Composite particle metal coating as well as preparation method and application thereof

Abstract

The invention provides a composite particle metal coating as well as a preparation method and application thereof. The coating comprises an inhibition composition and a powder coating composition from the surface of the base body to the outside; the inhibiting composition includes particulate metal, an organic liquid, a thickener, and a silane binder; the granular metal comprises zinc metal and non-zinc metal, the zinc metal accounts for 50-99 wt% of the granular metal, and the non-zinc metal accounts for 1-50 wt% of the granular metal; the non-zinc metal is selected from at least one of aluminum, manganese, cadmium, nickel, tin, iron and magnesium. The powder coating composition comprises a thermoplastic resin and a thermosetting resin. Particle metal in the composite particle metal coating has a high corrosion prevention effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating, and particularly relates to a composite granular metal coating, a preparation method and application. BACKGROUND

[0002] Powder coating technology is used in the field of petrochemical industry, such as corrosion protection of equipment such as boiler, reaction kettle, heat conduction furnace, heat exchanger, desulfurization tower. Generally, powder coating involves applying a certain amount of powder coating on the coated object, and then fusing the powder particles together to form a continuous whole coating, which is usually carried out by subjecting the coated object to high temperature fusion. Powder coating can be formed on various surfaces, most commonly metal surfaces.

[0003] It has been found that certain phosphate coatings applied to steel surfaces inhibit corrosion of the underlying steel. Phosphate conversion coating compositions are known and are commercially available. 1000 is available from Henkel Corporation, Germany, and is a ferric phosphate conversion coating designed specifically for steel surfaces. Although phosphate coatings are popular, they do not always provide long-term protection between the underlying metal and the adjacent powder layer. Therefore, there is a need for a coating system that can provide both good adhesion properties and long-term corrosion protection. SUMMARY

[0004] To solve the above problems in the prior art, the present application provides a composite granular metal coating, a preparation method and application.

[0005] In a first aspect, the present application provides a composite granular metal coating, which comprises from the surface of the substrate outwardly a suppression composition and a powder coating composition;

[0006] The suppression composition comprises granular metal, organic liquid, thickening agent and silane binder;

[0007] The granular metal comprises zinc metal and non-zinc metal, wherein the zinc metal accounts for 50-99 wt% of the granular metal, and the non-zinc metal accounts for 1-50 wt% of the granular metal; the non-zinc metal is selected from at least one of aluminum, manganese, cadmium, nickel, tin, iron, and magnesium.

[0008] The powder coating composition comprises thermoplastic resin and thermosetting resin, preferably, the mass ratio of the thermoplastic resin and the thermosetting resin is 1:(2-3).

[0009] As a specific embodiment of the present application, the granular metal accounts for 10-35 wt% of the total mass of the suppression composition.

[0010] As a specific embodiment of the present application, the particle size of the granular metal is 100 mesh to 325 mesh.

[0011] As a preferred embodiment of the present application, the particulate metal includes zinc metal and non-zinc metal, such as finely divided aluminum, manganese, cadmium, nickel, stainless steel, tin, ferrous alloys, magnesium, or zinc; the particulate metal can be a mixture of any of the foregoing, and includes alloys and intermetallic mixtures thereof. Preferably, the non-zinc metal is aluminum; further preferably, zinc powder or zinc flakes and aluminum powder or aluminum flakes. Typically, the aluminum content is at least about 10 wt%, and the weight ratio of aluminum to zinc is typically at least about 1 :9. Economically, the proportion of aluminum to the total weight of the particulate metal should not exceed 50%.

[0012] According to the present application, for economy, the zinc alloy will be in the form of a paste-like flake. In the paste-like zinc-aluminum alloy, the aluminum content is about 8 wt%. The total amount of zinc alloy flakes typically comprises 90 - 95 wt% or more of the slurry, with the balance being the slurry liquid. The alloy flake paste can contribute some minor amount of liquid, such as dipropylene glycol or mineral spirits.

[0013] As a specific embodiment of the present application, the organic liquid includes at least one of triethylene glycol and tetraethylene glycol, dipropylene glycol and tripropylene glycol, dimethyl and ethyl ether, and polypropylene glycol. The organic liquid is generally a high boiling organic liquid, which as a medium should have a boiling point above about 100°C at atmospheric pressure, and is preferably water soluble.

