ANTICORROSION COATING AND ARTICLE MADE THEREFROM

Abstract

A corrosion inhibiting coating is applied to a target substrate that includes dual- or poly-terminus siloxane having pendant and/or terminal amine or thiol moieties reacted with a strained ring alkoxysilane. The siloxanes adhered to susceptible surface with a tertiary amine or divalent mercaptan chain linker extending therebetween. The resulting coating functions as a corrosion inhibitor, and in some embodiments as a primer for subsequent painting. The resulting coating is generally invisible to the unaided human eye. A process of forming the corrosion inhibiting coating includes forming a water or solvent based emulsion solution by combining a solvent and/or water with suitable surfactants, an amine functional silicone fluid, and a strained ring containing alkoxysilane reactive with a nitrogen or sulfur containing curative chain linker.

Claims

1. A structure comprising: a target substrate having a surface; and a coating formed by the reaction of at least one equivalent of a formula (IA or IB) with a formula (II) or (V) covalently bonded to the surface; where a strained ring alkoxysilane operative herein is a monomer or oligomer that typically has an average molecular weight of less than 4,000 Daltons having the formula (IA or IB):
(OCH.sub.2CH)R.sup.1XR.sup.2Si(OR.sup.3).sub.3(IA), or
(OCH.sub.2CH)R.sup.1XR.sup.2Si(Y.sub.n)(OR.sup.3).sub.3-n(IB) where R.sup.1 is C.sub.1-C.sub.4 alkyl, (CH.sub.2).sub.xCHCH.sub.2, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 4 inclusive, (CH.sub.2).sub.jCC, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 4 inclusive, an aromatic, a heteroaromatic, or together with (OCH.sub.2CH) forms epoxycyclopentyl (OC.sub.5H.sub.7), epoxycyclohexyl (OC.sub.6H.sub.9), or epoxycycloheptyl (OC7H.sub.11); X is a nullity or oxygen, R.sup.2 is C.sub.2-C.sub.6 alkyl, (CH.sub.2).sub.xCHCH.sub.2, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 20 inclusive, (CH.sub.2).sub.jCC, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 20 inclusive, an aromatic, a heteroaromatic, R.sup.3 in each occurrence is independently C.sub.1-C.sub.6 alkyl, Y is C.sub.1-C.sub.4 alkyl, and n is an integer of 0 or 1; the functional siloxane having a formula (II):
R.sup.4(Si(R.sup.5)(R.sup.6)O).sub.nR.sup.4(II) where R.sup.4 is independently in each occurrence Si(C.sub.1-C.sub.4 alkyl).sub.3 and R.sup.4 is Si(C.sub.1-C.sub.4 alkyl).sub.3-O, R.sup.5 is independently in each occurrence C.sub.1-C.sub.4 alkyl, R.sup.6 is independently in each occurrence C.sub.1-C.sub.4 alkyl, (C.sub.1-C.sub.6 alkyl)-NH.sub.2, (C.sub.1-C.sub.6 alkyl)-N(H)C.sub.1-C.sub.6 alkyl, (C.sub.1-C.sub.6 alkyl)-N(H)(C.sub.1-C.sub.6 alkyl)-NH.sub.2, or (C.sub.1-C.sub.6 alkyl)-SH, with the proviso that at least one occurrence of R.sup.6 includes a primary amine, secondary amine, or a mercaptan, and n is an integer between 1 and 200 inclusive. or the alkoxy silane having a formula (VA or VB):
Q-R.sup.7ZR.sup.7Si(OR.sup.3)(VA), or
Q-R.sup.7ZR.sup.7Si(Y.sub.n)(OR.sup.3).sub.3-n(VB) where Q is H2N or HS, R.sup.7 is independently in each occurrence (CH.sub.2).sub.m, or (CH(C.sub.1-C.sub.4 alkyl)CH.sub.2).sub.m, or (CH.sub.2).sub.mAr(CH.sub.2).sub.p, Z is a nullity (yielding a covalent bond R.sup.7R.sup.7) or N(H) or S, m is independently in each occurrence an integer of 0 to 12 inclusive, p is an integer of 0 to 12 inclusive, R.sup.3 is independently in each occurrence C.sub.1-C.sub.6 alkyl, and Ar is an aromatic of C.sub.6H.sub.4, or a substituted aromatic in which at least one hydrogen is replaced with a substituent of a halide, thiol, an amine, hydroxyl, carboxyl, carbonyl, sulfonyl, or alkyl, Y is C.sub.1-C.sub.4 alkyl, and n is an integer of 0 or 1.

