Preparation and application of a composite chitosan polyvinyl acetate metal anticorrosion film

Abstract

Chitosan (CS) and polyvinyl acetate (PVAc) two materials have been widely used in food, beverage industry and anticorrosion coating industry respectively. The application provides a kind of polyvinyl acetate (PVAc) composite chitosan (abbreviated as PVAc-G / CS) metal anticorrosion film, the metal anticorrosion film has excellent biodegradability, and has no significant influence on water quality when applied in water treatment, and the surface morphology and adsorption performance have the characteristics of metal surface corrosion prevention and desalination. A new method is provided for solving the practical application of composite membrane in metal pipeline corrosion prevention, fouling and desalination.

Description

Technical Field

[0001] This invention relates to the preparation and application of a composite chitosan polyvinyl acetate metal anticorrosion film, belonging to the field of environmental protection science and technology. Background Technology

[0002] With the development of the pipeline transportation industry, the problem of scale buildup on the inner walls of pipelines has been a persistent challenge for various industries using pipeline transportation. Scale buildup leads to continuously increasing energy costs and reduced output. Furthermore, it can cause: ① thinning of the pipe wall, reducing its pressure-bearing capacity and potentially causing pipe bursts; ② formation of nodules on the inner wall, increasing the friction coefficient and reducing flow rate; ③ pipeline corrosion and perforation, causing media leakage, pollution, and economic losses; ④ severe corrosion can cause deposits and blockages in water-passing equipment, leading to system malfunctions and even system failure; ⑤ corrosion in water supply pipeline systems can pollute water quality and endanger human health.

[0003] Pipeline corrosion protection technology is a crucial approach to addressing scaling on pipeline walls. Currently, many effective pipeline corrosion protection technologies have been developed both domestically and internationally, with common methods including electrochemical corrosion protection and coating (or membrane) corrosion protection. Electrochemical corrosion protection includes impressed current cathodic protection and sacrificial anode protection. Impressed current protection can negatively impact other pipelines besides the protected one; sacrificial anode protection requires periodic anode replacement, resulting in higher costs. Therefore, anti-corrosion coatings or membranes are a key area for improving metal pipeline corrosion protection. Related to metal anti-corrosion coatings is the treatment of industrial wastewater. Industrial wastewater is characterized by high ion concentration, high salinity, and strong acidity, posing a significant challenge to its transportation.

[0004] For high-concentration ion wastewater, salt ions often deposit in pipelines, forming uneven scale zones on the inner walls of metal pipes. On the one hand, scale formation reduces the pipe's inner diameter, decreasing transport efficiency; on the other hand, areas with scale are more prone to electrochemical corrosion and catalytic reactions. Electrochemical corrosion is faster than chemical corrosion; therefore, one of the primary issues in solving corrosion problems is wastewater desalination. In other words, the metal anti-corrosion film must achieve both corrosion protection and desalination. Therefore, developing composite metal coating technology for metal surface corrosion protection, i.e., metal pipeline corrosion protection and wastewater desalination, is of significant practical importance. Summary of the Invention

[0005] The purpose of this invention is to prepare a composite chitosan-based polyvinyl acetate (PVAc) metal anti-corrosion film or coating. This coating uses non-toxic materials with good biodegradability, achieving both anti-corrosion and desalination effects on metal surfaces. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0006] 1. A composite chitosan-based polyvinyl acetate metal corrosion protection film preparation and application, characterized by comprising the following steps:

[0007] (1) The purchased carbon steel sheet base is sanded, degreased, dehydrated and dried to achieve uniform surface roughness;

[0008] (2) Prepare polyvinyl acetate (PVAc) solutions with concentrations of 0 to 300 g / L, uniformly dip and coat them onto the treated carbon steel sheet substrate, and then screen them by corrosion with NaCl solutions of different concentrations to obtain carbon steel sheet substrates with stable surface properties and excellent hydrophilicity.

[0009] (3) The selected composite chitosan has an adsorption effect on heavy metal copper ions in copper chloride solution with a concentration of 0.5 to 1.5 mmol / L;

[0010] (4) Prepare a chitosan solution with a concentration of 0-1.5%, and uniformly dip it onto the carbon steel sheet substrate of PVAc layer to obtain a polyvinyl acetate metal anti-corrosion film or coating with composite chitosan.

[0011] (5) The polyvinyl acetate composite chitosan is a composite film for metal surface corrosion protection, with excellent corrosion protection and desalination effects.

