Description:TECHNICAL FIELD
The present disclosure relates to field of material sciences. The present disclosure particularly relates to coating composition that provides for improved anticorrosion properties. The present disclosure further relates to an article coated with composition and methods of preparing the composition and the article.

BACKGROUND OF THE DISCLOSURE
Metals such as steel, aluminium are widely employed for various applications such as automobile parts or construction materials. Unfortunately, these metals tend to corrode over time. Variety of coating compositions and methods have been widely used for protecting such metals and alloys to extend their life in corrosive environment.

Protective coating fall into multiple categories. The largest of these categories is the topical coating such as paint, that acts as a physical barrier against the environment. The second category consists of sacrificial coatings, such as zinc or cadmium, that are designed to preferentially corrode to save the base metal from crack. Further, there are proposed organic coatings including epoxy, phenolic, polyester, phthalic acid, fluorine and silicone. However, these coatings were found to be unsatisfactory because they gave only limited corrosion protection and/or relatively soluble and/or result in a toxic waste disposal problem.

Protective coating such as phosphate conversion coating is used to improve the corrosion performance of painted ferrous substrate, particularly painted steel. The corrosion process of painted steel involves high pH conditions at the paint-metal substrate interface. Since, phosphate coatings are unstable in an alkaline environment, phosphate steel are rinsed with solutions containing chromium or chromate ions to improve their alkaline stability. However, recent studies suggest that the improvement is marginal and although dry paint adhesion on chromated phosphate steel is good, wet paint adhesion is unacceptable. The bond between the paint-phosphate interface is weak when water or other corrosion species are present.

Protective coating such as chromate coating is used to improve corrosion resistance of cold-rolled steel by minimizing red rusting, and of galvanized steel by minimizing white rusting. Unfortunately, hexavalent chromium has carcinogenic properties. Because of their toxic nature, rinses containing chromate ions are undesirable for industrial usage.
It also has been proposed previously to improve corrosion resistance and paint adhesion of cold-rolled or galvanized steel sheet using organic polymeric coatings containing a silane or using inorganic coatings including a combination of silane and silicate. It also has been proposed to improve alkaline corrosion resistance and paint adhesion of phosphate cold-rolled or galvanized steel sheet using a two-step process including rinsing the sheet in an alkaline waterglass solution to form a silicate coating and subsequently rinsing the silicate coated sheet in an aqueous silane containing solution. However, higher dross formation was noted with these coatings and was noted that normal pad wiping was inefficient.

Thus, there is a need for coating composition having improved properties. The present disclosure describes a coating composition having improved properties and overcomes the problems noted above.

STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure relates to a coating composition comprising metal oxide, inorganic acid and nanosilica. The coating composition is low cost, non-toxic, insoluble and provides for improved corrosion resistance to metallic substrates.

The present disclosure further relates to a process of preparing the coating composition, said method comprises: i) adding metal oxide in a solvent, followed by adding organic acid to obtain a mixture; and ii) adding the nanosilica to the mixture, followed by mixing to obtain the composition.

The present disclosure further relates to an article coated with the coating composition.

The present disclosure further relates to a method of producing the article coated with the composition, comprising- heating a metal substrate, followed by applying the coating composition to the substrate to obtain the article coated with the composition.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the present disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, where:

FIGURE 1 illustrates scanning electron microscope (SEM) micrograph of uncoated metal substrate (bare article).

FIGURE 2 (a to e) illustrates energy dispersive X ray analysis (EDX) analysis plot of different locations on the uncoated metal substrate (bare article).

FIGURE 3 illustrates scanning electron microscope (SEM) micrograph of the article coated with the composition of the present disclosure.

FIGURE 4 (a to b) illustrates energy dispersive X ray analysis (EDX) analysis plot of different locations on the article coated with the composition of the present disclosure.

FIGURE 5 illustrates Tafel test result plot of uncoated metal substrate (bare article).

FIGURE 6 illustrates Tafel test result plot of article coated with the composition of the present disclosure.

FIGURE 7 illustrates electrochemical impedance spectroscopy (EIS) test result plot of uncoated metal substrate (bare article).

