A method for preparing a metal corrosion protection composite film containing polyvinyl acetate

Abstract

The application is a preparation method of a metal anticorrosion composite film containing polyvinyl acetate. Polyvinyl acetate (PVAc) is a non-toxic, non-carcinogenic, biodegradable and biocompatible polymer material. The application provides a new method for preparing a metal anticorrosion coating of a polyvinyl acetate-glutaraldehyde / chitosan (PVAc-G / CS) composite film coated on the surface of a carbon steel sheet. After polishing, oil removal and dehydration and drying treatment, the surface roughness of the carbon steel sheet is consistent. First, the carbon steel sheet is vertically immersed in a PVAc solution for 30 s by using a dip coating method, and is hung to dry for 24 h. Then, the sheet is treated by a plasma instrument for 75 min to adjust the hydrophilicity of the surface of the sheet, and is vertically immersed in a G / CS solution for 30 s, and is hung to dry for 24 h to obtain an environmentally friendly PVAc-G / CS composite film. The composite film is non-toxic, simple and environmentally friendly in the preparation process, and has the effects of long-time inhibition of corrosion of the surface of the carbon steel and salt removal, and can open up a new way for metal anticorrosion composite material technology.

Description

Technical Field

[0001] This invention relates to a method for preparing a metal anti-corrosion composite film containing polyvinyl acetate on the surface of a carbon steel sheet substrate. This composite film provides both metal corrosion protection and desalination. It belongs to the field of membrane preparation for environmental protection and surface coatings. Background Technology

[0002] Metal corrosion is a bottleneck hindering increased energy costs and reduced output in pipeline transportation. Globally, approximately 10% of annual metal production is scrapped due to corrosion, resulting in economic losses exceeding one trillion US dollars. The 7th Corrosion Loss Survey in the United States indicates that direct corrosion losses account for about 3.1% of GDP annually. Reports also indicate that my country's economic losses due to corrosion exceeded 3.3 trillion yuan in 2015, approximately 5% of GDP. Therefore, seeking suitable new technologies and materials for metal corrosion prevention or protection has significant economic and social value.

[0003] With the continuous research and development of new material preparation methods and applications, metal surface protective materials have formed four main systems: organic protective coatings, metallic protective coatings, inorganic protective coatings, and composite protective layers, each with its own distinct advantages and disadvantages. Metallic protective coatings primarily rely on sacrificial anodes for protection, resulting in high material consumption, severe pollution, and significant industrial limitations. Organic protective coatings suffer from poor temperature and weather resistance, are prone to aging and cracking, and are highly susceptible to environmental factors, making them difficult to operate in extreme environments. Inorganic protective coatings possess unique advantages such as corrosion resistance, high temperature resistance, and strong adhesion, and are also inexpensive. However, their application requires high precision, hindering widespread adoption. Composite coatings, on the other hand, offer numerous advantages including good protective performance, convenient application, and cost-effectiveness, making them a widely used corrosion protection method. Many studies have also shown that composite coating protection technology, due to its unique metallic structure, is highly favored by researchers in complex and harsh corrosive environments.

[0004] The novel composite layer protection technology employs multiple technologies, structures, and layers to mitigate the performance deficiencies of traditional protective materials while overcoming the limitations of single-layer coatings. This results in more comprehensive, detailed, and long-lasting integrated protection for metal components. In particular, research into environmentally friendly new metal protective coating technologies and materials has become a key direction for the development of metal surface protection technology.

[0005] Polyvinyl acetate (PVAc) is a non-toxic, non-carcinogenic, biodegradable, and biocompatible polymer material that has been widely used in the production of adhesives, varnishes, and coatings. PVAc can adsorb onto metal surfaces to form an anti-corrosion protective coating and slow down the corrosion process. At the same time, PVAc is biodegradable and can decompose through biodegradation after being stripped and discarded when it reaches its expected lifespan. Therefore, it has the potential to prepare environmentally friendly metal anti-corrosion coating materials. That is, the polymer synthesized by chemicals can reduce the impact on the environment. Its biggest features are (1) the use of durable materials that are corrosion-resistant and can be used for a long time, and (2) the materials used can easily decompose into small molecule components that are compatible with the living environment after their expected lifespan. Chitosan (CS) is a commonly used binder, thickener, stabilizer, and gelling agent in industry, and it is also biodegradable. It can be used as a polymeric flocculant for wastewater treatment to effectively capture heavy metal ions and treat wastewater from food processing plants. It is also a natural polymeric chelating agent that can chelate transition metal ions and is used for the enrichment of transition metal ions in salt solutions, natural water, seawater, and saline wastewater. Summary of the Invention

