ARTICLE COMPRISING A CORROSION INHIBITING COATING, AND METHOD FOR PRODUCING SUCH AN ARTICLE

Abstract

An article including a substrate and a corrosion inhibiting coating present on at least part of a surface of the substrate, wherein the corrosion inhibiting coating is a cross-linked inorganic organic hybrid coating comprising at least one functional group R.sup.1, wherein R.sup.1 comprises one or more functional groups selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.20 cycloalkyl, C.sub.1-C.sub.10 aryl, amide, amine, mercapto, and epoxy, and substituted with at least one halogen atom, wherein the coating comprises silicon and/or titanium, and is covalently bonded to the metallic element or the alloy thereof by oxygen-silicon bonds or oxygen-titanium bonds, respectively. Also, a method for producing such an article.

Claims

1. An article comprising a substrate and a corrosion inhibiting coating present on at least part of a surface of the substrate, wherein the substrate comprises a metallic element and/or an alloy of a metallic element, wherein the corrosion inhibiting coating is a cross-linked inorganic organic hybrid coating comprising at least one functional group R.sup.1, wherein R.sup.1 comprises one or more functional groups selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.20 cycloalkyl, C.sub.1-C.sub.10 aryl, amide, amine, mercapto, and epoxy, wherein R.sup.1 is further substituted with at least one halogen atom, that the cross-linked inorganic organic hybrid coating comprises silicon and/or titanium, and wherein the cross-linked inorganic organic hybrid coating is covalently bonded to the metallic element or the alloy thereof by means of oxygen-silicon bonds or oxygen-titanium bonds, respectively.

2. Article according to claim 1, wherein the cross-linked inorganic organic hybrid coating further comprises carbon-silicon bonds.

3. Article according to claim 1, wherein the halogen atom is fluorine, chlorine, bromine, iodine, or a combination of two or more thereof.

4. Article according to claim 1, wherein R.sup.1 is (CH.sub.2).sub.x(CF.sub.2).sub.yCF.sub.3, wherein x is between 0 and z1, y is zx1, and z is the number of carbon atoms and is between 1 and 20.

5. Article according to claim 4, wherein R.sup.1 is (CH.sub.2).sub.2(CF.sub.2).sub.5CF.sub.3.

6. Article according to claim 1, wherein R.sup.1 is (CH.sub.2).sub.3NHC(O)OCH.sub.2CF(CF.sub.3)OCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CF.sub.3.

7. Article according to claim 1, wherein the metallic element is iron or copper.

8. Article according to claim 7, wherein the metallic element is iron and the substrate comprises steel.

9. Article according to claim 7, wherein the metallic element is copper and the substrate comprises a copper alloy.

10. Article according to claim 1, wherein the article is a watch component.

11. A method for producing an article comprising a substrate and an corrosion inhibiting coating present on at least part of a surface of the substrate, the article according to claim 1, wherein the method comprises: providing a substrate comprising a metallic element and/or an alloy of a metallic element, providing a first compound according to formula (I) and a second compound according to formula (II) ##STR00003## wherein M is silicon or titanium, R.sup.1 is a group comprising one or more functional groups selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.20 cycloalkyl, C.sub.1-C.sub.10 aryl, amide, amine, mercapto, and epoxy; and comprises at least one halogen atom, R.sup.5 is a cross-linkable functional group, R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7, and R.sup.8 are each independently from each other H, a C.sub.1-C.sub.20 alkyl, a C.sub.1-C.sub.10 aryl, C.sub.1-C.sub.20 alkenyl, C.sub.1-C.sub.20 alkylaryl, or C.sub.1-C.sub.20 arylalkyl, hydrolysing the first compound and the second compound in the presence of water, condensing the hydrolysed first compound and the hydrolysed second compound, thereby obtaining a pre-polymer comprising R.sup.1 and R.sup.5 as functional groups, applying the pre-polymer to at least part of a surface of the substrate, and inducing cross-linking of the cross-linkable functional group R.sup.5 by exposing the pre-polymer to one or more of a temperature up to 250 C., UV radiation or IR radiation, thereby obtaining an article comprising a substrate and a corrosion inhibiting coating covering at least part of a surface of the substrate, wherein the corrosion inhibiting coating is a cross-linked inorganic organic hybrid coating comprising at least one functional group R.sup.1, and wherein the cross-linked inorganic organic hybrid coating is covalently bonded to the metallic element or the alloy thereof by means of oxygen-M bonds.

12. Method according to claim 11, wherein R.sup.5 is a functional group selected from the group consisting of an epoxy, a (meth)acrylate, an ester, a mercapto, a vinyl, and a (meth)acrylated urethane.

