SOLVENT-FREE FUNCTIONALIZED MESOPOROUS CARBON/ZINC OXIDE NANOADDITIVES FOR REMARKABLE IMPROVEMENT IN CORROSION RESISTANCE OF POLYMERIC COATINGS

Abstract

A nanocomposite material is provided. The nanocomposite material includes a mesoporous carbon functionalized with ZnO-loaded polyethyleneimine. The nanocomposite material is a nanocomposite coating used to mitigate corrosion in saline water. The mesoporous carbon is a filler to enhance corrosion resistance properties of an epoxy coating. Additionally, methods for preparing a nanocomposite material and an epoxy coating for use in mitigating corrosion in saline water are provided. The method includes providing epoxy, mesoporous carbon, zinc acetate, polyethyleneimine, methanol, and NaOH; dispersing mesoporous carbon in methanol and zinc acetate to create a mixture; adding NaOH to the mixture; and filtering the nanocomposite material from the first mixture.

Claims

1. A nanocomposite material comprising a mesoporous carbon functionalized with ZnO-loaded polyethyleneimine.

2. The nanocomposite material of claim 1, wherein the nanocomposite material used to mitigate corrosion in saline water.

3. The nanocomposite material of claim 1, wherein the polyethyleneimine is absorbed on a surface of mesoporous carbon.

4. The nanocomposite material of claim 1, wherein the ZnO-loaded polyethyleneimine is 1.2 wt. % of the mesoporous carbon.

5. The nanocomposite material of claim 1, wherein the mesoporous carbon is a filler to enhance corrosion resistance properties of an epoxy coating.

6. The nanocomposite material of claim 5, wherein the epoxy coating is a polymeric coating.

7. The nanocomposite material of claim 1, wherein the nanocomposite material is free of solvents.

8. A method of preparing a nanocomposite material and an epoxy coating for use in mitigating corrosion in saline water, comprising: providing epoxy, mesoporous carbon, zinc acetate, polyethyleneimine, methanol, and NaOH; dispersing mesoporous carbon in methanol and zinc acetate to create a mixture; adding NaOH to the mixture; and filtering the nanocomposite material from the mixture.

9. The method of claim 8, wherein the nanocomposite material is a mesoporous carbon functionalized with ZnO-loaded polyethyleneimine.

10. The method of claim 8, wherein the polyethyleneimine is prepared in a solution with 50 wt. % H.sub.2O.

11. The method of claim 8, further comprising annealing the nanocomposite material.

12. The method of claim 11, wherein the annealing the nanocomposite material occurs at 450 C.

13. The method of claim 8, further comprising coating the nanocomposite material onto a steel substrate.

14. The method of claim 13, wherein the nanocomposite material has a thickness of approximately 1115 m when coated onto a steel substrate.

15. The method of claim 13, further comprising curing the nanocomposite material and steel substrate.

16. The method of claim 15, wherein the curing of the nanocomposite material and steel substrate occurs at approximately 20 C. to 25 C.

17. The method of claim 8, further comprising adding 3.5 wt. % NaCl to the mixture.

18. The method of claim 8, further comprising loading mesoporous carbon with ZnO nanoparticles.

19. The method of claim 18, wherein the ZnO nanoparticles are 1.2 wt. % of the mesoporous carbon.

20. The method of claim 8, further comprising adding a hardener to the mixture.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0037] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the office upon request and payment of the necessary fee.

[0038] Features and advantages of the present disclosure, including, for example, a nanocomposite material and a process and system for solvent-free functionalized mesoporous carbon/zinc oxide nanoadditives, described herein may be better understood by reference to the accompanying drawings in which:

[0039] FIG. 1 is a graph illustrating a thermogravimetric analysis (TG-A) of the functionalized mesoporous carbon (MC-ZnO) and the nanocomposite epoxy coating, according to an embodiment of the present disclosure.

