Description:FIELD OF INVENTION
[001] The present invention provides a corrosion-resistant, matt finish primer formulation with increased adhesion strength and durability.

BACKGROUND OF THE INVENTION
[002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[003] Zinc-based primers (Zinc Silicates or Zinc rich primers) are used as a primary base coat for protecting carbon steel substrates from corrosion. The purpose of using a primer is that it acts as a bonding agent that allows subsequent paint coatings to better adhere to metal and helps in increasing the metal’s resistance against corrosion. Zinc-based primers provide active corrosion protection (sacrificial protection) to the carbon steel substrate as a result of the preferential dissolution of zinc in the presence of oxygen and moisture. Exemplary conventional anticorrosive compositions are discussed herein below.
[004] US20220049362A1 discloses a method using silicon dioxide that improves the cathodic anticorrosion effect of ground coats, preferably of a zinc primer based on epoxy-functional polymers and at least one metal particle.
[005] US20170066928A1 discloses an anti-corrosive coating compositions for protecting iron and steel structures. In particular, coating compositions comprising particulate zinc, conductive pigments, and microspheres are disclosed. The document furthermore concerns a kit of parts containing the composition, a method for its application, as well as metal structures coated with the composition.
[006] CN105623473A is related to the field of anti-corrosive paints, and provides a zinc-containing anti-corrosive primer based on graphene dispersion. The dispersion and stability problems of graphene in paints are solved, so that when the content of metallic zinc in the paint is relatively low, the anti-corrosive performance of the paint can exceed that of a zinc-rich primer with high zinc content, the consumption of metal zinc resource is reduced, and excellent storage stability, mechanical property and construction performance are achieved.
[007] CN113637387B is related to the field of coatings, and particularly relates to a graphene anti-corrosion primer and a preparation method thereof. According to the graphene anticorrosion primer and the preparation method thereof, the synergistic effect between the graphene and the zinc powder is realized through the surface modification of the zinc powder, so that the electrochemical protection effect of the zinc powder is improved, the utilization rate of the zinc powder in the coating is improved, the amount of the zinc powder is reduced, the compactness of the coating is increased, and the anticorrosion performance of the coating is improved.
[008] Despite developments in the state of the art, the conventionally used zinc primers suffer from major drawbacks as they possess inferior abrasion resistance owing to poor adhesion strength of Zn film. Additionally, the Zn primers when used in coastal areas lead to blistering problems, thereby corroding the underlying metal. Furthermore, surface preparation (sand blasting) of structural material for better adhesion of paints using the existing zinc primers still remains a challenge.
[009] While several approaches have been tried in the past, none of them have been successful in providing a zinc formulation with high adhesion strength and increased durability. Therefore, there is a need in the art for an improved zinc formulation, which alleviates, at least in part, one or more disadvantages or shortcomings of conventional formulations.

OBJECTS OF THE INVENTION
[0010] The primary objective of the present invention is to provide a corrosion resistant, matt finish primer formulation for application areas having temperature upto 70℃.
[0011] Another objective of the present invention is to provide a matt finish primer formulation with improved adhesion strength and durability.
[0012] It is an object of the present disclosure to provide a matt finish primer formulation with enhanced corrosion protection and adhesion that requires least surface preparation/modification.
[0013] Another objective of the present invention is to provide a Zn based primer that can provide cathodic protection while having acceptable mechanical strength.
[0014] Yet another object of the present disclosure is to provide a process for production of a corrosion resistant, matt finish primer formulation that is facile, economical and industrially applicable.

