WO2015195670A1

WO2015195670A1 - Aluminum phosphate ceramics and coatings

Info

Publication number: WO2015195670A1
Application number: PCT/US2015/036038
Authority: WO
Inventors: Ramkumar Natarajan; Sameerkumar V. PATEL; Vadym Drozd
Original assignee: Latitude 18, Inc.
Priority date: 2014-06-16
Filing date: 2015-06-16
Publication date: 2015-12-23

Abstract

A low temperature setting aluminum-divalent metal phosphate ceramic coating composition comprising a first aqueous based mixture comprising a solution of monoaluminum phosphate; polyphosphate, pyrophosphate, or salts thereof; and a second aqueous based mixture comprising a divalent metal oxide or hydroxide; a hydrocarboxylic acid in an amount sufficient to retard the reaction of the monoaluminum phosphate and the divalent metal oxide or hydroxide is provided. The composition and methods of forming coatings where the first aqueous based mixture and the second aqueous based mixture are configurable for combination together at a temperature between 0 C and less than about 140 C so as to provide, after combination, an aluminum-divalent metal phosphate ceramic coating, is also provided.

Description

ALUM I NUM PHOSPHATE CERAM ICS AND COATI NGS

Technical Field

[0001] This disclosure relates to aluminum phosphate ceramic and coatings therefrom. .

BACKGROUN D

[0002] Previous attempts a providing coatings and solid form of aluminum phosphate ceramics, typically prepared from the combining of divalent metal oxide or hydroxide and monoaluminum phosphate (MALP) was unsuccessful because the reaction was extremely exothermic, which prevents the formation of a homogenous solid product.

[0003] The use of trivalent metal oxides to form MALP requires external heating to increase the rate of the reaction as trivalent metal oxides are very slow in reacting with MALP at room temperature resulting in significant limitations to the application of this approach, especially in spray coatings and thin film forming processes.

SUM MARY

[0004] In a first embodiment, a low temperature setting aluminum-divalent metal phosphate ceramic coating composition is provided. The composition comprises a first aqueous based mixture having a pH of between 0-2 comprising: a solution of monoaluminum phosphate; polyphosphate, pyrophosphate, or salts thereof, optionally phosphoric acid; and a second aqueous based mixture comprising: a divalent metal oxide or hydroxide; and a hydrocarboxylic acid in an amount sufficient to retard the reaction of the monoaluminum phosphate and the divalent metal oxide or hydroxide; where the first aqueous based mixture and the second aqueous based mixture are configurable for combination together at a temperature between 0° C and less than about 140° C so as to provide, after combination, an aluminum-divalent metal phosphate ceramic coating. I n a first aspect, the divalent metal oxide or hydroxide is magnesium hydroxide.

[0005] In a second aspect, alone or in combination with any of the previous aspects, the hydrocarboxylic acid is a Ci_₂o alkyl, phenyl, or aryl, monoprotic, diprotic, or polyprotic organic acid; where alkyl includes straight-chain, branched, or cyclic alkyl, and haloalkyl. I n another aspect, alone or in combination with any of the previous aspects of the first embodiment, the hydrocarboxylic acid is a diprotic organic acid. I n yet another aspect, alone or in combination with any of the previous aspects of the first embodiment, the hydrocarboxylic acid is maleic acid, malonic acid, oxalic acid, succinic acid, adipic acid, or tartaric acid. In yet another aspect, alone or in combination with any of the previous aspects of the first embodiment, the hydrocarboxylic acid is acetic acid or citric acid.

[0006] In a third aspect, alone or in combination with any of the previous aspects, the first aqueous based mixture comprises: 5 to 50 weight percent solution of the monoaluminum phosphate; 0.1 to 25 weight percentage of phosphoric acid; 0.1 to 45 weight percent of the polyphosphate salt and/or pyrophosphate salt; and wherein the second aqueous based mixture comprises: 5 to 50 weight percent of the divalent metal oxide or hydroxide; and 0.1 to 25% of the hydrocarboxylic acid.

[0007] In a fourth aspect, alone or in combination with any of the previous aspects, the coating composition further comprises, in either or both of the first or the second aqueous based mixture, one or more of an inorganic mineral silicate, talc, amorphous magnesium silicate, amorphous calcium silicate, diatomaceous earth, aluminosilicate, olivine, feldspar, calcined Kaolin, mullite, colloidal silica, silicon dioxide, glass fibers in powder, floccular, or particle form, and amorphous silicon dioxide. In yet another aspect, alone or in combination with any of the previous aspects, the second aqueous based mixture excludes wollastonite.