[0006] The purpose of this invention is to utilize the corrosion inhibition effect of polyvinyl acetate (PVAc) on metal surfaces and the natural polymeric chelating agent properties of chitosan. An environmentally friendly preparation method is established for coating metal surfaces with a polyvinyl acetate (PVAc) monolayer film and a polyvinyl acetate-glutaraldehyde / chitosan (PVAc-G / CS) composite film. The resulting PVAc-G / CS composite film exhibits film-forming effect, corrosion resistance, and desalination properties on metal surfaces. To achieve the above objectives, the technical solution adopted by this invention is as follows:

[0007] 1. A method for preparing a metal anti-corrosion composite film containing polyvinyl acetate, characterized by comprising the following steps:

[0008] (1) The carbon steel is sanded, degreased with acetone, and dehydrated and dried with anhydrous ethanol. After treatment, the surface roughness of the substrate is uniform.

[0009] (2) The treated carbon steel sheet substrate was vertically immersed in the PVAc solution by dip coating method, and then hung to dry for 24 hours after 30 seconds to obtain a carbon steel sheet substrate with PVAc coating.

[0010] (3) Use low-temperature plasma to treat carbon steel substrates with PVAc coating to improve the hydrophilicity of PVAc coating and obtain carbon steel substrates with PVAc-G / CS composite film with surface properties that can prevent corrosion and desalinate.

[0011] 2. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1 is characterized in that: in step (1), the carbon steel sheet substrate is a base material of iron-carbon alloy with a carbon content of 0.0218% to 2.11%, and the sheet substrate specifications are 50mm×25mm×2mm and 10mm×10mm×2mm respectively.

[0012] 3. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1 is characterized in that: in step (2), 2.0-3.0g of PVAc is placed in 20-30mL of methanol and stirred for 30-40min at 300-400r / min under constant temperature magnetic stirrer at 300-315K. The prepared PVAc solution is a free-flowing milky white colloidal liquid.

[0013] 4. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1 is characterized in that: in step (2), the concentration of the prepared PVAc solution is 50-200 g / L, and it is uniformly coated on the surface of carbon steel sheet by dip coating.

[0014] 5. A method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1, characterized in that: in step (3), the mass fractions of chitosan solution are 0.1%, 0.2%, 0.3%, 0.5%, 1.0%, and 1.5%, respectively, dissolved in 45-55 mL of 2% acetic acid solution, stirred and dissolved, and allowed to stand for 12-24 hours, and then 0.04-0.06 mL of glutaraldehyde is added to obtain a glutaraldehyde / chitosan (G / CS) solution.

[0015] 6. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1 is characterized in that: in step (3), the carbon steel sheet substrate containing PVAc coating is placed upright in a low-temperature plasma instrument for continuous treatment for 15 to 75 minutes, and then vertically immersed in G / CS solution for 30 seconds by dip coating method, and then hung to dry for 24 hours.

[0016] 7. A method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1, characterized in that: the low-temperature plasma treatment technology in step (3) is used to improve the surface energy of the PVAc-containing carbon steel substrate and the hydrophilicity of the film surface, so that the aqueous G / CS solution adheres to the surface of the carbon steel substrate, and the contact angle of the front side of the carbon steel substrate is reduced to 34.33° by a static contact angle measuring instrument, thus obtaining the carbon steel substrate of the PVAc-G / CS composite film.

[0017] 8. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to technical solution 1 is characterized in that: in step (3), carbon steel substrates of PVAc-G / CS composite films of different concentrations are placed in a NaCl solution with a mass fraction of 1-10%, and the conductivity is measured and the morphology and structure of the composite film are analyzed by scanning electron microscopy (SEM) to confirm that the carbon steel substrates coated with PVAc-G / CS composite film have the effect of inhibiting corrosion on the surface of carbon steel for a long time.