[0040] FIG. 2(a) is a scanning electron microscope (SEM) image of the surface of MC-ZnO loaded with polyethyleneimine (PEI) and corresponding energy dispersive x-ray (EDX) mapping, according to an embodiment of the present disclosure.

[0041] FIG. 2(b) is a SEM image of the surface of MC-ZnO loaded with PEI and corresponding EDX mapping of zinc, according to an embodiment of the present disclosure.

[0042] FIG. 2(c) is a SEM image of the surface of MC-ZnO loaded with PEI and corresponding EDX mapping of nitrogen, according to an embodiment of the present disclosure.

[0043] FIG. 3 is a transmission electron microscopy (TEM) image of MC-ZnO loaded with PEI and an accompanying line mapping, according to an embodiment of the present disclosure.

[0044] FIG. 4(a) is a high-angle annular dark-field (HAADF)-STEM image, according to an embodiment of the present disclosure.

[0045] FIG. 4(b) is a HAADF-STEM elemental mapping image of C, Zn, O, and N within ZnO-loaded PEI functionalized mesoporous carbon, according to an embodiment of the present disclosure.

[0046] FIG. 4(c) is a HAADF-STEM elemental mapping image of Zn within ZnO-loaded PEI functionalized mesoporous carbon, according to an embodiment of the present disclosure.

[0047] FIG. 4(d) is a HAADF-STEM elemental mapping image of N within ZnO-loaded PEI functionalized mesoporous carbon, according to an embodiment of the present disclosure.

[0048] FIG. 5 illustrates views (a) and (b), where (a) is an x-ray diffraction (XRD) graph illustrating the intensity of ZnO particles before loading on mesoporous carbon, according to an embodiment of the present disclosure, and where (b) is an XRD graph illustrating the intensity of ZnO particles after loading on mesoporous carbon, according to an embodiment of the present disclosure

[0049] FIG. 6 is a graph illustrating the evolution of the storage modulus, G, as a function of temperature for pure epoxy coating and nanocomposite MC-ZnO/PEI coating, according to an embodiment of the present disclosure.

[0050] FIG. 7 is an illustration of equivalent electrical circuits for nanocomposite coatings, according to an embodiment of the present disclosure.

[0051] FIG. 8(a) is an electrochemical impedance spectroscopy (EIS) measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 1 day of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0052] FIG. 8(b) is an EIS measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 7 days of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0053] FIG. 8(c) is an EIS measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 15 days of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0054] FIG. 8(d) is an EIS measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 21 days of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0055] FIG. 8(e) is an EIS measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 30 days of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0056] FIG. 8(f) is an EIS measurement of the as-prepared MC-ZnO/PEI nanocomposite coatings after 60 days of immersion in 3.5 wt. % NaCl, according to an embodiment of the present disclosure.

[0057] The reader will appreciate the foregoing details, as well as others, upon considering the following detailed description of certain non-limiting embodiments of the present disclosure.

DETAILED DESCRIPTION

[0058] The present disclosure is generally related to nanocomposite material. More specifically, the present disclosure relates to a nanocomposite coating that includes epoxy and solvent-free zinc oxide (ZnO) nanoparticles decorated mesoporous carbon (MC) loaded with polyethyleneimine (PEI), such as, a corrosion inhibitor referred to as MC-ZnO/PEI. Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are not intended to be drawn to scale.

[0059] A nanocomposite coating, MC-ZnO/PEI, includes epoxy and solvent-free ZnO nanoparticles decorated MC loaded with PEI as a corrosion inhibitor. The nanocomposite material is cost-effective and easy to synthesize which allows the system to be effectively commercialized. The functionalization of mesoporous carbon with ZnO greatly alleviated the amount of zinc powder required in the coating (lower than that required by the existing standard of HG/T3668-2009). Functionalization of mesoporous carbon significantly enhances the corrosion resistance of the epoxy coating rather than the traditional approaches of physically mixing a high content of zinc with epoxy. Additionally, it substantially reduces the amount of ZnO vapor produced during welding, which makes it more environmentally friendly. Accordingly, utilizing this coating eliminates the need for zinc-rich coatings, which compromise zinc powder in exchange for anti-corrosion features.