[0008] In a fifth aspect, alone or in combination with any of the previous aspects, the coating composition further comprises, in either or both of the first or the second aqueous based mixture, at least one rheology modifier and/or suspending agent.

[0009] In a second embodiment, a method of forming an aluminum-divalent metal phosphate coating is provided. The method comprising the steps of: combining: (i) a first aqueous based mixture of monoaluminum phosphate and polyphosphate, pyrophosphate, or salts thereof; and (ii) a second aqueous based mixture of a divalent metal oxide or hydroxide and a hydrocarboxylic acid; contacting a surface with the combination of (i) and (ii); and maintaining the surface at a temperature between 0° C and less than about 140° C for a time sufficient so as to form the aluminum-divalent metal phosphate coating on the surface. In one aspect the polyphosphate, pyrophosphate, or salts thereof is ammonium polyphosphate.

[0010] In a first aspect, the first aqueous based mixture comprises: 5 to 50 weight percent solution of the monoaluminum phosphate; 0.1 to 25 weight percentage of phosphoric acid; 0.1 to 45 weight percent of the polyphosphate salt and/or pyrophosphate salt; and wherein the second aqueous based mixture comprises: 5 to 50 weight percent of the divalent metal oxide or hydroxide; and 0.1 to 25% of the hydrocarboxylic acid.

[0011] In other aspect, alone or in combination with any of the previous aspects, the divalent metal oxide or hydroxide is magnesium hydroxide.

[0012] In another aspect, alone or in combination with any of the previous aspects, the hydrocarboxylic acid is a Ci_₂₀ alkyl, phenyl, or aryl, monoprotic, diprotic, or polyprotic organic acid; where alkyl includes straight-chain, branched, or cyclic alkyl, and haloalkyl. In another aspect, alone or in combination with any of the previous aspects of the second embodiment, the hydrocarboxylic acid is acetic acid or citric acid. In yet another aspect, alone or in combination with any of the previous aspects of the second embodiment, the hydrocarboxylic acid is a diprotic organic acid such as maleic acid, malonic acid, oxalic acid, succinic acid, adipic acid, or tartaric acid.

[0013] In another aspect, alone or in combination with any of the previous aspects, the first or the second aqueous-based mixtures further comprise one or more of an inorganic mineral silicate, talc, amorphous magnesium silicate, amorphous calcium silicate, diatomaceous earth, aluminosilicate, olivine, calcined Kaolin, mullite, colloidal silica, silicon dioxide, and amorphous silicon dioxide. In another embodiment, alone or in combination with any of the previous aspects of the second embodiment, the second aqueous based mixture excludes wollastonite.

[0014] In another aspect, alone or in combination with any of the previous aspects, the first or the second aqueous-based mixtures further comprises at least one rheology modifier and/or suspending agent. In a another aspect, alone or in combination with any of the previous aspects, the first and/or the second aqueous based mixtures, independently, is shear thinned and spray coated on the surface simultaneously or sequentially.

[0015] In a third embodiment, a corrosion resistant article prepared by the method defined in any of the aspects of the second embodiment is provided.

[0016] In a fourth embodiment, a fire resistant article prepared by the method defined in any of the aspects of the second embodiment is provided.

[0017] In a fifth embodiment, an aluminum-magnesium phosphate ceramic coating formed by a method is provided. The coating formed by the method comprising the steps of: combining: (i) a first aqueous based mixture of monoaluminum phosphate and polyphosphate, pyrophosphate, or salts thereof, optionally phosphoric acid; and (ii) a second aqueous based mixture of magnesium oxide or hydroxide and a hydrocarboxylic acid in an amount sufficient to retard the reaction of the monoaluminum phosphate and the magnesium hydroxide; contacting a surface with the combination of (i) and (ii); and maintaining the surface at a temperature between 0° C and less than about 140° C for a time sufficient so as to form the aluminum-magnesium phosphate coating on the surface.