[0018] The advantages of this invention are: (1) By utilizing plasma treatment technology, the surface energy and hydrophilicity of PVAc carbon steel substrate are significantly improved, and an environmentally friendly PVAc-G / CS polymer composite membrane is successfully prepared. This preparation method is simple, environmentally friendly, and feasible. (2) By measuring the corrosion of the carbon steel substrate of the PVAc-G / CS composite membrane under different salt concentrations, its conductivity is determined, and its morphology is characterized by scanning electron microscopy (SEM). The PVAc-G / CS composite membrane with an optimal PVAc concentration of 50-200 g / L and a chitosan percentage of 0.1-0.3% has a long-term inhibitory effect on metal surface corrosion and desalination. Attached Figure Description

[0019] Figure 1 Preparation of PVAc monolayers with different concentrations.

[0020] From left to right, the concentrations are 50g / L, 100g / L, 150g / L, 200g / L, 250g / L, and 300g / L.

[0021] Figure 2 The change in contact angle of PVAc monolayer film substrate with plasma treatment duration.

[0022] The horizontal axis in the graph represents time (min), and the vertical axis represents the contact angle.

[0023] Figure 3 Changes in contact angle of carbon steel sheet substrate under different treatment durations.

[0024] The order shown in the figure represents before treatment, after 15 minutes of treatment, after 45 minutes of treatment, and after 75 minutes of treatment.

[0025] Figure 4 Changes in solution conductivity before and after 48 hours of PVAc composite film corrosion

[0026] The order in the diagram is blank, PVAc single-layer membrane, and composite membranes with 0.1%, 0.2%, 0.3%, 0.5%, 1.0%, and 1.5% content.

[0027] Figure 5 Morphological analysis of carbon steel sheet substrate before and after corrosion using SEM

[0028] Figures (a), (b), and (c) show the blank before etching, a PVAc monolayer film, and a 0.2% PVAc-G / CS composite film, respectively.

[0029] (d), (e), and (f) represent the blank after etching, the PVAc monolayer film, and the 0.2% PVAc-G / CS composite film, respectively. Detailed Implementation

[0030] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto. The equipment or raw materials used in the embodiments are all commercially available.

[0031] Example 1

[0032] (1) Treatment of carbon steel sheet base

[0033] The carbon steel sheet substrate is sanded, degreased with acetone, and dehydrated and dried with anhydrous ethanol to make the surface roughness of the carbon steel sheet substrate uniform.

[0034] (2) Preparation of PVAc solution

[0035] Weigh 15g of PVAc particles and place them in 100mL of high-purity water, acetone and methanol. Heat the mixture in a constant temperature water bath at 313K and stir at 400r / min for 30min to obtain a free-flowing, milky white, colloidal PVAc solution.

[0036] (3) Preparation of PVAc monolayer film

[0037] The dip-coating method was used, in which carbon steel sheets treated with different concentrations were vertically immersed in PVAc solution for 30 seconds, hung to dry for 24 hours, and then used. The results are as follows: Figure 1 As shown, a uniform coating can be achieved with a PVAc solution concentration of 50–200 g / L.

[0038] (4) Preparation of G / CS solution

[0039] Weigh 0.05 g of chitosan and add it to 50 mL of 2% acetic acid solution to prepare a 0.1% chitosan solution. After stirring to dissolve, let it stand for 24 h, then add 0.05 mL of glutaraldehyde. Stir in a 313 K constant temperature water bath at 300 r / min for 30 min to obtain a milky white to yellowish gel-like G / CS solution.

[0040] (5) Treatment of PVAc monolayer film and preparation of PVAc-G / CS

[0041] Carbon steel substrates with PVAc monolayers were treated with a low-temperature plasma instrument, and their contact angles were measured after 15 minutes. Figure 2This describes the change in contact angle of a carbon steel sheet coated with a PVAc monolayer film over plasma treatment time. After the contact angle decreased to 54.39°, the sheet was vertically immersed in a G / CS solution for 30 seconds using a dip-coating method, and then hung to dry for 24 hours before use. Figure 3 (a) Blank, Figure 3 (b) shows the change in contact angle after 15 minutes.

[0042] Example 2

[0043] Similar to Example 1, the difference is that in step (5), the carbon steel substrate of the PVAc monolayer film was treated with a plasma analyzer. After 45 minutes, its contact angle was measured. After the contact angle decreased to 45.80°, it was vertically immersed in G / CS solution for 30 seconds using the dip-coating method, and then hung to dry for 24 hours before use. The results are as follows. Figure 3 As shown in (c).

[0044] Example 3

[0045] Similar to Example 1, the difference is that in step (5), the carbon steel substrate of the PVAc monolayer film was treated with a plasma analyzer. After 75 minutes, its contact angle was measured. After the contact angle decreased to 34.33°, it was vertically immersed in G / CS solution for 30 seconds using the dip-coating method, and then hung to dry for 24 hours before use. The results are as follows. Figure 3 As shown in (d).

