A corrosion-resistant coating material based on metal coordination structure, its preparation method and application

Abstract

This invention discloses an anti-corrosion coating material based on a metal coordination structure, its preparation method, and its application. The anti-corrosion coating material is based on a traditional zinc anti-corrosion system, incorporating a metal coordination polymer containing a dihydroxy-p-benzoquinone (DHBQ) ligand. This polymer self-assembles to form a stable coordination complex Co(dhbq)₃@Zn. Due to the highly ordered and dense structural characteristics of the metal coordination polymer Co(dhbq)₃ and the dynamic response properties of its reversible coordination bonds, it can effectively construct a dense barrier layer to prevent the penetration of corrosive media. Furthermore, its dynamically reversible metal coordination bonds can spontaneously reconstruct under environmental stimuli after the coating is damaged, thereby achieving in-situ self-repair of the metal surface. This anti-corrosion coating material not only significantly inhibits corrosion propagation but also effectively extends the service life of the zinc coating, improving the long-term protective performance of the entire coating system and providing a durable, efficient, and environmentally friendly anti-corrosion solution for the protected metal materials.

Description

Technical Field

[0001] This invention belongs to the field of marine equipment corrosion protection, specifically relating to an ultrathin self-healing anti-corrosion coating material based on metal coordination structure, its preparation method, and its application. Background Technology

[0002] The application of ultra-thin self-healing anti-corrosion coatings primarily stems from the need to protect metallic materials in corrosive environments, particularly in marine, chemical, and construction fields. Metallic materials, especially steel, aluminum alloys, and zinc, are prone to oxidation and corrosion when exposed to corrosive environments such as moisture, salt spray, and acids / alkalis for extended periods, leading to decreased structural performance and increased maintenance costs. While traditional anti-corrosion methods such as coatings, cathodic protection, and sacrificial anode methods are effective, they may present problems such as environmental pollution and limited service life. Therefore, it is essential to protect the coating surface to inhibit seawater corrosion. Currently, corrosion protection in marine environments both domestically and internationally mainly utilizes three technologies: 1. Anti-corrosion coating technology; 2. Cathodic protection technology; 3. Cathodic protection combined with coating protection technology.

[0003] Technique 1: Organic Anti-corrosion Coatings. Anti-corrosion technology is one of the most common methods. It primarily involves applying a protective coating (such as epoxy resin, polyurethane, or polyvinyl chloride) to the metal surface to isolate the metal from seawater or corrosive media, thus preventing corrosion. Coating anti-corrosion technology is widely used and suitable for offshore platforms, ships, and marine facilities. However, in seawater environments, coatings may peel, crack, or age due to mechanical damage, ultraviolet radiation, and chemical corrosion, leading to reduced anti-corrosion effectiveness or even failure. Furthermore, the effective protection period of the coating is limited, especially in marine environments, where regular maintenance and recoating require significant manpower and resources.

[0004] Technique 2: Cathodic protection technology avoids anodic corrosion by connecting a metal surface to a sacrificial anode (typically zinc, aluminum, or magnesium) or an applied current source (such as a current-driven cathodic protection system), making the metal surface the cathode. Sacrificial anode protection uses a metal more susceptible to corrosion than the substrate (such as zinc, aluminum, or magnesium) as the anode, mounted on the metal structure. The anode corrodes first, protecting the substrate from corrosion. This method is widely used in ship hulls, marine structures, and subsea pipelines. However, the sacrificial anode gradually corrodes and is consumed, requiring regular inspection and replacement, increasing maintenance costs. Using an external power source further increases operating costs and system complexity. Using welded zinc blocks or hot-dip galvanizing, the most significant drawback is that the sacrificial anode gradually wears down during use and must be replaced periodically, increasing maintenance complexity and cost.