2. The structure of claim 1 wherein said strained ring alkoxysilane where R.sup.1 is C.sub.1-C.sub.4 alkyl and R.sup.2 is C.sub.2-C.sub.6 alkyl.

3. The structure of claim 1 wherein said strained ring alkoxysilane where R.sup.1 together with (OCH.sub.2CH) forms (OC.sub.6H.sub.9).

4. The structure of claim 1 wherein said strained ring alkoxysilane is at least one of 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl methyldiethoxysilane, 3-glycidoxypropyl triethoxysilane, and combinations thereof.

5. The structure of claim 1 wherein said functional siloxane having the formula (II) is present.

6. The structure of claim 5 where R.sup.4 is in every occurrence the same.

7. The structure of claim 5 where R.sup.6 in at least one occurrence is (C.sub.1-C.sub.6 alkyl)-NH.sub.2, (C.sub.1-C.sub.6 alkyl)-N(H)C.sub.1-C.sub.6 alkyl, (C.sub.1-C.sub.6 alkyl)-N(H)(C.sub.1-C.sub.6 alkyl)-NH.sub.2, or (C.sub.1-C.sub.6 alkyl)-SH.

8. The structure of claim 1 wherein said amine functional silicone has a formula (III) or (IV): ##STR00003## where x is an integer between 1 and 1,000 inclusive, and y is an integer between 1 and 200 inclusive.

9. The structure of claim 1 wherein said alkoxy silane having the formula (VA or VB) is present.

10. The structure of claim 9 where Q is H.sub.2N.

11. The structure of claim 9 where R.sup.7 is in every occurrence the same.

12. The structure of claim 9 where Z is a nullity.

13. The structure of claim 9 where Z is N(H) or S.

14. The structure of claim 1 wherein said coating has a thickness of between 0.1 and 20 microns and transparent to an unaided normal human eye.

15. The structure of claim 1 wherein said coating is hydrophobic.

16. The structure of claim 1 wherein target substrate is metal.

17. The structure of claim 1 wherein target substrate is steel.

18. The structure of claim 1 wherein target substrate is an external vehicle component.

19. The structure of claim 1 wherein target substrate is aluminum.

20. The structure of claim 1 wherein the surface of said target substrate is metal oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 illustrates the prior art chemical reactions that occur during the corrosion of steel;

[0017] FIGS. 2A-2C illustrate a prior art existing passivation process that involves modifying the surface of a material by oxidation in order to isolate the anode and cathode;

[0018] FIG. 3 illustrates a prior art process of forming a hydrophobic barrier on a material substrate;

[0019] FIGS. 4A and 4B illustrate prior art chemical reactions for formation of surface corrosion inhibitors including alkyl dicarboxylates, and triethanolamine and triethanolamine borate, respectively; and

[0020] FIG. 5 illustrates an exemplary bonding reaction between mono ethanolamine and two strained ring alkoxy silanes depicted as gamma glycidoxy propyl trimethoxy silane (GLYMO).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention has utility as a corrosion inhibiting coating that includes the reaction product of a strained ring alkoxysilane with a functional silicone fluid or an alkoxysilane, and the combination of this reaction product with the surface of a target metal substrate, most particularly steel or aluminum. It is appreciated that metal oxides, ceramics, concrete, and cellulosics such as wood also benefit from the inventive coatings. Embodiments of the inventive coating composition, when applied to the surface of a target substrate, provide resistance to corrosion from salt spray, acid environments, and atmospheric moisture. Embodiments of the inventive coating composition form an extremely thin (<10 microns) solid coating on the metal surface unlike prior art existing coatings that are generally thicker (>20 microns), and generally need to be removed before secondary operations (e.g., painting), or have potentially hazardous vapors. Target substrates specifically include external metal components of a vehicle.

[0022] Embodiments of the inventive corrosion inhibiting coating provide a hard and thin film which is not greasy, oily, or waxy, has no significant vapor pressure, and the coated object is amenable to being directly painted over or powder coated. The inventive corrosion inhibiting coating may be applied by wiping or spraying and cures within 24 hours. The corrosion inhibiting coating is thin enough not to affect dimensional tolerances of surfaces, holes, protrusions, or threads and is invisible (i.e, optically transparent) to the unaided normal human eye. Objects with the composition coating resist direct salt spray and exposure to formic acid vapors, and hence may make transit coatings to prevent corrosion of packaged and shipped and/or stored metal objects.

