A method for preparing a gallic acid-isopropanol amine-terminated hydroxyamide type rust converter

Abstract

This invention discloses a method for preparing a gallic acid-isopropanolamine-terminated hydroxyamide rust converter, belonging to the field of new materials technology for steel protection, and solving the problem of rust protection for steel. The method of this invention includes the following steps: (1) drying gallic acid and isopropanolamine to remove water; (2) dissolving the pretreated gallic acid and isopropanolamine in deionized water and stirring to obtain a water-soluble salt-forming intermediate; (3) heating the water-soluble salt-forming intermediate under reflux to carry out a dehydration condensation reaction to generate a condensation reaction solution; (4) cooling the condensation reaction solution to room temperature, filtering to remove impurities, and obtaining a gallic acid-isopropanolamine-terminated hydroxyamide rust converter. The preparation process of this invention is mild, simple to operate, free of toxic raw materials, and does not produce harmful byproducts. The obtained rust converter has strong chelating and rust-converting ability, dense film formation, and excellent adhesion. It can achieve integrated corrosion protection of rust conversion, passivation, and sealing with a single reagent, and is suitable for direct protection of rusted steel components.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology for steel protection, specifically a method for preparing a gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter. Background Technology

[0002] Steel components are highly susceptible to oxidation and corrosion in natural environments. The rust products are porous, chemically reactive, and continuously accelerate the corrosion of the substrate, significantly shortening the service life of the steel structure. Traditional rust removal methods often employ mechanical grinding, sandblasting, and acid pickling, which are cumbersome, pollute the environment, are costly, and difficult to handle complex structures. Using rust conversion agents can directly transform active rust into an inert passivation film, achieving direct corrosion protection even with rust present, representing an important technological direction for steel protection.

[0003] Existing rust converters mostly use single organic acids such as tannic acid, oxalic acid, and citric acid as their core components. They generally suffer from drawbacks such as weak chelating ability, incomplete rust conversion, poor film formation, insufficient water resistance, easy rust recurrence, and low adhesion to the substrate. Furthermore, their functions are limited, failing to simultaneously achieve integrated protection through rust conversion, passivation, and sealing. While some modified rust converters improve water solubility, they sacrifice chelating activity and film stability, making it difficult to meet long-term corrosion protection requirements. Therefore, developing a novel rust converter with high chelation, strong film formation, high anchoring, and synergistic multi-layered corrosion protection is crucial to solving the problem of efficient protection against rust on steel. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing gallic acid-isopropanolamine terminal hydroxyl amide type rust converter. The rust converter obtained by the method retains the strong chelating site of the ortho-triphenol hydroxyl group and has both amide bond and terminal hydroxyl bifunctional group. It can completely convert rust, form a dense film, have excellent adhesion, and resist water and rust recurrence, thus realizing the triple functions of rust conversion, passivation and sealing.

[0005] The present invention solves the above-mentioned technical problems by means of the following technical solution:

[0006] The preparation method of the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter of the present invention includes the following steps:

[0007] (1) Raw material pretreatment: Gallic acid and isopropanolamine are dried to remove water;

[0008] (2) Preparation of water-soluble salt-forming intermediate: Gallic acid and isopropanolamine, which were pretreated in step (1), are dissolved in deionized water and stirred at room temperature. The molar ratio of gallic acid to isopropanolamine is 1: (1-3), so that the carboxyl group and the primary amine undergo acid-base salt formation to obtain the water-soluble salt-forming intermediate.

[0009] (3) Preparation of condensation reaction solution: The water-soluble salt-forming intermediate obtained in step (2) is heated to 65-80°C and refluxed with a condenser to carry out dehydration condensation reaction, generating crude product condensation reaction solution containing amide bonds and retaining ortho-triphenol hydroxyl groups;

[0010] (4) Preparation of rust conversion agent: Cool the condensation reaction solution obtained in step (3) to room temperature, filter to remove impurities, and obtain gallic acid-isopropanol amine-terminated hydroxy amide rust conversion agent.

[0011] In step (1) of this invention, the drying and dehydration refers to drying in a vacuum drying oven at a temperature of 50-60°C for 15-30 minutes.

[0012] In step (1) of this invention, the purity of gallic acid is ≥99%, and isopropanolamine is analytical grade.

[0013] In step (2) of this invention, the stirring is carried out by magnetic stirring or mechanical stirring, and the stirring speed is 400-600 r / min.