13. Method according to claim 11, wherein the cross-linking is performed at a temperature between 50 C. and 200 C.

14. Method according to claim 11, wherein R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7, and R.sup.8 are each independently from each other C.sub.1-C.sub.8 alkyl.

15. Use of the article according to claim 1 in a watch.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0057] Aspects of the invention will now be described in more detail with reference to the appended drawings, wherein same reference numerals illustrate same features and wherein:

[0058] FIG. 1 schematically represents an article of the invention;

[0059] FIG. 2 shows the open circuit potential values for substrate coated with inventive and reference coatings.

DETAILED DESCRIPTION OF THE INVENTION

[0060] FIG. 1 schematically shows an article 1 according to the invention. The article comprises a substrate 2 and a corrosion inhibiting coating 3 covering at least part of a surface of the substrate 2.

[0061] The substrate 2 comprises a metallic element and/or an alloy of a metallic element. Advantageously, at least a portion of a surface of the substrate 2 comprises the metallic element and/or the alloy thereof. Advantageously, at least a portion, for example all, of the portion of the surface comprising the metallic element and/or an alloy thereof is covered with the corrosion inhibiting coating 3. By doing so, any areas of the substrate prone to corrosion during handling, storage, manufacturing and manipulation can be efficiently protected against corrosion. Advantageously, substantially the entire surface of the substrate 2 is covered with a corrosion inhibiting coating 1, as shown in FIG. 1.

[0062] Non-limiting examples of the metallic element include iron, copper, aluminium, zinc, silver, gold, tin, manganese, and nickel. The substrate can comprise two or more metallic elements and/or alloys thereof. Advantageously, substrate comprises iron and/or copper.

[0063] For example, the substrate can comprise or substantially consist of iron. For example, when the substrate comprises iron, the substrate can comprise or can be steel, such as carbon steel.

[0064] For example, the substrate can comprise or substantially consist of copper. For example, when the substrate comprises copper, the substrate can comprise or can be brass or bronze.

[0065] With substantially consisting is meant in the present invention that the amount of impurities or other components present in the substrate is advantageously below 1% by weight, preferably below 0.5% by weight, more preferably below 0.1% by weight, such as below the detection limit of analysis techniques used to determine the composition, such as X-ray photoelectron spectroscopy (XPS).

[0066] Optionally, the substrate can comprise further non-metallic elements and/or non-metallic compounds. Non-limiting examples of such non-metallic elements include phosphorous, or metalloids such as silicon and arsenic. Non-limiting examples of non-metallic compounds include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyurethane, polyamide, polyimide, polyamide-imide, epoxy resins such as FR4, and glass.

[0067] Advantageously, the corrosion inhibiting coating is an inorganic organic hybrid coating. Advantageously, the corrosion inhibiting coating is a cross-linked inorganic organic hybrid coating. Advantageously, the corrosion inhibiting coating is at least partially covalently bonded to the surface of the substrate, in particular to the metallic element or, when the metallic element is present as an alloy, to the metallic element comprised in the alloy. Advantageously, the corrosion inhibiting coating is covalently bonded to the metallic element by oxygen-comprising bonds, such as oxygen-atoms of the coating covalently bonded to the metallic element.

[0068] Advantageously, the cross-linked inorganic organic hybrid coating comprises one or more of silicon, titanium, zirconium, aluminium, iron, or boron, preferably silicon and/or titanium. Advantageously, when the cross-linked inorganic organic hybrid coating comprises silicon and/or titanium, the coating is at least partially covalently bonded to the metallic element of the substrate by silicon-oxygen-metallic element and/or titanium-oxygen-metallic element bonds, respectively.

[0069] Advantageously, the inorganic organic hybrid coating comprises at least one functional group R.sup.1. Advantageously, R.sup.1 comprises or consists of one or more functional groups selected from the group consisting of C.sub.1-C.sub.20 alkyl, C.sub.1-C.sub.20 cycloalkyl, C.sub.1-C.sub.10 aryl, amide, amine, ether, mercapto (i.e. thiol), and epoxy.

[0070] Advantageously, C.sub.1-C.sub.20 alkyl includes alkyl functional groups comprising between 1 and 20 carbon atoms in the chain. Advantageously, the C.sub.1-C.sub.20 alkyl is C.sub.1-C.sub.12 alkyl, preferably C.sub.1-C.sub.10 alkyl, such as C.sub.1-C.sub.8 alkyl, C.sub.1-C.sub.6 alkyl, or C.sub.1-C.sub.4 alkyl.

