A method for achieving high corrosion resistance by dynamically converting zinc alloy coatings from superhydrophilic to superhydrophobic

Abstract

The present invention provides a method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic, belonging to the technical field of metal coating anti-corrosion. The method comprises salt spray corrosion, cleaning of the zinc alloy coating, and adsorption in an organic volatile solvent atmosphere. A composite corrosion product film of nano-layered double hydroxide (LDH), basic zinc chloride (ZHC), basic zinc carbonate (HZ), and zinc oxide (ZnO) is generated in situ by salt spray corrosion, and the dynamic adsorption effect of the ambient organic atmosphere is coordinated to achieve a super-hydrophilic to super-hydrophobic conversion on the material surface, thereby improving the material's corrosion resistance. This invention overcomes the limitations of traditional coating technology that relies on complex processes, and has the advantages of being green and environmentally friendly (chromium-free passivation), low cost (material costs reduced by 40%), and long-lasting protection. It is particularly suitable for protecting steel structures in harsh corrosive environments such as marine engineering and shipbuilding.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal coating anti-corrosion, and in particular relates to a method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic. Background Art

[0002] With the rapid development of marine engineering equipment (such as cross-sea bridges and offshore wind power), steel structures serving in wave splash zones face extreme corrosion environments with salt spray, high humidity, and alternating dry and wet conditions. Although traditional hot-dip galvanizing can provide cathodic protection, it suffers from the problems of failure of the coating passivation film and red rust caused by local corrosion in complex marine environments. In order to improve the reliability of the galvanized layer in protecting steel from corrosion, the requirements for the corrosion resistance of the coating are increasing. The development of highly corrosion-resistant Zn-Al-Mg (ZAM) coatings has become a research hotspot. However, the preparation methods of super-hydrophobic coatings in the existing technology often have the following defects: (1) The construction of super-hydrophobic surfaces relies on chemical vapor deposition (CVD) or sol-gel methods, which require the use of toxic reagents such as fluorosilane. (2) The coating is difficult to self-repair after damage, and its long-term protective performance is unstable.

[0003] The atmospheric corrosion behavior of zinc alloy coatings is regulated by the composition structure of corrosion products, which mainly include layered double hydroxides (Zn6Al2(OH) 16 CO3, LDH), basic zinc carbonate (Zn5(OH)6(CO3)2·H2O, HZ), basic zinc chloride (Zn5(OH)8Cl2·H2O, ZHC) and zinc oxide (ZnO), etc. Currently, research on the corrosion protection mechanism of zinc alloy coatings mainly focuses on the effect of corrosion product compactness, while less attention is paid to the contribution of corrosion product hydrophobicity to the corrosion resistance of the coating.

[0004] The applicant's previous research found that the composite corrosion product film of layered double hydroxide (LDH), basic zinc chloride (ZHC), basic zinc carbonate (HZ) and zinc oxide (ZnO) formed on zinc alloy has a unique micro-nano structure, providing an ideal carrier for the adsorption of environmental organic matter. Summary of the Invention

[0005] The present invention addresses the problems existing in the preparation of super-hydrophobic coatings and provides a method for dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic to achieve high corrosion resistance.

[0006] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic is provided, comprising the following steps: (1) salt spray corrosion: subjecting the zinc alloy coating to neutral salt spray corrosion in a salt spray corrosion chamber, and continuously spraying for 3-7 days; (2) cleaning the zinc alloy coating: rinsing the corroded zinc alloy coating with clean water, and allowing it to stand in an environment of 35-40°C for 4-6 hours to form a composite corrosion film layer comprising basic zinc carbonate (HZ), basic zinc chloride (ZHC), zinc oxide (ZnO) and / or nano-layered double hydroxide (LDH); (3) organic solvent adsorption: placing the cleaned zinc alloy coating in a sealed container containing a volatile organic solvent atmosphere at 20-30°C and allowing it to stand for 24-72 hours, and combining the directional adsorption of organic matter in the environment to achieve superhydrophilic-superhydrophobic conversion, thereby forming a superhydrophobic protective layer with corrosion resistance.

[0007] Preferably, in step (1), the salt spray corrosion process parameters are: temperature 33-37 ° C, solution is 5% NaCl solution (pH 6.5-7.2), spray pressure is 0.8-1.2 MPa, salt spray deposition is 1.0-2.0 mL / (80 cm 2 ·h).

[0008] Preferably, in step (3), the organic solvent is one or a mixture of four of benzoin, tetramethyloctanoic acid, butanol and isooctyl alcohol.

[0009] Preferably, the zinc alloy coating comprises the following components: Mg: 0-3%; Al: 0-11%; and the balance is Zn.