FIGURE 8 illustrates electrochemical impedance spectroscopy (EIS) test result plot article coated with the composition of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE
Unless otherwise defined, all terms used in the disclosure, including technical and scientific terms, have meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. By means of further guidance, term definitions are included for better understanding of the present disclosure.

As used herein, the singular forms ‘a’, ‘an’ and ‘the’ include both singular and plural referents unless the context clearly dictates otherwise.

The term ‘comprising’, ‘comprises’ or ‘comprised of’ as used herein are synonymous with ‘including’, ‘includes’, ‘containing’ or ‘contains’ and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

The term ‘about’ as used herein when referring to a measurable value such as a parameter, an amount, a temporal duration, and the like, is meant to encompass variations of ±10% or less, preferably ±5% or less, more preferably ±1% or less and still more preferably ±0.1% or less of and from the specified value, insofar such variations are appropriate to perform the present disclosure. It is to be understood that the value to which the modifier ‘about’ refers is itself also specifically, and preferably disclosed.

Reference throughout this specification to ‘some embodiments’, ‘one embodiment’ or ‘an embodiment’ means that a particular feature, structure or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. thus, the appearances of the phrases ‘in some embodiments’, ‘in one embodiment’ or ‘in an embodiment’ in various places throughout this specification may not necessarily all refer to the same embodiment. It is appreciated that certain features of the disclosure, which are for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The present disclosure relates to a coating composition.

The coating composition is non-toxic, insoluble, economical and provides improved resistance to corrosion.

In some embodiments of the present disclosure, the coating composition comprises metal oxide, inorganic acid and nanosilica.

In some embodiments of the present disclosure, the metal oxide is selected from a group comprising zinc oxide, magnesium oxide, manganese oxide and any combinations thereof.

In some embodiments of the present disclosure, the metal oxide is in an amount ranging from about 0.5 wt.% to 5 wt.%, including all the values in the range, for instance, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.% and so on and so forth.

In some embodiments of the present disclosure, the inorganic acid is selected from a group comprising phosphoric acid, citric acid, boric acid and any combinations thereof.

In some embodiments of the present disclosure, the inorganic acid is in an amount ranging from about 2.5 wt.% to 5 wt.%, including all the values in the range, for instance, 2.6 wt.%, 2.7 wt.%, 2.8 wt.%, 2.9 wt.% and so on and so forth.

In some embodiments of the present disclosure, the nanosilica is in an amount ranging from about 1 wt.% to 5 wt.%, including all the values in the range, for instance, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.% and so on and so forth.

In some embodiments of the present disclosure, the nanosilica has particle size ranging from about 40 nm to 80 nm, including all the values in the range, for instance, 41 nm, 42 nm, 43 nm, 44 nm and so on and so forth.

In some embodiments of the present disclosure, the coating composition comprises solvent. In an embodiment, the solvent is selected from a group comprising water, waste pickling liquor, and a combination thereof.

In some embodiments of the present disclosure, the coating composition comprises about 0.5 wt.% to 5 wt.% of the metal oxide, about 2.5 wt.% to 5 wt.% of the inorganic acid, about 1 wt.% to 5 wt.% and solvent. In an embodiment, remaining amount in the composition is solvent.
The inventors have particularly identified that, in the composition, the nanosilica acts as nucleating agent, thus making the grain size of the crystals finer. As a result, it is noted that the coating composition is highly compact, thus imparting improved corrosion resistance properties. The inventors have also identified that finer particle size of the components in the coating composition provides for improved compactness, thus better corrosion resistance property.

In some embodiments of the present disclosure, the composition has pH ranging from about 2 to 4.5, including all the values in the range, for instance, 2.1, 2.2, 2.3, 2.4 and so on and so forth.

In some embodiments of the present disclosure, the composition has solid content ranging from about 1 wt.% to 10 wt.%, including all the values in the range, for instance, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.% and so on and so forth.

The inventors have particularly identified that combination of metal oxide, inorganic acid and nanosilica in the composition imparts improved corrosion resistance property. However, the improved corrosion resistance is not achieved if any of the mentioned component is omitted from the composition. It is particularly noted that combination of the metal oxide in an amount ranging from about 0.5 wt.% to 5 wt.%, the inorganic acid in an amount ranging from about 2.5 wt.% to 5 wt.% and the nanosilica in an amount ranging from about 1 wt.% to 5 wt.%, provides for improved corrosion resistance property.

