for stabilizing rust layers on weathering bridge steel, characterized in that, Includes the following steps: S1. Substrate pretreatment: The surface of the weathering bridge steel substrate is blown to remove floating rust and dust. No sandblasting is required to obtain a rusted surface to be treated. S2. Preparation of stabilization solution: Using deionized water as solvent, mix the components according to the following concentration range and stir until uniformly dispersed: laccase 50~100 U / L, phytic acid 0.8~1.5 g / L, manganese nitrate (Mn(NO3)2·4H2O) 0.1~0.5 g / L, γ-aminopropyltriethoxysilane (KH550) 0.3~1.0 vol%, citrate-sodium citrate buffer pair 0.1~0.3 mol / L, sodium dodecylbenzenesulfonate (SDBS) 0.05~0.1 g / L, glycerol 0.5~1.0 vol%. The pH of the treatment solution is 4.5~6.

5. S3. Coating treatment: The treatment liquid prepared in step S2 is applied to the surface of the substrate after pretreatment in step S1 by spraying.

2. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S1, the purging is carried out using 0.8 MPa high-pressure air, and the rust layer thickness on the substrate surface is 0.05~0.5 mm.

3. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S1, the thickness of the rust layer on the substrate surface is 0.05~0.5 mm.

4. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S2, the laccase is derived from white-rot fungi.

5. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S2, the molar ratio of the citrate-sodium citrate buffer pair is 1:1 to 1:

2.

6. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S3, the amount of treatment liquid used in the spraying method is 100~150 mL / m².

7. The rust stabilization treatment method for weathering bridge steel according to claim 1, characterized in that, In step S3, the spraying pressure is 0.2~0.5 MPa, the soaking time is 6~12 h, and the treatment temperature is 20~35℃.

8. The method for stabilizing rust layers on weathering bridge steel according to any one of claims 1 to 7, characterized in that, The weathering bridge steel is of grade Q420NH, Q420qNH or Q500qENH.

9. The rust stabilization treatment method for weathering bridge steel according to any one of claims 1 to 7, characterized in that, The α-FeOOH phase content in the rust layer 12 hours after treatment is ≥85%.

10. The application of the rust stabilization treatment method for weathering bridge steel according to any one of claims 1 to 9 in bridge engineering in marine atmosphere and acidic industrial atmosphere areas.