CN113088158B

CN113088158B - Water-based epoxy coating and preparation method and application thereof

Info

Publication number: CN113088158B
Application number: CN202110295164.1A
Authority: CN
Inventors: 廖伯凯; 汪鸿; 万闪; 陈汇凯; 郭兴蓬
Original assignee: Guangzhou University
Current assignee: Guangzhou University
Priority date: 2021-03-19
Filing date: 2021-03-19
Publication date: 2022-04-19
Anticipated expiration: 2041-03-19
Also published as: CN113088158A

Abstract

The invention belongs to the technical field of corrosion prevention, and relates to a water-based epoxy coating, and a preparation method and application thereof. In the epoxy coating, 99.8 percent of epoxy resin and 0.2 percent of nano filler are calculated according to weight fraction, wherein in the nano filler, 20-40 percent of boron nitride, 55-75 percent of ZIF-7 filler and 5 percent of corrosion inhibitor are contained. The two-dimensional nano filler and the ZIF-7 filler responding to pH are added on the basis of the traditional waterborne epoxy resin, so that the corrosion inhibition effect is obvious, the preparation method is simple, safe and nontoxic, and the environment-friendly coating is obtained.

Description

Water-based epoxy coating and preparation method and application thereof

Technical Field

The invention belongs to the technical field of corrosion prevention, and relates to a water-based epoxy coating, and a preparation method and application thereof.

Background

Carbon steel has low price, high yield and excellent strength, and is widely applied to the fields of industry, military, civil use and the like. However, in the process of open-air use, carbon steel is easily subjected to atmospheric corrosion under the action of corrosive particles such as oxygen, water vapor, chloride ions and the like in the atmospheric environment, so that the service life of the carbon steel is influenced, and huge economic loss and potential safety hazards are caused. According to statistics, the loss of carbon steel caused by atmospheric corrosion accounts for more than half of all corrosion types in China every year.

Atmospheric corrosion can be controlled by a plurality of methods, the most applied at present is the use of organic coatings, and with the improvement of environmental protection requirements, the traditional organic coatings can not meet the environmental protection requirements more and more. The water-based epoxy coating uses water to replace an organic solvent, is green, environment-friendly and low in pollution, and is gradually applied to the fields of infrastructure, oil gas, electric power industry and the like. However, the water surface tension is large, the substrate is difficult to infiltrate, shrinkage holes are easy to generate, the water-based epoxy coating has high requirements on the cleanliness of the surface of the material in the construction process, and cannot reach high fullness in high-decoration occasions, so that troubles are brought to the large-scale application of the water-phase coating. The water-based epoxy coating applied in the market at present has poor anti-corrosion effect, and the development of the water-based epoxy coating agent which is pollution-free, pollution-free and highly anti-corrosive has great research significance and market value. Chinese patent application No. 108559361 discloses a preparation method and application of a modified graphene water-based epoxy composite coating, wherein graphene oxide and tannic acid are added into an epoxy resin coating, and a labyrinth effect is formed in the coating by the graphene to inhibit the permeation of water molecules and the like, but the graphene has conductivity, and local galvanic couples are easily generated after moisture is permeated, and the corrosion is promoted. Chinese patent application No. 109181469 discloses a preparation method of graphene-based water-based epoxy resin composite anticorrosive coating liquid, which is characterized in that graphene oxide, a dispersing agent and chitosan are added into an epoxy resin coating, the graphene forms a labyrinth effect in the coating to inhibit the permeation of water molecules and the like, the chitosan is used as a corrosion inhibitor to inhibit the corrosion of metal, but the chitosan has no pH response function, cannot actively protect a metal substrate, and has general corrosion inhibition performance. The boron nitride nanosheet has high specific surface area, good two-dimensional structure and non-conductivity, can form a good labyrinth effect to inhibit water molecules and the like from permeating when being added into a coating, and cannot form galvanic corrosion, so that the boron nitride nanosheet attracts wide attention of various national scholars. ZIF-7 is a nano container, which can encapsulate corrosion inhibitor molecules and actively release the corrosion inhibitor to protect metal under the stimulation of external corrosion medium. According to the invention, the boron nitride nanosheet and the ZIF-7 are combined and added into the water-based epoxy resin, so that the active and passive protection of the coating is realized, the occurrence of galvanic corrosion of the coating is avoided, and the corrosion inhibitor can be actively released to protect metal when the coating is damaged.

