Corrosion protection of the metal substrate

Abstract

A composition comprising a carrier medium, a first corrosion inhibitor, and a second corrosion inhibitor having a barrier mechanism, wherein the first corrosion inhibitor comprises at least one of ion-exchanged pigment, silica, calcium-exchanged silica, magnesium oxyaminophosphate, and / or a mixture of an organic amine, phosphoric acid and / or inorganic phosphate, and a metal oxide and / or metal hydroxide, and the second corrosion inhibitor comprises one or more 2D material platelets, wherein the 2D material platelets comprise one or more 2D material nanoplates and / or one or more layered 2D material nanoplates and / or graphite flakes, wherein the graphite flakes have one nanoscale dimension and 35 or fewer atomic layers.

Description

Technical Field

[0001] The present invention relates to the corrosion protection of metal substrates. In particular, this application is related to the corrosion protection of metal substrates such as, but not limited to, steel, aluminum, aluminum alloys, and magnesium alloys.

Background Art

[0002] The corrosion of metals is estimated to cost about 3% of the world's gross domestic product (GDP) and constitutes an important aspect of the world economy. There is great interest in the development of new and improved rust prevention technologies, particularly rust prevention coatings. Rust prevention coatings are generally classified according to the mechanisms by which they function. Two common mechanisms are barrier protection and inhibition or passivation of the substrate.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Coatings that employ the barrier mechanism, so-called barrier coatings, can be used as primer, intermediate or topcoat coatings and are commonly used for structures immersed in water or on the ground. Barrier coatings are typified by the use of inert pigments such as micaceous iron oxide, glass flakes, and lamellar aluminum. These systems are usually used as high pigment volume concentration (PVC) systems and provide high density coatings with significantly reduced permeability to water and other aggressive species. The level of protection depends greatly on the thickness of the coating and the number of coats, and it has been reported that the highest performance is provided when the coating thickness is composed of several thin coats.

[0004] The most common pigments used in barrier coatings are micaceous iron oxides. Optimal performance is obtained with a reduced PVC in the range of 0.5% to 1.5%. When lamellar aluminum is used as a pigment, it is typically of the leafing grade. Aluminum-based paints or coatings need to be applied as the first coating that affects cathodic disbonding. Aluminum can also corrode at high and low pH and can therefore corrode by reaction with hydroxyl groups formed at the cathode of any electrochemical cell formed at the metal substrate / coating interface. The use of glass flakes is typically limited to very thick coatings because of the large size of the flakes (100 μm to 1000 μm).

[0005] Coatings that employ a suppression or passivation mechanism, so-called inhibitive coatings, function by the reaction of the components / pigments of the coating with the metal substrate and are therefore mainly applied as primers. These coatings are preferentially used where the substrate is exposed to atmospheric corrosion and are not used where it is immersed in water or soil. The inhibition mechanism relies on the passivation of the metal and the formation of a layer of metal complexes as a result of the passivation reaction. The metal complexes prevent the transport of aggressive species such as Cl - or H + ions and dissolved oxygen to the metal of the substrate.

[0006] The active ingredients / pigments of inhibitive coatings are typically slightly water-soluble and generate cations in solution. Phosphates are commonly used, but chromates, molybdates, nitrates, borates, and silicates are also used. The choice of active ingredients is increasingly subject to regulatory pressure due to growing concerns about the environment and health and safety.

[0007] Current regulations limit the materials that can be used in inhibitor coatings. Chromium(VI) compounds are subject to authorization under REACH (2008 Annex XIV). Other legislation related to anti-corrosion pigments includes the ELV (End of Life Vehicle) Directive, which phased out lead pigments since 2003, and the inclusion of chromium(VI) in primers and pretreatments since 2007. Other regulations include the WEEE (Waste Electrical and Electronic Equipment Directive 2006) and the RoHS (Restriction of Hazardous Substances Directive 2002), which restricted the use of Cr(VI) in white goods. In the United States, OSHA (Occupational Safety and Health Administration Regulations 2006) limits the permissible exposure of employees to Cr(VI) to 52 μg / m 3 to 5 μg / m 3 The zinc phosphate content has been reduced to 100%. Zinc phosphate is highly toxic to aquatic organisms and has raised concerns due to its potential long-term adverse effects on the aquatic environment. Accidental ingestion of the material can be harmful to an individual's health. Soluble zinc salts cause gastrointestinal irritation and corrosion, accompanied by pain and vomiting. Therefore, reducing or eliminating such materials from anticorrosion coatings is beneficial.

[0008] The inhibitory pigment mechanism is based on the partial dissolution of the pigment by water diffusing into the coating. At the surface of the metal substrate, the dissolved ions react with the metal, forming reaction products that passivate the surface. It is important that the inhibitory pigment has a high enough solubility to release ions for the reaction. However, too high a solubility can lead to blistering at the metal substrate / coating interface. An ideal inhibitor coating must form a barrier against water and harmful ions while simultaneously releasing a sufficient amount of inhibitor ions. These two requirements are essentially antagonistic, and an inhibitor coating must balance the barrier properties of the coating (the lower the permeability, the better the barrier properties) with the ability of the pigment to solvate (the higher the permeability, the greater the solvation and migration of ions), generating ions that migrate to the coating-substrate interface. Pigments used in inhibitor coatings can be classified according to their effect on the anodic and cathodic reactions formed at the metal substrate / coating interface in an electrochemical cell.