[0005] Technology 3: The combined corrosion protection technology of cathodic protection and coating protection is a comprehensive technology widely used in the corrosion protection of metal structures, especially suitable for facilities such as underground pipelines, storage tanks, ship hulls, steel piles, and offshore platforms that are exposed to corrosive environments for a long time. The coating, as the first line of defense, isolates the metal surface from direct contact with corrosive media (such as water, electrolytes, and oxygen), reducing the possibility of corrosion. When the coating has defects or ages and peels off, cathodic protection reduces the potential of the protected metal to below its corrosion potential by applying an external current or using a sacrificial anode, thereby inhibiting the corrosion process. Another widely used approach is the composite coating system, which uses coatings with cathodic protection, such as epoxy zinc-rich coatings, inorganic zinc-rich coatings, or hot-dip galvanized layers, as the base coat, topped with intermediate and top coats that provide physical barriers. This typically forms a thick film protection, increasing costs and introducing problems such as cracking and peeling of the thick film, failing to achieve long-term corrosion protection. Summary of the Invention

[0006] The technical problem this invention aims to solve is to address the issues of weakened anti-corrosion effect, high maintenance costs, environmental pollution, uneven protection, and biofouling faced by traditional marine anti-corrosion technologies. This invention provides an ultrathin self-healing anti-corrosion coating material based on a metal coordination structure, its preparation method, and its applications. By introducing a metal coordination polymer Co(dhbq)3 with dynamically reversible metal coordination bonds to construct a stable and dense ultrathin anti-corrosion coating, a novel ultrathin self-healing anti-corrosion technology is achieved, providing continuous protection for the metal substrate, reducing maintenance costs, using environmentally friendly materials, avoiding pollution, uniformly protecting the metal surface, inhibiting marine biofouling, and improving anti-corrosion effect and service life. Furthermore, it can be applied to the treatment of fouling on the coating surfaces of marine equipment.

[0007] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0008] An anti-corrosion coating material based on a metal coordination structure is disclosed. This material uses cobalt nitrate hexahydrate and 2,5-dihydroxy-1,4-benzoquinone (DHBQ) as raw materials. A metal coordination polymer, Co(dhbq)3, is prepared via precipitation. The resulting Co(dhbq)3 solution is then applied to a zinc-containing or zinc-based anti-corrosion primer using a water bath method to form an anti-corrosion film, ultimately creating a composite material Co(dhbq)3@Zn. The zinc can be a zinc plate, and the zinc-based anti-corrosion primer can be a Zn-plated layer or a zinc-powder-containing coating.

[0009] A method for preparing an anti-corrosion coating material based on a metal coordination structure, the method comprising the following preparation steps:

[0010] S1. Preparation of Co(dhbq)3: Co(dhbq)3 was prepared by precipitation method using cobalt nitrate hexahydrate and 2,5-dihydroxy-1,4-benzoquinone (dhbq) as raw materials.

[0011] S2. Preparation of Co(dhbq)3 solution: Dissolve the prepared metal coordination polymer Co(dhbq)3 in water to obtain an aqueous solution of Co(dhbq)3.

[0012] S3. Preparation of Co(dhbq)3@Zn: An anti-corrosion film is coordinated onto metallic zinc or a zinc-containing anti-corrosion primer by water bath method to obtain the composite Co(dhbq)3@Zn.

[0013] Preferably, the preparation method of the above-mentioned anti-corrosion coating material based on metal coordination structure includes the following steps:

[0014] S11. Add 1.0 mmol of cobalt nitrate hexahydrate to a 100 ml round-bottom flask containing 10 ml of methanol;

[0015] S12. Dissolve 2.0 mmol of 2,5-dihydroxy-1,4-benzoquinone and 4.0 mmol of triethylamine in 10 ml of methanol, and add the solution dropwise to the round-bottom flask mentioned above, and stir at 50 °C for 0.5 h;

[0016] S13. After cooling to room temperature, remove 2 / 3 of the solvent by rotary evaporation and add 30 ml of diethyl ether; filter the solution after 20 minutes to obtain a dark red precipitate, and then dry it under vacuum at 80 °C for 12-16 h to assemble the metal coordination polymer Co(dhbq)3.

[0017] S14. Dissolve the Co(dhbq)3 obtained in step S13 in deionized water to prepare a 20 g / L Co(dhbq)3 aqueous solution, and keep it in a 60℃ water bath for 30 min.