SUMMARY
[0015] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in Detailed Description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
[0016] According to one aspect of the present disclosure a corrosion resistant, matt finish primer formulation is provided. The formulation comprises:
i. 20-50 wt% of an Epoxy resin of the total weight of the formulation;
ii. 10-30 wt% of a curing agent of the total weight of the formulation;
iii. 0.1-1 wt% of a functionalized graphene of the total weight of the formulation;
iv. 10-40 wt% of Zinc dust of the total weight of the formulation;
v. 10-40 wt% of a filler of the total weight of the formulation;
vi. 0.1-1 wt% of a dispersing agent of the total weight of the formulation; and
vii. 20-50 wt% of a solvent of the total weight of the formulation.
[0017] In some embodiments, the epoxy resin is categorized as type 1 solid epoxy resin.
[0018] In some embodiments, the epoxy resin is bisphenol-A-(epichlorhydrin) epoxy resin.
[0019] In some embodiments, the epoxy resin is a 75 wt% solid epoxy resin in a secondary solvent.
[0020] In some embodiments, the solvent is selected from the group consisting of xylene, methyl ethyl ketone, toluene or combinations thereof.
[0021] In some embodiments, the secondary solvent is selected from the group consisting of xylene, glycidyl ether or combinations thereof.
[0022] In some embodiments, the dispersing agent is selected from a group consisting of polyethylene, polyoxyethylene, polyhydric alcohol, or mixtures thereof.
[0023] In some embodiments, the dispersing agent is a mixture of polyethylene and polyhydric alcohol, and has carbon atoms ranging between 10 to 16.
[0024] In some embodiments, the functionalized graphene is nitrogen-based functionalized graphene.
[0025] In some embodiments, the curing agent is selected from polyaminoamide, phenyl alkylamines, phenol, polyamide, amine-adduct and combinations thereof.
[0026] In some embodiments, the epoxy resin is cured at a temperature ranging from 20 to 35℃.
[0027] In some embodiments, the filler is selected from a group consisting of SiO2, CaO, Na2O, MnO2, K2O, Al2O3, Fe2O3, MgO, and combinations thereof.
[0028] Another aspect of the present disclosure relates to a method of preparing a corrosion resistant, matt finish primer formulation, the method comprising the steps of:
i. mixing 10-40 wt% of Zinc dust with 20-50 wt% of an epoxy resin for 3-15 minutes to obtain a mixture I;
ii. mixing 0.1-1 wt% of nitrogen based functionalized graphene, 0.1-1 wt%- of a dispersing agent, 10-40 wt% of a filler, and optionally, 20-50 wt% of a solvent or part thereof with the mixture 1, simultaneously or sequentially to prepare a mixture II;
iii. mixing 10-30 wt% of a curing agent with mixture II for 5-20 minutes to obtain a mixture III; and
iv. mixing the remainder of the solvent with the mixture III to obtain the corrosion resistant, matt finish primer formulation.
[0029] In some embodiments, the mixing is done at a speed of 250-350 RPM.
[0030] Various objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like features.

BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The accompanying drawing(s) are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. The diagrams are for illustration only, which thus is not a limitation of the present disclosure.
[0032] FIG. 1 illustrates the bode plot of different components used in primer formulation of the present disclosure vis-à-vis commercial Primer formulation.
[0033] FIG. 2 illustrates the adhesion strengths of commercially available primer formulation vis-à-vis that of the primer formulation of the present disclosure with different components.
[0034] FIG. 3 illustrates the adhesion strengths of commercially available primer formulation vis-à-vis that of the primer formulation of the present disclosure with different components with top coat.
[0035] FIG. 4 illustrates the performance of commercial primer and primer formulation of the present disclosure. Specifically, it demonstrates the salt spray test results of Commercial and primer formulation of the present disclosure.
[0036] FIG. 5 represents the photographs of the Visual Examination of Commercial and primer formulation of the present disclosure after 1 month from the application at a refinery.
[0037] FIG. 6 represents the photographs of the Visual Examination of Commercial and primer formulation of the present disclosure after 2 months from the application at a refinery.