[0018] In an aspect of the fifth embodiment, the first aqueous based mixture comprises: 5 to 50 weight percent solution of the monoaluminum phosphate; 0.1 to 10 weight percent of the polyphosphate, pyrophosphate, or salts thereof, 0.1 to 45% phosphoric acid; and wherein the second aqueous based mixture comprises: 5 to 50 weight percent of the magnesium hydroxide; and 0.1 to 25% of the hydrocarboxylic acid. In another aspect, alone or in combination with any of the previous aspects, the aluminum-magnesium phosphate coating is essentially amorphous as determined by X-ray diffraction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] NONE

DETAILED DESCRIPTION

[0020] The invention provides a fire and corrosion resistant quick drying coating system, particularly for coating steel, aluminum concrete, mineral and/or ceramic substrates. The coating system comprises a binder consisting at least in part of an inorganic phosphatic binder, a metal oxide or hydroxide, retarder and fillers. The inorganic phosphate binder consists of an aqueous mono aluminum phosphate solution (MALP), comprising component (i) a mixture mono aluminum phosphate, optionally phosphoric acid, polyphosphate, pyrophosphate, or salts thereof and component (ii) a salt of a metal selected from the group consisting of alkali metals, alkaline earth metals and aluminum and mixtures thereof and component (iii) a retarder selected from hydrocarboxylic acid and component (iv) non reactive filler. The methods herein, when practiced with ammonium salts of polyphosphate or pyrophosphate, for example, provide for the use of a mono aluminum phosphate as acid source instead of KH₂P0₄, which may reduce or eliminate potassium leach out and provide a stable, storable, reduced exothermic coating that provides very high temperature resistance and corrosion resistance to articles. [0021] Typically, acid phosphate solutions are used to react with a metal oxide/hydroxide curing agent. In the case of aluminum phosphate and divalent metal oxides, e.g., magnesium oxide, the reaction is highly exothermic and does not lend itself to coating processes. The present disclosure provides a solution to this problem by using a hydrocarboxylic acid with the divalent metal oxide or hydroxide to modulate the thermodyanmics of the acid-base chemistry and provide for stable Part A/Part B formulations that can be spray coated to produce thin, robust coatings. The steel or concrete aluminum coated with compositions of the present disclosure does not require subsequent heat treatment to cure the coating, which typically, has been the case with existing mono aluminum phosphate based compositions used in monolith and form casting.

[0022] As used herein, the phrases "acidic phosphate component" and "acid-phosphate" and "acid component" and "Part A" are used interchangeably unless otherwise indicated. As used herein, the phrase "sparingly soluble acidic phosphate component" refers to inorganic phosphates of chemical formula A_m(H₂P0₄)_m.nH₂0, where A is metal cation, or mixtures thereof; where m = 1-3, and n = 0-6 having low solubility product constants in aqueous media, e.g., e.g., solubility constants (Ksp) of at least 10^"4, 10^"5, 10^"6, 10^"7, 10^"8, 10^"9 or smaller. In particular, the disclosure relates to aluminum phosphates, where m=3.

[0023] As used herein phrases "metal oxide and hydroxide" and "basic component" and "alkaline component" and "alkaline precursor" are used interchangeably unless otherwise indicated. The phrases "sparingly soluble metal oxide or hydroxide" and "sparingly soluble alkaline component" and "sparingly soluble alkaline precursor" are inclusive of metal oxide and hydroxide materials that are sparingly soluble, e.g., have low solubility product constants in aqueous media, e.g., e.g., solubility constants (Ksp) of at least 10^"4, 10^"5, 10^"6, 10^"7, 10^"8, 10^"9 or smaller. In one aspect, the solubility of the metal oxide or hydroxide is less than about 0.1 moles/liter water. In one aspect, the phrases sparingly soluble basic metal oxide and sparingly soluble basic metal hydroxide component" and "sparingly soluble metal oxide and hydroxide" and "sparingly soluble alkaline component" and "sparingly soluble alkaline precursor" are exclusive of materials that are readily soluble, e.g., have high solubility product constants in aqueous media.

[0024] As used herein, the product of the "acid-phosphate" and the "metal oxide and hydroxide" provides for a metal phosphate phase having, in one aspect, have low solubility product constants in aqueous media, e.g., e.g., solubility constants (Ksp) of 10^"8, 10^"9 or smaller. [0025] As used herein, the phrase "aqueous based mixture" refers to a combination of at least a quantity of water and at least one other component. For example, the aqueous based mixture can contain mostly water and suspended, dispersed, or slurried components, and may also contain non-aqueous components such as alcohols and other solvents. Preferably, water is the major liquid phase. The component can be soluble, partially soluble, or sparingly soluble in the aqueous based mixture.

[0026] As used herein, the term "carboxylic acid" refers to the univalent radical, -COOH, characteristic of an organic acid. "Hydrocarboxylic acid" refers to Ci-C₅₀ mono, diprotic and polyprotic carboxylic acids.