[0014] As a specific embodiment of the present application, the organic liquid comprises 1 - 30 wt% of the total mass of the inhibiting composition.

[0015] As a specific embodiment of the present application, the thickening agent includes at least one of an ether of hydroxyethyl cellulose, methyl cellulose, methylhydroxypropyl cellulose, ethyl-hydroxyethyl cellulose, and methyl ethyl cellulose.

[0016] As a specific embodiment of the present application, the thickening agent comprises 0.05 - 2.0 wt% of the total mass of the inhibiting composition.

[0017] As a specific embodiment of the present application, the silane adhesion agent is selected from the group consisting of beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 4 (trimethoxysilyl)butane-1,2-epoxide, and gamma-glycidoxypropyltrimethoxysilane. The silane adhesion agent includes a water-reducible organofunctional silane, and the selected silane must have a co-solvent present at the time of water reduction to prevent gelling or precipitation upon water reduction.

[0018] As a specific embodiment of the present application, the silane adhesion agent comprises 1 - 5 wt% of the total mass of the inhibiting composition.

[0019] As a specific embodiment of the present application, the thermoplastic resin is selected from the group consisting of at least one of polyvinyl chloride, polyamide, polyethylene, polypropylene, and polyvinylidene fluoride.

[0020] As a specific embodiment of the present invention, the thermoset resin is selected from the group consisting of epoxy resins, polyurethane polyesters, unsaturated polyesters, acrylic resins, and combinations thereof.

[0021] According to the present invention, the resin used as a powder coating should have the property of low melt viscosity to provide a smooth, continuous film; good adhesion to the substrate; good physical properties, such as high toughness and impact resistance, after proper curing; good heat and chemical resistance; and good weatherability. The resin should be storage stable at about 25°C for at least six months and should have a sufficiently high glass transition temperature, Tg, to resist sintering during storage.

[0022] The thermoplastic resin must melt and flow at the application temperature without significant degradation. Efforts to improve the melt flow properties of the polymer by reducing the molecular weight and plasticizing or blending with a lower molecular weight compatible resin are limited by the thermal stability of the polymer. If the application temperature is too high, the coating exhibits significant color change or signs of thermal degradation. Most thermoplastic powder coatings are applied between about 200 and 300°C, well above the generally accepted upper temperature limit, but the application time is usually less than about 5 minutes. The preferred polymer types are based on plasticized polyvinyl chloride (PVC), polyamides, polyethylene, polypropylene, polyvinylidene fluoride, and other specialty thermoplastics.

[0023] The molecular weight or glass transition temperature, Tg, of several preferred thermoset coating powders must be sufficiently high to prevent individual particles from sintering or fusing during shipping and storage. The minimum Tg required is in the range of about 40-50°C, preferably higher than 50°C. Epoxy resins, due to their aromatic backbone, have the required Tg at relatively low molecular weight and corresponding low melt viscosity. However, other thermoset resins require some linear comonomer to achieve flexibility. This results in a lower Tg and higher molecular weight resins should be used. Therefore, in the equivalent range of Tg, polyester resins have a melt viscosity of about 4000 to about 9000 mPa-s (e.g. cP) at 200°C or about 2 to about 10 times that of epoxy resins. The difference in flowability becomes more pronounced as the amount of pigments and fillers increases.

[0024] As a specific embodiment of the present invention, additives including catalysts, accelerators, flow control agents, polymers can also be included in the composite type particulate metal coating of the present invention; catalysts and accelerators are added to modify the reaction rate and curing characteristics; flow control agents are added to prevent cratering and promote leveling of the molten polymer film and wetting of the substrate; the most widely used type of polymer is a low molecular weight polymer of butyl acrylate and copolymers of ethyl acrylate and 2-ethylhexyl acrylate.

[0025] The above raw materials in the present application can be self-made or commercially available, and the present application does not make special limitation thereto.

[0026] In a second aspect, the present application provides a preparation method of the composite particulate metal coating of the first aspect, comprising the following steps:

[0027] S1: uniformly mixing particulate metal, organic liquid, thickening agent and silane binder to obtain an inhibiting composition;

[0028] S2: coating the inhibiting composition obtained in step S1 on the surface of the substrate;

[0029] S3: mixing thermoplastic resin powder and thermosetting resin powder to obtain a powder coating composition;

[0030] S4: coating the powder coating composition obtained in step S3 on the inhibiting composition layer on the surface of the substrate obtained in step S2, and curing to obtain the composite particulate metal coating.