DETAILED DESCRIPTION OF THE INVENTION
[0038] The following is a detailed description of embodiments of the disclosure. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0039] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0040] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0041] In some embodiments, numbers have been used for quantifying weights, percentages, ratios, and so forth, to describe and claim certain embodiments of the invention and are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable.
[0042] The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0043] Unless the context requires otherwise, throughout the specification which follows, the word “comprise” and variations thereof, such as “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0044] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0045] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0046] All methods described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples or exemplary language (e.g., “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0047] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified.
[0048] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles and aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure.
[0049] It should also be appreciated that the present disclosure can be implemented in numerous ways, including as a system, a method or a device. In this specification, these implementations, or any other form that the invention may take, may be referred to as processes. In general, the order of the steps of the disclosed processes may be altered within the scope of the invention.
[0050] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0051] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus, if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[0052] The term “or”, as used herein, is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0053] Various terms are used herein to the extent a term used is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0054] Generally, the application of protective coatings is one of the most effective ways to protect steel structures from corrosion. For decades, zinc-based primers have been used where protection of metallic structure is required for a longer duration of time. Unlike conventional coatings, the advantage of using zinc-rich coatings is that they can provide cathodic protection and good mechanical strength.
[0055] The corrosion products of zinc further protect from corrosion by forming a passive layer on the surface of the metal. At an early stage, the zinc-rich coatings provide the cathodic protection, and later on, the corrosion product of zinc provides the barrier protection. However, presence of a large number of zinc particles creates high porosity, weak adhesion, and poor surface leveling problems. Consequently, the sacrificial cathodic protection of the coating gradually decreases and eventually fades away.
[0056] To mitigate these issues, it was envisaged to develop durable primers having improved corrosion resistance. The formulations of the present disclosure is based on an inventive selection of additives with variable resin/hardener ratios. The conventionally used zinc primers contain 80-85 wt.% of zinc dust in the dry film that provides required corrosion protection. On the contrary, the formulation of the present disclosure contains substantially lower amounts of zinc with novel combinations of additives, which not only enhance the corrosion protection, but also result in improved adhesion resistance.
[0057] In the present context, “primer” refers to a preparator coating put on a substrate or material before painting. Typically, a primer is a paint product that allows finishing paint to adhere much better than if it were used alone.
[0058] “HP-PRIMER” or “HP-PRIMER-MATT”, used interchangeably in the disclosure, refer to corrosion resistant matt finish primer as disclosed herein below.
[0059] Accordingly, an aspect of the present disclosure relates to a corrosion-resistant, matt finish primer formulation.
[0060] In an embodiment, the formulation comprises:
i. 20-50 wt% of an Epoxy resin of the total weight of the formulation;
ii. 10-30 wt% of a curing agent of the total weight of the formulation;
iii. 0.1-1 wt% of a functionalized graphene of the total weight of the formulation;
iv. 10-40 wt% of Zinc dust of the total weight of the formulation;
v. 10-40 wt% of fillers of the total weight of the formulation;
vi. 0.1-1 wt% of dispersing agent of the total weight of the formulation; and
vii. 20-50 wt% of a solvent of the total weight of the formulation.
[0061] In some embodiments, the epoxy resin is categorized as type 1 solid epoxy resin. A “type” resin is a general term referring to the advancement in molecular weight of an epoxy resin. This term is predominately used with regard to solid epoxy resins. In the present context, a TYPE 1 (or 1-type) epoxy resin has an epoxide equivalent weight (EEW) for 100% solid ranging between 400 to 600.
[0062] In some embodiments, the epoxy resin is bisphenol-A-(epichlorohydrin) epoxy resin.
[0063] In some embodiments, the epoxy resin is a 70-85 wt% solid epoxy resin in the secondary solvent. In some embodiments, the epoxy resin is a 75 wt% solid epoxy resin in the secondary solvent. In some embodiments, the secondary solvent is selected from the group consisting of xylene, toluene, benzene, diphenyl ether, glycidyl ether, or combinations thereof. In some embodiments, the secondary solvent is selected from the group consisting of xylene, glycidyl ether, or combinations thereof.
[0064] In some embodiments of the present disclosure, the corrosion-resistant matt finish formulation comprises 20-50 wt% of the epoxy resin of the total weight of the formulation, for example, 20-40 wt%, or 20-30 wt%, or 25-35 wt%, or 35-45 wt%, or 30-45 wt%, or 25-45 wt % of the Epoxy resin of the total weight of the formulation.
[0065] In some embodiments, the solvent is selected from the group consisting of xylene, methyl ethyl ketone, toluene and combinations thereof.
[0066] In some embodiments of the present disclosure, the corrosion-resistant matt finish formulation comprises 20-50 wt% solvent based on the total weight of the formulation,for example, 20-40 wt%, or 20-30 wt%, or 25-35 wt%, or 35-45 wt%, or 30-45 wt%, or 25-45 wt % solvent based on the total weight of the formulation.