Disclosure of Invention

Aiming at the defects that the existing waterborne epoxy coating is poor in corrosion resistance and cannot be actively protected, the invention aims to provide the waterborne epoxy coating, and aims to prepare the waterborne epoxy coating by doping modified h-BN nanosheets and ZIF-7 fillers, so that the technical problem that the existing waterborne epoxy coating is poor in corrosion resistance is solved.

The invention also aims to provide a preparation method of the waterborne epoxy coating.

The invention further aims to provide the application of the waterborne epoxy coating in metal corrosion prevention.

A water-based epoxy coating comprises, by weight, 99.7-99.9% of epoxy resin and 0.1-0.3% of nano filler, preferably 99.8% of epoxy resin and 0.2% of nano filler;

wherein, the nanometer filler comprises 20-40 percent of boron nitride, 55-75 percent of ZIF-7 filler and 5 percent of corrosion inhibitor by weight.

Preferably, the corrosion inhibitor in the ZIF-7 filler containing the corrosion inhibitor is at least one of 5-aminotetrazole, 2,4, 6-triaminopyrimidine, 4-amino-6-hydroxy-2-mercaptopyrimidine and the like, and more preferably, the content of the corrosion inhibitor in the epoxy coating is 5%.

According to another aspect of the present invention, there is provided a method for preparing the water-based epoxy coating, comprising the steps of:

(1) adding boron nitride into DMF, performing ultrasonic treatment on the mixture, centrifuging the centrifuged suspension, filtering, washing and drying to obtain Boron Nitride Nanosheets (BNNS);

(2) adding zinc gluconate, a corrosion inhibitor and benzimidazole into a DMF solution, stirring for reaction, centrifuging, filtering, washing and drying to obtain a nano composite filler corrosion inhibitor @ ZIF-7@ BNNS;

(3) and (3) adding the nano composite filler prepared in the step (2) into water-based epoxy resin, and curing to obtain the epoxy resin coating.

Preferably, the boron nitride in the step (1) is obtained by separation by a mechanical stripping method; the mass volume ratio of the boron nitride to the DMF is 1g: 160-200 mL, preferably 1g:180 mL.

The mixed ultrasound in the step (1) is performed for 2-6 hours at 40-60 ℃; more preferably ultrasonic sound at 50 ℃ for 4 h.

The centrifugal rotating speed in the step (1) is 2000-4000 rpm, preferably 3000 rpm; the centrifugation time is 20-40 min, preferably 30 min.

The mass ratio of the zinc gluconate, the corrosion inhibitor, the benzimidazole and the BNNS in the step (2) is 2-6: 0.4-1.5: 1.5: 0.05-0.4; preferably, the ratio of 2: 0.6: 1.5: 0.1.

the mass-to-volume ratio of the zinc gluconate to the DMF in the step (2) is 2g: 160-200 mL, preferably 2g:180 mL.

The stirring temperature in the step (2) is 25-40 ℃, and preferably 35 ℃; the stirring time is 60-80 h, preferably 72 h.

Preferably, the centrifugation rotating speed in the step (2) is 5000-7000 rpm, preferably 6000rpm, and the centrifugation time is 10-30 min, preferably 20 min. And (3) washing the product prepared in the step (2) by using methanol, and then drying to obtain the composite nano filler.

The curing temperature in the step (3) is 40-60 ℃, preferably 50 ℃, and the curing time is 8-15 hours, preferably 12 hours. The thickness of the epoxy coating is 30-70 μm, preferably 50 μm.

The use of the aqueous epoxy coating for corrosion protection of metals.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) in the waterborne epoxy coating provided by the invention, boron nitride nanosheets and ZIF-7 filler are used as main active ingredients. The boron nitride nanosheet is a two-dimensional material, has a very high specific surface area, can generate a labyrinth effect in a coating, and prolongs the path of water permeating into the metal surface; the raw material zinc gluconate prepared from ZIF-7 is also a corrosion inhibitor and can inhibit the corrosion of metals. The ZIF-7 has a pH response function, and after a metal matrix is corroded, the corrosion inhibitor wrapped by the ZIF-7 can be released to inhibit the metal corrosion behavior.