[0060] In the present disclosure, solvent-free nanoadditives were developed to modify the properties of polymeric coatings. Towards this direction, PEI was absorbed on the surface of mesoporous carbon/loaded with ZnO nanoparticles demonstrating high anti-corrosion properties in saline water. Mesoporous carbon with a surface area of nearly 300 m.sup.3/g exhibits a high-capacity loading of ZnO up to 32%, which acts as inactive nanoparticles preventing the ingress of the hydrated species of chloride. This combination provides superior corrosion protection due to synergistic effects. The corrosion resistance is considerably increased by the addition of 3 wt. % of MC-ZnO/PEI to the epoxy coating (i.e., 1.2 wt. % ZnO added to the epoxy coating). It is noteworthy that the mechanical properties of the epoxy coatings are significantly increased with the addition of the functionalized MC-ZnO/PEI.

[0061] In the present disclosure, mesoporous carbon functionalized with ZnO-loaded PEI was synthesized as a filler to enhance the corrosion resistance properties of the epoxy coating. Mesoporous carbon was loaded with ZnO nanoparticles employing the sol-gel process of created a gel by solvent dissolution. To prepare for synthesis, the materials including epoxy, mesoporous carbon, zinc acetate, polyethyleneimine (having a molecular weight of 60,000 and 50 wt. % in H.sub.2O), methanol, NaOH, and Epicure 3223 from Miller-Stephenson is obtained. First, 0.6 g of mesoporous carbon is dispersed ultrasonically in a 30 mL methanol solution containing 1.2 g of zinc acetate (Zn(CH.sub.3COO).sub.2.Math.2H.sub.2O) for 90 minutes. Then, 15 mL of 0.4 M NaOH/methanol solution was slowly added to the above methanol solution under magnetic stirring. A black powder (Zn(OH).sub.2/MC) within the solution is collected by filtration after 60 minutes of reaction. Finally, ZnO/MC was produced by annealing the black powder at 450 C. for 2 hours under purging of nitrogen.

[0062] Epoxy coatings generally contain only mesoporous carbon. The modified coating contains mesoporous carbon coated with ZnO nanoparticles/PEI loaded. As a first step, 3.0 wt. % of MC-ZnO/PEI is carefully dispersed into the epoxy resin at 815 C. After stirring for 15 minutes, the hardener (Epicure 3223) is added at a 4:1 ratio and is stirred for 5 minutes. Then, the formulated epoxy is coated on the surface of steel substrates by the doctor's blade technique of spreading a thin, uniform layer of the formulated epoxy on the surface of the steel substrate. The coated substrates are kept for curing at room temperature (approximately between 20 C. to 25 C. From this process, a dry film having a thickness of 1115 m is attained.

[0063] Several characterization tools were used to characterize the material. The particle size and the morphology are understood using transmission electron microscopy. The dynamic mechanical properties are explored employing a mechanical analyzer. The corrosion resistance of the as-prepared nanocomposite coatings is evaluated at different immersion time intervals in saline water. Thermogravimetric analysis (TG-A) is performed to explore the loading capacity of zinc nanoparticles.

[0064] FIG. 1 utilizes TG-A to illustrate the loaded amount of ZnO nanoparticles in the mesoporous carbon before and after the addition of MC-ZnO to epoxy. It was found that the remaining weight percentage of ZnO nanospecies after burning in the air was around 32 wt. % loaded in mesoporous carbon. However, after the addition of 3 wt. % of MC-ZnO to the epoxy coating, the loading amount is 1.2 wt. %. The TG-A was performed in the presence of air with a heating rate of 10 C./min.