[0067] In some embodiments, the corrosion-resistant matt finish formulation comprises 0.1-1 wt% of the dispersing agent of the total weight of the formulation, for example,0.5-1 wt%, or 0.8-1 wt%, or 0.3-1 wt%, or 0.7-1 wt%, or 0.3-0.8 wt% of the dispersing agent of the total weight of the formulation.
[0068] In some embodiments, the dispersing agent is selected from a group consisting of polyethylene, polyoxyethylene, polyhydric alcohols, or mixtures thereof.
[0069] In some embodiments, the dispersing agent is a mixture of polyethylene and polyhydric alcohol, and has carbon atoms ranging between 10 to 16.
[0070] In some embodiments, the functionalized graphene is nitrogen-based functionalized graphene. In an embodiment, the nitrogen-based functionalized graphene is an amino functionalized graphene. Suitable amino functionalizing agents for obtaining the amino functionalized graphene are known to the person skilled in the art. In an embodiment, the amino- functionalizing agent includes highly soluble diamino molecules, such as 1, 3- diaminopropane, ethylenediamine, and 1 ,4-diaminobutane, but not limited thereto.
[0071] In some embodiments, the corrosion-resistant matt finish formulation comprises 0.1-1 wt% of the nitrogen-based functionalized graphene of the total weight of the formulation, for example, 0.5-1 wt%, or 0.8-1 wt%, or 0.3-1 wt%, or 0.7-1 wt%, or 0.3-0.8 wt% of a functionalized graphene of the total weight of the formulation.
[0072] In some embodiments, the corrosion-resistant matt finish formulation comprises 10-40 wt% of Zinc dust of the total weight of the formulation, for example, 10-20 wt%, or 10-30 wt%, or 20-40 wt%, or 20-30 wt%, or 25-35 wt%, or 35-40 wt%, or 15-40 wt%, or 25-40 wt % of the Zinc dust of the total weight of the formulation.
[0073] In some embodiments, the curing agent is selected from polyaminoamide, phenyl alkylamines, phenols, polyamide, amine-adducts or mixtures thereof. In some embodiments, the curing agent is polyaminoamide. In some embodiments, the curing agent is polyaminoamide having an amine value ranging between 50 mgKOH/gm to 200 mgKOH/gm, when determined according to ASTM D2073. Preferably, the amine value ranges between 100 mgKOH/gm to 200 mgKOH/gm, or 130 mgKOH/gm to 180 mgKOH/gm.
[0074] In some embodiments, the epoxy resin is cured at room temperature. In some embodiments, the epoxy resin is cured at a temperature ranging from 10 to 40 degrees Celsius. In some embodiments, the epoxy resin is cured at a temperature ranging from 20 to 35 degrees Celsius.
[0075] In some embodiments of the present disclosure, the corrosion-resistant matt finish formulation comprises 10-30 wt% of curing agent of the total weight of the formulation. In other embodiments the formulation comprises 10-20 wt%, or 15-30 wt%, or 20-30 wt%, or 25-30 wt%, or 15-20 wt%, or 15-25 wt% of the filler of the total weight of the formulation.
[0076] In some embodiments, fillers are employed for imparting excellent impedance value to the primer formulation, for example, carbon black, SiO2, CaO, Na2O, MnO2, K2O, Al2O3, Fe2O3, MgO, diatomaceous earth, talc, calcium carbonate and combinations thereof. In some embodiments, fillers are selected from a group consisting of SiO2, CaO, Na2O, MnO2, K2O, Al2O3, Fe2O3, MgO and combinations thereof.
[0077] In some embodiments, the corrosion-resistant matt finish formulation comprises 10-40 wt% of fillers of the total weight of the formulation. In some embodiments the formulation comprises 10-20 wt%, or 10-30 wt%, or 20-40 wt%, or 20-30 wt%, or 25-35 wt%, or 35-40 wt%, or 15-40 wt%, or 25-40 wt % of the filler of the total weight of the formulation.
[0078] In some embodiments, the corrosion-resistant matt finish primer is characterized by comprising two components i.e., component A and component B in a mass ratio of 3-7: 1-5. Component A comprises the following parts by weight: 20-50 wt% of epoxy resin, 10-40 wt% of zinc dust powder, 10-40 wt% of fillers, 0.1 -1 wt.% of dispersing agent, 0.1-1 wt% nitrogen-based functionalized graphene and 20-50 wt% of a solvent. Component B comprises 10-30 wt% of curing agent and 20-50 wt% of the solvent.
[0079] Another aspect of the present disclosure provides a method of preparing the corrosion resistant, matt finish primer formulation described above. Accordingly, the embodiments described hereinabove in respect of the formulation are applicable here as well.
[0080] In an embodiment, the method comprises the steps of:
i. mixing 10-40 wt% of Zinc dust with 20-50 wt% of an epoxy resin for 3-15 minutes to obtain a mixture I;
ii. mixing 0.1-1 wt% of nitrogen based functionalized grapheme, 0.1-1 wt%- of a dispersing agent, 10-40 wt% of a filler, and optionally, 20-50 wt% of a solvent or part thereof with the mixture 1, simultaneously or sequentially to prepare a mixture II;
iii. mixing 10-30 wt% of a curing agent with mixture II for 5-20 minutes to obtain a mixture III; and
iv. mixing the remainder of the solvent with the mixture III to obtain the corrosion resistant, matt finish primer formulation.
[0081] In some embodiments, the stirring is done at 250-350 RPM.
[0082] The first step involves mixing 10-40 wt% of Zinc dust with 20-50 wt% of the epoxy resin to obtain mixture I. This mixture is stirred for 3-15 minutes. In preferred embodiments, mixture I is stirred for 5 minutes.
[0083] The second step involves mixing 0.1-1 wt% of nitrogen based functionalized graphene, 0.1-1 wt%- of the dispersing agent, 10-40 wt% of a filler, and optionally, 20-50 wt% of a solvent or part thereof with the mixture I, simultaneously or sequentially to prepare a mixture II.
[0084] The next step involves mixing 10-30 wt% of a curing agent with mixture II for 5-20 minutes to obtain a mixture III. This mixture is stirred for 5-20 minutes. In some embodiments mixture III is stirred for 10 minutes.
[0085] The final step comprises mixing the remainder of the solvent with the mixture III to obtain the corrosion resistant, gloss finish primer formulation.
[0086] In some embodiments of the present disclosure, the stirring is done at 250-350 RPM.

