US-12624226-B2 - Drop casting method to form corrosion protective composite layer

Abstract

A method of reducing corrosion, including coating a surface of a substrate with a corrosion inhibitor to form a coated substrate, and contacting the coated substrate with a corrosive medium, wherein the coated substrate in the corrosive medium has an i corr of less than 0.01 μA cm −2 . The corrosion inhibitor includes polyvinylidene fluoride (PVDF), and a layered double hydroxide (LDH) having a formula of X 2 Al, wherein X is Mg or Zn.

Inventors

• Jwaher M. Alghamdi
• Hissah A. ALQAHTANI
• Nuhu Dalhat Mu'azu

Assignees

• IMAM ABDULRAHMAN BIN FAISAL UNIVERSITY

Dates

Publication Date

20260512

Application Date

20241015

Claims (17)

1. 1 . A method of reducing corrosion, comprising: coating a surface of a substrate with a corrosion inhibitor to form a coated substrate, wherein the coating includes drop casting the corrosion inhibitor onto the surface of the substrate; and wherein the coated substrate when contacted with a corrosive medium has an i corr of less than 0.01 μA cm −2 , wherein the corrosion inhibitor comprises: polyvinylidene fluoride (PVDF); and a layered double hydroxide (LDH) having a formula of X 2 Al, wherein X is Mg or Zn.
2. 2 . The method of claim 1 , wherein the corrosion inhibitor comprises 1-5 wt. % of the LDH and 95-99 wt. % of the PVDF, based on a total weight of the corrosion inhibitor.
3. 3 . The method of claim 1 , wherein the LDH is delaminated and in a form of dispersed flakes in the PVDF.
4. 4 . The method of claim 3 , wherein the PVDF penetrates between and is interfacially bonded with the dispersed flakes of the LDH.
5. 5 . The method of claim 1 , wherein an interlayer anion of the LDH is NO 3 − .
6. 6 . The method of claim 1 , wherein when coated on the substrate the PVDF is porous with an average pore size of 100 nm to 2 μm.
7. 7 . The method of claim 6 , wherein the LDH penetrates and at least partially fills the pores of the PVDF.
8. 8 . The method of claim 6 , wherein the LDH fills at least 80% of the pores of the PVDF.
9. 9 . The method of claim 1 , wherein the coating is performed a single time to form a single layer of the corrosion inhibitor on the surface of the substrate.
10. 10 . The method of claim 1 , wherein the coating is performed by: sonicating the LDH in a solvent for 20-50 minutes to form a homogeneous dispersion; mixing the PVDF into the homogeneous dispersion at a temperature of 30-50° C. for 20-50 minutes to form the corrosion inhibitor; and and drying the drop-casted surface of the substrate at temperature of 140-170° C. for 1-5 hours to form the coated substrate.
11. 11 . The method of claim 10 , wherein the drop-casting is performed a single time.
12. 12 . The method of claim 1 , wherein the substrate is made from at least one material selected from the group consisting of carbon steel, stainless steel, iron, copper, nickel, and alloys thereof.
13. 13 . The method of claim 1 , wherein the corrosive medium comprises an aqueous solution at least one salt selected from the group consisting of an alkali metal salt, an alkaline earth metal salt, and hydrates thereof.
14. 14 . The method of claim 1 , wherein the i corr is determined when the corrosive medium has a temperature of 30-70° C.
15. 15 . The method of claim 1 , wherein the corrosion inhibitor reduces the i corr by at least 200 times compared to the same substrate but without the corrosion inhibitor.
16. 16 . The method of claim 1 , wherein the i corr is determined after contacting the coated substrate with the corrosive medium for at least 24 hours.
17. 17 . The method of claim 1 , wherein the LDH is made by a method comprising: mixing a salt of X and aluminum nitrate in a solvent to form a first mixture; adding sodium nitrate to the first mixture while maintaining a constant pH of 9.5±0.5 and while bubbling with nitrogen to form a second mixture; heating the second mixture to a temperature of 100-150° C. in a sealed autoclave for 1-5 days to form a precipitate; and separating, washing, and drying the precipitate to form the LDH.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a Continuation of U.S. application Ser. No. 18/351,840, now U.S. Pat. No. 12,146,073, having a filing date of Jul. 13, 2023. BACKGROUND Technical Field The present disclosure is directed to a corrosion inhibitor, particularly to a method of reducing corrosion using layered double hydroxide composites. Description of Related Art The “background” description provided herein is to present the context of the disclosure generally. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention. Corrosion causes major issues, whether economic or environmental, in a variety of applications. Thus, research has been performed on determining problems and minimizing damages by lowering the kinetics and altering the mechanism of corrosion. Numerous techniques to preserve metals from corrosion, such as the addition of corrosion-resisting materials (inhibitors), cathodic protection, and coatings, have been developed. Particularly for steel, the most common approach to protect the surface of the metal from corrosion is adding barriers between the surface and the corrosive media. Physical barrier films are formed on the surface as a coating between the metal and the surrounding environment. The application of protective coatings, which typically consist of several layers depending on the final application, delay the chemical corrosion reactions on the surface by isolating the substrate from a corrosive medium. Chromates, which are well-known for their potent ability to prevent corrosion, have been used to prepare two of these layers, the primer, and the pre-treatment. However, hexavalent chromium is known to cause cancer, and numerous efforts have been made to replace it with a more eco-friendly alternative. Therefore, development of corrosion-inhibiting species for chromate-free coatings has been investigated. Polymeric coatings are an effective method to protect metals due to their ability to reduce the rate of diffusion of electrolytes by reducing the permeability of coatings. Polyvinylidene fluoride (PVDF), a semi-crystalline polymer with amorphous and crystalline phases, has excellent processing properties, and chemical and thermal stability and has been employed in coatings. However, the delicate quality of PVDF causes the superhydrophobic covering to be effectively harmed by the grating surface, which diminishes the adhesion to most substrates, bringing about a decline or loss of super-hydrophobicity. Further, the PVDF matrix's free volumes cause a variety of pores or scratches to form, causing the protective film to become permeable to oxygen, water, and ions and allowing the metallic surface to be exposed to the corrosive medium more easily. Long-term corrosion protection is compromised by this, thereby preventing its use in industry. Nanofillers, such as graphene, carbon nanotube, silica, and nano-clay, have been added to the polymeric coatings to overcome this issue and create nanocomposites that are suitable for preventing corrosion on a metallic surface. The incorporated nanomaterials not only impede the diffusion of the penetrant species but also strengthen the structure of the nanocomposite coatings. Inorganic fillers have shown great potential due to improving the properties and reducing the porosity of polymers. Recently, layered double hydroxides (LDHs) (anionic clays) have received attention due to their high reactivity towards organic anionic species. Layered clay materials have a unique two-dimensional structure with hydroxyl groups on the edges and surface. LDHs are considered an inorganic host for different species with positively charged brucite-like layers that are balanced by anions and water molecules between the interlayer regions which allow the possibility to use a wide variety of intercalation compounds. LDH can be represented by the formula [MII1-x MIIIx(OH)2]x+(Ay−)x/y·zH2O where MII (e.g., Mg2+, Ca2+, Cu2+, Mn2+, Ni2+, Zn2+) and MIII are the divalent and trivalent metallic cations (e.g., Al3+, Cr3+, Fe3+, Mn3+, Co3+), respectively. Moreover, LDHs are typically hydrophilic in nature. Many options of modifications are possible by either changing the chemical composition of the hydroxide layer by grafting or replacing the anions at the interlayer galleries. Polymer-clay nanocomposites have advantages such as practicality, low cost, ability to be modified, and potential for improving adhesive properties. Prior to use, the surface of the clay minerals can be altered to be organophilic in order to make them compatible with organic polymers. The organic modification expands the space between layers, which in turn raises the d spacing. As a result, the organic modification encourages polymer or its precursor d