[0065] FIGS. 2(a)-(c) illustrate a field emission scanning electron microscopy (FE-SEM) image of the surface of MC-ZnO loaded with polyethyleneimine (PEI) and corresponding energy dispersive x-ray (EDX) mapping. FIG. 2(a) illustrates a FE-SEM image of MC-ZnO/PEI. FIG. 2(b) illustrates a FE-SEM image of the MC-ZnO/PEI and corresponding EDX mapping of zinc. FIG. 2(c) illustrates a FE-SEM image of the MC-ZnO/PEI and corresponding EDX mapping of nitrogen.

[0066] FIG. 3 illustrates the transmission electron microscopy (TEM) image and accompanying line scan analysis. This data illustrates that the ZnO has successfully decorated the mesoporous carbon surface with a particle size in the range of 4 nm. In addition, the elemental mapping analysis confirmed that the loading and functionalization of mesoporous carbon with ZnO nanoparticles coated with PEI inhibitors is shown in FIGS. 4(a)-(d).

[0067] FIG. 4(a) depicts a high-angle annular dark-field (HAADF)-STEM image. FIGS. 4(b) to 4(d) depict elemental mapping images of ZnO-loaded PEI functionalized mesoporous carbon where FIG. 4(b) is a HAADF-STEM elemental mapping image of C, Zn, O, and N within ZnO-loaded PEI functionalized mesoporous carbon; FIG. 4(c) is a HAADF-STEM elemental mapping image of Zn within ZnO-loaded PEI functionalized mesoporous carbon; and FIG. 4(d) is a HAADF-STEM elemental mapping image of N within ZnO-loaded PEI functionalized mesoporous carbon.

[0068] FIGS. 5(a) and 5(b) depict the results of the x-ray diffraction (XRD) graph of the as-prepared ZnO particles before and after loading on the mesoporous carbon. The diffraction peaks located at 31.9, 34.52, 36.4, 47.5, 56.6, 63.01, 68.08, and 69.2 are attributed to the hexagonal wurtzite phase of ZnO nanospecies. However, the peak located at 20=19.3 and 29 are ascribed to the PEI.

[0069] FIG. 6 illustrates the dynamic thermomechanical properties (DMA), such as the storage modulus, of the epoxy coating before and after the addition of MC-ZnO/PEI. Specifically, the data of FIG. 6 illustrates the evolution of the storage modulus, G, as a function of temperature for pure epoxy coating and nanocomposite MC-ZnO/PEI coating. It is worth mentioning that the storage modulus of the epoxy and MC-ZnO/PEI significantly increase compared to the pure epoxy indicating the increase of the mechanical properties and the tensile strength. The storage modulus, G, may be dramatically affected by the mass fraction of ZnO nanospecies in the epoxy matrix in glass or rubber states. In addition to the uniform dispersion of the ZnO nanoparticles in the epoxy matrix, the storage modulus of nanocomposite coating is higher than that of pure epoxy which is attributed to the generated van der Waals force between the ZnO nanoparticle surface and the epoxy resin leading to obstructing the movement of the epoxy resin chain segments.

[0070] The corrosion resistance of the pure epoxy and modified coatings was evaluated in saline water using electrochemical impedance spectroscopy (EIS) and was fitted employing the depicted equivalent circuit in FIG. 7. The Nyquist EIS plots of the modified epoxy coatings after immersion in saline water are provided in FIGS. 8(a)-(f). FIG. 8(a) illustrates measurements of the nanocomposite coating after 1 day of immersion in 3.5 wt. % NaCl. FIG. 8(b) illustrates measurements of the nanocomposite coating after 7 days of immersion in 3.5 wt. % NaCl. FIG. 8(c) illustrates measurements of the nanocomposite coating after 15 days of immersion in 3.5 wt. % NaCl. FIG. 8(d) illustrates measurements of the nanocomposite coating after 21 days of immersion in 3.5 wt. % NaCl. FIG. 8(e) illustrates measurements of the nanocomposite coating after 30 days of immersion in 3.5 wt. % NaCl. FIG. 8(f) illustrates measurements of the nanocomposite coating after 60 days of immersion in 3.5 wt. % NaCl.