(2) The waterborne epoxy coating provided by the invention is natural and nontoxic in components, safe to use, environment-friendly, nuisanceless and easy to degrade.

(3) The water-based epoxy coating provided by the invention has the advantages of easily available raw materials and low cost.

(4) The water-based epoxy coating provided by the invention is suitable for large-scale production.

Drawings

FIG. 1 is a three-electrode test system for electrochemical testing of an effect example;

FIG. 2 is an electrochemical impedance spectrum of the epoxy coatings of example 2 and comparative examples 1-3;

FIG. 3 is an electrochemical impedance spectrum of the epoxy coatings of example 2 and comparative examples 1-3 immersed in 3.5 wt% NaCl solution for 12 days;

FIG. 4 is an equivalent circuit diagram of the electrochemical impedance spectroscopy of the epoxy coating of FIG. 2;

FIG. 5 is a polarization curve for the epoxy coatings of example 2 and comparative examples 1-3.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The waterborne epoxy resin in the embodiment and the comparative example of the invention is D-1900 waterborne epoxy resin of Delivery new material company, and other medicines are purchased in the market, and the purity is analytically pure.

Example 1

The preparation method of the corrosion-resistant waterborne epoxy coating comprises the following steps:

(1) adding 1g of boron nitride into 180ml of DMF, performing ultrasonic treatment on the mixture at 50 ℃ for 4h, centrifuging, filtering, washing and drying the centrifuged suspension to obtain Boron Nitride Nanosheets (BNNS);

(2) adding 2g of zinc gluconate, 0.6g of 5-aminotetrazole, 1.5g of benzimidazole and 0.1g of BNNS prepared in the step (1) into 180ml of DMF solution, stirring for 72 hours at 35 ℃, and obtaining the composite nano filler 5-ATZ @ ZIF-7@ BNNS through centrifugation, filtration, washing and drying;

(3) and (3) adding the nano composite nano filler prepared in the step (2) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.05%.

Example 2

The corrosion-resistant epoxy coating comprises the following preparation steps:

(3) and (3) adding the nano composite filler prepared in the step (2) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.1%.

Example 3

(3) and (3) adding the nano composite nano filler prepared in the step (2) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.2%.

Example 4

(2) adding 2g of zinc gluconate, 1.2g of 5-aminotetrazole, 1.5g of benzimidazole and 0.2g of BNNS prepared in the step (1) into 180ml of DMF solution, stirring for 72 hours at 35 ℃, and obtaining the composite nano filler 5-ATZ @ ZIF-7@ BNNS through centrifugation, filtration, washing and drying;

(3) and (3) adding the nano composite nano filler prepared in the step (2) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.1%.

Example 5

(2) adding 2g of zinc gluconate, 0.1g of 5-aminotetrazole, 1.5g of benzimidazole and 0.1g of BNNS prepared in the step (1) into 180ml of DMF solution, stirring for 72 hours at 35 ℃, and obtaining the composite nano filler 5-ATZ @ ZIF-7@ BNNS through centrifugation, filtration, washing and drying;

Example 6

(2) adding 4g of zinc gluconate, 0.6g of 5-aminotetrazole, 1.5g of benzimidazole and 0.1g of BNNS prepared in the step (1) into 180ml of DMF solution, stirring for 72 hours at 35 ℃, and obtaining the composite nano filler 5-ATZ @ ZIF-7@ BNNS through centrifugation, filtration, washing and drying;

Comparative example 1

Initial epoxy coating

Epoxy coatings from commercial sources without any added nanomaterials.

Comparative example 2

The preparation method of the modified epoxy coating without adding the boron nitride nanosheet comprises the following steps

(1) Adding 2g of zinc gluconate, 0.6g of 5-aminotetrazole and 1.5g of benzimidazole into 180ml of DMF solution, stirring for 72 hours at 35 ℃, centrifuging, filtering, washing and drying to obtain a composite nano filler 5-ATZ @ ZIF-7;

(2) and (2) adding the nano composite filler prepared in the step (1) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.1%.

Comparative example 3

The preparation method of the modified epoxy coating without adding ZIF-7 comprises the following steps

(2) and (2) adding the BNNS prepared in the step (1) into the water-based epoxy resin to prepare an epoxy resin coating with the mass fraction of 0.1%.