[0018] S15. Immerse the polished zinc in the Co(dhbq)3 aqueous solution prepared in step S14 for 20 min, and maintain a water bath at 60℃ to form a Co(dhbq)3 anti-corrosion film on the zinc surface to obtain Co(dhbq)3@Zn. Then wash it several times with pure water and dry it at 60℃ for 4 h.

[0019] Preferably, the thickness of the Co(dhbq)3 anti-corrosion film is 500nm-20μm.

[0020] Preferably, the anti-corrosion coating material or the anti-corrosion coating material preparation method described above is applied to metal structures or steel structures to achieve corrosion protection.

[0021] The working principle of this invention is as follows: Based on metal coordination structures, this invention introduces a metal coordination polymer, Co(dhbq)3, containing dihydroxy-p-benzoquinone (DHBQ) ligands, into the traditional zinc corrosion protection system. Utilizing its highly ordered and dense molecular structure and the reversible coordination bonds (M-L bonds) between the metal and ligands, a Co(dhbq)3@Zn ultrathin composite anti-corrosion coating is constructed on the zinc layer surface through self-assembly. During service, this coating effectively blocks the penetration of corrosive media such as moisture, oxygen, and chloride ions (Cl⁻) through its dense coordination polymer structure, forming a barrier effect and reducing the likelihood of corrosion reactions. Furthermore, when the coating is subjected to mechanical damage or environmental stress, the coordination bonds can undergo reversible breakage and recombination under external environmental stimuli (such as changes in moisture, temperature, and pH), driving spontaneous reconstruction of the coating in the damaged area and achieving localized in-situ self-repair. This dynamic repair mechanism of "coordination bond breakage-recombination" effectively prevents corrosion propagation, extends the service life of the zinc layer and substrate, and comprehensively improves the long-term stability and environmental adaptability of the anti-corrosion system.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The anti-corrosion coating material of this invention is applied to ultra-thin self-healing marine corrosion protection. It combines the high density of the metal coordination structure with the dynamic self-healing ability, which can significantly reduce the coating thickness while ensuring excellent anti-corrosion performance, thereby reducing structural weight, reducing material consumption and simplifying the construction process.

[0024] Traditional corrosion protection technologies often face the problem of pitting or localized corrosion due to uneven surface protection. In particular, cathodic protection or sacrificial anodes may not provide sufficient protection in certain locations, leading to localized corrosion. This invention's ultra-thin self-healing marine corrosion protection technology utilizes dynamically reversible metal-ligand (M-L) bonds in the coating to rapidly respond to environmental changes (such as changes in moisture, pH, or temperature) after damage, achieving in-situ automatic repair of the coating. This ensures uniform and durable protection of the entire metal surface, significantly inhibiting localized corrosion. Furthermore, this technology uses environmentally friendly metal coordination polymer materials, avoiding the environmental pollution caused by traditional heavy metal corrosion inhibitors, offering advantages in green and sustainable development. Simultaneously, the re-repairable nature of the coating reduces the frequency and cost of subsequent maintenance, making it particularly suitable for harsh service environments such as marine environments characterized by high humidity, high corrosion, and difficulty in frequent maintenance. The corrosion protection coating system of this invention is ultra-thin, dense, and re-repairable, making it especially suitable for corrosion protection in high-humidity and high-corrosion environments such as marine energy equipment, offshore platforms, submarine cables, and nuclear power plant water pipelines, demonstrating significant engineering application prospects and economic value. Attached Figure Description

[0025] Figure 1The above is a characterization diagram of Co(dhbq)3 with ultrathin self-healing function according to an embodiment of the present invention; wherein, a is a synthetic route diagram of metal coordination polymer Co(dhbq)3; b is the Fourier transform infrared spectrum of DHBQ and Co(dhbq)3; and c is the X-ray diffraction pattern of DHBQ and Co(dhbq)3.