[0071] Advantageously, C.sub.1-C.sub.20 cycloalkyl includes cycloalkyl functional groups comprising in total between 1 and 20 carbon atoms in the chain.

[0072] Advantageously, C.sub.1-C.sub.10 aryl includes aryl functional groups comprising between 1 and 10 carbon atoms in the chain. For example, R.sup.1 can comprise a phenyl functional group, or can be C.sub.1-C.sub.20 alkyl phenyl.

[0073] Advantageously, when R.sup.1 comprises an amide functional group, R.sup.1 has the formula (CH.sub.2).sub.a(CF.sub.2).sub.bC(O)NH.sub.2, wherein a is between 0 and c2, b is ca1, and c is the total number of carbon atoms. Advantageously, c is between 2 and 20, preferably between 2 and 10, such as between 2 and 8, between 2 and 6, or between 2 and 4, such as 2, 3 or 4.

[0074] Advantageously, when R.sup.1 comprises an amine functional group, R.sup.1 has the formula (CH.sub.2).sub.p(CF.sub.2).sub.qNH.sub.2, wherein p is between 0 and r1, q is rp1, and r is the total number of carbon atoms. Advantageously, r is between 1 and 20, preferably between 1 and 10, such as between 1 and 8, between 1 and 6, or between 1 and 4, such as 1, 2, 3 or 4.

[0075] Advantageously, when R.sup.1 comprises a mercapto (thiol) functional group, R.sup.1 has the formula (CH.sub.2).sub.u(CF.sub.2).sub.vSH, wherein u is between 0 and w1, v is wu1, and rwis the total number of carbon atoms. Advantageously, w is between 1 and 20, preferably between 1 and 10, such as between 1 and 8, between 1 and 6, or between 1 and 4, such as 1, 2, 3 or 4.

[0076] Advantageously, the inorganic organic hybrid coating further comprises at least one halogen atom. Advantageously, the halogen atom is fluorine, chlorine, bromine, or iodine. When R.sup.1 comprises two or more halogen atoms, they can be the same or different, i.e. a combination of two or more of fluorine, chlorine, bromine, and iodine. The corrosion inhibiting coating further comprises silicon and/or titanium.

[0077] Advantageously, R.sup.1 comprises or consists of C.sub.1-C.sub.20 alkyl according to formula (III)

(CH.sub.2).sub.x(CF.sub.2).sub.yCF.sub.3(III) [0078] wherein [0079] x is between 0 and z1, [0080] y is z1-x, and [0081] z is the number of carbon atoms in the chain, and is between 0 and 20.

[0082] For example, R.sup.1 can be (CH.sub.2).sub.2(CF.sub.2).sub.5CF.sub.3, i.e. z is 8, x is 2 and y is 5. For example, R.sup.1 can be (CH.sub.2).sub.5CF.sub.3, i.e. z is 6, x is 5 and y is 0.

[0083] R.sup.1 can be a C.sub.1-C.sub.20 perfluoroalkyl, i.e. an alkyl wherein all hydrogen atoms are replaced by fluorine atoms, according to (CF.sub.2).sub.yCF.sub.3, i.e. wherein in formula (III) x is 0, y is z1, and z is between 1 and 20. For example, R.sup.1 can be a C.sub.8 perfluoroalkyl, i.e. (CF.sub.2).sub.7CF.sub.3 (z=8, x=0 and y=7 in formula (III)), a C.sub.6 perfluoroalkyl, i.e. (CF.sub.2).sub.5CF.sub.3 (z=6, x=0 and y=5 in formula (III)), or a C.sub.4 perfluoroalkyl, i.e. (CF.sub.2).sub.3CF.sub.3 (z=4, x=0 and y=3 in formula (III)).

[0084] Advantageously, the coating has a thickness between 1 m and 20 m, preferably between 1.2 m and 10 m, such as between 1.5 m and m. As will be understood, the optimal coating thickness depends, amongst others, on the substrate to be protected, in particular its composition and shape, and on the intended use of the article.

[0085] Advantageously, when the substrate comprises iron, such as steel, in particular carbon steel, the coating has a thickness of at least 2 m, for example at least 2.1 m, preferably at least 2.2 m, such as at least 2.3 m, at least 2.4 m, or at least 2.5 m. When the coating has such a thickness, efficient corrosion protection is provided to the substrate.

[0086] Advantageously, when the substrate comprises copper, such as brass or bronze, the coating has a thickness of at least 1 m, preferably at least 1.2 m, such as at least 1.3 m, at least 1.4 m, or at least 1.5 m. When the coating has such a thickness, efficient corrosion protection is provided to the substrate.