[0009] Cathodic inhibitors (typically inorganic salts of magnesium and manganese) inhibit corrosion at the cathode by reacting with hydroxyl ions to form insoluble deposits, increasing the cathodic resistance to polarization. Anodic inhibitors similarly reduce the corrosion rate by increasing anodic polarization at the anode.

[0010] Phosphates, and especially zinc phosphate, are widely used on some metals, such as steel. Zinc phosphate relies on the passivation of the steel by precipitation of basic salts and polarization of the negative cathodic zone. The mechanism of formation of insoluble iron phosphate occurs via: [ka] [Means for solving the problem]

[0011] According to the present invention, there is provided a composition comprising a carrier medium, a first corrosion inhibitor (wherein the first corrosion inhibitor comprises at least one of an ion-exchange pigment, silica, calcium-exchanged silica, magnesium oxyaminophosphate, and / or a mixture of an organic amine, phosphoric acid and / or inorganic phosphate, and a metal oxide and / or a metal hydroxide), and a second corrosion inhibitor (wherein the second corrosion inhibitor comprises one or more 2D material platelets, and wherein the 2D material platelets comprise one or more nanoplatelets of a 2D material and / or one or more nanoplatelets of a layered 2D material and / or graphite flakes, and wherein the graphite flakes have a nanoscale dimension and 35 or fewer atomic layers).

[0012] 2D materials (sometimes also called monolayer materials) are crystalline materials consisting of a single layer of atoms. Layered 2D materials are composed of layers of 2D materials that are weakly stacked or bonded to form a three-dimensional structure. The thickness of the nanoplatelets of 2D materials and layered 2D materials is below the nanoscale, and the other two dimensions are generally at a scale larger than the nanoscale.

[0013] The 2D materials used in the composition of the present invention can be graphene (C), hexagonal boron nitride (hBN), molybdenum disulfide (MoS2), tungsten diselenide (WSe2), silicene (Si), germanene (Ge), graphyne (C), borophene (B), phosphorene (P), or a 2D in-plane heterostructure of two or more of the aforementioned materials.

[0014] The layered 2D materials can be graphene (C), hexagonal boron nitride (hBN), molybdenum disulfide (MoS2), tungsten diselenide (WSe2), silicene (Si), germanene (Ge), graphyne (C), layers of borophene (B), phosphorene (P), or a 2D vertical heterostructure of two or more of the aforementioned materials.

[0015] A preferred 2D material is graphene.

[0016] Preferred graphene includes graphene nanoplatelets, bilayer graphene nanoplatelets, trilayer graphene nanoplatelets, few-layer graphene nanoplatelets, and graphene nanoplatelets with 6 to 10 layers of carbon atoms. The thickness of the graphene nanoplatelets is usually 0.3 nm to 3 nm, and the lateral dimension ranges from about 100 nm to 100 μm.

[0017] Graphite flakes having at least one nanoscale dimension are composed of at least 10 layers of carbon atoms. Preferred graphite flakes are graphite flakes having nanoscale dimensions and 10 to 35 layers of carbon atoms, graphite flakes having nanoscale dimensions and 10 to 30 layers of carbon atoms, graphite flakes having nanoscale dimensions and 25 to 35 layers of carbon atoms, graphite flakes having nanoscale dimensions and 20 or fewer layers of carbon atoms, graphite flakes having nanoscale dimensions and 25 or fewer layers of carbon atoms, graphite flakes having nanoscale dimensions and 30 or fewer layers of carbon atoms, and graphite flakes having nanoscale dimensions and 15 to 25 layers of carbon atoms. The graphite flakes preferably have a lateral dimension in the range of about 100 nm to 100 μm.

[0018] In some embodiments of the present invention, the 2D material platelet is a graphene platelet. The graphene platelet includes two or more graphene nanoplatelets, bilayer graphene nanoplatelets, few-layer graphene nanoplatelets, and / or one or a mixture of graphite flakes having 25 or fewer layers at the nanoscale dimension.

[0019] According to a second aspect of the present invention, a corrosion protection coating comprising the composition according to the first aspect of the present invention is provided. Such a coating may further include other components known to be used in the formulation and / or manufacture of corrosion protection coatings.

[0020] In some embodiments of the present invention, the second corrosion inhibitor is present in the range of 0.05% to 1.0% by weight, 0.05% to 0.8% by weight, 0.05% to 0.6% by weight, or 0.1% to 0.5% by weight. In some embodiments of the present invention, the second corrosion inhibitor is present at a rate of 0.1% or 0.5% by weight.

[0021] The first corrosion inhibitor includes at least one of an ion-exchange pigment, silica, calcium-exchanged silica, a magnesium oxyaminophosphate salt, and / or a mixture of an organic amine, phosphoric acid and / or an inorganic phosphate with a metal oxide and / or a metal hydroxide.

[0022] All of the magnesium ion-exchange pigment, silica, calcium-exchanged silica, and oxyaminophosphate are generally regarded as non-hazardous substances. The mixture of an organic amine, phosphoric acid and / or an inorganic phosphate with a metal oxide and / or a metal hydroxide is generally regarded as a non-hazardous substance that depends on the metal used. Therefore, such substances are beneficial in that they pose far fewer environmental problems than previously used corrosion inhibitors.