[0010] Preferably, the zinc alloy coating is a zinc-aluminum-magnesium alloy coating, and the components of the composite corrosion film layer are a composite of ZHC, LDH, and HZ; further preferably, the zinc alloy is Zn11Al3Mg, and the ratio of ZHC:LDH:HZ in the composite corrosion film layer is 15:4:1.

[0011] Preferably, the super-hydrophobic protective layer obtained in step (3) has a thickness of 3-10 μm, a surface contact angle of >150°, and a surface having a micro-nano multi-level rough structure.

[0012] Beneficial effects of the present invention: The innovation of the present invention lies in that a composite corrosion film comprising basic zinc carbonate (HZ), basic zinc chloride (ZHC) and zinc oxide (ZnO) and / or nano-layered double hydroxide (LDH) is formed in situ by salt spray corrosion, and the dynamic adsorption of the organic atmosphere in the environment is coordinated to accelerate the super-hydrophilic-super-hydrophobic conversion of the material surface. Compared with the existing technology (such as CVD method), the present invention achieves super-hydrophobic properties through a natural adsorption mechanism without the need for an external electric field or toxic reagents. Its technical effects are: (1) Environmental synergistic regulation: By controlling the zinc alloy composition and salt spray corrosion parameters, the LDH and ZHC / ZnO phase ratio and film thickness are precisely controlled. (2) Dynamic adsorption of organic atmosphere: The corrosion product film layer achieves super-hydrophobic coating transformation by dynamically adsorbing / desorbing environmental organic matter. Compared with existing solutions such as immersion in organic solution, the amount used is small and the environmental harm is small. (3) Self-repair function: When the super-hydrophobic protective layer of the zinc alloy coating is mechanically damaged (e.g., scratch width ≤ 200 μm), the exposed corrosion products can re-adsorb organic matter within 24 hours to restore super-hydrophobicity. (4) The core of this invention lies in providing a long-term protection solution for marine engineering equipment (such as steel box girders of cross-sea bridges and offshore wind power foundations) through a ternary synergistic mechanism of corrosion product structure design, organic matter adsorption, and self-repair regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a graph showing the surface contact angle test results of the zinc alloy super-hydrophobic protective layer obtained in Example 1.

[0014] Figure 2 This is a graph showing the surface contact angle test results of the zinc alloy super-hydrophobic protective layer obtained in Example 2.

[0015] Figure 3 This is a graph showing the surface contact angle test results of the zinc alloy super-hydrophobic protective layer obtained in Example 3.

[0016] Figure 4 This is a graph showing the surface contact angle test results of the zinc alloy super-hydrophobic protective layer obtained in Example 4.

[0017] Figure 5 This is a graph showing the surface contact angle test results of the zinc alloy super-hydrophobic protective layer obtained in Example 5.

[0018] Figure 6 1 is the Tafel polarization curve of the zinc alloy super-hydrophobic protective layer 72h obtained in Example 1 and Example 2.

[0019] Figure 7 Nengquist diagram of the electrochemical impedance measurement of the zinc alloy super-hydrophobic protective layer 72h obtained in Example 1 and Example 2. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0021] Example 1:

[0022] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic is provided, comprising the following steps: (1) salt spray corrosion: a zinc-aluminum alloy (Zn5Al) coating is subjected to neutral salt spray corrosion in a salt spray corrosion chamber, wherein the process parameters are: temperature 35°C, solution 5% NaCl solution (pH 7.0), spray pressure 1.0 MPa, and salt spray deposition volume 1.5 mL / (80 cm 2 h), spray continuously for 7 days; (2) cleaning the zinc-aluminum alloy (Zn5Al) coating: rinse the corroded zinc-aluminum alloy (Zn5Al) coating with clean water and let it stand in a 35°C environment for 5 hours to form a composite corrosion film containing nano-layered double hydroxide (LDH), basic zinc carbonate (HZ), basic zinc chloride (ZHC) and zinc oxide (ZnO); (3) volatile organic solvent gas adsorption: place the cleaned zinc-aluminum alloy (Zn5Al) coating in a sealed container containing a volatile organic solvent atmosphere at 30°C and let it stand for 72 hours to allow the organic volatiles to be directionally adsorbed, achieve superhydrophilic-superhydrophobic transformation, and form a superhydrophobic protective layer with corrosion resistance. The ratio of ZHC:LDH:HZ:ZnO in the composite corrosion film obtained in step (2) is 14:3:2:1. In step (3), the volatile organic solvent gas is tetramethyloctanoic acid.

[0023] The zinc alloy super-hydrophobic protective layer obtained in this embodiment has a thickness of 6 μm, a surface contact angle of 164.864°, and a surface with a micro-nano multi-level rough structure.