[0026] Figure 2 This is a comparison of the surface corrosion of the embodiments of the present invention and the comparative example of traditional cathodic protection corrosion prevention technology after 30 days of seawater immersion;

[0027] Figure 3 This is a comparison chart of the EIS curves representing the anti-corrosion effect of the embodiments of the present invention and the comparative examples of traditional anti-corrosion technologies, which characterize the self-healing ability of the coating. Detailed Implementation Example 1

[0028] An ultrathin self-healing anti-corrosion coating material based on a metal coordination structure is disclosed. This coating material uses cobalt nitrate hexahydrate and 2,5-dihydroxy-1,4-benzoquinone (DHBQ) as raw materials. A metal coordination polymer, Co(dhbq)3, is prepared via precipitation. This Co(dhbq)3 solution is then prepared and applied to a Zn plate or a zinc-containing anti-corrosion primer using a water bath method to form a Co(dhbq)3@Zn composite film. Specifically, the preparation steps of this ultrathin self-healing anti-corrosion coating material based on a metal coordination structure are as follows:

[0029] S11. Add 1.0 mmol of cobalt nitrate to a 100 ml round-bottom flask containing 10 ml of methanol.

[0030] S12. Dissolve 2.0 mmol of 2,5-dihydroxy-1,4-benzoquinone and 4.0 mmol of triethylamine in 10 ml of methanol, and add the solution dropwise to the round-bottom flask mentioned above, and stir at 50 °C for 0.5 h.

[0031] S13. After cooling to room temperature, remove 2 / 3 of the solvent by rotary evaporation and add 30 ml of diethyl ether; filter the solution after 20 minutes to obtain a dark red precipitate, and then dry it under vacuum at 80 °C for 12 h to assemble the metal coordination polymer Co(dhbq)3.

[0032] S14. Dissolve the Co(dhbq)3 obtained in step S13 in deionized water to prepare a 20 g / L Co(dhbq)3 aqueous solution, and keep it in a 60℃ water bath for 30 min.

[0033] S15. Immerse the polished zinc in the Co(dhbq)3 aqueous solution prepared in step S14 for a certain period of time, maintaining a water bath at 60°C, so that a Co(dhbq)3 anti-corrosion film with a thickness of 1-10 mm is formed on the zinc surface, to obtain Co(dhbq)3@Zn.

[0034] Comparative Example 1

[0035] The sacrificial anode protection method is directly adopted by installing zinc as the anode on the metal structure.

[0036] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0037] First, the synthetic route was designed, such as Figure 1 a. Co(dhbq)3 was synthesized under atmospheric pressure using a precipitation method. Figure 1 b shows the Fourier transform infrared (FT-IR) spectrum of the prepared complex. It can be seen that after the ligand DHBQ coordinates with Co, the C=O region is at 1670 cm⁻¹. -1 The peak at that location also shifted to 1659 cm. -1 . Figure 1 c depicts the XRD patterns of DHBQ and Co(dhbq)3. The sharp peaks at 15, 22, and 25° after coordination are attributed to the DHBQ crystals. Notably, the Co(dhbq)3 spectrum lacks some characteristic peaks that appear in the DHBQ spectrum. All these observations demonstrate the successful stepwise synthesis of Co(dhbq)3. These findings lay a solid material foundation for subsequent composites with Zn, as well as for its self-healing and corrosion-resistant properties.

[0038] Subsequently, an ultra-thin self-healing coating was applied to the protected metal surface, and the surface corrosion was compared with that of metal without this technology after 30 days of seawater immersion. Figure 2 As shown, the number of corrosion pits increased significantly after immersion for 30 days. The metal surface after the treatment remained smooth, with a much lower degree of corrosion, indicating that the carbon steel was effectively protected. Furthermore, long-term comparison also shows that the synthesized Co(dhbq)3@Zn can spontaneously self-repair during prolonged use, providing protection for metallic materials.