[0027] As used herein the compound "monoaluminum phosphate" or "mono aluminum tris(dihydrogen phosphate)" is intended to mean AI(H₂P0₄)₃ that has a phosphorus/aluminum molar ratio of 3 or less, and is exclusive of acid aluminum phosphates and the like generally having a phosphorus/aluminum molar ratio of greater than 3.

[0028] The amount of solids (e.g., the acid phosphate, divalent metal oxide or hydroxide and/or other solids) present in the aqueous mixture can be between 1 weight percent to about 95 weight percent, preferably 35-90 weight percent, or 50-80 weight percent solids.

[0029] The present disclosure provides manufacturing methods that optimize the preparation of the acidic phosphate components and the divalent metal oxide or hydroxides prior to combination so as to manage the chemical reactions and/or pH of the chemical reactions of the metallic surface and the acidic phosphate components and the divalent metal oxide or hydroxides. The manufacturing methods provide insoluble, substantially amorphous non-porous phosphate coatings that can eliminate the need for conventional pre- and/post- treatment of a surface, post-high temperature set, and provide corrosion resistance to corrodible surfaces, and fire protection.

[0030] In one aspect, the aqueous mixture of acidic phosphate component optionally comprises, with or without phosphoric acid, one or more of fillers, pigments, and processing adis.

[0031] The aqueous suspension of divalent metal oxide or hydroxide comprises alkali minerals, optionally comprising one or more hydrocarboxylic acids, having a pH between about 8 to about 12, preferably about 9 to about 14, more preferably a pH between about 11 to about 13. Hydrocarboxylic acids alone or in combination with amorphous magnesium silicate, silica, amorphous silicon dioxide, diatomaceous earth, olivine, and the like can be added to the acidic phosphate and/or the basic metal oxide/hydroxide component. In one aspect, wollastonite is excluded in the combination of hydrocarboxylic acid and metal oxide or hydroxide, as the hydrocarboxylic acid has a tendency to react with the wollastonite and form solids, thus reducing the self-life and storage time of the Part B.

[0032] Because of the difference in solubility, the acidic phosphate component, with a higher solubility than that of the divalent metal oxide or hydroxide, can enter into solution first or in slight excess, and can react with the metallic surface (e.g., iron/steel) to provide metallic ions (e.g., ferrous ions) at the surface and/or in the aqueous phosphate suspension, which is relatively acidic at the metallic surface. As the divalent metal oxide or hydroxide goes into solution, it can react with the acidic phosphate component and/or the metallic ions, and chemically combine with the metallic phosphate at the surface and/or in solution. It is generally believed that the suspension can become temporarily alkaline in the local environment of the metallic surface, which may result in more acidic phosphate from the suspension to enter into solution such that the local environment about the metallic surface slurry becomes acidic again. This acid-base equilibrium process can repeat multiple times, with the system ultimately reaching a thermodynamic and/or kinetic equilibrium at the metallic surface that is believed to be in the alkaline range. In this process, it is further believed that the hydrocarboxylic acids chemically interact with the metal oxide or hydroxide and provide favorable reaction kinetics between the aluminum phosphate acid and base and/or the surface (if metal). The hydrocarboxylic acids can also be chemically incorporated into the metallic- phosphate and/or chemically bond to the metallic surface or a portion of the hydrocarbon of the acid can migrate to the surface (air-facing) of the set ceramic and provide additional functionality, such as hydrophobicity.

[0033] To be clear, such hydrocarboxylic acids are not simply "additives" in the ceramic. The hydrocarboxylic acid is added and intended to chemically interact with one or more of the divalent metal oxide or hydroxide. The hydrocarboxylic acids can be combined, synergistically, for example, to Part B , and is stable in the presence of such fillers and pigments such as inorganic silicates talc, amorphous magnesium silicate, amorphous calcium silicate, diatomaceous earth, silicon dioxide, olivine, calcined kaolin, mullite, alumino silicate, feldspar, and amorphous silicon dioxide, which also can combine with one or more of the acidic phosphate component, the divalent metal oxide or hydroxide, and/or the metallic surface, and/or the metallic phosphate moieties present and/or created.