The present disclosure further relates to a process of preparing the coating composition described above.

In some embodiments of the present disclosure, the process of preparing the coating composition comprises:
i. adding the metal oxide in a solvent, followed by adding the inorganic acid to obtain a mixture; and
ii. adding the nanosilica to the mixture, followed by mixing to obtain the composition.

In some embodiments of the present disclosure, the process of preparing the coating comprises:
i. adding about 0.5 wt.% to 5 wt.% of the metal oxide in a solvent, followed by adding about 2.5 wt.% to 5 wt.% of the inorganic acid to obtain a mixture; and
ii. adding about 1 wt.% to 5 wt.% of the nanosilica to the mixture, followed by mixing to obtain the composition.

In some embodiments of the present disclosure, the nanosilica is added to the mixture only upon complete dissolution of the metal oxide.

In some embodiments of the present disclosure, the mixing of the nanosilica in the mixture is carried out at a temperature ranging from about 40 ? to 75 ?, including all the values in the range, for instance, 41?, 42?, 43?, 44? and so on and so forth. In an embodiment, the mixing is carried out for a duration ranging from about 0.1 second to 3 seconds, including all the values in the range, for instance, 0.2 seconds, 0.3 seconds, 0.4 seconds and so on and so forth. In an embodiment, the mixing is carried out at a speed ranging from about 90 mpm to 400 mpm, including all the values in the range, for instance, 91 mpm, 92 mpm, 93 mpm, 94 mpm and so on and so forth.

In some embodiments of the present disclosure, the solvent is selected from a group comprising water, waste pickling liquor and a combination thereof.

The present disclosure further relates to an article comprising the composition described above.

In some embodiments of the present disclosure, the article is coated with the composition described above.

In some embodiments of the present disclosure, the coating of the composition on the article is stable, hard, compact, impermeable, insoluble and resistant to corrosion.

In some embodiments of the present disclosure, the coating of the composition on the article is at a thickness ranging from about 0.5 microns to 3 microns, including all the values in the range, for instance, 0.6 microns, 0.7 microns, 0.8 microns, 0.9 microns.

In some embodiments of the present disclosure, the article comprising the composition is resistant to corrosion. In an embodiment, the article comprising the composition has reduced corrosion rate ranging from about 0.132 mpy to 1.563 mpy, including all the values in the range, for instance, 0.133 mpy, 0.134 mpy, 0.135 mpy, 0.136 mpy and so on and so forth.

In some embodiments of the present disclosure, the article is selected from a group comprising ferrous metal, ferrous alloy, non-ferrous metal and non-ferrous alloy.

In some embodiments of the present disclosure, the article is selected from a group comprising steel substrate, aluminium substrate, stainless steel substrate, aluminium-magnesium substrate, titanium substrate, titanium alloy substrate, copper substrate and copper alloy substrate.

In some embodiments of the present disclosure, the article includes but it is not limited to steel wire, steel plate, steel nails, steel TMT (thermos mechanically treatment) rebar, steel tube, steel sheet, or any other steel material that is capable of undergoing corrosion. In an embodiment, the steel sheet includes cold rolled and hot rolled steel sheet. The cold rolled steel sheet includes CQ, EDD (extra deep drawable), IF (interstitial free), IF-HS (interstitial free high strength), and DP (Dual Phase).

The present disclosure further relates to method of producing the article coated with the composition as described above.

In some embodiments of the present disclosure, the method of producing the article coated with the composition, comprises:
- heating a metal substrate; and
- applying the coating composition to the metal substrate to obtain the article coated with the composition.

In some embodiments of the present disclosure, the method of producing the article comprises curing the article coated with the composition.

In some embodiments of the present disclosure, the method of producing the article, comprises:
- heating a metal substrate; and
- applying the coating composition to the metal substrate, followed by curing to obtain the article coated with the composition.