[0039] Electrochemical impedance spectroscopy (EIS) was performed on metal materials with self-healing corrosion protection via the attached metal coordination complex Co(dhbq)3@Zn and metal materials with corrosion protection via a simple traditional Zn layer. (See attached EIS). Figure 3Electrochemical impedance spectroscopy (EIS) is also one of the electrochemical methods for studying metal corrosion. An EIS spectrum consists of an arc and a tail line, where the radius of the arc represents the charge transfer resistance (Rct). The smaller the radius of the semicircle, the smaller the charge transfer resistance, indicating that the electrochemical reaction is more likely to occur on the metal surface. Figure 3 As shown, after the self-healing coating treatment, the radius of the EIS arc is smaller than that of the untreated arc, and Rct is significantly reduced. This indicates that the surface is more prone to electrochemical reactions after the self-healing coating is applied, facilitating timely self-repair after damage. It also inhibits seawater corrosion of Zn and the protected material to a certain extent. This demonstrates the effective protection of metallic materials by Co(dhbq)3@Zn, achieving the goal of inhibiting metal corrosion.

[0040] This invention is not limited to the specific embodiments described above. For those skilled in the art, all modifications made based on the above concept without creative effort fall within the protection scope of this invention.

Claims

1. A corrosion-resistant coating material based on metal coordination structure, characterized in that, The material comprises cobalt nitrate hexahydrate and 2,5-dihydroxy-1,4-benzoquinone (dhbq). The anti-corrosion coating material is a stable coordination complex Co(dhbq)3@Zn formed by self-assembly of a metal coordination polymer Co(dhbq)3 containing a dihydroxy-1,4-benzoquinone ligand onto a zinc metal or zinc-containing anti-corrosion primer.

2. The anti-corrosion coating material according to claim 1, characterized in that, The zinc anti-corrosion base coating is a Zn-plated layer or a zinc-containing powder coating.

3. A method for preparing an anti-corrosion coating material according to claim 1, characterized in that, Includes the following steps: S1. Preparation of Co(dhbq)3: Co(dhbq)3 was prepared by precipitation method using cobalt nitrate hexahydrate and 2,5-dihydroxy-1,4-benzoquinone (dhbq) as raw materials. S2. Preparation of Co(dhbq)3 solution: Dissolve the prepared metal coordination polymer Co(dhbq)3 in water to obtain an aqueous solution of Co(dhbq)3; S3. Preparation of Co(dhbq)3@Zn: An anti-corrosion film is coordinated onto metallic zinc or a zinc-containing anti-corrosion primer by water bath method to obtain the composite Co(dhbq)3@Zn.

4. The preparation method according to claim 3, characterized in that, The method for preparing Co(dhbq)3 in step S1 includes the following steps: S11. Add 1.0 mmol of cobalt nitrate to a 100 ml round-bottom flask containing 10 ml of methanol; S12. Dissolve 2.0 mmol of 2,5-dihydroxy-1,4-benzoquinone and 4.0 mmol of triethylamine in 10 ml of methanol, and add the solution dropwise to the round-bottom flask mentioned above, and stir at 50 °C for 0.5 h; S13. After cooling to room temperature, remove 2 / 3 of the solvent by rotary evaporation and add 30 ml of diethyl ether; filter the solution after 20 minutes to obtain a dark red precipitate, and then dry it under vacuum at 80 °C for 12 h to assemble the metal coordination polymer Co(dhbq)3.

5. The preparation method according to claim 4, characterized in that, The method for preparing the Co(dhbq)3 solution in step S2 is as follows: the obtained Co(dhbq)3 is dissolved in deionized water to prepare a 20 g / L Co(dhbq)3 aqueous solution, and kept in a 60℃ water bath for 30 min.

6. The preparation method according to claim 5, characterized in that, The method for preparing Co(dhbq)3@Zn in step S3 is as follows: the polished zinc is immersed in the Co(dhbq)3 aqueous solution prepared in step S2 for 20 min and kept in a 60°C water bath to form a Co(dhbq)3 anti-corrosion film on the zinc surface. The obtained Co(dhbq)3@Zn is washed several times with pure water and then dried at 60°C for 4 h to obtain the final composite Co(dhbq)3@Zn.

7. The preparation method according to claim 6, characterized in that, The thickness of the anti-corrosion film is 500nm-20μm.

8. The anti-corrosion coating material according to any one of claims 1-2 or the anti-corrosion coating material prepared by the preparation method according to any one of claims 3-7 is applied to metal structures to achieve corrosion protection.

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