[0012] 2. The preparation and application of a composite chitosan polyvinyl acetate metal anti-corrosion film according to claim 1, characterized in that: in step (1), the substrate material is a carbon steel sheet with a carbon content of 0.02% to 2%, which can be degreased by surface polishing, degreasing with organic solvents (such as acetone and ethanol), and drying with anhydrous ethanol or natural dehydration;

[0013] 3. The preparation and application of a composite chitosan polyvinyl acetate metal anti-corrosion film according to claim 1, characterized in that: in step (2), 0-300g of PVAc is placed in 1000mL of methanol and stirred evenly. When its concentration is 0-100g / L, it can be evenly coated on the surface of carbon steel sheet to obtain a carbon steel sheet with PVAc coating.

[0014] 4. The preparation and application of a composite chitosan polyvinyl acetate metal anti-corrosion film according to claim 1, characterized in that: after the carbon steel sheet substrate with PVAc coating in step (2) is placed in a NaCl solution with a mass fraction of 1-10% for 12 days and 30 days, the surface properties of the carbon steel sheet substrate with PVAc coating are stable in a 10% NaCl solution.

[0015] 5. The preparation and application of a composite chitosan polyvinyl acetate metal anti-corrosion film according to claim 1, characterized in that: in step (2), the carbon steel sheet substrate with PVAc coating is subjected to low-temperature plasma treatment for 50 min to obtain a carbon steel sheet substrate with excellent hydrophilicity with PVAc coating.

[0016] 6. The preparation and application of a composite chitosan polyvinyl acetate metal anticorrosion film according to claim 1, characterized in that: in step (3), the Langmuir adsorption model and the Freundlich adsorption model are used to determine the effect of chitosan on Cu in the solution. 2+ The adsorption process is more consistent with the Freundlich isothermal adsorption model;

[0017] 7. The preparation and application of a composite chitosan polyvinyl acetate metal anticorrosion film according to claim 1, characterized in that: in step (4), the chitosan solution can be dissolved in 1.5-3% acetic acid solution, and 0.05 mL of glutaraldehyde solution is added to obtain a chitosan solution containing acetic acid and glutaraldehyde (abbreviated as G / CS solution);

[0018] 8. Preparation and application of a composite chitosan polyvinyl acetate metal anti-corrosion film according to claim 1, characterized in that: in step (4), the carbon steel sheet substrate with hydrophilic PVAc coating is vertically immersed in G / CS solution for 25-35s, hung to dry, and the static contact angle is 34-35° to obtain the carbon steel sheet substrate of the composite chitosan polyvinyl acetate metal anti-corrosion film;

[0019] 9. The preparation and application of a composite chitosan polyvinyl acetate metal anticorrosion film according to claim 1, characterized in that: in step (5), the carbon steel sheet substrate without PVAc coating, the carbon steel sheet substrate without G / CS coating, and the carbon steel sheet substrate composite with 0.1-1.5% PVAc-G / CS are immersed in a 1% NaCl solution for 48 hours, and the morphology of the metal anticorrosion film with 0.2% PVAc-G / CS is analyzed by scanning electron microscopy (SEM) and has the characteristics of anticorrosion and desalination.

[0020] The advantages of this invention are: (1) Polyvinyl acetate and chitosan are both materials with excellent biodegradability and have no significant impact on water quality when applied in water treatment; (2) The polyvinyl acetate metal anti-corrosion film with chitosan has good adsorption performance and morphological characteristics, and can achieve both metal surface anti-corrosion and desalination at the same time. Attached Figure Description

[0021] Figure 1 This describes the corrosion of the PVAc monolayer film under different salt concentrations.

[0022] The figures (a), (b), and (c) show corrosion after immersion in 1%, 5%, and 10% NaCl solutions for 12 days, respectively.

[0023] The PVAc concentrations in the diagram are 0, 20, 40, 60, 80, and 100 g / L.

[0024] Figure 2 The corrosion of the PVAc monolayer film after soaking in a 10% salt solution for 30 days.

[0025] The PVAc concentrations in the diagram are 50, 100, 150, 200, 250, and 300 g / L.

[0026] Figure 3 It is a PVAc anti-corrosion film composed of different concentrations of G / CS.

[0027] The order in the figure is: uncoated, 150 g / L PVAc, 0.2%, 0.4%, 0.6%, 0.8%, 1.0%, 1.2% G / CS-PVAc.

[0028] Figure 4 Analysis of the adsorption model of chitosan for copper ions.