EXAMPLES
[0087] The present invention is further explained in the form of following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
[0088] For the formulations, the additives were chosen in such a way that they can improve the adhesion strength of the Zn film. With higher adhesion strength, the paint will be more durable. In addition, the additive’s inherent layered structure will delay the permeation of corrosive ions to the metal surface thereby enhancing the corrosion resistance.
EXAMPLE 1: Method of preparing the coating
[0089] To make 1 kg of paint/coating, 400 g of zinc dust was mixed with 278 g of Epoxy resin and stirred for 5-10 minutes to obtain Mixture I. 6 g of the nitrogen based Functionalized graphene, 5 g of the dispersing agent (mixture of polyethylene and polyhydric alcohols having 10 to 16 carbon atoms) and 200 g of the fillers (according to the technical data sheet) were mixed with mixture I and stirred for 10-15 minutes to prepare a mixture II. In the last step, 111 g of polyaminoamide was added in mixture II as a curing agent and stirred for 10 min. Xylene or Suitable Epoxy Thinner was added to obtain the desired consistency of the Zinc primer.
[0090] Electrochemical Impedance Spectroscopy
[0091] To evaluate the corrosion performance of the coating, Electrochemical Impedance Spectroscopy (ASTM G 106) was carried out on the Primer formulation prepared in example 1 and compared against the conventionally used zinc silicate and zinc rich primers (such as Interzinc® 52 and Transozinc 155) in the refinery. The method involves immersing the coated sample in 3.5 wt% NaCl, as it resembles Sea Water and provides an accelerated corrosive environment. The electrochemical impedance spectra were measured over a range of frequencies ranging from 10-2 to 105 Hz with a sine perturbation of 10 mV. The impedance values at lower frequencies depict the corrosion resistance and the impedance values at higher frequencies indicate the solution resistance. At lower frequencies the electrolyte (3.5 wt% NaCl) has sufficient time to interact with the surface. Table 1 below provides impedance values for commercial and primer formulation prepared in example 1 with different components. Bode Plot of different component used in HP-PRIMER and commercial Primer is shown in FIG. 1.
Table 1: Impedance Value of Commercial and primer formulation of example 1 with different component