[0014] In step (2) of this invention, when preparing the water-soluble salt-forming intermediate, gallic acid is first dissolved in deionized water, with the mass ratio of deionized water to gallic acid being 1:(4-8). Then isopropanolamine is added, and the mixture is stirred at room temperature for 25-40 min until the system is homogeneous.

[0015] In step (3) of this invention, when preparing the condensation reaction solution, the water-soluble salt-forming intermediate is heated to 65-80°C at a heating gradient of 3-5°C / min.

[0016] In step (3) of this invention, when preparing the condensation reaction solution, the time for the condensation and dehydration condensation reaction by condensing and refluxing with a condenser is 4 to 6 hours.

[0017] The filtration and impurity removal in step (4) of this invention is carried out in a rotary evaporator at a temperature of 50-60°C.

[0018] The method of the present invention has the following beneficial effects:

[0019] (1) The rust converter prepared by the method of the present invention has strong chelating rust-converting properties: the present invention can completely retain the ortho-triphenolic hydroxyl structure of gallic acid, and has strong chelating rust-converting properties for Fe. 2+ / Fe 3+ Its chelating ability is far superior to that of ordinary single organic acids such as tannic acid, oxalic acid, and citric acid. It can completely convert active rust into inert phenol-iron chelates that are insoluble in water, thus stopping corrosion at its source.

[0020] (2) The rust converter prepared by the method of the present invention has excellent film-forming and water-resistant properties: The present invention adopts a special structure of amide bond skeleton + terminal hydroxyl group, which significantly improves film-forming properties, water resistance and aging resistance.

[0021] (3) The rust conversion agent prepared by the present invention has excellent rust penetration ability: The present invention contains a variety of polar groups, which have excellent rust penetration ability. The terminal hydroxyl groups can form hydrogen bonds / chemical bonds with the steel matrix, resulting in high film adhesion and no peeling.

[0022] (4) The rust conversion agent prepared by the present invention has multiple synergistic anti-corrosion properties. It can achieve integrated protection of rust conversion, passivation and sealing with a single reagent, and is easy to construct.

[0023] (5) The preparation process adopted in this invention is green and safe: the preparation process of this invention is mild, simple to operate, has no toxic raw materials, does not produce harmful by-products, is energy-saving and environmentally friendly, the raw materials are readily available and the cost is low, and the condensation reaction can be carried out under normal pressure and closed conditions. Attached Figure Description

[0024] Figure 1 The images show surface and cross-sectional scanning electron microscope (SEM) images of Q235 steel plates before and after treatment with the rust-converting agent obtained in Example 1 of this invention. Figure 1 a is a scanning electron microscope image of the surface before processing. Figure 1 b is a scanning electron microscope image of the processed surface. Figure 1 c is a cross-sectional scanning electron microscope image before processing. Figure 1 d is the processed cross-sectional scanning electron microscope image.

[0025] Figure 2 This is an electrochemical polarization curve of the rust converter obtained in Example 1 of the present invention after rust conversion.

[0026] Figure 3 This is an electrochemical polarization curve of the rust converter obtained in Example 2 of the present invention after rust conversion.

[0027] Figure 4 This is an electrochemical polarization curve of the rust converter obtained in Example 3 of the present invention after rust conversion. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] A method for preparing a gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter is as follows:

[0031] (1) Raw material pretreatment: Gallic acid with a purity of ≥99% and analytical grade isopropanolamine were selected. 17.01g of gallic acid and 7.51g of isopropanolamine (the molar ratio of gallic acid to isopropanolamine was 1:1) were weighed and placed in a vacuum drying oven at 50℃ for 20min to remove water.

[0032] (2) Preparation of water-soluble salt-forming intermediate: Add the dried gallic acid to deionized water at a mass ratio of 1:4. Stir magnetically at room temperature until completely dissolved. Then slowly add isopropanolamine and stir at 400 r / min for 30 min until the system is homogeneous and transparent to obtain the water-soluble salt-forming intermediate.

[0033] (3) Preparation of condensation reaction solution: The water-soluble salt-forming intermediate is heated to 65°C at a heating rate of 4°C / min, and the dehydration condensation reaction is carried out by reflux condensation with a condenser for 4 hours to generate a crude product condensation reaction solution containing amide bonds and retaining the ortho-triphenol hydroxyl groups.