[0023] It is to be understood that in instances where a range of values are provided, for example with respect to a weight percentage range of a composition component, that the range is intended to encompass not only the end point values of the range but also intermediate values of the range as explicitly being included within the range and varying by the last significant figure of the numeral. By way of example, a recited range of from 1 to 4 is intended to include 1-2, 1-3, 2-4, 3-4, and 1-4.

[0024] Embodiments of the inventive corrosion inhibiting coating employ chemical coupling based on ethanolamines to form ultra-thin layers (<10 microns) with customizable adhesion and surface characteristics that include tunable hydrophobicity and increased adhesion of finishes including but not limited to paints, E-coatings, and powder coatings.

[0025] An inventive coating is created by the amine or thiol cure of a strained ring to form a secondary or tertiary amine or thiol with a silane functionality used to adhere with a target substrate.

[0026] A strained ring alkoxysilane operative herein is a monomer or oligomer that typically has an average molecular weight of less than 4,000 Daltons having a formula (IA):

(OCH.sub.2CH)R.sup.1XR.sup.2Si(OR.sup.3).sub.3(IA)

where R.sup.1 is C.sub.1-C.sub.4 alkyl, (CH.sub.2).sub.xCHCH, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 4 inclusive, (CH.sub.2).sub.jCC, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 4 inclusive, an aromatic, a heteroaromatic, or together with (OCH.sub.2CH) forms epoxycyclopentyl (OC.sub.5H.sub.7), epoxycyclohexyl (OC.sub.6H.sub.9), or epoxycycloheptyl (OC7H.sub.11); X is a nullity, nitrogen, sulfur, or oxygen, R.sup.2 is C.sub.2-C.sub.6 alkyl, (CH.sub.2).sub.xCHCH, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 20 inclusive, (CH.sub.2).sub.jCC, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 20 inclusive, an aromatic, a heteroaromatic, R.sup.3 in each occurrence is independently C.sub.1-C.sub.6 alkyl. It is appreciated that an alkyl as used herein is linear, branched or cyclic with the proviso that cyclic alkyls are C.sub.4-C.sub.6. Strained ring alkoxysilanes operative herein illustratively include 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, and combinations thereof.

[0027] In other inventive embodiments, a strained ring alkoxysilane operative herein is a monomer or oligomer that typically has an average molecular weight of less than 4,000 Daltons having a formula (IB):

(OCH.sub.2CH)R.sup.1XR.sup.2Si(Y.sub.n)(OR.sup.3).sub.3-n(IB)

where R.sup.1 is C.sub.1-C.sub.4 alkyl, (CH.sub.2).sub.xCHCH, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 4 inclusive, (CH.sub.2).sub.jCC, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 4 inclusive, an aromatic, a heteroaromatic, or together with (OCH.sub.2CH) forms epoxycyclopentyl (OC.sub.5H.sub.7), epoxycyclohexyl (OC.sub.6H.sub.9), or epoxycycloheptyl (OC7H.sub.11); X is a nullity, nitrogen, sulfur, or oxygen, R.sup.2 is C.sub.2-C.sub.6 alkyl, (CH.sub.2).sub.xCHCH.sub.2, or (CH.sub.2).sub.yCHCH(CH.sub.2).sub.z where x or (y+z) is an integer of 0 to 20 inclusive, (CH.sub.2).sub.jCCH, or (CH.sub.2).sub.kCC(CH.sub.2).sub.r where j or (k+r) is an integer of 0 to 20 inclusive, an aromatic, a heteroaromatic, R.sup.3 in each occurrence is independently C.sub.1-C.sub.6 alkyl, Y is C.sub.1-C.sub.4 alkyl, and n is an integer of 0 or 1. Again, it is appreciated that an alkyl as used herein is linear, branched or cyclic with the proviso that cyclic alkyls are C.sub.4-C.sub.6. Strained ring alkoxysilanes operative herein illustratively include 3-glycidoxypropyl methyldiethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, 2-(3,4 epoxycyclohexyl) methyldiethoxysilane, and combinations thereof, along with combinations of formula (IA).

[0028] Without intending to be bound to a particular theory, a strained ring alkoxysilane reacts with water to form a silanol with highly reactive hydroxyl groups from the displacement of the alkoxyl groups by hydroxyls. The hydroxyl groups are well-suited to covalently bond to a corrosion prone metal surface or an oxide formed thereon. FIG. 5 illustrates the chemical formation of linked structures that have nitrogen bonded to the ethanol moiety. Crosslinking or chain extension then occurs between the alcoholyzed methoxy groups. Mono ethanolamine and two strained ring alkoxy silanes of gamma glycidoxy propyl trimethoxy silane (GLYMO). Without intending to be bound to a particular theory, it is believed that the reaction of a lower molecular weight amine with an epoxy is a catalyst for alcoholyzation and subsequent oligomerization of the product through removal of water and formation of siloxane bonds.