[0031] As a specific embodiment of the present application, in the step S2, the coating method comprises spraying, soaking or exposure to a fluidized bed, electrostatic spraying.

[0032] As a specific embodiment of the present application, in the step S4, the coating method comprises flame spraying.

[0033] In a third aspect, the present application provides an application of the composite particulate metal coating of the first aspect or the composite particulate metal coating prepared by the preparation method of the second aspect in the field of steel materials.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] 1. In the chemical corrosion process, due to the negative potential of manganese, the metals of aluminum, manganese, cadmium, nickel, tin, iron and magnesium form a corrosive micro-battery with the surrounding solution, the oxidation of the metal in the anode region produces cations, and the high concentration of metal ions and acid radicals form a passivation layer on the steel surface, thereby inhibiting the corrosion reaction; on the other hand, the barrier coating formed by the thermoplastic resin and the thermosetting resin can block the penetration of water, oxygen and corrosive ions in the environment, thereby further delaying the corrosion process.

[0036] 2. Compared with the prior art, the composite particulate metal coating of the present application has the beneficial effect of prolonging the corrosion time of the metal substrate by one time.

[0037] 3. Compared with the prior art, the composite particulate metal coating of the present application can be applied to various different corrosion environments, such as seawater erosion, desulfurization tower, industrial heat exchanger, etc. DETAILED DESCRIPTION

[0038] The present application will be further described in conjunction with specific examples, but does not constitute any limitation to the present application.

[0039] The reagent information used in each embodiment of the present application is as follows:

[0040] The average particle size of the zinc powder is 10 μm of flat zinc powder.

[0041] The silane binder is ethyl silicate 40, and its components are: ethyl silicate, tetraethoxysilane, solvent: ethanol.

[0042] Example 1

[0043] The present embodiment provides a composite granular metal coating and a preparation method thereof, wherein the raw materials and proportions are shown in Table 1, and the specific details are as follows:

[0044] S1: uniformly mixing the granular metal, organic liquid, thickening agent and silane binder to obtain an inhibiting composition;

[0045] S2: coating the inhibiting composition obtained in step S1 on the surface of the substrate;

[0046] S3: mixing the thermoplastic resin powder and the thermosetting resin powder to obtain a powder coating composition;

[0047] S4: coating the powder coating composition obtained in step S3 on the inhibiting composition layer on the surface of the substrate obtained in step S2, and curing to obtain the corrosion-resistant coating.

[0048] The thickness of the corrosion-resistant coating obtained in Example 1 is 100 μm.

[0049] Examples 2-4

[0050] Examples 2-4 provide a composite granular metal coating and a preparation method thereof, and the preparation method is the same as that of Example 1, except for the raw materials and proportions, and the detailed data are shown in Table 1, and the specific details are as follows:

[0051] Table 1

[0052]

[0053] Comparative Example 1

[0054] The IPN8710 zinc-rich anticorrosive coating in the present comparative example is purchased from Japan Lubo Company.

[0055] Test Example

[0056] The composite granular metal coatings obtained in Examples 1-4 and the purchased coating of Comparative Example 1 are subjected to corrosion-resistant tests according to the following procedures.

[0057] According to the composite cycle test method as a promotion test, the corrosion prevention test was performed by repeating cycles. The brine was prepared by dissolving sodium chloride to 50 ± 5 g / L per 1 L of test solution, and adjusting to pH 6.5. The evaluation time of the composite cycle test was 168 hours (21 cycles), 360 hours (45 cycles), and surface observation was performed.

[0058] The base material of the test body for the composite cycle test was SPCC steel material (JIS G3141 cold rolled steel sheet and steel strip), and the shape was 70 mm x 150 mm x 1.6 mm in plate thickness. The coating surface was subjected to sand blasting treatment with sand particles as the abrasive material. The paints of Examples 1 to 4 and Comparative Example 1 were applied by brush coating on the adjusted plate surface. The film thickness at the time of curing was 75 μm ± 15 μm for Examples 1, 3, 4, and Comparative Example 1, and 150 μm ± 30 μm for Example 2.