Composition Impedance (Ω) at 10-2 Hz Impedance (Ω) at 105 Hz
Commercial (zinc rich primer) 7.49 10
HP-PRIMER Matt
(example 1) 2.47 x 105 1.88 x 102
Zinc 2.64 x 102 1.04 x 101
Functionalized Graphene 4.49 x 109 2.22 x 105
Non-functionalized Graphene 3.01 x 103 1.76 x 102
Fillers 5.58 x 104 2.95 x 102

[0092] As can be seen from the aforementioned values, the Primer formulation prepared in example 1 containing functionalized graphene and fillers shows excellent impedance values. To further evaluate their performance, adhesion test was conducted.
[0093] Adhesion Strength Evaluation
[0094] ASTM D4541-17 was used to evaluate the pull-off strength or adhesion strength of the formulation from metal substrates using a Pull-off adhesion tester. This test determines the greatest perpendicular force that a surface area can bear before a plug of material is detached. Also, it determines if the coated surface remains intact on the metal at a defined load. Adhesion Strength of Commercial and In-House HP-PRIMER with different component are shown in FIG. 2.

Table 2: Adhesion Strength data of Commercial and Primer formulation prepared in example 1 with different components
Commercial Primer
(zinc rich primer)
(MPa) HP-PRIMER-Matt
(MPa) Zinc
(MPa) Functionalized graphene
(MPa) Non-functionalized graphene (MPa) Fillers
(MPa)
1 2.45 5.7 3.15 4.23 2.06 3.55
2 3.34 6.93 3.93 4.15 2.14 3.67
3 3.33 6.43 3.22 4.11 2.78 3.47
4 2.76 6.58 2.16 3.56 1.99 3.18
5 2.25 6.25 2.98 4.98 2.22 2.79
6 2 6.03 3.09 4.25 2.61 3.38

[0095] As seen from the results, although the impedance value of functionalized graphene and filler alone are higher than the Primer formulation prepared in example 1, their adhesion strength is not good. The adhesion strength of Primer formulation prepared in example 1 is excellent as compared to other component used alone.
[0096] To further evaluate the performance of the primer for a two-coat system, a coating was made using HP-Primer (100 μm) and topcoat (Marathon XHB, 150-200 μm). The data for two coat system is mentioned below. Adhesion Strength of Commercial and In-House HP-PRIMER with different component + top coat are shown in FIG. 3.

Table 3: Adhesion Strength data of Commercial and In-House HP-PRIMER with different component + top coat
Commercial Primer
(zinc rich primer)
(MPa) HP-PRIMER-Matt
(MPa) Zinc
(MPa) Functionalized graphene
(MPa) Non-functionalized graphene (MPa) Fillers
(MPa)
1 2.84 7.59 4.12 5.02 3.09 4.22
2 4.24 7.55 4.55 4.88 3.66 4.98
3 5.18 7.22 4.03 4.68 3.47 4.57
4 3.55 7.24 3.75 5.08 3.33 5.12
5 2.99 6.11 3.98 5.22 2.88 5.64
6 2.51 7.21 4.98 3.98 3.67 4.77