[0024] Example 2:

[0025] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic is provided, comprising the following steps: (1) salt spray corrosion: a zinc-magnesium alloy (Zn3Mg) coating is subjected to neutral salt spray corrosion in a salt spray corrosion chamber, wherein the process parameters are: temperature 37°C, solution 5% NaCl solution (pH 7.2), spray pressure 1.2 MPa, and salt spray deposition volume 2.0 mL / (80 cm 2h), spray continuously for 3 days; (2) cleaning the zinc-magnesium alloy (Zn3Mg) coating: rinse the corroded zinc-magnesium alloy (Zn3Mg) coating with clean water and let it stand in a 40°C environment for 4 hours to form a composite corrosion film containing basic zinc carbonate (HZ), basic zinc chloride (ZHC) and zinc oxide (ZnO); (3) volatile organic solvent gas adsorption: place the cleaned zinc-magnesium alloy (Zn3Mg) coating in a closed container containing a volatile organic solvent atmosphere at 25°C and let it stand for 72 hours to allow the organic volatiles to be directionally adsorbed, achieve superhydrophilic-superhydrophobic transformation, and form a superhydrophobic protective layer with corrosion resistance. In the step (2), the ratio of ZHC:HZ:ZnO in the composite corrosion film is 16:3:1. In the step (3), the volatile organic solvent gas is butanol.

[0026] The zinc alloy super-hydrophobic protective layer obtained in this embodiment has a thickness of 10 μm, a surface contact angle of 158.449°, and a surface with a micro-nano multi-level rough structure.

[0027] Example 3:

[0028] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic is provided, comprising the following steps: (1) salt spray corrosion: a zinc-aluminum alloy (Zn4Al) coating is subjected to neutral salt spray corrosion in a salt spray corrosion chamber, wherein the process parameters are: temperature 33°C, solution 5% NaCl solution (pH 6.5), spray pressure 0.8 MPa, and salt spray deposition volume 1.0 mL / (80 cm 2 h), spray continuously for 7 days; (2) cleaning the zinc-aluminum alloy (Zn4Al) coating: rinse the corroded zinc-aluminum alloy (Zn4Al) coating with clean water and let it stand in a 35°C environment for 6 hours to form a composite corrosion film containing nano-layered double hydroxide (LDH), basic zinc carbonate (HZ), basic zinc chloride (ZHC) and zinc oxide (ZnO); (3) volatile organic solvent gas adsorption: place the cleaned zinc-aluminum alloy (Zn4Al) coating in a sealed container containing a volatile organic solvent atmosphere at 25°C and let it stand for 24 hours to allow the organic volatiles to be directionally adsorbed, achieve super-hydrophilic-super-hydrophobic transformation, and form a super-hydrophobic protective layer with corrosion resistance. The ratio of ZHC:LDH:HZ:ZnO in the composite corrosion film obtained in step (2) is 14:2:2:1. In the step (3), the volatile organic solvent gas is a mixed gas of benzoin, tetramethyloctanoic acid, butanol and isooctyl alcohol.

[0029] The zinc alloy super-hydrophobic protective layer obtained in this embodiment has a thickness of 3 μm, a surface contact angle of 161.107°, and a surface with a micro-nano multi-level rough structure.

[0030] Example 4:

[0031] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic is provided, comprising the following steps: (1) salt spray corrosion: a zinc-magnesium alloy (Zn2Mg) coating is subjected to neutral salt spray corrosion in a salt spray corrosion chamber, wherein the process parameters are: temperature 37°C, solution 5% NaCl solution (pH 7.2), spray pressure 1.2 MPa, and salt spray deposition volume 2.0 mL / (80 cm 2 h), spray continuously for 3 days; (2) cleaning the zinc-magnesium alloy (Zn2Mg) coating: rinse the corroded zinc-magnesium alloy (Zn2Mg) coating with clean water and let it stand in a 40°C environment for 4 hours to form a composite corrosion film containing basic zinc carbonate (HZ), basic zinc chloride (ZHC) and zinc oxide (ZnO); (3) volatile organic solvent gas adsorption: place the cleaned zinc-magnesium alloy (Zn2Mg) coating in a sealed container containing a volatile organic solvent atmosphere at 25°C and let it stand for 48 hours to allow the organic volatiles to be directionally adsorbed, achieving a super-hydrophilic-super-hydrophobic transition and forming a super-hydrophobic protective layer with corrosion resistance. In the composite corrosion film obtained in step (2), the ratio of ZHC:HZ:ZnO is 15:3:2. In step (3), the volatile organic solvent gas is benzoin.

[0032] The zinc alloy super-hydrophobic protective layer obtained in this embodiment has a thickness of 10 μm, a surface contact angle of 158.074°, and a surface with a micro-nano multi-level rough structure.