[0023] In some embodiments of the present invention, the first corrosion inhibitor includes one or more of zinc chromate, zinc molybdate, zinc tungstate, zinc vanadate, zinc phosphite, zinc polyphosphate, zinc borate, zinc metaborate, magnesium chromate, magnesium molybdate, magnesium tungstate, magnesium vanadate, magnesium phosphate, magnesium phosphite, magnesium polyphosphate, magnesium borate, magnesium metaborate, calcium chromate, calcium molybdate, calcium tungstate, calcium vanadate, calcium phosphate, calcium phosphite, calcium polyphosphate, calcium borate, calcium metaborate, strontium chromate, strontium molybdate, strontium tungstate, strontium vanadate, strontium phosphate, strontium phosphite, strontium polyphosphate, borate, strontium metaborate, barium chromate, barium molybdate, barium tungstate, barium vanadate, barium phosphate, barium phosphite, barium polyphosphate, barium borate, barium metaborate, aluminum chromate, aluminum molybdate, aluminum tungstate, aluminum vanadate, aluminum phosphite, aluminum borate, and / or aluminum metaborate.

[0024] In some embodiments of the present invention, the carrier medium is an epoxy resin. As a result, a coating composed of the composition according to some embodiments of the present invention will be composed of an epoxy resin encapsulating the first and second corrosion inhibitors.

[0025] In some embodiments of the present invention, the carrier medium is composed of one or more suitable crosslinkable resins, non-crosslinkable resins, thermosetting acrylics, aminoplasts, urethanes, carbamates, polyesters, alkyd epoxies, silicones, polyureas, silicates, polydimethylsiloxanes, vinyl esters, unsaturated polyesters, and mixtures and combinations thereof.

[0026] Epoxy resins and other materials suitable for use as carrier media in the present invention, after relatively short periods of exposure to water or humidity, are saturated with water, dissolved oxygen, and possibly Cl - ions from sodium chloride or H + ions from water. Oxygen and dissolved ions, when they reach the interface between the coating and the metal substrate, can lead to the creation of an electrochemical cell and the possibility of wet corrosion of the metal substrate. Such corrosion mechanisms are well known and need not be described here.

Embodiments for Carrying Out the Invention

[0027] A first method of coating comprising a composition according to the present invention provides protection to the metal surface or substrate to which it is applied, thereby providing a barrier that reduces access of water and corrosive ions such as Cl - or H + to the metal substrate. The level of protection depends on the integrity of the coating, its hydrophobicity, affinity for water, and the thickness of the coating.

[0028] It has been found that a graphene film can effectively isolate the metal substrate on which the film is deposited from the environment. A single-atom and defect-free film of graphene has been shown to be impermeable to gases, water, and dissolved gases and ions in that water. However, it is estimated that water transport through graphene can occur at a rate exceeding 1 m / s (>1 m / s) when the defect density is 1 μm -2 . Such a mass transport rate can explain the observed corrosion effects.

[0029] Graphene has many forms, and the growth of films by CVD (Chemical Vapor Deposition) is well understood, and graphene films with 1 to 3 atomic layers can be produced. Such films are frequently used in experiments related to graphene. Such techniques are limited in commercial applicability because they only enable the creation of relatively small areas of the film or the coating of a substrate. In commercial applications, it is more typical for graphene to be used in the form of graphene nanoplatelets. Graphene nanoplatelets can be produced by either the exfoliation of graphite or a synthetic solvothermal process. Such graphene nanoplatelets can vary significantly in the number of atomic layers, surface area, functionality, and sp 2 content. Such variations affect the physical properties of graphene, such as its conductivity. Similarly, graphite flakes with 35 or fewer layers of carbon atoms at the nanoscale, graphite flakes with 25 - 30 layers of carbon atoms at the nanoscale, graphite flakes with 20 - 35 layers of carbon atoms at the nanoscale, or graphite flakes at the nanoscale and 25 - 35 layers of carbon atoms can be produced by either the exfoliation of graphite or a synthetic solvothermal process.

[0030] The inclusion of 2D material platelets as a second corrosion inhibitor in the composition according to the present invention will result in multiple layers of 2D material platelets in a coating comprising the composition according to the present invention, depending on the concentration of incorporation of the 2D material platelets and the applied dry film thickness. Each platelet is potentially only a few atomic layers thick. The presence of multiple layers of 2D material platelets within the coating is related to water, the dissolved oxygen it carries, and Cl - and H +This provides a complex, tortuous (maze-like) pathway for the penetration of aggressive ions such as argon, argon, and argon. This maze-like pathway significantly reduces the diffusion rate of water and water-dissolved substances across the coating. This is evidenced by the water vapor transmission rate test results for coatings containing two commercially available graphene / graphite platelets (A-GNP35 with 6-14 carbon atom layers and A-GNP10 with 25-35 carbon atom layers, both available from Applied Graphene Materials Plc) and a control. The results are shown in Table 1.

[0031] Graphene / graphite platelets are typically 0.3 nm to 12 nm thick with lateral dimensions ranging from approximately 100 nm to 100 μm. As a result, and due to the high lateral aspect and surface area of graphene / graphite platelets, coatings comprised of compositions according to the present invention can be significantly thinner than comparable coatings containing other barrier mechanism materials / pigments, such as micaceous iron oxide / aluminum flakes. The same applies to platelets of other 2D materials. Furthermore, it has been found that the use of graphene platelets results in coatings with good adhesion and mechanical properties. In some embodiments of the present invention, the 2D material platelets are graphene platelets having a D50 particle size of less than 45 μm, less than 30 μm, or less than 15 μm, as measured by a Mastersizer 3000.