[0029] Figure (a) and (b) show the Langmuir adsorption model and the Freundlich adsorption model, 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) Preparation of PVAc metal anti-corrosion film

[0033] Carbon steel sheet substrates that have undergone surface polishing, degreasing with organic solvents (such as acetone and ethanol), and drying with anhydrous ethanol or natural dehydration are vertically immersed in PVAc methanol-water solutions of different concentrations to uniformly coat the surface of the carbon steel sheet substrate, thereby obtaining a carbon steel sheet substrate with a PVAc metal anti-corrosion film.

[0034] (2) Effect of salt concentration on PVAc metal anti-corrosion film

[0035] NaCl solutions with mass fractions of 1-10% were prepared, and the prepared PVAc metal anti-corrosion films were immersed in the salt solutions for 12 days. Uncoated carbon steel sheets were used as a control to observe the anti-corrosion effect. Figure 1 As shown.

[0036] (3) Preparation of composite chitosan-polyvinyl acetate metal anti-corrosion film

[0037] After carbon steel sheets of PVAc were treated on a low-temperature plasma instrument for 45 minutes, the contact angle was reduced to 45.80°. Then, they were vertically immersed in a chitosan solution containing acetic acid and glutaraldehyde at a mass fraction of 0.2% for 30 seconds and hung to dry. The static contact angle reached 34-35°, thus obtaining a polyvinyl acetate metal anti-corrosion film with composite chitosan.

[0038] Example 2

[0039] PVAc solutions with concentrations of 0, 20, 40, 60, 80, and 100 g / L were prepared (uniform coating at low concentrations). NaCl solutions with mass fractions of 1%, 5%, and 10% were selected. The corrosion experiment lasted for 12 days. The corrosion protection effect is as follows: Figure 1 As shown.

[0040] Example 3

[0041] PVAc solutions with concentrations of 50, 100, 150, 200, 250, and 300 g / L were prepared, with a NaCl solution mass fraction of 10%. The corrosion test was conducted for an extended period of 30 days, and the anti-corrosion effect was as follows: Figure 2 As shown.

[0042] Example 4

[0043] PVAc solutions with concentrations of 0.1%, 0.2%, 0.3%, 0.5%, 1.0%, and 1.5% G / CS-150 g / L were prepared. Blank steel sheets and PVAc monolayer films were used as blank groups. The corrosion medium (NaCl solution) had a mass fraction of 1%, and the corrosion experiment lasted for 48 hours. The polyvinyl acetate metal anti-corrosion film with chitosan composite is described below. Figure 3 .

[0044] Example 5

[0045] (1) Measurement of PVAc-G / CS conductivity

[0046] Different concentrations of PVAc-G / CS were immersed in a 1% NaCl solution, and the changes in conductivity before and after immersion for 48 hours were measured using a conductivity meter. The conductivity of the PVAc-G / CS composite membrane decreased compared to the blank system and the single-layer membrane.

[0047] (2) Characterization of the microscopic surface morphology of PVAc-G / CS

[0048] The microstructure and surface conditions of the blank, PVAc-coated monolayer film and PVAc-G / CS composite film before and after corrosion were analyzed by SEM. The corrosion time was 48 h, the corrosion medium was 1% NaCl solution, the concentration of PVAc was 150 g / L, and the composite film with 0.2% chitosan added achieved the anti-corrosion effect on the metal surface.

Claims

1. A method for preparing a composite chitosan polyvinyl acetate metal anticorrosive film, characterized by The method comprises the following steps: (1) treating the purchased carbon steel sheet substrate by sandpaper polishing, oil removal and dehydration drying to achieve uniform surface roughness; (2) preparing a polyvinyl acetate solution with a concentration of 250-300 g / L, uniformly coating the treated carbon steel sheet substrate surface to obtain a carbon steel sheet substrate with a polyvinyl acetate layer; (3) after the carbon steel sheet substrate with the polyvinyl acetate layer is treated by low-temperature plasma for 50 min, it is vertically immersed in a chitosan solution containing acetic acid and glutaraldehyde with a mass fraction of 0.2% to obtain a polyvinyl acetate metal anticorrosive film with a composite chitosan.

2. A method of preparing a composite chitosan polyvinyl acetate metal anticorrosive film according to claim 1, characterized by: In step (1), the substrate material is a carbon steel sheet substrate containing 0.02%-2% carbon, which is treated by surface polishing, organic solvent oil removal and dehydration drying with anhydrous ethanol or natural dehydration.

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