[0029] The glycidyl functionality of the strained ring alkoxysilane is readily cured by reaction with an amine or mercaptan functionality associated with a linker chain. The linker chain illustratively includes an aliphatic, a silicone, a perfluorosilicone, an alkoxy silane, an aminoalkyl, a thioalkyl, an aromatic, or a combination thereof. A functional siloxane operative herein has a formula (II):

R.sup.4[Si(R.sup.5)(R.sup.6)O].sub.nR.sup.4(II)

where R.sup.4 is independently in each occurrence Si(C.sub.1-C.sub.4 alkyl).sub.3, and R.sup.4 is Si(C.sub.1-C.sub.4 alkyl).sub.3-O, R.sup.5 is independently in each occurrence C.sub.1-C.sub.4 alkyl, R.sup.6 is independently in each occurrence C.sub.1-C.sub.4 alkyl, (C.sub.1-C.sub.6 alkyl)-NH.sub.2, (C.sub.1-C.sub.6 alkyl)-N(H)C.sub.1-C.sub.6 alkyl, (C.sub.1-C.sub.6 alkyl)-N(H)(C.sub.1-C.sub.6 alkyl)-NH.sub.2, or (C.sub.1-C.sub.6 alkyl)-SH, with the proviso that at least one occurrence of R.sup.6 includes a primary amine, secondary amine, a mercaptan, or a combination thereof, and n is an integer between 1 and 50 inclusive. A specific amine functional silicone operative in the present invention is shown in formulas (III) or (IV):

##STR00001##

where x is an integer between 1 and 1,000 inclusive, and y is an integer between 1 and 200 inclusive. A corresponding exemplary mercaptan functional silicone is the same as (III) or (IV) with the proviso that the NH.sub.2 moiety is replaced with SH and the NH moiety is replaced by S.

[0030] An alkoxy silane operative herein and reactive with the strained ring alkoxy silane has a formula (VA) or (VB):

Q-R.sup.7ZR.sup.7Si(OR.sup.3)(VA), or

Q-R.sup.7ZR.sup.7Si(Y.sub.n)(OR.sup.3).sub.3-n(VB)

where Q is H.sub.2N or HS, R.sup.7 is independently in each occurrence (CH.sub.2).sub.m, or (CH(C.sub.1-C.sub.4 alkyl)CH.sub.2).sub.m, or (CH.sub.2).sub.mAr(CH.sub.2).sub.p, Z is a nullity (yielding a covalent bond R.sup.7R.sup.7) or N(H) or S, m is independently in each occurrence an integer of 0 to 12 inclusive, p is an integer of 0 to 12 inclusive, R.sup.3 is independently in each occurrence C.sub.1-C.sub.6 alkyl, and Ar is an aromatic of C.sub.6H.sub.4, or a substituted aromatic in which at least one hydrogen is replaced with a substituent of a halide, thiol, amine (primary, secondary, tertiary or ammonium), hydroxyl, carboxyl, carbonyl, sulfonyl, or alkyl, Y is C.sub.1-C.sub.4 alkyl, and n is an integer of 0 or 1.

[0031] The resulting coating has the formula associated with the condensation reaction of one or more equivalents of (I) with (II)-(VB) to form covalent linkages associated with amine or mercaptan cure of epoxides:

##STR00002##

FIG. 5 is a schematic illustrating exemplary bonding to a surface according to the present invention based on amine reaction with the strained ring (I). It is appreciated that the ethoxyl groups extending from the amine nitrogen or aliphatic unsaturation in (I) are amenable to further reaction to modify the properties of the resulting coating. By way of example, such groups are readily esterified to modify coating properties to hydrophobicity of the coating, tether substances to the coating such as nanoparticulate, pigment particles, dye molecules, optical brighteners, electroactive polymers, transition metal complexes, or combinations thereof.

[0032] It is appreciated that the curing of the inventive coating constituents readily occurs under a variety of conditions of temperature, pressure, solvents, and atmospheres. These conditions illustratively include ambient temperatures of 10 to 200 C., pressures from 0.0001 to 100 atmospheres pressure, water as a solvent, and atmospheres of air, nitrogen, inert gases; with the only proviso being that the precursors and coating composition are not degraded by the cure conditions. In some inventive embodiments, cure occurs at standard temperature and pressure (STP) cure from a water based or organic solvent.

