TECHNICAL FIELD

The present disclosure relates to the field of material sciences. Particularly, the present disclosure relates to zinc (Zn) based electroplating composition, a substrate comprising a coating of the Zn based electroplating composition and methods of preparing them.

BACKGROUND OF THE DISCLOSURE
Zinc coating have extensively been used for improving the corrosion resistance of substrate, such as steel. Zinc is well known for imparting sacrificial corrosion resistance to steel, along with the benefit of a low cost. Hot dip galvanized steel is the most popular coated steel product used in automotive segment. However, hot dip galvanized technique has certain disadvantages like poor coating, thickness control and impossibility of single sided coatings. Another problem with the hot dipping of the zinc for high strength alloy steels is that they suffer from selective oxidation of alloying elements in the steel during annealing, resulting in poor wettability of molten zinc.

One of the ways by which these problems can be addressed is by electrodeposition of zinc (electrogalvanizing) instead of hot dipping. Electrogalvanizing offers many advantages in comparison to hot-dipping, like coating at room temperature, production of more compact coatings, better control over coating thickness, and the possibility of one-sided coating. However, there is a lot of scope to introduce special functionalities in the coating as demanded by the automotive segments. At present, functionalities like self-passivation and self-lubrication are achieved through additional inorganic or organic coating over and above the zinc metallic coating.

The present disclosure aims to provide a comprehensive coating composition where the multifunctional requirements of the automotive industry can be achieved through a single coating system.

STATEMENT OF THE DISCLOSURE
Accordingly, the present disclosure describes a zinc based electroplating composition comprising metallic nanoparticle having improved dispersion of metallic nanoparticle and improved stability. The Zinc based electroplating composition provides for improved corrosion resistance to a substrate.

The present disclosure also relates to a method of preparing the zinc based electroplating composition, comprising- i. preparing a zinc based electrolyte solution; and ii. dispersing the metallic nanoparticle into the electrolyte solution to obtain the zinc based electroplating composition.

The present disclosure further relates to a substrate comprising coating of the zinc based electroplating composition described herein.

The present disclosure further relates to a method of preparing the substrate comprising a coating of the zinc based electroplating composition, said method comprising electrodepositing the composition described herein on a substrate.

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: depicts Transmission electron microscope (TEM) image of Al nanoparticles and X-ray powder diffraction (XRD) analysis of Al nanoparticles.

Figure 2: depicts Transmission electron microscope (TEM) image of Si nanoparticles and X-ray powder diffraction (XRD) analysis of Si nanoparticles.

Figure 3: illustrates zeta potential plot of Al nanoparticle and Si nanoparticle with varying pH.

Figure 4: illustrates flow chart of the process of preparation of the Zn based electroplating composition.

Figure 5: illustrates hydrodynamic particle size analysis plot of Al and Si nanoparticles, respectively during the preparation of the Zn based electroplating composition.

Figure 6: illustrates a plot depicting corrosion properties (Icorr) of a substrate coated with pure zin (Zn (Pr)), Zinc comprising additive (Zn (additive)) and Zn based electroplating composition (comprising Al nanoparticles) of the present disclosure, respectively. Coating is obtained through DC and pulsed electrodeposition, respectively.

Figure 7: illustrates top surface morphology and Al nanoparticle content in the Zn based electroplating composition coating on a substrate.

Figure 8: illustrates a plot depicting corrosion properties (Icorr) of a substrate coated with pure zin (Zn (Pr)), Zinc comprising additive (Zn (additive)) and Zn based electroplating composition comprising Si nanoparticles (comparative composition), respectively. Coating is obtained through DC and pulsed electrodeposition, respectively.

Figure 9: illustrates top surface morphology and Si nanoparticle content in the Zn based electroplating composition coating on a substrate.

Figure 10: illustrates plot depicting corrosion properties (Icorr) of a substrate coated with Zn based electroplating composition comprising Al nanoparticles (composition of the present disclosure) and Zn based electroplating composition comprising Si nanoparticles (comparative composition).

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.