[0034] In some embodiments, polyphosphate, pyrophosphate, or salts thereof, are used in Part A in combination with the use of hydrocarboxylic acids in Part B, so as to provide additional and/or synergistic thermodynamic control of the reaction kinetics so as to provide a method of coating onto surfaces an amorphous aluminum phosphate. Salts of polyphosphates and pyrophosphates include ammonium salts and alkali metal (Sodium, Potassium) salts, for example. Salts of pyrophosphate can include ammonium pyrophosphate (NH₄)₄P₂0₇, tetrasodium pyrophosphate (Na₄P₂0₇), calcium pyrophosphate (CaH₂P₂0₇), and disodium pyrophosphate (Na₂H₂P₂0₇), for example.

[0035] The final pH of the metal phosphate coating prepared from same can be provided in the passivation range of steel, e.g., between about pH 9 and about pH 12, between about pH 9.5 and about pH 11.5, between about pH 10.0 and about pH 11.0, between about pH 9.0 and about pH 10.5, between about pH 9.5 and about pH 10.0, between about pH 10.0 and about pH 10.5. In one aspect, the surface of a coated article can be provided with a basic nature, for example between about pH 9 and about pH 12, between about pH 9.5 and about pH 11.5, between about pH 10.0 and about pH 11.0, between about pH 9.0 and about pH 10.5, between about pH 9.5 and about pH 10.0, between about pH 10.0 and about pH 10.5 to prevent or inhibit bacterial and/or microorganism growth or colonization on the surface of the coated article. The coated article can be, for example, a medical article, ship hull, surface, or water treatment facility component.

[0036] Similar conversion coatings can be provided for aluminum or aluminum alloys using the methods and compositions herein disclosed, and optionally, the addition of hydrocarboxylic acids selected from those which are of optimal pKa for aluminum or aluminum alloys. Other corrosion inhibitors, in addition to or independently, can be added to the acidic phosphate component/divalent metal oxide or hydroxide composition prior to set. Addition of other hydrophobic agents in the acidic phosphate Part A or divalent metal oxide or hydroxide Part B, can be employed.

[0037] In one aspect, the instant compositions can be configured as separate, atomizible, sprayable inorganic phosphate precursors that can be sprayed at a relatively thin thickness. The compositions can hold high solids contents and yet still hold the solids until setting and thus avoiding the solids migrating or dislodging from the point of application, e.g., down a wall, beam, curved surface, or from a ceiling surface. Such spray coated phosphate ceramic compositions produce high-strength, rapid-setting phosphate ceramic coatings that provide corrosion protection and/or be used as an undercoating in combination with a polymeric coating or paint, such as an acrylic- or urethane-based coating or paint. In one aspect, said phosphate spray coating compositions are suitable for spray coating on metal surfaces, for example, structural elements and chassis of transportation vehicles such as automobiles, trains, cycles, aerospace vehicles, trucks, and buses.

[0038] One or more of the components (acid-phosphate or metal oxide or hydroxide) of the instant composition can be wet milled to an average particle size of about 1 to about 150 micron, or to about 1 to about 100 micron, or to about 5 to about 50 micron, or about 10-25 micron. In one aspect, the acidic phosphate or basic precursor is wet-milled so that the average particle size passes through 230 mesh sieve (less than 70 micron). To improve atomization and/or cure/set and/or appearance qualities of the coating and to reduce or eliminate pit-defects in the coating, a small average particle size for the metal oxide or hydroxide is used, for example, 1 micron to less than 50 micron, or 1 micron to less than 25 micron.

[0039] In one aspect, the atomizable phosphate ceramic composition can comprise an acidic phosphate component comprising an aqueous mixture of monoaluminum-phosphate, for adjusted to a pH of about 1.2 to 1.8 with ammonium poly phosphate; a divalent metal oxide or hydroxide, comprising, for example, an aqueous mixture of an magnesium hydroxide adjusted to a pH of between 8-10 with the hydrocarboxylic acid; and optionally a rheology modifier/suspending agent in an amount capable of providing shear thinning of either the first component or the second component and further capable of suspending a high solids content of either the first component or the second component for atomization. Optionally, pigments and/or aggregate material can be present in an amount in at least one of the acidic phosphate and the divalent metal oxide or hydroxide capable of imparting an observable color and/or texture, to increase the pH of mono aluminum phosphate from