[0033] The reactive compounds of the present invention may be formulated as oil in water emulsions.

[0034] In some inventive embodiments, one or more additives are provided to enhance the performance of the resulting adhesive or storage properties of the adhesive composition. Such additive(s) can function as cure inhibitors, open-time promoters, wetting agents, thixotropic agents, thickeners, pH control, preservatives antioxidants, plasticizers, dyes, pigments, and combinations thereof. Examples can include polyamides, polyureas, polyacrylic acids, silica, polyhydroxycarboxylic acid amides, organotitanate and zirconate additives, polyanilines, and metal oxide pigments. Typical addition ranges for these materials range from 0.1-20% by weight.

[0035] The present invention is further detailed with respect to the following non-limiting examples. These examples are intended to be illustrative of particular formulations and properties of the inventive coating, and not intended to limit the scope of the appended claims.

EXAMPLES

Example 1

[0036] A composition of the following is made with the following components:

TABLE-US-00001 Isopropyl alcohol 300 g Formula III, where x = 58, and y = 4 40 g 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane 12 g Distilled water 5 g
The components are mixed overnight at room temperature, then applied by spraying or wiping onto the bottom half of a steel panel (QD-36, Q-Lab Corporation). The coated panel is allowed to dry and cure at room temperature for 24 hours. The coated half surface is smooth, hard, and non-greasy to the touch, and the coating thickness is estimated to be below 5 microns. The panel is sprayed with a 3% aqueous aquarium salt solution to stimulate corrosion, then dried at room temperature. During the drying, the upper (uncoated) half of the panel rusted badly. The coated half showed no visible rusting, though salt crystals form from the drying process.

Example 2

[0037] A second steel panel (QD-36, Q-Lab Corporation) was coated with the composition according to the procedure of Example 1. The coated panel is sprayed with a white enamel spray paint (RUST-OLEUM) and allowed to dry at room temperature for 24 hours. The paint adhesion is tested using a cross-hatched tape test and showed excellent adhesion.

Comparative Example A

[0038] A composition of the following was made:

TABLE-US-00002 Isopropyl alcohol 300 g Formula III, where x = 58, and y = 4 40 g Distilled water 5 g
These components are mixed overnight at room temperature, then applied by spraying or wiping onto the bottom half of a steel panel (QD-36, Q-Lab Corporation). The coated panel is allowed to dry and cure at room temperature for 24 hours. The panel felt oily to the touch. The panel is sprayed with a 3% aqueous aquarium salt solution to stimulate corrosion, then dried at room temperature.

[0039] During the drying, the entire panel showed significant rusting.

Comparative Example B

[0040] A composition of the following was made:

TABLE-US-00003 Isopropyl alcohol 300 g 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane 12 g Distilled water 5 g

[0041] These components are mixed overnight at room temperature, then applied by spraying or wiping onto the bottom half of a steel panel (QD-36, Q-Lab Corporation). The coated panel is allowed to dry and cure at room temperature for 24 hours. The panel felt dry to the touch. The panel is sprayed with a 3% aqueous aquarium salt solution to stimulate corrosion, then dried at room temperature. During the drying, the entire panel showed significant rusting.

Examples 3 and 4

[0042] A composition of Example 1 is made with the exception that the composition of Formula III, where x=58, and y=4 is replaced with a like weight amount of Formula IV, where x=400, and y=3.4 (average) and tested per the procedures of Examples 1 and 2, respectively, with like results being obtained.

Examples 5 and 6

[0043] A composition of Example 1 is made with the exception that the composition of 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane is replaced with a like weight amount of 3-glycidoxypropyl methyldiethoxysilane and panels are tested per the procedures of Examples 1 and 2, respectively, with like results being obtained.

Examples 7 and 8

[0044] A composition of Example 1 is made with the exception that the composition Formula III, where x=58, and y=4 is replaced with a like weight amount of GP-988-1 amino-functional siloxane (Genessee Polymers, Burton, Mich.) and the composition of 2-(3,4 epoxycyclohexyl) ethyltrimethoxysilane is replaced with a like weight amount of 3-glycidoxypropyltrimethoxysilane. The panels are tested per the procedures of Examples 1 and 2, respectively, with like results being obtained.

Example 9

[0045] A composition of Example 1 is made with the exception that the isopropyl alcohol is replaced by acetone. The panels are tested per the procedures of Examples 1 and 2, respectively, with like results being obtained.

[0046] As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.