[0059] In addition, in order to prevent the corrosion liquid for the casting test from entering from the edge portion of the test body, the back surface of the test body and the edge surface of the corrosion liquid exposure surface were maintained with an insulation material having a width of 5 mm. As the insulation material, a modified epoxy resin primer was applied with a film thickness of 100 μm or more.

[0060] In order to observe the corrosion prevention film defect and the corrosion occurrence state due to scratching on the corrosion liquid exposure surface of each test body, the film surface was subjected to cross-cutting using the method prescribed in JIS H8502-1999 "Plated layer corrosion resistance test method", and used for the test.

[0061] The test results after 168 hours: regarding Examples 2 to 4, although slight rusting was observed in a part of the cross-cut portion, rusting was hardly observed except for the cross-cut portion, and a good corrosion prevention effect was exhibited to the same degree as Comparative Example 1. In Example 1, although the rusting of the cross-cut portion was extremely slight, slight point-like rusting was found in the portion other than the cross-cut portion.

[0062] The test results after 360 hours: in Examples 1, 2, and 4, slight point-like rusting was observed in the portion other than the cross-cut portion, and in Example 3, point-like rusting was also observed, but was extremely slight compared to Examples 1, 2, and 4. In Comparative Example 1, although point-like rusting was not found, white rusting occurred on the entire surface. The rusting of the cross-cut portion in any one of Examples 1 to 4 was extremely slight; in Comparative Example 1, rusting of the cross-cut portion was not found.

[0063] With respect to the results of Example 1, in the coating consisting of aluminum and magnesium using an inorganic binder not containing zinc and titanium, at the beginning of the study, by the sacrificial anode reaction of magnesium, which dissolves earlier than zinc, coating the surface of iron material and expecting to play a high anticorrosion effect. In fact, only very slight rusting could be seen in the cross section, and the high anticorrosion effect thereof could be seen. However, due to the safety problems in manufacturing, the particle size of magnesium could not be reduced, and thus, the coating of the iron ground surface had numerous porous portions in which there were no magnesium metal particles. Therefore, it is thought that the rusting did not occur in the cross section, but in the form of spots on the coated surface. In Example 2, in which the same coating was applied in a higher film thickness, the occurrence of rusting on the coated surface was slight compared to Example 1, and this can be thought to be due to the reduction of the porous portions by the layering of the metal particles.

[0064] On the other hand, in Examples 3 and 4, in which a small amount of zinc and titanium, which can further reduce the particle size, were incorporated, it is thought that by the zinc and titanium acting in the form of supplementing the porous portions of magnesium, the initial anticorrosion reaction proceeds more smoothly.

[0065] With respect to the inorganic zinc-rich coating of Comparative Example 1, since the sacrificial anode reaction of zinc occurs very early, it can be thought that the initial anticorrosion reaction proceeds very well. However, by the 360-hour composite cycle test, white rusting occurred on the entire surface thereof. It is well known that the white rusting portion increases and the reactivity of zinc decreases, and thus, if a longer test is performed, it is predicted that the high anticorrosion performance cannot be maintained.

[0066] According to the above results, in the use of the composite particulate metal coating of the present application, in the case where the metal component is substantially only aluminum and magnesium, it is preferable to increase the film thickness, and in the case where the film thickness is reduced, it can be said that it is preferable to incorporate a small amount of zinc in the metal component. However, the problem of the spot rusting occurring from the porous portions of magnesium can be solved by performing a sealing treatment using an alkyl inorganic composite resin, a polyurethane-based resin, a silicon-based resin, or the like on the surface after the composite particulate metal coating is applied to the steel material.

[0067] Any numerical values recited herein include all values from and between the lowest value and the highest value of the range. For example, if a concentration range is stated as 1-90, it is intended that values such as 45, 55, 61, 62, 65, 75, 85, 70-71, 69-71, 70-72, 71-72, etc. are expressly enumerated in this specification. For values which are less than one, one unit in the highre place is considered to be 0.1, 0.01, 0.001, 0.0001, etc. This same principle applies to ranges recited in the specification. In addition, it is intended that every dose and every concentration range between the dose and the upper value is disclosed. All such concentrations and doses are part of the disclosure taught herein.