In some embodiments of the present disclosure, the heating is carried out at a temperature ranging from about 400 ? to 600 ?, including all the values in the range, for instance, 401 ?, 402 ?, 403 ?, 404 ? and so on and so forth. In an embodiment, the heating is carried out for a duration ranging from about 10 seconds to 60 seconds, including all the values in the range, for instance, 11 seconds, 12 seconds, 13 seconds, 14 seconds and so on and so forth.

In some embodiments of the present disclosure, the heating of the metal substrate is carried out in controlled atmosphere. In an embodiment, the heating of the metal substrate is carried out in presence of nitrogen. In another embodiment, the heating of the metal substrate is carried out in presence of hydrogen gas.

In some embodiments of the present disclosure, the applying the coating composition on the metal substrate is carried out by technique including but it is not limited to spray coating, dip coating, roll coating and wiping method. In an embodiment, the applying the coating composition is carried out at a temperature ranging from about 20 ? to 40 ?, including all the values in the range, for instance, 21?, 22 ?, 23 ?, 24 ? and so on and so forth.

In some embodiments of the present disclosure, the coating composition is continuously applied on the surface of metal substrate.

In some embodiments of the present disclosure, the curing is carried out at a temperature ranging from about 30 ? to 300 ?, including all the values in the range for instance, 31 ?, 32 ?, 33 ?, 34 ? and so on and so forth. In an embodiment, the curing is carried out for a duration ranging from about 2 seconds to 60 seconds, including all the values in the range, for instance, 3 seconds, 4 seconds, 5 seconds, 6 seconds and so on and so forth.

In some embodiments of the present disclosure, the curing is carried out in presence of curing agent selected from a group comprising zinc oxide, phosphoric acid, nanosilica, and any combinations thereof.

In some embodiments of the present disclosure, the metal substrate is selected from a group comprising ferrous metal, ferrous alloy, non-ferrous metal and non-ferrous alloy.

In some embodiments of the present disclosure, the metal substrate is selected from a group comprising steel substrate, aluminium substrate, stainless steel substrate, aluminium-magnesium substrate, titanium substrate, titanium alloy substrate, copper substrate and copper alloy substrate.

In some embodiments of the present disclosure, the metal substrate includes but it is not limited to steel wire, steel plate, steel nails, steel TMT (thermos mechanically treatment) rebar, steel tube, steel sheet, or any other steel material that is capable of undergoing corrosion. In an embodiment, the steel sheet includes cold rolled and hot rolled steel sheet. The cold rolled steel sheet includes CQ, EDD (extra deep drawable), IF (interstitial free), IF-HS (interstitial free high strength), and DP (Dual Phase).

In some embodiments of the present disclosure, the method of producing the article additionally comprises cleaning and pickling the surface of the metal substrate prior to the heating. In an embodiment, the cleaning includes but it is not limited to degreasing and rinsing.

In some embodiments of the present disclosure, the cleaning of the metal substrate prior to heating is carried out by techniques selected from a group comprising alkali cleaning, ultrasonic cleaning, brush cleaning and any combinations thereof. In an embodiment, the cleaning of the metal substrate is carried out to degrease or remove contaminants such as dirt present on the surface of the metal substrate.

In some embodiments of the present disclosure, the pickling is carried out by employing hydrochloric acid and/or sulfuric acid. In an embodiment, the pickling removes impurities, such as stains, inorganic contaminants, rust or scale.

It is to be understood that the foregoing description is illustrative not a limitation. While considerable emphasis has been placed herein on particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. Those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein. Similarly, additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based upon description provided herein.

Descriptions of well-known/conventional methods/steps and techniques are omitted so as to not unnecessarily obscure the embodiments herein. Further, the disclosure herein provides for examples illustrating the above-described embodiments, and in order to illustrate the embodiments of the present disclosure, certain aspects have been employed. The examples used herein for such illustration are intended merely to facilitate an understanding of ways in which the embodiments may be practiced and to further enable those of skill in the art to practice the embodiments. Accordingly, following examples should not be construed as limiting the scope of the embodiments herein.