[0032] The thinness of the coating made from the composition according to the invention can have the advantage of reducing the weight of the coating.

[0033] In coatings containing compositions according to the present invention, the 2D material platelets only have a barrier effect in protecting the metal substrate. Without being bound by theory, it is believed that in the case of conductive 2D material platelets, once encapsulated in a carrier medium such as an epoxy resin, the conductivity of the 2D material platelets is insufficient to substantially affect the flow of electrons within the coating and / or the metal substrate. It is also possible that the surface of the 2D material platelets may be modified by the absorption of various coating additives (such as wetting agents, antifoaming agents, and flow aids used in formulating compositions according to the present invention). This lack of electrical connection between the platelets results in the 2D material platelets appearing to have no effect on slowing or preventing corrosion of the metal substrate once it has been initiated.

[0034] In some embodiments of the present invention, the 2D material platelets have a density of 2.0×10 at 20° C. -5 The 2D material platelets have a conductivity of around or less than S / m. In some embodiments, the 2D material platelets comprise graphite platelets, reduced graphite, or graphene oxide platelets having 35 or fewer layers of carbon atoms. In some embodiments, the 2D material platelets comprise graphite platelets, reduced graphite, or graphene oxide platelets having 25 to 35 layers of carbon atoms. In these embodiments, the 2D material platelets have a relatively low conductivity, which has the advantage that the 2D material platelets continue to act as a barrier mechanism if encapsulation of the 2D material platelets in the carrier medium is not completed, for example, as a result of damage to the structure of the carrier medium.

[0035] In the composition according to the present invention, the inclusion of at least one first corrosion inhibitor comprising at least one of ion-exchange pigment, silica, calcium-exchanged silica, oxyaminophosphate salt of magnesium, and / or a mixture of organic amine, phosphoric acid and / or inorganic phosphate and metal oxide and / or metal hydroxide helps to prevent corrosion or contain initiated corrosion.

[0036] These compounds of the first corrosion inhibitor are inorganic oxides with a large surface area and are filled with ionic corrosion inhibitors by ion exchange with surface hydroxyl groups. The oxides are selected for their acidic or basic properties that provide either cation or anion exchange (silica is used as a cation support and alumina is used as an anion support). The corrosion inhibition behavior of the first corrosion inhibitor is controlled by the rate of ion release caused by the solution of the ion-exchange pigment.

[0037] Calcium-exchanged silica ion-exchange pigments provide an environmentally friendly alternative to chromium and zinc-based systems. Calcium-exchanged silica functions by controlled diffusion when water and aggressive ions penetrate the coating. The ions released by the ion-exchange pigment react with the metal substrate in a manner known in relation to passivation. There are both anodic and cathodic reactions. Depending on the pH of the coating, the silica of the ion-exchange pigment may dissolve as silicate ions. When the metal substrate is an iron alloy such as low or medium or high non-alloy carbon steel or low or high alloy steel, these silicate ions, which are the soluble fraction of the pigment, may react with ferrous ions at the interface of the coated metal substrate. This forms a protective layer on the surface of the metal. In parallel with this reaction, calcium cations or other metal cations on the silica surface are released and react with soluble silica to form a calcium silicate film in the alkaline region of the metal surface. This, together with iron silicate, helps to strengthen the protective layer by forming a mixed oxide layer on the metal surface. At the same time, calcium or other metal cations are released and the silica captures the aggressive cations that enter the calcium silicate film. These processes of film and compound formation result in the suppression of the corrosion reaction via a two-fold passivation mechanism, the adsorption of aggressive ions and the formation of a protective layer on the metal substrate.

[0038] In some embodiments of the present invention, the first corrosion inhibitor comprises at least one oxyaminophosphate salt of magnesium. Magnesium oxyaminophosphate salts constitute an alternative, environmentally friendly anticorrosion material. Shortly after exposure of the magnesium oxyaminophosphate salt to moisture, the salt's amines passivate the metal surface via a known passivation mechanism. As a result of this passivation, a protective layer consisting primarily of magnesium oxide is deposited on the surface of the metal substrate, the layer being approximately 25-50 nm thick. When the metal substrate is steel, the protective layer keeps the metal surface passive by providing anodic inhibition. When the metal substrate is aluminum or an aluminum alloy, the magnesium oxide layer provides cathodic inhibition by maintaining a potential higher than the corrosion potential of the aluminum or aluminum alloy.

[0039] Electrochemical impedance spectroscopy (EIS) studies show that while graphene has a high level of electrical conductivity in its native state, this conductivity is significantly reduced when incorporated as platelets into epoxy resins (epoxy resins are generally good electrical insulators). This is particularly true when the epoxy resin contains other amorphous or crystalline additives, such as pigments or fillers, creating a homogeneous but highly disordered matrix. In such a matrix, the graphene platelets do not exhibit any significant electrical conductivity and, as a result, do not provide any cathodic protection or benefit the corrosion potential of the surface of the metal substrate.