[0034] (4) Preparation of gallic acid-isopropanolamine-terminated hydroxyamide rust converter: The condensation reaction solution was cooled to room temperature and then purified by rotary evaporation at 50°C to obtain a dark brown gallic acid-isopropanolamine-terminated hydroxyamide rust converter, named RC-HTA rust converter.

[0035] The rust converter obtained in this embodiment retains the strong chelating site of the ortho-triphenolic hydroxyl group of gallic acid, while introducing a bifunctional group consisting of an amide bond and a terminal hydroxyl group. When the prepared RC-HTA rust converter is applied to the surface of Q235 rust-prone steel plate, it can form a stable and dense chelate with the rust, achieving complete rust conversion. See Figure 1 , Figure 1 Image a is a surface SEM image of a pure rust layer, showing numerous needle-like and spherical structures, typical of rust morphology. Figure 1 As can be seen from b, after treatment with the rust-converting agent RC-HTA of this invention, a continuous, dense, and non-porous dense chelated film is formed on the steel surface. The film uniformly covers the original rust layer, achieving complete encapsulation and transformation of the rust layer. Figure 1 As can be seen from c, the cross-sectional morphology before RC-HTA treatment shows many voids, corrosive media, and interfacial gaps. Figure 1 After RC-HTA treatment, there are no obvious interface gaps.

[0036] The preparation process used in this embodiment is carried out entirely under normal pressure and ≤70℃ conditions. It is simple to operate, does not use toxic raw materials, and produces no harmful byproducts. It meets the design requirements for energy conservation and environmental protection and is suitable for direct corrosion protection of rusted steel components such as carbon steel and cast iron.

[0037] The electrochemical polarization curves of the carbon steel samples treated with the rust-converting agent obtained in this embodiment are shown in the figure. Figure 2 The corrosion potential of the treated sample (RC-HTA) was significantly positively shifted compared to the bare steel (Q235), and the corrosion current density of Q235 was above 10. -4 ~10 -3 A / cm 2The corrosion current density of the treated sample (RC-HTA) was 10. -6 ~10 -5 A / cm 2 It is two orders of magnitude lower than the substrate.

[0038] Example 2

[0039] A method for preparing a gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter is as follows:

[0040] (1) Raw material pretreatment: Gallic acid with a purity of ≥99% and analytical grade isopropanolamine were selected. 17.01g of gallic acid and 15.02g of isopropanolamine (the molar ratio of gallic acid to isopropanolamine was 1:2) were weighed and placed in a vacuum drying oven at 60℃ for 15min to remove water.

[0041] (2) Preparation of water-soluble salt-forming intermediate: Add the dried gallic acid to deionized water at a mass ratio of 1:6. Stir mechanically at room temperature until completely dissolved, then slowly add isopropanolamine and stir at 500 r / min for 25 min until the system is homogeneous and transparent to obtain the water-soluble salt-forming intermediate.

[0042] (3) Preparation of condensation reaction solution: The water-soluble salt-forming intermediate is heated to 70°C at a heating rate of 5°C / min, refluxed by condenser, and condensed under normal pressure for 5h to generate crude product condensation reaction solution containing amide bond and retaining ortho-triphenol hydroxyl group.

[0043] (4) Preparation of gallic acid-isopropanolamine-terminated hydroxyamide rust converter: The condensation reaction solution was cooled to room temperature and then purified by rotary evaporation at 55°C to obtain a dark brown gallic acid-isopropanolamine-terminated hydroxyamide rust converter, named RC-HTA rust converter.

[0044] In this embodiment, a higher proportion of isopropanolamine is introduced, which increases the content of terminal hydroxyl groups in the rust converter, further enhancing its chelating ability with rust and its bonding force with the matrix.

[0045] The electrochemical polarization curves of the carbon steel samples treated with the rust-converting agent obtained in this embodiment are shown in the figure. Figure 3 The corrosion potential of the treated sample (RC-HTA) was significantly positively shifted compared to the bare steel (Q235), and the corrosion current density of Q235 was above 10. -4 ~10 -3 A / cm 2 The corrosion current density of the treated sample (RC-HTA) was 10. -8 ~10 -7 A / cm 2 It is four orders of magnitude lower than the substrate.

[0046] Example 3

[0047] A method for preparing a gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter is as follows:

[0048] (1) Raw material pretreatment: Gallic acid with a purity of ≥99% and analytical grade isopropanolamine were selected. 17.01 g of gallic acid and 22.53 g of isopropanolamine (the molar ratio of gallic acid to isopropanolamine was 1:3) were weighed and placed in a vacuum drying oven at 55℃ for 30 min to remove water.