[0087] Advantageously, when the article is a watch component, i.e. is used in a watch, the thickness advantageously is 5 m or lower. As is known in the field of watch components, higher thicknesses might impact the functioning of the watch, and may require redesign of the component, which involves significant costs. The inventors have discovered that the articles of the present invention, wherein the coating thickness is at most 5 m, allow to show significant reduction in corrosion while avoiding the need for redesigning.

[0088] For example, when the substrate comprises iron, such as carbon steel, the coating has advantageously a thickness between 2 m and 5 m, preferably between 2.2 m and 5 m, more preferably between 2.4 m and m.

[0089] For example, when the substrate comprises copper, such as bronze or brass, the coating has advantageously a thickness between 1 m and 5 m, preferably between 1.2 m and 5 m, for example between 1.3 m and 5 m, more preferably between 1.5 m and 5 m.

EXAMPLES

[0090] Two types of substrates were provided: a carbon steel plate and a brass plate.

[0091] A reference article was obtained by applying a reference corrosion inhibiting coating to both substrates. The reference corrosion inhibiting coating was a halogen-free coating.

[0092] Four different pre-polymers according to the invention were prepared. Details on the functional groups are listed in Table 1. Two pre-polymers comprised a fluorinated alkyl group having the formula (CH.sub.2).sub.2(CF.sub.2).sub.5CF.sub.3 as functional group (B1 and B2 of Table 1). B1 comprised a low ratio of the fluorinated alkyl functional group and B2 comprised a high ratio of the fluorinated alkyl functional group, based on the total weight of the respective pre-polymer. Two further pre-polymers comprised a functional group comprising an amide functional group and ether functional groups, having the formula (CH.sub.2).sub.3NHC(O)OCH.sub.2CF(CF.sub.3)OCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CF.sub.3 (C1 and C2 of Table 1). C1 comprised a low ratio of the functional group and C2 comprised a high ratio of the functional group, based on the total weight of the respective pre-polymer.

TABLE-US-00001 TABLE 1 overview of coatings tested Coating Functional group Ratio A Reference halogen-free B1 (CH.sub.2).sub.2(CF.sub.2).sub.5CF.sub.3 Low B2 (CH.sub.2).sub.2(CF.sub.2).sub.5CF.sub.3 High C1 (CH.sub.2).sub.3NHC(O)OCH.sub.2CF(CF.sub.3)OCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CF.sub.3 Low C2 (CH.sub.2).sub.3NHC(O)OCH.sub.2CF(CF.sub.3)OCF.sub.2CF(CF.sub.3)O(CF.sub.2).sub.2CF.sub.3 High

[0093] The pre-polymers of the invention were applied to the carbon steel and the brass substrate by dipping the substrates in the pre-polymer, followed by thermal curing at 160 C. The coatings obtained on the carbon steel substrate all had a thickness between 1 m and 3 m, and the coatings on the brass substrate all had a thickness between 1.5 m and 2.5 m.

[0094] It was noticed that all four inventive coatings (B1, B2, C1, C2) were transparent and covered in a homogeneous way the substrate. Further, it was noticed that coating C2 showed a higher flexibility (a lower rigidity) than coating C1, which can contribute to a reduced risk of formation of defects, such as cracks, upon higher thicknesses. It was also noticed that coating B2 was easier to clean, and presented a slightly lower surface energy than coating B1, which comprised a lower amount of fluorinated functional groups. The surface energy was measured by measuring the water contact angle according to standard ASTM D5946, and converting the water contact angle to a surface energy value by using known and publicly available conversion tables.

[0095] The corrosion protective properties of all five articles, as well as the substrates without any corrosion protection was tested in a 0.1% NaCl solution by measuring the open circuit potential (OCP). Higher OCP values are a measure for better protection against corrosion, as damage such as short circuiting caused by corrosion is significantly reduced. The OCP was measured by the EC-pen method against the saturated calomel electrode (SCE) as the reference electrode, at 24 C. The results are shown in FIG. 2, wherein non-coated represents the OCP-value for the substrates without any corrosion protection. The values indicated with a triangle 4 represent the OCP values for the carbon steel substrate and the values indicated with a circle 5 represent the OCP values for the brass substrate.

[0096] From FIG. 2 it is clear that all corrosion inhibiting or corrosion protecting coatings applied to carbon steel lead to higher OCP values than the uncoated, unprotected substrate. As it is commonly known, carbon steel without any protection easily corrodes. The results thus indicate that all coatings provide protection against corrosion for the carbon steel substrate. Further, the coatings based on the epoxy-comprising functional group (C1 and C2) provide better protection than the reference coating, whereas the alkyl functional group (B1 and B2) show a slightly lower protection, which is still significant when compared to the bare substrate.