[0040] The advantage of the composition according to the present invention is that the first and second corrosion inhibitors act synergistically with each other. In particular, the combination of the first and second corrosion inhibitors in the same carrier medium has the advantage of increasing the service life of the coating composed of the composition according to the present invention. The enhancement can be significant and can exceed twice, three times, or four times the service life of known anticorrosion coatings. In this context, the service life should be understood as the period between the application of the coating and the need to reapply the coating due to the deterioration of the initially applied coating. From the perspective of the standard 4628-3:2005 of the International Organization for Standardization, the service life is the period from the application of the coating until the evaluation of rust grade Ri3 is carried out.

[0041] Although not wishing to be bound by theory, it is understood that the extension of the service life of the coating is achieved for the reasons described below. The reason is that the second corrosion inhibitor is called graphene, but the same reason applies to the platelets of all 2D materials. The reasons are as follows. - The first and second corrosion inhibitors in the form of graphene platelets are substantially uniformly mixed in the carrier medium. As a result, some of the first corrosion inhibitor is close to the interface between the coating and the metal substrate, and there are also some where there is no graphene platelet between the first corrosion inhibitor and the metal substrate. That part of the first corrosion inhibitor is called the "first corrosion inhibitor proximal to the metal".; - The first corrosion inhibitor proximal to the metal may dissociate from the humidity experienced during the application of the coating, and as a result, the released ions passivate the surface of the metal substrate.; - The graphene platelets distributed through the carrier medium create a maze-like path between the surface of the coating away from the metal substrate and the surface of the coating adjacent to the metal substrate.; - The part of the first corrosion inhibitor that is not the first corrosion inhibitor proximal to the metal is distributed throughout the matrix of graphene platelets that define the maze-like path.; - The maze-like paths created by the graphene platelets suppress the diffusion of water, dissolved oxygen, and / or dissolved ions from the surface of the coating away from the metal substrate to the surface of the coating adjacent to the metal substrate.; - Water, dissolved oxygen, and dissolved ions diffuse along the maze-like paths from the surface of the coating away from the metal substrate, but encounter the first corrosion inhibitor in these paths and dissolve and dissociate the first corrosion inhibitor.; - Ions from the first corrosion inhibitor then react with the ions in the water or diffuse between the maze-like paths leading towards the metal substrate.; - The slow diffusion of water, dissolved oxygen, and / or dissolved ions along the maze-like paths takes a considerable amount of time for the first corrosion inhibitor of the coating to completely dissolve, resulting in a significant period occurring before the first corrosion inhibitor of the coating is exhausted and the benefits of the first corrosion inhibitor end. That period is longer than that of known anticorrosive coatings, and thus the service life of the coating is prolonged.

[0042] The application of corrosive coatings is expensive in terms of both labor and material costs, and since there are significant ecological benefits, the extension of the service life of coatings containing the composition according to the present invention brings significant economic benefits. This is because fewer coatings are used and, as described above, the coating content may be more ecologically superior to known coatings.

Examples

[0043] Examples The composition according to the present invention is manufactured using the components shown in Table 2.

[0044] Components 1 to 5 are placed in a high-speed overhead mixer and mixed at 2000 rpm for 10 minutes. The resulting gel is checked to confirm whether it is homogeneous and free of bits. If not, mixing is continued until the gel becomes homogeneous and free of bits.

[0045] Add components 6 - 8 to the mixer and mix at 2000 rpm for 15 minutes. Check the mixture to confirm that the grinding (maximum particle size) is less than 25 μm. This is known as the grinding stage of manufacturing.

[0046] Component 9 is pre - dispersed in component 10. Then, the following dispersion is added together with component 11 and mixed at 1000 rpm for 15 minutes. This is known as the let - down stage of manufacturing. If component 9 is added after this mixing step, such addition would be in the post - addition stage of manufacturing.

[0047] Add polyamide hardener 12 at 10 wt% (85% stoichiometry), then the composition is ready to be applied to a substrate to form a corrosion - resistant coating.

[0048] To conduct a comparative test of the composition according to the present invention, such a composition was manufactured as described above. Further compositions were manufactured using the same method, but without including components 7 and / or 9 and including component 10.

[0049] For component 7, different compositions were made using one of four commercially available corrosion - resistant pigments. They were zinc phosphate (part of Delaphos 2M - JPE Holdings Ltd, commercially available from Delaphos), Pigmentan E with a loading range of 0.5 - 2.4 wt% available from Banner Chemicals, Inhibisil® 75 with a loading range of 1.0 - 10.0 wt% available from PPG Industries, Inc., part of 2M Holdings Limited, and Shieldex AC5 with a loading range of 1.2 - 2.4 wt% available from W.R. Grace & Co. Pigmentan E contains an active ingredient of magnesium oxyaminophosphate. Inhibisil 75 and Shieldex AC5 have ion - exchange pigments in the form of silica or calcium - exchanged silica as the active ingredient.

[0050] The graphene / graphite platelet used was commercially available from Applied Graphene Plc as grade A-GNP10 or A-GNP35 (A-GNP35 with 6 - 14 layers of carbon atoms and A-GNP10 with 25 - 35 layers of carbon atoms, both available from Applied Graphene Materials Plc).

[0051] The samples for testing were prepared in the following manner.:

[0052] The cold-rolled steel substrates were prepared by grit blasting to SA2-1 / 2 using irregularly shaped chromium / nickel steel shots and subsequently degreasing with acetone. Each of compositions numbered 1 to 18 was applied to the substrates by spray coating using a gravity-fed gun with a 1.2 mm tip, giving a coating thickness of DFT 60 - 75 μm. The substrates were cured for 7 days.