EXAMPLES
Example 1: Preparing the coating composition
About 5gm of zinc oxide was added to about 1000 ml of distilled water. Further, about 6 ml of phosphoric acid was added slowly to obtain a mixture, followed by mixing until zinc oxide was completely dissolved. About 2 ml of the nanosilica was added, followed by mixing at a temperature of about 35 ?, for a duration of about 30 seconds, to obtain the coating composition.

Example 2: Preparing the coating composition
About 5 gm of magnesium oxide was added to about 1000 ml of distilled water. Further, about 6 ml of phosphoric acid was added slowly to obtain a mixture, followed by mixing until zinc oxide was completely dissolved. About 2 ml of the nanosilica was added, followed by mixing at a temperature of about 35 ?, for a duration of about 30 seconds, to obtain the coating composition.

Example 3: Preparing the coating composition
About 5 gm of manganese oxide was added to about 1000 ml of distilled water. Further, about 6 ml of phosphoric acid was added slowly to obtain a mixture, followed by mixing until zinc oxide was completely dissolved. About 2 ml of the nanosilica was added, followed by mixing at a temperature of about 35 ?, for a duration of about 60 seconds, to obtain the coating composition.

Example 4: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 400 °C, followed by applying (by dipping) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 2 to 3.
Whitish-brownish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had corrosion rate of about 1.563 mpy.

Example 5: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 600 °C, followed by applying (by dipping) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 2 to 3.
Whitish-brownish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 1.523 mpy.

Example 6: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 400 °C, followed by applying (by spraying) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 3.5 to 4.5.
Greyish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 1.251 mpy.

Example 7: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 600 °C, followed by applying (by spraying) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 3.5 to 4.5.
Greyish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 1.034 mpy.

Example 8: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 400 °C, followed by applying (by dipping) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 3 to 3.5.
Blackish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 0.733 mpy.

Example 9: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature of about 600 °C, followed by applying (by dipping) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 3 to 3.5.
Blackish coating was observed on the surface of steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 0.521 mpy.

Example 10: Preparing the article coated with the coating composition.
The steel substrate was heated to a temperature range of about 480 °C to 520 °C, followed by applying (by dipping) the coating composition having about 1 to 10 wt.% of solid concentration under control environment (atmosphere). The pH of the coating composition was in the range of 3 to 3.5.
Dark blackish coating was observed on the surface steel. The coating that was formed was compact. The coated steel had excellent resistance to corrosion with corrosion rate of about 0.132 mpy.

Example 11: Analysis of article coated with the composition of the present disclosure and uncoated metal substrate (bare article).
Figure 1 illustrates depth microstructural image (SEM micrograph) of bare article. Figure 2 (2a to 2e) illustrates EDX point (SEM-EDX) analysis at different locations on the bare article.

Figure 3 illustrates the dept microstructural image (SEM micrograph) of article coated with the composition obtained in Example 10. Figure 4 (4a to 4b) illustrates EDX depth point (SEM-EDX) analysis at different locations on the surface of the article obtained in Example 10.

Figures 5 and 6 illustrates Tafel test results of the bare article and article coated with the composition of the present disclosure, respectively. It was demonstrated that the article coated with the composition has superior resistance against corrosion with Icorr of about 50.70 nA and corrosion rate of about 0.132 mpy when compared to bare article which had Icorr of about 5.87 µA and corrosion rate of about 2.681 mpy, when the article coated with the composition of the present disclosure and bare article was subjected to aggressive corrosive environment, respectively.

Figures 7 and 8 illustrates electrochemical impedance test results of the bare article and the article coated with the composition of the present disclosure. It can be noted that the article coated with the composition of the present disclosure has more resistivity and less phase angle shift when compared to bare article. Thus, implying that the article coated with the composition of the present disclosure has superior (excellent) resistance to corrosion when compared to bare article.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

The foregoing description of the specific embodiments fully reveals the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