[0068] It should be noted that the foregoing examples have been provided merely for the purposes of illustration and are not intended to limit the application under claim in any way. Description of the application has been presented in terms of typical embodiments with reference to a drawing and various configurations. These and other modifications within the scope of the application are intended to be included and reserved. The language used in the specification should not be taken as indicative of any exclusive or preferred embodiment. Other configurations of the application will be apparent to those skilled in the art upon consideration of this disclosure or can be learned from practice of the application. The general principles defined herein can be applied to other embodiments and applications without departing from the scope of the application. The application is not limited to the examples and applications described herein and can be practiced with modification and alteration within the scope of the appended claims. The description is thus to be considered as given by way of example only and is afforded all modifications and alterations as the art discloses. Accordingly, the application is not intended to be limited by the method, materials, and examples described herein, but is to be accorded the widest scope consistent with the claims.

Claims

1. A composite particulate metal coating, characterized by, The coating comprises an inhibiting composition and a powder coating composition from outside to the surface of the substrate; The inhibiting composition comprises particulate metal, organic liquid, thickening agent and silane binder; The particulate metal comprises zinc metal and non-zinc metal, wherein the zinc metal accounts for 50-99wt% of the particulate metal, and the non-zinc metal accounts for 1-50wt% of the particulate metal; the non-zinc metal is selected from at least one of aluminum, manganese, cadmium, nickel, tin, iron, magnesium; The powder coating composition comprises thermoplastic resin and thermosetting resin, preferably, the powder coating composition is a mixture of thermoplastic resin and thermosetting resin, wherein the mass ratio of thermoplastic resin to thermosetting resin is 1:(2-3).

2. The composite particulate metal coating of claim 1, wherein, The particulate metal accounts for 10-35wt% of the total mass of the inhibiting composition; and / or The particle size of the particulate metal is 100-325 mesh.

3. The composite particulate metal coating according to claim 1 or 2, characterized in that The organic liquid comprises at least one of triethylene glycol and tetraethylene glycol, dipropylene glycol and tripropylene glycol, dimethyl and ethyl ether, polypropylene glycol; the organic liquid accounts for 1-30wt% of the total mass of the inhibiting composition.

4. The composite particulate metal coating according to any one of claims 1 to 3, wherein The thickening agent comprises at least one of ethers of hydroxyethyl cellulose, methyl cellulose, methylhydroxypropyl cellulose, ethyl-hydroxyethyl cellulose, methyl ethyl cellulose; the thickening agent accounts for 0.05-2.0wt% of the total mass of the inhibiting composition.

5. The composite particulate metal coating according to any one of claims 1 to 4, wherein The silane binder is selected from β-(3,4-epoxycyclohexyl)ethyl trimethoxysilane, 4(trimethoxysilyl)butane-1,2 epoxide or γ-glycidoxypropyl trimethoxysilane; the silane binder accounts for 1-5wt% of the total mass of the inhibiting composition.

6. The composite particulate metal coating according to any one of claims 1 to 5, wherein The thermoplastic resin is selected from at least one of polyvinyl chloride, polyamide, polyethylene, polypropylene, polyvinylidene fluoride.

7. The composite particulate metal coating according to any one of claims 1 to 6, wherein The thermosetting resin is selected from epoxy resin, polyurethane polyester, unsaturated polyester, acrylic resin and combinations thereof.

8. A method of producing the composite particulate metal coating according to any one of claims 1 to 7, characterized in that The method comprises the following steps: S1: uniformly mixing particulate metal, organic liquid, thickening agent and silane binder to obtain an inhibiting composition; S2: coating the inhibiting composition obtained in step S1 on the surface of the substrate; S3: mixing thermoplastic resin powder and thermosetting resin powder to obtain a powder coating composition; S4: coating the powder coating composition obtained in step S3 on the inhibiting composition layer obtained in step S2 on the surface of the substrate, and curing to obtain the composite particulate metal coating.

9. The production method according to claim 8, characterized by, In step S2, the coating method comprises spraying, soaking or exposure to a fluidized bed, electrostatic spraying; and / or In step S4, the coating method comprises flame spraying.

10. Use of the composite particulate metal coating of any one of claims 1-7 or the composite particulate metal coating prepared by the method of claim 8 or 9 in the field of steel materials.

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