[0033] Embodiment 5:

[0034] A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from superhydrophilic to superhydrophobic comprises the following steps: (1) salt spray corrosion: a zinc-aluminum-magnesium alloy (Zn11Al3Mg) coating is subjected to neutral salt spray corrosion in a salt spray corrosion chamber, wherein the process parameters are: temperature 35°C, solution 5% NaCl solution (pH 6.8), spray pressure 1.2 MPa, and salt spray deposition volume 2.0 mL / (80 cm 2h), spray continuously for 5 days; (2) cleaning the zinc-aluminum-magnesium alloy (Zn11Al3Mg) coating: rinse the corroded zinc-aluminum-magnesium alloy (Zn11Al3Mg) coating with clean water and let it stand for 6 hours in a 38°C environment to form a composite corrosion film containing nano-layered double hydroxide (LDH), basic zinc carbonate (HZ), and basic zinc chloride (ZHC); (3) volatile organic solvent gas adsorption: place the cleaned zinc-aluminum-magnesium alloy (Zn11Al3Mg) coating in a closed container containing a volatile organic solvent atmosphere at 25°C and let it stand for 60 hours to allow the organic volatiles to be directionally adsorbed, achieving a super-hydrophilic-super-hydrophobic transition and forming a super-hydrophobic protective layer with corrosion resistance. The ratio of ZHC:LDH:HZ in the composite corrosion film obtained in step (2) is 15:4:1. In step (3), the volatile organic solvent gas is isooctyl alcohol.

[0035] The zinc alloy super-hydrophobic protective layer obtained in this embodiment has a thickness of 8 μm, a surface contact angle of 172.266°, and a surface having a micro-nano multi-level rough structure.

[0036] The surface contact angle of the super hydrophobic protective layer of the zinc alloy coating obtained in Example 1 to Example 5 was measured, and the measurement results are as follows: Figure 1-5 As shown. From the measurement results of the surface contact angle of the zinc alloy coating super hydrophobic protective layer, Examples 1 to 5 are all greater than 150°, showing excellent hydrophobicity. The zinc alloy coating super hydrophobic protective layer obtained in Example 1 and Example 2 was electrochemically tested, and the Tafel polarization curve of 72h is shown as follows Figure 6 As shown in the figure, the Nerquist plot of the electrochemical impedance spectroscopy for 72 h is as follows: Figure 7 As shown. Figure 6 and Figure 7 It can be seen that the zinc alloy super-hydrophobic protective layer obtained in Example 1 and Example 2 has good corrosion resistance.

[0037] The super-hydrophobic protective layer of the zinc alloy coating obtained in Example 1 to Example 5 was subjected to a mechanical damage repair performance test. The scratch width was set to 200um and the depth was set to 4um. The layers were placed in the corresponding organic solvent atmospheres of Example 1 to Example 5, respectively, and the organic solvent was adsorbed for 24 hours. The surface contact angles of the super-hydrophobic protective layer of the zinc alloy coating obtained in Example 1 to Example 5 were measured, and the measured surface contact angles were 162.786°, 156.228°, 158.232°, 155.063°, and 170.205°, respectively, all greater than 150°, indicating excellent hydrophobicity and good self-healing properties.

Claims

1. A method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic, characterized in that: The method comprises the following steps: (1) salt spray corrosion: subjecting the zinc alloy coating to neutral salt spray corrosion in a salt spray corrosion chamber, and continuously spraying for 3-7 days; (2) cleaning the zinc alloy coating: rinsing the corroded zinc alloy coating with clean water, and allowing it to stand in an environment of 35-40°C for 4-6 hours to form a composite corrosion film layer containing basic zinc carbonate, basic zinc chloride and zinc oxide and / or nano-layered double metal hydroxide; (3) volatile organic solvent gas adsorption: placing the cleaned zinc alloy coating in a sealed container containing a volatile organic solvent atmosphere at 20-30°C and allowing it to stand for 24-72 hours to allow the organic volatiles to be directionally adsorbed, thereby achieving a super-hydrophilic-super-hydrophobic transformation and forming a super-hydrophobic protective layer with corrosion resistance.

2. The method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic according to claim 1, wherein: In step (1), the salt spray corrosion process parameters are: temperature 33-37 ° C, solution concentration 5% NaCl solution, solution pH value controlled between 6.5-7.2, spray pressure 0.8-1.2 MPa, salt spray deposition 1.0-2.0 mL / (80 cm 2 ·h).

3. The method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic according to claim 1, wherein: In the step (3), the organic solvent is one or a mixture of four of benzoin, tetramethyloctanoic acid, butanol and isooctyl alcohol.

4. The method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic according to claim 1, wherein: The zinc alloy coating is one of a zinc-magnesium alloy coating, a zinc-aluminum alloy coating or a zinc-magnesium-aluminum alloy coating.

5. The method for achieving high corrosion resistance by dynamically converting a zinc alloy coating from super-hydrophilic to super-hydrophobic according to claim 1, wherein the super-hydrophobic protective layer obtained in step (3) has a thickness of 3-10 μm, a surface contact angle of >150°, and a surface having a micro-nano multi-level rough structure.

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