[0053] The substrates coated with each composition were subjected to a cyclic salt spray test (Appendix 5 of ASTM G85) and evaluated at intervals of 1, 2, 3, and 4000 hours. The results of the evaluation are as shown in Tables 3, 4, 5, and 6.

[0054] The substrates coated with each composition were evaluated in relation to the mechanical properties of the coating. Specifically, the coating was evaluated in relation to impact resistance (using the Elcometer Impact Test), abrasion resistance (using a Taber abrasion machine with 100 cycles, 1 Kg weight, and CS-10 disc), adhesion (using a PAT device), and flexibility (using a conical mandrel). The results of that evaluation are shown in Tables 7, 8, 9, and 10. The following test methods were used.:

[0055] Abrasion resistance: Taber abrasion - ASTM 5144 Flexibility: Conical mandrel - ISO6860:2006 Impact resistance: - ISO6272 Adhesion: - ISO4624 The evaluation reveals that the compositions according to the present invention provide better corrosion resistance than known coating compositions, are more environmentally friendly than known compositions, and have a longer service life than known coating compositions.

[0056] In the formulations of compositions 1 to 18, the graphene platelets can be incorporated into the composition at the milling stage, the letdown stage, or after all other components have been combined. The time of incorporation of the graphene platelets has been found to affect the corrosion protection properties of the coating resulting from the composition. The best properties were achieved when the incorporation of the graphene platelets occurred during the letdown stage of production.

[0057] To test the theory that the graphene / graphite platelets in the compositions of the present invention have only a barrier effect, and without wishing to be bound by theory, AC electrochemical impedance spectroscopy (AC EIS) and corrosion potential (E corr Measurements of AC, EIS, and E were carried out on some of the test samples prepared as described above. corr The measurements allow quantitative determination of several properties related to the corrosion resistance of the samples without the lengthy tests required for artificial weathering.

[0058] E corr - Electrochemical corrosion potential (ECP) is the voltage difference between a metal immersed in a particular environment and an appropriate standard reference electrode (SRE) or an electrode with a stable, well-known electrode potential. Electrochemical corrosion potential is also called resting potential, open circuit potential, or free corrosion potential, and is expressed in the equation E corr It is expressed as E corr A higher value indicates a lower corrosion rate, and a lower value indicates a higher corrosion rate.

[0059] In the case of a coating where the carrier body medium is an epoxy resin or other suitable organic composition, the barrier properties of the organic coating are such that it exhibits high impedance throughout the thickness of the coating. Traditionally, as the coating ages, it is understood that the interconnected network of pores within the coating becomes saturated with water and salt, exposing the metal substrate to a corrosive environment and simultaneously reducing the electrical resistance of the coating. An aged organic coating also has other electrical properties where the coating behaves as a capacitor to current. When corrosion occurs on the metal surface, the electric double layer operates as a capacitor while the polarization resistance may be related to the corrosion rate. The measurements conducted below were used to explain the performance of the coatings of various samples prepared as described above.

[0060] To demonstrate the mechanism of graphene / graphite platelets in the coating of the composition of the present invention and its relationship with the active inhibitor in providing corrosion prevention, the samples were evaluated with and without scribes through the coating. The scribes provide direct access of the salt solution to the metal surface and, through the electrochemical reaction, show any resistance properties to corrosion due to damage to the coating. Evaluating the coating in this way makes it possible to demonstrate the mechanism of the action acting on the intact film.

[0061] All electrochemical measurements were recorded using a Gamry 1000E potentiostat in combination with a Gamry ECM8 multiplexer, enabling simultaneous testing of up to 8 samples per experiment. Each individual channel was specially designed for electrochemical testing of coated samples with an exposed paint surface of 14.6 cm 2Connected to the Gamry PCT-1 paint test cell. For each formulation and control, one panel was scribed with a 25 mm scribe using a knife. Due to the relatively small surface area of the study, care was taken to ensure that the scribes were as consistent as possible throughout. Panels for each formulation and control were tested in duplicate with both scribed and unscribed forms.

[0062] Within each paint test cell, a conventional three-electrode system was formed, with bare steel, epoxy-coated steel, and scribed epoxy-coated steel panels functioning as the working electrode, a graphite rod functioning as the counter electrode, and a saturated calomel electrode (SCE) functioning as the reference electrode. All tests were performed using a 3.5 wt% NaCl electrolyte. All measurements of the corrosion potential (E corr ) were recorded with respect to the SCE reference electrode. EIS analysis was performed with reference to a modified Randel cell incorporating pore resistance.

[0063] The AC EIS data shown in Tables 11 - 23 were obtained by fitting an equivalent circuit to the EIS data.

[0064] Pore resistance, i.e., R pore , is the electrical resistance to the current flowing through the pore network of the coating. When the pore network is filled with electrolyte, R pore changes. A higher value indicates a lower corrosion rate, and a lower value indicates a higher corrosion rate.

[0065] C DL is the capacitance generated by the electrical double layer at the water / substrate interface. Measurable C DL indicates the presence of water on the substrate. A higher value indicates a larger wetted area of the substrate.