[0097] The coatings on the brass substrate did not seem to provide a significantly improved corrosion protection in terms of OCP value. However, it should be noted that, as it is commonly known, brass itself, i.e. without any protection provided, has already a certain resistance against corrosion. This is visible by the bare brass substrate which had a significantly higher OCP value than the bare carbon steel substrate. Consequently, it follows from FIG. 2 that none of the coatings decreased the inherent corrosion protection of the brass substrate. Further, coating B1 showed a significantly higher OCP value than the uncoated substrate.

[0098] As a second test to evaluate the corrosion protection, the release of ions from the substrate was measured. A higher release, or leaching, of ions comprised in the substrate is an indication for a higher damage to the substrate, by side-reactions such as corrosive reactions.

[0099] The untreated substrates, as well as the substrates with coatings B1 and C1 were tested for the release of ions. The substrates were placed in a 0.9% NaCl solution at 37 C. for 7 days. Any ions released were measured by Inductively Coupled Plasma Spectroscopy (ICP-MS).

[0100] Table 2 shows the results for the carbon steel substrate and table 3 for the brass substrate. <LOD means that the concentration of ions released was below the limit of detection.

TABLE-US-00002 TABLE 2 Concentration of ions released from carbon steel substrate in 0.9% NaCl solution at 37 C. during 7 days Ion Non-coated B1 C1 Al 28.69 g/cm.sup.2 <LOD <LOD Si <LOD <LOD <LOD P <LOD <LOD <LOD Mn 9.87 g/cm.sup.2 2.39 g/cm.sup.2 2.70 g/cm.sup.2 Fe 4118.16 g/cm.sup.2 816.38 g/cm.sup.2 756.28 g/cm.sup.2 Ni <LOD <LOD <LOD Cu <LOD <LOD <LOD Zn <LOD <LOD <LOD Sn <LOD <LOD <LOD Pb 1.78 g/cm.sup.2 <LOD <LOD Total 4158.50 g/cm.sup.2 818.77 g/cm.sup.2 758.98 g/cm.sup.2

[0101] From Table 2 it is clear that a significantly lower concentration of iron (Fe) and manganese (Mn) ions is dissolved from the substrate into the NaCl solution for the coated carbon steel substrates, when compared to the substrates without any corrosion protection (non-coated). Further, no release or leaching of any lead (Pb) ions was detected for the coated substrates, contrary to the uncoated substrate. This indicates an efficient protection of the carbon steel substrate by the inventive coatings.

TABLE-US-00003 TABLE 3 Concentration of ions released from brass substrate in 0.9% NaCl solution at 37 C. during 7 days Ion Non-coated B1 C1 Al <LOD <LOD <LOD Si <LOD <LOD <LOD P <LOD <LOD <LOD Mn <LOD <LOD <LOD Fe <LOD <LOD <LOD Ni <LOD <LOD <LOD Cu 2.16 g/cm.sup.2 <LOD <LOD Zn 143.85 g/cm.sup.2 <LOD <LOD Sn <LOD <LOD <LOD Pb 5.33 g/cm.sup.2 0.34 g/cm.sup.2 0.34 g/cm.sup.2 Total 151.34 g/cm.sup.2 0.34 g/cm.sup.2 0.34 g/cm.sup.2

[0102] From Table 3 it is clear that no release of cupper (Cu) and zinc (Zn) ions, the main components of brass, is dissolved from the brass substrate into the NaCl solution for the coated brass substrates, contrary to the substrates without any corrosion protection (non-coated). This indicates an efficient protection of the brass substrate by the inventive coatings.

[0103] It was further noticed that the brass substrates without any coating changed colour, or shiny, within 3 to 5 days exposure to the atmosphere (sunshine, air). The gold-like colour changed in an orange shine. When such brass components are used in watches, and are visible from the outside, this change of shade, shine or colour is an unwanted change from aesthetic point of view. Contrary to uncoated brass, it was noticed that the same substrate coated with coatings according to the invention did not show any signs of corrosion after exposure to the atmosphere for months (up to 6 months was tested without any visible change noticed).

[0104] The adhesion strength of coatings B1 and C1 on both substrates was measured according to EN ISO 2409 (the so-called cross-cut test). All tested samples scored 0, indicating that the edges of the cuts were smooth and that none of the squares of the lattice had detached.

NOMENCLATURE

[0105] 1. article [0106] 2. substrate [0107] 3. corrosion inhibiting coating [0108] 4. carbon steel OCP values [0109] 5. brass OCP values