[0040] The above atomizible spray coating can provide a thin, paint-like coating for imparting hydrophobicity and/or corrosion resistance to metallic surfaces. Water may be added to the precursor component to reduce the viscosity thereof, or other types of viscosity reducing agents and/or rheology modifiers may be used. Optionally, a rheology modifier/suspending agent in an amount capable of providing shear thinning of either the first component or the second component and further capable of suspending a high solids content of either the first component or the second component for atomization can be added. In one aspect, the rheology modifier is added in an amount of 0.01 to about 10 weight percent of the composition. The rheology modifier/suspending agent can be at least one of guar gum, diutan gum, welan gum, and xanthan gum. By using a rheology modifier/suspending agent in an amount capable of providing shear thinning of either the acidic component or the metal oxide or hydroxide and further capable of suspending a high solids content of either the acidic component or the metal oxide or hydroxide for atomization, excellent paint-like coatings for imparting corrosion resistance to metallic surfaces are obtained. Commercial additives that prevent algae growth may also added to this precursor so that no algae growth occurs during storage of this precursor.

[0041] In certain aspects of the present disclosure, the metallic surface is that of a transition metal or its alloy, for example, iron, chromium, aluminum, copper, etc. Processes and articles prepared therefrom disclosed and described herein overcome many if not all of the problems related to conventional passivation processes of iron, steels, aluminum, and other corrodible metals. The instant processes also provide a more economical, environmentally- friendly method of coating steel and other metal surfaces with acid-base inorganic phosphate based coatings that not only passivate the layer but also provide abrasion resistance along with good aesthetics in one step.

[0042] The metal phosphate ceramics, when used as a coating as disclosed herein can comprise, in part, the formation of poly phosphates, and in particular, poly phosphates formed by phosphites at the interfacial regions of the substrate surface in the instant passivation layer. Polyphosphate alone or in combination with the hydrocarboxylic acid can provide impermeablity to water and humidity, and, independently, can improve corrosion resistance to the metallic surface. In one aspect, polyphosphates in combination with metal silicates are present at the metallic surface and/or interfacial regions of the metal substrate as comprising the passivation layer and/or providing water resistance or water proofing of the ceramic.

[0043] Acidic phosphate component - In one aspect, the acidic phosphate component consists of an acid-phosphate representative of the formula, AI(H₂P0₄)3.nH₂0. nH₂0 in the formula above is simply the bound water, where n can be any number, normally ranging from 0 to 25. In one aspect, monoaluminum phosphate solution is used. [0044] It is possible to use hydrophosphates of trivalent metals such as aluminum, iron and manganese represented by the formula AH₃(P0₄)₂.nH₂0, where A is a transition metal that includes aluminum, iron, manganese, yttrium, scandium, and all lanthanides such as lanthanum, cerium, etc.

[0045] In case the pH of the acidic precursor is higher than needed for instant reaction, phosphoric acid may be added and the pH may be adjusted to bring down the pH.

[0046] Divalent metal oxide or hydroxide includes, for example, basic oxides, hydroxides and basic minerals. The divalent metal oxide or hydroxide generally consists of a sparsely soluble oxide, or preferably a hydroxide with a solubility product constant less than the acid phosphate precursor. The oxide may be represented by the formula B₂0 or B(OH)₂, where B is a divalent metal. In one aspect, divalent oxides are magnesium oxide or magnesium hydroxide. In other aspects of the instant disclosure, 0 to about 10 molar excess of divalent metal oxide or hydroxide relative to acidic component is used. For example, about 0.1-10 molar excess of Mg(OH)₂ based on acid-phosphate can be used. In one aspect, the molar ratio of acid:base components can be between about 0.9:1.0 to about 1.0:3.0; preferably about 1.0:2.0; and most preferably, about 1.0:1.8. For example, the composition comprising Mg(OH)₂:AIH₂P0₄)₃ =1.8:1.0 provides equal volumes of Parts A and B during spraying. In other aspects, spray coatings of the instant compositions having a molar ratio of about 1:2 or about 1: 1.5 (acid:base components) with mixing, sprayed well and corrosion-protected and/or water proofed effectively.

[0047] It has been observed that without the hydrocarboxylic acid with the metal oxide or hydroxide (in Part B), the composition, upon mixing is unsuitable for coating and for thin film formation. Surprisingly, the particular stabilizing agent is not intuitive. Thus, an effective amount of the hydrocarboxylic acid provides thermodynamic and/or kinetic control of the acid- phosphate-divalent inorganic oxide/hydroxide reaction. In one aspect, the minimum loading of the hydrocarboxylic acid is about 0.5 to about 20 weigh percent, or about 1 to about 10 weight percent (of the basic metal oxide/hydroxide).