[0071] Below, Table 1 illustrates the electrochemical fitting parameters of the nanocomposite epoxy coating including the immersion time, R.sub.c, R.sub.ct, C.sub.dl1, and C.sub.dl2. The results were obtained from the fitting of the equivalent circuit as illustrated in FIG. 7.

TABLE-US-00001 TABLE 1 Electrochemical fitting parameters of the nanocomposite epoxy coating. Immersion R.sub.c (k R.sub.ct (k time (days) cm.sup.2) cm.sup.2) C.sub.dl1 (F) C.sub.dl2 (F) Pure epoxy 1 26 3 32 4 0.007 0.002 0.003 0.001 7 8 3 11 2 0.006 0.001 0.004 0.002 14 4.3 3 6.4 1 0.008 0.002 0.006 0.002 21 2.5 2 3.2 4 0.02 0.01 0.008 0.001 28 1.8 3 2.6 3 0.06 0.02 0.04 0.02 60 0.4 4 0.76 0.09 0.03 0.05 0.03 MC-ZnO/PEI 1 44 10.sup.6 2 56 10.sup.6 3 1.2 10.sup.5 1 3.2 10.sup.8 1 nanocomposite 7 6.0 10.sup.6 3 8.0 10.sup.6 2 2.8 10.sup.5 1 2.5 10.sup.7 2 coatings 14 2.8 10.sup.6 2 3.8 10.sup.6 1 1.4 10.sup.4 2 5.1 10.sup.5 2 21 1.6 10.sup.6 1 2.0 10.sup.6 2 1.3 10.sup.4 1 3.2 10.sup.4 1 28 1.2 10.sup.6 2 1.7 10.sup.6 1 9.6 10.sup.5 2 8.4 10.sup.11 2 60 0.98 10.sup.6 1 1.5 10.sup.6 1 5.4 10.sup.5 2 2.3 10.sup.11 1

[0072] R.sub.s signifies electrolyte resistance. The capacitive element is represented by a constant phase element (CPE), where CPE.sub.dl is double-layer capacitance and R.sub.ct is charge transfer resistance. On the other hand, the CPE.sub.c and R.sub.c are attributed to the coating capacitance and coating resistance, respectively. As listed in Table 1. The modified epoxy coating shows a charge transfer resistance (R.sub.ct) of 5.810.sup.10 cm.sup.2 after one day of immersion which is significantly higher than that of the pure epoxy by six orders of magnitude. However, the corrosion resistance alleviated after 7 days of immersion to 810.sup.9 cm.sup.2 compared to 1.110.sup.4 cm.sup.2 of the pure epoxy. It is worth mentioning that the corrosion resistance decreased to 1.510.sup.9 cm.sup.2 after immersion of the modified coating in the saline water for 60 days in comparison to 0.7610.sup.3 cm.sup.2 of the R.sub.ct pure epoxy. Further, the double layer capacitance of the modified epoxy dropped from 3.210.sup.8 F to 3.210.sup.4 F as a result of permeation of the hydrated chloride species through the internal defects of the pure epoxy coating leading to attack the metal surface. The high corrosion resistance is attributed to the effective suppression of the ion exchange between the electrolyte and the steel surface and therefore extends the ions diffusion pathway to reach the carbon steel surface. In addition, the uniform distribution of the ZnO-loaded mesoporous carbon in the epoxy matrix promotes the crosslinking of organic molecules leading to alleviating the crack propagation and consequently declining the corrosion rate.

[0073] The as-prepared material can be easily uniformly dispersed in epoxy resin without any necessity for solvent. In comparison to zinc-rich epoxy coating, the nanocomposite coating with a loading content of 1.2% of ZnO nanoparticles, displayed a high corrosion resistance under continuous immersion in 3.5 wt. % NaCl for 60 days in saline water.

[0074] In other embodiments, this material may be further modified through the inclusion of different nanoparticles and inhibitors to further enhance the corrosion resistance of the epoxy coating.

[0075] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.