[0066] [[ID=३०]]C c is the capacitance generated by the dielectric properties of the coating. C cIt is related to the dielectric strength of the coating and the water absorption rate by the coating. The higher the value, the higher the moisture content.

[0067] The tabular representation of the measured data is as shown in Tables 11 to 23. Each table shows in the title the composition used to coat the samples to be tested.

[0068] Explanation of Tables 11 to 23: Corrosion potential:

[0069] Tables 11 to 15 show the behavior of E corr over time during the test period. In Composition 1, without scribing, there is a gradual decrease in the corrosion potential over time, indicating slow water diffusion and the onset of corrosion. In the scribed case, there is no difference between the expected E of the uncoated steel corr and the determined E corr .

[0070] Table 12 shows the effect on the unscribed panel by including graphite platelet (A - GNP10) in Composition 2. The graphene - containing panel retains a higher corrosion potential compared to Composition 1 and thus retains corrosion resistance. However, Table 13 shows that when scribed, there is no difference between the graphite platelet containing Composition 2 and Composition 1 or the actually uncoated steel. The behavior of the graphite platelet is based only on the barrier performance, suggesting no additional electrochemical activity on the steel surface.

[0071] Tables 14 and 15 show the behavior of Compositions 4 and 12. The unscribed Composition 12 has a higher E corris shown, suggesting higher corrosion protection. The results of the scribed composition 12 indicate that the activities of both compositions 4 and 12 are close to that of the uncoated steel, with composition 12 being slightly worse. This is not reflected in the results of artificial weathering (salt spray test), possibly due to the short test period and the activity of the active ingredients within that time frame.

[0072] Pore resistance R pore and coating capacitance C c :

[0073] Tables 16 to 19 show the behavior of pore resistance and coating capacitance. The comparison between the unscribed compositions 1 and 2 is as expected. The graphite platelet in composition 2 increases the pore resistance, resulting in a lower coating capacitance and less moisture at the coating / metal interface. Scribing the sample panel shows no difference in performance.

[0074] Comparing the unscribed compositions 4 and 12, it can be seen that the performance of composition 12 is excellent. However, no significant difference is seen in the scribed panels.

[0075] Double-layer capacitance C DL : Tables 20 to 23 show the double-layer capacitance of the coating and the capacitance of water at the surface of the coating / metal interface. In both scribed and unscribed panels, compositions containing graphene / graphite platelets have less moisture at the coating / metal interface and improved barrier performance of the coating. This confirms the barrier properties of graphene. This is also reflected in the tests of compositions 4 and 12 where the double-layer capacitance of composition 12 appears lower. This is reflected in the accelerated corrosion test (salt spray) test.

[0076] It is expressly intended that within the scope of this application, the various aspects, embodiments, examples, and alternatives described in the preceding paragraphs and / or claims, particularly their individual features, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, except where such features are incompatible. Applicant reserves the right to modify the originally filed claims or to submit new claims accordingly, including the right to amend the originally filed claims to depend on and / or incorporate features of other claims. [Brief explanation of the drawings]

[0077]