[0097] Salt Spray Test
[0098] To evaluate the reliability of coating in corrosive environments, ASTM B117- Salt Spray Test method was used. In the test method, the coated metals were exposed to a salt fog environment over an extended period. For the test, a scratch or scribed line was made through the coating with a sharp scriber to expose the underlying metal to a corrosive environment. The test was conducted for 1440 hours (60 days).
[0099] FIG. 4 shows the performance of commercial primer and the Primer formulations prepared according to the present disclosure. It is important to note that the Primer formulations prepared according to the present disclosure showcased better corrosion protection until 600h. It is possible for such behavior as these are primer coats with a thickness of ~100 microns.
[00100] Field study and analysis
[00101] The HP Primer was tested in a refinery during the month of Dec-2022. The table below shows the various locations where the primer was tested and the number of samples that were tested at these locations in the refinery.

S.No Location No. of Samples
1 Lube Region Cooling Tower Area 12
2 New Hydrogen Generation Unit (NHGU) 12
3 Diesel Hydrotreating Unit (DHT) 12
4 Prime-G 12
5 Isomerization Unit (ISOM) 12
6 Continuous Catalytic Reforming (CCR) 12
7 Fuel Region Cooling Tower Area 8

Sample No: 1-28 (HP-Primer Coated Samples at refinery by Brush)
Sample No: 29-56 (Blasted Coated Samples of Zinc Silicate by Spray gun at refinery)
Sample No: G1-G12 & M1-M12 (HP-Primer Coated Sample in lab by spray gun)
[00102] 1st Month Assessment:
[00103] FIG. 5 depicts the photographs of Visual Examination of Commercial and Primer formulation prepared according to the present disclosure after 1 month in the Refinery.
[00104] Adhesion Test (Method-B: Pull-off adhesion):

Location Sample No. Adhesion Strength (MPa)
Isomerization Unit (ISOM) M-11 5.35
Sample No 6 5.17
Sample No 41 1.38
Continuous Catalytic Reforming (CCR) M-12 4.84
Sample No 5 4.71
Sample No 32 2.45
FR-Cooling Tower Sample No 10 4.91
Sample No 40 2.35
Lube Region Cooling Tower Area G-3 3.8
Sample No 23 3.95
Sample No 49 2.13
New Hydrogen Generation Unit (NHGU) G-6 4.12
Sample No 17 5.2
Sample No 42 1.9
Diesel Hydrotreating Unit (DHT) M-3 5.7
Sample No 20 5.2
Sample No 35 1.9
Prime-G M-7 5.9
Sample No 14 5.4
Sample No 39 2.1

[00105] 2nd Month Assessment:
[00106] FIG. 6 depicts the photographs of Visual Examination of Commercial and Primer formulations prepared according to the present disclosure after 2 months in the refinery.
[00107] Adhesion Test (Method-B: Pull-off adhesion):

Location Sample No. Adhesion Strength (MPa)
Isomerization Unit (ISOM) G-8 4.80
Sample No 15 7.38
Sample No 51 2.48
Continuous Catalytic Reforming (CCR) G-12 3.01
Sample No 3 7.17
Sample No 48 1.88
FR-Cooling Tower Sample No 2 5.16
Sample No 53 2.96
Lube Region Cooling Tower Area G-1 5.52
Sample No 24 5.43
Sample No 46 2.34
New Hydrogen Generation Unit (NHGU) M-5 12.11
Sample No 16 6.41
Sample No 29 1.34
Lube Region Cooling Tower Area G-2 3.23
Sample No 27 (HP Primer at refinery) 5.95
Sample No 34 (Zinc Silicate at refinery) 1.27
New Hydrogen Generation Unit (NHGU) G-10 (HP Primer at lab) 5.96
Sample No 26 (HP Primer at refinery) 6.19
Sample No 47 (Zinc Silicate at refinery) 1.44

[00108] Conclusions
1. All Primer formulation prepared according to the present disclosure coated samples in both lab scale and Refinery did not show any corrosion marks after two months of exposure.
2. The adhesion strength of Primer formulation prepared according to the present disclosure coated samples coated sample was found to be superior than Zinc silicate primer.