As used herein, the term ‘Zn based electroplating composition’ refers to an electroplating bath composition comprising Zn electrolytes. The Zn electrolytes includes but it is not limited to zinc sulphate and zinc chloride.

The present disclosure describes an Zn based electroplating composition comprising metallic nanoparticles.

In some embodiments of the present disclosure, the metallic nanoparticle includes but it is not limited to aluminium (Al) nanoparticle.

In some embodiments of the present disclosure, the metallic nanoparticle is aluminium (Al) nanoparticle.

In some embodiments of the present disclosure, the metallic nanoparticle is in an amount ranging from about 1 g/L to 10 g/L, including all the values in the range, for instance 1.1 g/L, 1.2 g/L, 1.3 g/L, 1.4 g/L and so on and so forth.

In some embodiments of the present disclosure, the metallic nanoparticle has particle size ranging from about 30 nm to 50 nm, including all the values in the range, for instance 31 nm, 32 nm, 33 nm, 34 nm and so on and so forth.

In some embodiments of the present disclosure, the metallic nanoparticle, such as aluminium (Al) nanoparticle has zeta potential ranging from about 42 mV to 48 mV, including all the values in the range, for instance 42.1 mV, 42.2 mV, 42.3 mV, 42.4 mV and so on and so forth.

In some embodiments of the present disclosure, the Zn based electroplating composition is devoid of additive and surfactant. The Zn based electroplating composition despite being devoid of additive and surfactant, provides for improved corrosion resistance properties as a coating on a substrate.

In some embodiments of the present disclosure, in the Zn based electroplating composition, the metallic nanoparticle, such as Al nanoparticle is highly stable with excellent dispersion and without any agglomeration.

The present disclosure further describes a method of preparing zinc (Zn) based electroplating composition described above.

In some embodiments of the present disclosure, the method of preparing the Zn based electroplating composition, comprises-
- Preparing a zinc-based electrolyte solution; and
- Dispersing the metallic nanoparticle into the electrolyte solution to obtain the zinc based electroplating composition.

In some embodiments of the present disclosure, preparing the zinc electrolyte solution comprises mixing zinc sulphate, zinc chloride and boric acid with demineralized water, followed by adjusting pH of the solution to a range of from about 3 to 4.5, including all the values in the range, for instance, 3.1, 3.2, 3.3, 3.4 and so on and so forth.

In some embodiments of the present disclosure, the zinc sulphate is in an amount ranging from about 200 g/L to 300 g/L, including all the values in the range for instance, 201 g/L, 202 g/L, 203 g/L, 204 g/L and so on and so forth.

The inventors found that zinc sulphate in the amount ranging from about 200 g/L to 300 g/L, including all the values in the range for instance, 201 g/L, 202 g/L, 203 g/L, 204 g/L and so on and so forth provides for improved zinc-based electrolyte solution with desired morphology that plays an important role in achieving effective dispersion of metallic nanoparticle, such as Al nanoparticle. The inventors found that concentration of zinc sulphate in the composition of lower than 200 g/L caused burnt deposits at the edges (during coating), particularly at high current density. On the other hand, although higher concentrations of zinc sulphate in the composition provided higher deposition kinetics, the corrosion properties of the Zn-based electroplating composition coating were found to be better only when the zinc sulphate was employed in the range of about 200 g/L to 300 g/L.

In some embodiments of the present disclosure, the zinc chloride is in an amount ranging from about 5 g/L to 8 g/L, including all the values in the range for instance, 5.1 g/L, 5.2 g/L, 5.3 g/L, 5.4 g/L and so on and so forth.

In some embodiments of the present disclosure, the boric acid is in an amount ranging from about 22 g/L to 35 g/L, including all the values in the range for instance, 22.1 g/L, 22.2 g/L, 22.3 g/L, 22.4 g/L and so on and so forth.

The inventors have found that any combination of the individual amounts of the zinc sulphate, zinc chloride and boric acid described above can be employed to prepare the zinc-based electrolyte solution.