[0049] (2) Preparation of water-soluble salt-forming intermediate: Add the dried gallic acid to deionized water at a mass ratio of 1:8. Stir magnetically at room temperature until completely dissolved. Then slowly add isopropanolamine and stir at 600 r / min for 40 min until the system is homogeneous and transparent to obtain the water-soluble salt-forming intermediate.

[0050] (3) Preparation of condensation reaction solution: The water-soluble salt-forming intermediate is heated to 80°C at a heating rate of 3°C / min, refluxed by condenser, and condensed under normal pressure for 6 hours to generate crude product condensation reaction solution containing amide bond and retaining ortho-triphenol hydroxyl group.

[0051] (4) Preparation of gallic acid-isopropanolamine-terminated hydroxyamide rust converter: The condensation reaction solution was cooled to room temperature and then purified by rotary evaporation at 60°C to obtain a dark brown gallic acid-isopropanolamine-terminated hydroxyamide rust converter, named RC-HTA rust converter.

[0052] The electrochemical polarization curves of the carbon steel samples treated with the rust-converting agent obtained in this embodiment are shown in the figure. Figure 4 The corrosion potential of the treated sample (RC-HTA) was significantly positively shifted compared to the bare steel (Q235), and the corrosion current density of Q235 was above 10. -4 ~10 -3 A / cm 2 The corrosion current density of the treated sample (RC-HTA) was 10. -11 ~10 -10 A / cm 2 It is 7 orders of magnitude lower than that of the substrate.

[0053] The rust converter obtained in this embodiment retains the strong chelating site of the ortho-triphenol hydroxyl group of gallic acid, and introduces a bifunctional group of amide bond and terminal hydroxyl group, which can form a stable five-membered chelate with rust to achieve complete rust conversion.

Claims

1. A method for preparing a gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter, characterized in that, The following steps are included: (1) Raw material pretreatment: Gallic acid and isopropanolamine are dried to remove water; (2) Preparation of water-soluble salt-forming intermediate: Gallic acid and isopropanolamine, which were pretreated in step (1), were dissolved in deionized water and stirred and mixed at room temperature; the molar ratio of gallic acid to isopropanolamine was 1: (1-3), so that the carboxyl group and the primary amine could form an acid-base salt to obtain a water-soluble salt-forming intermediate. (3) Preparation of condensation reaction solution: The water-soluble salt-forming intermediate obtained in step (2) is heated to 65-80°C and condensed under reflux using a condenser to carry out dehydration condensation reaction to generate condensation reaction solution; (4) Preparation of rust conversion agent: Cool the condensation reaction solution obtained in step (3) to room temperature, filter to remove impurities, and obtain gallic acid-isopropanol amine-terminated hydroxy amide rust conversion agent.

2. The preparation method of the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1, characterized in that, In step (1), the drying and dehydration refers to drying in a vacuum drying oven at a temperature of 50-60℃ for 15-30 minutes.

3. The preparation method of the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1 or 2, characterized in that, In step (1), the purity of gallic acid is ≥99%, and isopropanolamine is of analytical grade.

4. The preparation method of the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1 or 2, characterized in that, In step (2), the stirring operation is carried out by magnetic stirring or mechanical stirring, and the stirring speed is 400-600 r / min.

5. The method for preparing the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1 or 2, characterized in that, In step (2), when preparing the water-soluble salt-forming intermediate, gallic acid is first dissolved in deionized water at a mass ratio of 1:(4-8) between deionized water and gallic acid. Then isopropanolamine is added and stirred at room temperature for 25-40 minutes until the system is homogeneous.

6. The method for preparing the gallic acid-isopropanol amine-terminated hydroxyl amide rust converter according to claim 1 or 2, characterized in that, In step (3), when preparing the condensation reaction solution, the water-soluble salt-forming intermediate is heated to 65-80°C at a heating gradient of 3-5°C / min.

7. The method for preparing the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1 or 2, characterized in that, In step (3), when preparing the condensation reaction solution, the condensation reaction time using a condenser tube for reflux dehydration is 4 to 6 hours.

8. The method for preparing the gallic acid-isopropanol amine-terminated hydroxyl amide type rust converter according to claim 1 or 2, characterized in that, The filtration and impurity removal in step (4) is carried out in a rotary evaporator at a temperature of 50-60°C.

Images