ADVANTAGES OF THE INVENTION
[00109] The proposed invention provides a corrosion resistant, matt finish primer formulation.
[00110] The proposed invention provides a matt finish primer formulation with increased adhesion strength and durability.
[00111] The proposed invention provides a matt finish primer formulation with enhanced corrosion protection and adhesion resistance with least surface preparation.
[00112] The proposed invention provides zinc-rich coatings that can provide cathodic protection and good mechanical strength.
[00113] The proposed invention also provides a process for production of a corrosion resistant, matt finish primer formulation that is facile, economical and industrially applicable.
[00114] Although the present invention has been described with reference to preferred embodiments, it is submitted that various modifications can be made to the exemplary embodiments without departing from the spirit and scope of the invention.
, Claims:1. A corrosion resistant, matt finish primer formulation comprising:
i. 20-50 wt% of an Epoxy resin of the total weight of the formulation;
ii. 10-30 wt% of a curing agent of the total weight of the formulation;
iii. 0.1-1 wt% of a functionalized graphene of the total weight of the formulation;
iv. 10-40 wt% of Zinc dust of the total weight of the formulation;
v. 10-40 wt% of fillers of the total weight of the formulation;
vi. 0.1-1 wt% of dispersing agent of the total weight of the formulation; and
vii. 20-50 wt% of a solvent of the total weight of the formulation.
2. The formulation as claimed in claim 1, wherein the epoxy resin is categorized as type 1 solid epoxy resin.
3. The formulation as claimed in claim 2, wherein the epoxy resin is bisphenol-A-(epichlorhydrin) epoxy resin.
4. The formulation as claimed in claim 1, wherein the epoxy resin is a 75 wt% solid epoxy resin in a secondary solvent.
5. The formulation as claimed in claim 1, wherein the solvent is selected from the group consisting of xylene, methyl ethyl ketone, toluene or combinations thereof.
6. The formulation as claimed in claim 4, wherein the secondary solvent is selected from the group consisting of xylene, glycidyl ether or combinations thereof.
7. The formulation as claimed in claim 1, wherein the dispersing agent is selected from a group consisting of polyethylene, polyoxyethylene, polyhydric alcohols, or mixture thereof.
8. The formulation as claimed in claim 7, wherein the dispersing agent is the mixture of polyethylene and polyhydric alcohols, and has carbon atoms ranging between 10 to 16.
9. The formulation as claimed in claim 1, wherein the functionalized graphene is nitrogen-based functionalized graphene.
10. The formulation as claimed in claim 1, wherein the epoxy resin is cured by polyaminoamide, phenyl alkylamines, phenols, polyamide, or amine-adducts for curing coating systems.
11. The formulation as claimed in claim 1, wherein the epoxy resin is cured at a temperature ranging from 20 to 35 degrees Celsius.
12. The formulation as claimed in claim 1, wherein the fillers are selected from a group consisting of SiO2, CaO, Na2O, MnO2, K2O, Al2O3, Fe2O3, MgO, and combinations thereof.
13. A method of preparing a corrosion resistant, matt finish primer formulation comprising the steps of:
i. mixing 10-40 wt% of Zinc dust with 20-50 wt% of an epoxy resin for 3-15 minutes to obtain a mixture I;
ii. mixing 0.1-1 wt% of nitrogen based functionalized grapheme, 0.1-1 wt%- of a dispersing agent, 10-40 wt% of a filler, and optionally, 20-50 wt% of a solvent or part thereof with the mixture 1, simultaneously or sequentially to prepare a mixture II;
iii. mixing 10-30 wt% of a curing agent with mixture II for 5-20 minutes to obtain a mixture III; and
iv. mixing the remainder of the solvent with the mixture III to obtain the corrosion resistant, matt finish primer formulation.
14. The method as claimed in claim 13, wherein the stirring is done at 250-350 RPM.