Effects of the embodiment

Since epoxy coatings are typically applied to metals, all electrochemical tests and characterization were sprayed on Q235 carbon steel. Q235 carbon steel (10 multiplied by 3mm) is polished by water-grinding sand paper of 180#, 400#, 800# and 1200#, and is dried by cold air of a hair drier for standby after being deoiled by ethanol. The treated sample was left on one side (10X 10mm) and the remaining five sides were sealed with a high temperature epoxy resin, and the epoxy resins prepared in comparative example and example were uniformly sprayed on the surface of carbon steel with a spray gun to a curing thickness of 50 μm, a curing temperature of 50 ℃ and a curing time of 12 hours, respectively.

(1) Open circuit potential testing

And (3) putting the sprayed coating into 3.5 wt% of NaCl solution, and adopting a three-electrode system, wherein the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum black electrode. The open circuit potential was measured using the CS350 electrochemical workstation until it stabilized (less than 2mV change in 1 min) and the results are shown in table 1:

TABLE 1 open-Circuit potential test results

(2) Electrochemical impedance testing

And (3) putting the sprayed coating into 3.5 wt% of NaCl solution, and adopting a three-electrode system, wherein the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum black electrode. Measuring electrochemical impedance with CS350 electrochemical workstation at frequency of 10⁵-10^-210 points per doubling. By Zview software to calculate the total resistance R of the circuit_tThe results are shown in table 2:

TABLE 2 open-circuit potential test results

(3) Polarization curve testing

And (3) putting the sprayed coating into 3.5 wt% of NaCl solution, and adopting a three-electrode system, wherein the reference electrode is a saturated calomel electrode, and the counter electrode is a platinum black electrode. The CS350 electrochemical workstation is adopted to measure the polarization curve, and the potential range is-0.2V (vs OCP). The scan rate was 0.5mV/s, and the results are shown in Table 3:

TABLE 3 open-Circuit potential test results

(4) Electrochemical impedance test after 12d of brine soaking

And (3) putting the sprayed coating into 3.5 wt% of NaCl solution, and soaking for 12 d. A three-electrode system is adopted, a reference electrode is a saturated calomel electrode, and a counter electrode is a platinum black electrode. Measuring electrochemical impedance with CS350 electrochemical workstation at frequency of 10⁵-10^-210 points per doubling. Adopting Zview software to carry out fitting and calculating the total resistance R of the circuit_tThe results are shown in table 4:

TABLE 4 open-Circuit potential test results

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A waterborne epoxy coating characterized by: according to weight fraction, the composite material contains 99.9 percent of epoxy resin and 0.1 percent of nano composite filler;

the preparation method of the water-based epoxy coating comprises the following steps:

(1) adding boron nitride into DMF, carrying out ultrasonic treatment on the mixture, and centrifuging, filtering, washing and drying the obtained suspension to obtain boron nitride nanosheets;

(2) adding zinc gluconate, 5-aminotetrazole, benzimidazole and the boron nitride nanosheet prepared in the step (1) into a DMF solution, stirring for reaction, centrifuging, filtering, washing and drying to obtain a nano composite filler;

(3) adding the nano composite filler prepared in the step (2) into water-based epoxy resin, and curing to obtain a water-based epoxy coating;

the mass ratio of the zinc gluconate to the 5-aminotetrazole to the benzimidazole to the boron nitride nanosheet in the step (2) is 2: 0.6: 1.5: 0.1.

2. the waterborne epoxy coating of claim 1, wherein: the mass volume ratio of the boron nitride to the DMF in the step (1) is 1g: 160-200 mL.

3. The waterborne epoxy coating of claim 1, wherein: the mass-to-volume ratio of the zinc gluconate to the DMF in the step (2) is 2g: 160-200 mL.

4. The waterborne epoxy coating of claim 1, wherein:

the stirring temperature in the step (2) is 25-40 ℃; the stirring time is 60-80 h.

5. The waterborne epoxy coating of claim 1, wherein:

the curing temperature in the step (3) is 40-60 ℃, and the curing time is 8-15 h;

the thickness of the epoxy coating is 30-70 mu m.

6. Use of a waterborne epoxy coating according to any of claims 1 to 5 for corrosion protection of metals.