[0046] Example 4

[0047] (1) Measurement of PVAc-G / CS conductivity

[0048] Different concentrations of PVAc-G / CS were immersed in a 1% NaCl solution, and the changes in conductivity before and after 48 hours of immersion were measured using a conductivity meter. The results are as follows: Figure 4 As shown, the conductivity of the PVAc-G / CS composite membrane is reduced compared to the conductivity of the blank system and the monolayer membrane.

[0049] (2) Microscopic surface morphology characterization of PVAc-G / CS

[0050] The microstructure and surface conditions of the blank, PVAc-coated monolayer, and PVAc-G / CS composite films before and after corrosion were analyzed using SEM. The corrosion time was 48 h, the corrosion medium was 1% NaCl solution, and the concentration of PVAc was 150 g / L. The composite film with 0.2% chitosan added achieved a corrosion protection effect on the metal surface. Figure 5 As shown.

Claims

1. A method for preparing a metal anti-corrosion composite film containing polyvinyl acetate, characterized in that... Includes the following steps: (1) The carbon steel sheet substrate is sanded, degreased with acetone, and dehydrated and dried with anhydrous ethanol. After treatment, the surface roughness of the sheet substrate is uniform. (2) The treated carbon steel sheet substrate was vertically immersed in the prepared PVAc solution using the dip coating method. After 30 seconds, it was hung to dry for 24 hours to obtain a carbon steel sheet substrate with PVAc coating. (3) Prepare glutaraldehyde / chitosan solution, denoted as G / CS solution, for later use; treat carbon steel sheet substrate with PVAc coating using low temperature plasma, and then vertically immerse it in G / CS solution by dip coating method to improve the hydrophilicity of PVAc coating and obtain carbon steel sheet substrate with PVAc-G / CS composite film on the surface that can prevent corrosion and desalinate.

2. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: In step (1), the carbon steel sheet substrate is a base material of iron-carbon alloy with a carbon content of 0.0218% to 2.11%, and the sheet substrate specifications are 50mm×25mm×2mm and 10mm×10mm×2mm respectively.

3. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: In step (2), the PVAc solution is prepared by placing 2.0-3.0g of PVAc into 20-30mL of methanol and stirring with a constant temperature magnetic stirrer at 300-315K at 300-400r / min for 30-40min. The prepared PVAc solution is a free-flowing milky white colloidal liquid.

4. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: In step (2), the concentration of the PVAc solution is 50-200 g / L, and it is uniformly coated on the surface of the carbon steel sheet using a dip-coating method.

5. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: In step (3), the preparation method of the glutaraldehyde / chitosan solution is as follows: the mass fraction of the chitosan solution is 0.1%, 0.2%, 0.3%, 0.5%, 1.0%, and 1.5%, respectively, and it is dissolved in 45-55 mL of 2% acetic acid solution. After stirring and dissolving, it is allowed to stand for 12-24 hours, and then 0.04-0.06 mL of glutaraldehyde is added to obtain the glutaraldehyde / chitosan solution.

6. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: The specific operation of step (3) is as follows: the carbon steel sheet substrate with PVAc coating is placed upright in the low-temperature plasma instrument for continuous treatment for 15 to 75 minutes, then vertically immersed in G / CS solution for 30 seconds by dip coating method, and then hung to dry for 24 hours.

7. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: The low-temperature plasma treatment in step (3) is used to improve the surface energy of the carbon steel substrate with PVAc coating and the hydrophilicity of the membrane surface, so that the aqueous G / CS solution adheres to the surface of the carbon steel substrate. The static contact angle meter measures that the contact angle of the front side of the carbon steel substrate is reduced to 34.33°, and the carbon steel substrate of PVAc-G / CS composite membrane is obtained.

8. The method for preparing a metal anti-corrosion composite film containing polyvinyl acetate according to claim 1, characterized in that: Step (3) also includes placing carbon steel substrates with different concentrations of PVAc-G / CS composite film into a 1-10% NaCl solution, measuring the conductivity and analyzing the morphology of the composite film using scanning electron microscopy (SEM), confirming that the carbon steel substrate coated with PVAc-G / CS composite film has the effect of inhibiting corrosion and desalination of carbon steel surface for a long time.

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