[0048] In another aspect, the instant compositions, either as bulk forms or as coatings can be formulated to provide aesthetic properties, such as color, proper shine, and texture. This effect may be achieved, for example, by adding pigments, color aggregate, crushed glass, sand, etc, to the instant acidic phosphate/alkaline metal oxide/hydroxide formulations with hydrocarboxylic acid. For example, the resulting coating comprising crushed glass prepared by the processes disclosed herein provides a very dense, glassy surface. Additional suitable ceramic pigments may be further added to produce colored paints. Soluble glass in combination with the instant compositions above can also be used in formulations for coating of solid objects, to provide very dense, glassy solid coatings having corrosion resistance.

Experimental Section

[0049] The following examples are illustrative of the embodiments presently disclosed, and are not to be interpreted as limiting or restrictive. All numbers expressing quantities of ingredients, reaction conditions, and so forth used herein may be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth herein may be approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of any claims in any application claiming priority to the present application, each numerical parameter should be construed in light of the number of significant digits and ordinary rounding approaches. Several experimental examples, listed below, were conducted in order to formulate, coat, and demonstrate the attributes of the instant compositions disclosed herein. pH values are provided using pH meters having +/- 0.5 accuracy.

Aluminum Inorganic Phosphate Coating Compositions

[0050] The following exemplary, non-limiting example is provided in Table 1:

Table 1. Exemplary Aluminum Phosphate Ceramic Compositions Part A Weight Percent

Mono Aluminum Phosphate Solution 5-50%

85% Phosphoric acid 0.1-25%

Poly Phosphate Salt 0.5-45%

Non reactive Filler (Feldspar) 2-60%

Colloidal Silica 2-10%

Glass Fiber 2-15%

Part B Weight Percent

Magnesium Hydroxide 5-50%

Citric acid 0.5-15%

Non reactive Filler (Olivine) 15-65%

X Gum 0.01-0.1%

Table 2. Exemplary Aluminum Phosphate Ceramic Compositions Ranges

[0051] The above sample in Table 1 was prepared with a slight molar excess of Part B and represent a single exemplary embodiment. Table 2 provides acceptable ranges of materials for Part A and Part B useful in carrying out the method of the present disclosure. In one aspect, ammonium polyphosphate was used. In other aspect, sod

[0052] Based on the above, a method of producing essentially an amorphous berlinite- like coating is provided without heating the combination at an elevated temperature (for example, above 140 degrees Centigrade, sufficient to form a berlinite phase. Coatings prepared under the present methods comprising the amorphous berlinite-like phase (AIP0₄) are detectable by and have been observed by x-ray diffraction.

Claims

WHAT IS CLAIMED:

1. A low temperature setting aluminum-divalent metal phosphate ceramic coating composition comprising a first aqueous based mixture having a pH of between 0-2 comprising: a solution of monoaluminum phosphate and or phosphoric acid; polyphosphate, pyrophosphate, or salts thereof; and a second aqueous based mixture comprising: a divalent metal oxide or hydroxide; a hydrocarboxylic acid in an amount sufficient to retard the reaction of the monoaluminum phosphate or phosphoric acid and the divalent metal oxide or hydroxide; wherein the first aqueous based mixture and the second aqueous based mixture are configurable for combination together at a temperature between 0° C and less than about 140° C so as to provide, after combination, an aluminum-divalent metal phosphate ceramic coating.

3. The coating composition of claim 1, wherein the divalent metal oxide or hydroxide is magnesium hydroxide.

5. The coating composition of claim 1, wherein the hydrocarboxylic acid is a Ci_₂₀ alkyl, phenyl, or aryl, monoprotic, diprotic, or polyprotic organic acid; where alkyl includes straight- chain, branched, or cyclic alkyl, and haloalkyl.

6. The coating composition of claim 1, wherein the hydrocarboxylic acid is a diprotic organic acid.

7. The coating composition of claim 6, wherein the hydrocarboxylic acid is maleic acid, malonic acid, oxalic acid, succinic acid, adipic acid, or tartaric acid.

8. The coating composition of claim 5, wherein the hydrocarboxylic acid is acetic acid or citric acid.

9. The coating composition of any one of the claims 1-7, wherein the first aqueous based mixture comprises: 5 to 50 weight percent solution of the monoaluminum phosphate; 0.1 to 25% phosphoric acid

0.1 to 45 weight percent of the polyphosphate, pyrophosphate, or salts thereof and wherein the second aqueous based mixture comprises:

5 to 50 weight percent of the divalent metal oxide or hydroxide; and 0.1 to 25% of the hydrocarboxylic acid.