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[0078] (Claim 1) A composition comprising a carrier medium, a first corrosion inhibitor having a passivation mechanism, and a second corrosion inhibitor having a barrier mechanism, wherein the first corrosion inhibitor comprises at least one of an ion exchange pigment, silica, calcium-exchanged silica, magnesium oxyaminophosphate, and / or a mixture of an organic amine, phosphoric acid and / or an inorganic phosphate and a metal oxide and / or a metal hydroxide, and wherein the second corrosion inhibitor comprises one or more 2D material platelets, wherein the 2D material platelets comprise one or more nanoplatelets of a 2D material and / or one or more nanoplatelets of a layered 2D material and / or graphite flakes, wherein the graphite flakes have a nanoscale dimension and 35 or fewer atomic layers. (Claim 2) The composition according to claim 1, wherein the 2D material is one or more of graphene (C), hexagonal boron nitride (hBN), molybdenum disulfide (MoS2), tungsten diselenide (WSe2), silicene (Si), germanene (Ge), graphyne (C), borophene (B), phosphorene (P), or a 2D in-plane heterostructure of two or more of the above materials. (Claim 3) The composition according to claim 1 or 2, wherein the layered 2D material can be a layer of graphene (C), hexagonal boron nitride (hBN), molybdenum disulfide (MoS2), tungsten diselenide (WSe2), silicene (Si), germanene (Ge), graphyne (C), borophene (B), phosphorene (P), or a 2D in-plane heterostructure of two or more of the above materials. (Claim 4) The 2D material platelet has a conductivity of 2.0×10 -5 S / m or less at 20 °C, and the composition according to any one of claims 1 to 3. (Claim 5) the first corrosion inhibitor is selected from the group consisting of zinc chromate, zinc molybdate, zinc tungstate, zinc vanadate, zinc phosphite, zinc polyphosphate, zinc borate, zinc metaborate, magnesium chromate, magnesium molybdate, magnesium tungstate, magnesium vanadate, magnesium phosphate, magnesium phosphite, magnesium polyphosphate, magnesium borate, magnesium metaborate, calcium chromate, calcium molybdate, calcium tungstate, calcium vanadate, calcium phosphate, calcium phosphite, calcium polyphosphate, calcium borate, calcium metaborate, strontium chromate, strontium molybdate 5. The composition of any of claims 1 to 4, comprising one or more of aluminum, strontium tungstate, strontium vanadate, strontium phosphate, strontium phosphite, strontium polyphosphate, borate, strontium metaborate, barium chromate, barium molybdate, barium tungstate, barium vanadate, barium phosphate, barium phosphite, barium polyphosphate, barium borate, barium metaborate, aluminum chromate, aluminum molybdate, aluminum tungstate, aluminum vanadate, aluminum phosphite, aluminum borate, and / or aluminum metaborate. (Claim 6) 6. The composition of claim 1, wherein the second corrosion inhibitor is present in the range of 0.05 wt.% to 1.0 wt.%, 0.05 wt.% to 0.8 wt.%, 0.05 wt.% to 0.6 wt.%, or 0.1 wt.% to 0.5 wt.%, 0.1 wt.% or 0.5 wt.%. (Claim 7) 7. The composition of claim 1, wherein the second corrosion inhibitor has a D50 particle size of less than 45 μm, less than 30 μm, or less than 15 μm. (Claim 8) 8. The composition of claim 1, wherein the first corrosion inhibitor is present in the range of 1 wt. % to 15 wt. %, 2 wt. % to 10 wt. %, 4 wt. % to 8 wt. %, 4 wt. %, or 8 wt. %. (Claim 9) When dependent on claim 1, wherein the first corrosion inhibitor is composed of calcium-exchanged silica and the second corrosion inhibitor is a graphite flake having one nanoscale dimension and 25 to 35 layers of carbon atoms or is composed of them, the composition according to any one of claims 6 to 8. (Claim 10) The carrier medium is selected from crosslinkable resins, non-crosslinkable resins, thermosetting acrylics, aminoplasts, urethanes, carbamates, polyesters, alkyd epoxies, silicones, polyureas, silicates, polydimethylsiloxanes, vinyl esters, unsaturated polyesters, and mixtures and combinations thereof, the composition according to any one of claims 1 to 9. (Claim 11) A coating comprising the composition according to any one of claims 1 to 10. (Claim 12) A method for producing the composition according to any one of claims 1 to 10, wherein the production includes a grinding step and a let-down step, and the 2D material platelet is added in the grinding step, in the let-down step, or as stirring of an additive after the let-down step, the method for producing a composition. (Claim 13) The method for producing the composition according to claim 12, wherein the 2D material platelet is added in the let-down step. (Claim 14) The method for producing the composition according to claim 12 or 13, wherein the grinding step includes mixing the carrier medium and the first corrosion inhibitor.

Claims

1. A method for manufacturing a composition, wherein the composition comprises a carrier medium, a first corrosion inhibitor having a passivation mechanism, and a second corrosion inhibitor having a barrier mechanism, wherein the first corrosion inhibitor comprises at least one of an ion-exchange pigment, silica, calcium-exchanged silica, magnesium oxyaminophosphate, and / or an inorganic phosphate, wherein the second corrosion inhibitor comprises one or more 2D material platelets, wherein the 2D material platelets comprise graphene nanoplatelets or graphite flakes, wherein the graphite flakes have one nanoscale dimension and up to 35 atomic layers, wherein the second corrosion inhibitor has a D50 particle size of less than 45 μm, the method having a grinding step and a let-down step, wherein the grinding step comprises mixing the carrier medium and the first corrosion inhibitor, wherein the 2D material platelets are added in the let-down step, wherein the graphene nanoplatelets or graphite flakes are produced by a synthetic solvothermal process.

2. The 2D material platelet has a conductivity of about 2.0×10 －５ S / m or less at 20 °C, the method according to claim 1.

3. The method according to claim 1 or 2, wherein the inorganic phosphate comprises one or more of zinc phosphate, zinc polyphosphate, magnesium phosphate, magnesium polyphosphate, calcium phosphate, calcium polyphosphate, strontium phosphate, strontium polyphosphate, barium phosphate, or barium polyphosphate.

4. The method according to any one of claims 1 to 3, wherein the second corrosion inhibitor is present in the range of 0.05% to 0.8% by weight.

5. The method according to any one of claims 1 to 4, wherein the first corrosion inhibitor is present in the range of 1% to 15% by weight.

6. wherein the first corrosion inhibitor is composed of calcium-exchanged silica, The method according to any one of claims 1 to 5, wherein the second corrosion inhibitor is composed of graphite flakes having one nanoscale dimension and 25 to 35 layers of carbon atoms.

7. The carrier medium is selected from a crosslinkable resin, a non-crosslinkable resin, a thermosetting acrylic, an aminoplast, a urethane, a carbamate, a polyester, an alkyd epoxy, a silicone, a polyurea, a silicate, a polydimethylsiloxane, a vinyl ester, an unsaturated polyester, a mixture thereof, and a combination thereof, according to the method of any one of claims 1 to 6.

8. The second corrosion inhibitor comprises graphene / graphite flakes having one nanoscale dimension and up to 35 atomic layers, according to the method of any one of claims 1 to 7.

9. The second corrosion inhibitor has a D50 particle size of less than 15 μm, according to the method of any one of claims 1 to 8.

10. The carrier medium has an epoxy resin containing an amorphous or crystalline additive that forms a homogeneous but highly disordered matrix, according to the method of any one of claims 1 to 9.

11. The first corrosion inhibitor comprises a magnesium oxyaminophosphate, according to the method of any one of claims 1 to 10.

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