As regards the embodiments characterized in this specification, it is intended that each embodiment be read independently as well as in combination with another embodiment. For example, in case of an embodiment 1 reciting 3 alternatives A, B and C, an embodiment 2 reciting 3 alternatives D, E and F and an embodiment 3 reciting 3 alternatives G, H and I, it is to be understood that the specification unambiguously discloses embodiments corresponding to combinations A, D, G; A, D, H; A, D, I; A, E, G; A, E, H; A, E, I; A, F, G; A, F, H; A, F, I; B, D, G; B, D, H; B, D, I; B, E, G; B, E, H; B, E, I; B, F, G; B, F, H; B, F, I; C, D, G; C, D, H; C, D, I; C, E, G; C, E, H; C, E, I; C, F, G; C, F, H; C, F, I, unless specifically mentioned otherwise.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

, Claims:WE CLAIM:
1. A coating composition comprising- metal oxide, inorganic acid and nanosilica.
2. The coating composition as claimed in claim 1, wherein the metal oxide is selected from a group comprising zinc oxide, magnesium oxide, manganese oxide and any combinations thereof.
3. The coating composition as claimed in claim 1, wherein the inorganic acid is selected from a group comprising phosphoric acid, citric acid, boric acid, and any combination thereof.
4. The coating composition as claimed in claim 1, wherein the metal oxide is in an amount ranging from about 0.5 wt% to 5 wt%; the inorganic acid is in an amount ranging from about 2.5 wt% to 5 wt%; and the nanosilica is an amount ranging from about 1 wt% to 5 wt%.
5. The coating composition as claimed in claim 1, wherein the composition comprises solvent, wherein the solvent is selected from a group comprising water, waste pickling liquor and a combination thereof.
6. The coating composition as claimed in claim 1, wherein the nanosilica has particle size ranging from about 40 nm to 80 nm.
7. The coating composition as claimed in claim 1, wherein the pH of the composition is ranging from about 2 to 4.5.
8. The coating composition as claimed in claim 1, wherein the composition has solid content ranging from about 1 wt% to 10 wt%.
9. A process of preparing the composition as claimed in claim 1, said process comprises-
i. adding the metal oxide in a solvent, followed by adding the organic acid to obtain a mixture; and
ii. adding the nanosilica to the mixture, followed by mixing to obtain the composition.
10. The process as claimed in claim 9, wherein the mixing in step ii) is carried out a temperature ranging from about 25 ? to 35 ?, for a duration ranging from about 10 seconds to 60 seconds.
11. The process as claimed in claim 9, wherein the solvent is selected from a group comprising water, waste pickling liquor, and a combination thereof.
12. An article coated with the composition as claimed in claim 1.
13. The article as claimed in claim 12, wherein the article is selected from a group comprising steel wire, steel plate, steel nail, steel Thermo Mechanically Treated (TMT) rebar, steel tube, steel strip, steel slab, aluminium substrate, aluminium-magnesium substrate, titanium substrate, titanium alloy substrate, copper substrate and copper alloy substrate.
14. The article as claimed in claim 12, wherein the coating has thickness ranging from about 0.5 microns to 3 microns.
15. The article as claimed in claim 12, wherein the article is resistant to corrosion and has corrosion rate ranging from about 0.132 mpy to 1.563 mpy.
16. A method of producing the article coated with the composition as claimed in claim 12, said method comprises- heating a metal substrate, followed by applying the coating composition as claimed in claim 1, to obtain the article coated with the composition.
17. The method as claimed in claim 16, wherein the heating is carried out at a temperature ranging from about 400 ? to 600 ?, for a duration ranging from about 10 seconds to 60 seconds.
18. The method as claimed in claim 16, wherein applying the composition is carried out by technique selected from a group comprising spray coating, dip coating, roll coating, wiping method, and any combinations thereof; and wherein the applying is carried out at a temperature ranging from about 20 ? to 40 ?.
19. The method as claimed in claim 16, wherein the method additionally comprises curing the article coated with the composition, wherein the curing is carried out at a temperature ranging from about 30 ? to 300 ?, for a duration ranging from about 2 seconds to 60 seconds.
20. The method as claimed in claim 19, wherein the curing is carried out by curing agent selected from a group comprising zinc oxide, phosphoric acid, nanosilica and any combinations thereof.
Dated this 31st day of August 2022
Signature:
Name: Sridhar R
To: IN/PA No. 2598
Of K&S Partners, Bangalore
The Controller of Patents Agent for the Applicant
The Patent Office, at Kolkata