In some embodiments of the present disclosure, the dispersion of the metallic nanoparticles into the Zn based electrolyte solution to obtain the Zn based electroplating composition is carried out by-
a) dividing the zinc based electrolyte solution into two batches;
b) adding the metallic nanoparticle to first batch of the electrolyte solution, followed by stirring and sonication to obtain an emulsion; and
c) adding the emulsion to second batch of the electrolyte solution, followed by stirring and sonication to obtain the Zn based electroplating composition.

The inventors have found that, adding metallic nanoparticle to the first batch of the electrolyte solution, followed by obtaining an emulsion, creates an environment whereby the metallic nanoparticles interact with the operative environment. Addition of the emulsion to second batch of the electrolyte solution provides for effective dispersion of the metallic nanoparticle and improves stability. The inventors have particularly found that this manner of dispersing the metallic nanoparticle prevents agglomeration of the metallic nanoparticles and provides for improved dispersion of the metallic nanoparticle.

In some embodiments of the present disclosure, after adding the metallic nanoparticle to the first batch of the electrolyte solution, the solution is stirred for a duration ranging from about 15 minutes to 20 minutes, including all the values in the range, for instance, 15.1 minutes, 15.2 minutes, 15.3 minutes, 15.4 minutes and so on and so forth. Further, the solution is subjected to sonication including but not limited to ultrasonication for a duration ranging from about 20 minutes to 40 minutes, including all the values in the range, for instance, 20.1 minutes, 20.2 minutes, 20.3 minutes, 20.4 minutes and so on and so forth.

In some embodiments of the present disclosure, after adding the emulsion to the second batch of the electrolyte solution, the solution is stirred for a duration ranging from about 8 hours to 12 hours, including all the values in the range for instance, 8.1 hours, 8.2 hours, 8.3 hours, 8.4 hours and so on and so forth. Further, the solution is subjected to sonication including but not limited to ultrasonication for a duration ranging from about 20 minutes to 40 minutes, including all the values in the range, for instance, 20.1 minutes, 20.2 minutes, 20.3 minutes, 20.4 minutes and so on and so forth.

In some embodiments of the present disclosure, the metallic nanoparticle in the emulsion has hydrodynamic particle size ranging from about 10 micron to 20 micron, including all the values in the range for instance, 10.1 micron, 10.2 micron, 10.3 micron, 10.4 micron and so on and so forth.

In some embodiments of the present disclosure, the metallic nanoparticle in the second batch of the electrolyte solution has hydrodynamic particle size ranging from about 1 µm to 2 µm, including all the values in the range, for instance, 1.1 µm, 1.2 µm, 1.3 µm, 1.4 µm and so on and so forth.

In an embodiment of the present disclosure, Figure 5 provides a plot depicting the hydrodynamic particle size of Al nanoparticle (for composition of the present disclosure) and Si nanoparticle (for comparative composition) during the preparation of the composition.

In an embodiment of the present disclosure, Figure 4 provides a flow chart depicting the preparation of the Zn-based electroplating composition.

In an embodiment of the present disclosure, Figure 3 provides a plot indicating zeta potential of Al nanoparticle (of composition of the present disclosure) and Si (for comparative composition). In the plot it can be observed that the Al nanoparticle has zeta potential of more than +30 mV in the pH range of about 3 to 4, indicating improved dispersion of the Al nanoparticle in the composition. However, the Si nanoparticle has zeta potential less than zero, indicating reduced dispersion of the Si nanoparticle in the comparative composition.

The present disclosure further relates to a substrate comprising coating of the zinc based electroplating composition described above.

In some embodiments of the present disclosure, the metallic nanoparticle content, such as Al nanoparticle in the coating on the substrate is present in a range of about 1 wt% to 4 wt%, including all the values in the range, for instance, 1.01 wt%, 1.02 wt%, 1.03 wt%, 1.04wt% and so on and so forth.

In an alternate embodiment of the present disclosure, the metallic nanoparticle content, such as Al nanoparticle in the coating on the substrate is present in a range of about 1.01 wt% to 3.55 wt%, including all the values in the range, for instance, 1.02 wt%, 1.03 wt%, 1.04 wt%, 1.05 wt% and so on and so forth.