10. The coating composition of claim 1, further comprising, in either or both of the first or the second aqueous based mixture, one or more of an inorganic mineral silicate, talc, amorphous magnesium silicate, amorphous calcium silicate, diatomaceous earth, aluminosilicate, olivine, feldspar, calcined Kaolin, mullite, tricalcium phosphate, colloidal silica, silicon dioxide, glass fibers in powder, floccular, or particle form, and amorphous silicon dioxide.

11. The coating composition of claim 1, wherein the second aqueous based mixture excludes wollastonite.

12. The coating composition of claim 1, further comprising, in either or both of the first or the second aqueous based mixture, at least one rheology modifier and/or suspending agent.

13. A method of forming an aluminum-divalent metal phosphate coating, the method comprising the steps of: combining:

(i) a first aqueous based mixture of monoaluminum phosphate, phosphoric acid and polyphosphate, pyrophosphate, or salts thereof;

(ii) a second aqueous based mixture of a divalent metal oxide or hydroxide and a hydrocarboxylic acid; contacting a surface with the combination of (i) and (ii); and maintaining the surface at a temperature between 0° C and less than about 140° C for a time sufficient so as to form the aluminum-divalent metal phosphate coating on the surface.

14. The method of claim 13, wherein the first aqueous based mixture comprises:

5 to 50 weight percent solution of the monoaluminum phosphate,

0.1 to 25% phosphoric acid and

5 to 50 weight percent of the divalent metal oxide or hydroxide; and

0.1 to 25% of the hydrocarboxylic acid.

16. The method of any one of claims 13 or 14, wherein the divalent metal oxide or hydroxide is magnesium hydroxide.

18. The method of any one of the claims 13 or 14, wherein the hydrocarboxylic acid is a Ci_₂o alkyi, phenyl, or aryl, monoprotic, diprotic, or polyprotic organic acid; where alkyi includes straight-chain, branched, or cyclic alkyi, and haloalkyl.

19. The method of claim 18, wherein the hydrocarboxylic acid is acetic acid or citric acid.

20. The method of claim 18, wherein the hydrocarboxylic acid is a diprotic organic acid.

21. The method of claim 18, wherein the hydrocarboxylic acid is maleic acid, malonic acid, oxalic acid, succinic acid, adipic acid, or tartaric acid.

22. The method of any one of claims 13 or 14, further comprising one or more of an inorganic mineral silicate, talc, amorphous magnesium silicate, amorphous calcium silicate, diatomaceous earth, aluminosilicate, olivine, calcined Kaolin, mullite, colloidal silica, silicon dioxide, and amorphous silicon dioxide.

23. The method of claim 22, wherein the second aqueous based mixture excludes wollastonite.

24. The method of claim 25, further comprising at least one rheology modifier and/or suspending agent.

25. The method of any one of claims 13 or 14, wherein the first and/or the second aqueous based mixtures, independently, is shear thinned and spray coated on the surface simultaneously or sequentially.

26. A corrosion resistant article prepared by the method defined in any one of claims 13-14.

27. A fire resistant article prepared by the method defined in any one of claims 13-14.

28. An aluminum-magnesium phosphate ceramic coating formed by the method comprising the steps of: combining:

(i) a first aqueous based mixture of monoaluminum phosphate, phosphoric acid and polyphosphate, pyrophosphate, or salts thereof; and

(ii) a second aqueous based mixture of magnesium oxide or hydroxide and a hydrocarboxylic acid in an amount sufficient to retard the reaction of the monoaluminum phosphate and the magnesium hydroxide; contacting a surface with the combination of (i) and (ii); and maintaining the surface at a temperature between 0° C and less than about 140° C for a time sufficient so as to form the aluminum-magnesium phosphate coating on the surface.

29. The aluminum phosphate coating of claim 28, wherein the first aqueous based mixture comprises:

5 to 50 weight percent solution of the monoaluminum phosphate; 0.1 to 25% phosphoric acid

0.1 to 45 weight percent of the polyphosphate, pyrophosphate, or salts thereof and wherein the second aqueous based mixture comprises: 5 to 50 weight percent of the magnesium hydroxide; and 0.1 to 25% of the hydrocarboxylic acid.

30. The aluminum phosphate coating of any one of claims 28 or 29, wherein the aluminum- magnesium phosphate coating is essentially amorphous as determined by X-ray diffraction.