The metallic nanoparticle, such as Al nanoparticle content in the range of about 1 wt% to 4 wt% or in the range of from about 1.01 wt% and 3.55 wt% indicates improved incorporation of the Al nanoparticles in the coating, which in turn indicates that the Al nanoparticle were effectively dispersed in the Zn based electroplating composition. The inventors found that, said range of the Al nanoparticle content in the coating provides for improved corrosion resistance properties for a substrate. On the contrary, the Inventors found that, upon employing the comparative composition (comprising Si nanoparticle), the Si nanoparticle content in the coating was noted to be in the range of from about 0.08 wt% to 0.3 wt%, as a result, the coating showed reduced corrosion resistance property when compared to the electroplating composition comprising Al nanoparticle. Figure 10 provides a plot depicting corrosion properties (Icorr) of a substrate coated with Zn based electroplating composition comprising Al nanoparticles (composition of the present disclosure) and Zn based electroplating composition comprising Si nanoparticles (comparative composition) in relation to benchmark data (commercially available Zn-Ni sample with surface passivation), coating having pure zinc (Zn (pr)), and the coating having zinc and additive (Zn (additive)).

In some embodiments of the present disclosure, the coating on the substrate has corrosion potential ranging from about -1.03 to -1.1, including all the values in the range, for instance, -1.04, -1.05, -1.06, -1.07 and so on and so forth.

In some embodiments of the present disclosure, the coating on the substrate has deposition kinetics ranging from about 2 micron/minute to 4 micron/minute, including all the values in the range for instance, 2.1 micron/minute, 2.2 micron/minute, 2.3 micron/minute, 2.4 micron/minute and so on and so forth.

In some embodiments of the present disclosure, the coating on the substrate has corrosion current density ranging from about 0.5 µA/cm2 to 19 µA/cm2, including all the values in the range for instance, 0.6 µA/cm2, 0.7 µA/cm2, 0.8 µA/cm2, 0.9 µA/cm2 and so on and so forth.

In some embodiments of the present disclosure, the coating on the substrate has thickness ranging from about 18 µm to 22 µm, including all the values in the range, for instance, 18.1 µm, 18.2 µm, 18.3 µm, 18.4 µm and so on and so forth, when the deposition is carried out for a duration of about 5 minutes. The thickness of the coating on the substrate depends on duration of the deposition.

The present disclosure further relates to a method of preparing the substrate comprising coating of the Zn based electroplating composition described above.

In some embodiments of the present disclosure, the method of preparing the substrate comprising coating of the Zn based electroplating composition, said method comprises- electrodepositing the composition on a substrate.

In some embodiments of the present disclosure, the electrodepositing is carried out by technique selected from a group comprising direct current (DC) electrodeposition and pulsed electrodeposition.

In some embodiments of the present disclosure, the substrate includes but it is not limited to steel, such as Interstitial Free steel (IF steel) and cold rolled close annealed steel (CRCA steel).

In some embodiments of the present disclosure, the DC electrodeposition of the Zn based electroplating composition on a substrate, such as steel is carried out by- a) providing the steel as a cathode; and b) depositing the electroplating composition on the steel substrate at a constant current with a current density of about 170 mA/cm2 to 190 mA/cm2 and at a stirring rate of about 250 rpm to 350 rpm to provide a substrate comprising coating of the Zn based electroplating composition.

In some embodiments of the present disclosure, the current density employed in the DC electrodeposition is about 170 mA/cm2, about 175 mA/cm2, about 180 mA/cm2, about 185 mA/cm2, or about 190 mA/cm2, including values and ranges thereof. In some embodiments, the current density employed in the DC electrodeposition is about 175 mA/cm2 to 185 mA/cm2, including values and ranges thereof. In an exemplary embodiment, the current density for the DC electrodeposition is about 180 mA/cm2.

In some embodiments of the present disclosure, the DC electrodeposition is carried out for about 5 minutes to 8 minutes such as for about 5 minutes, about 6 minutes, about 7 minutes, or about 8 minutes. In an exemplary embodiment, the DC electrodeposition is carried out for about 5 minutes.

In some embodiments of the present disclosure, the coating on the substrate provided by the DC electrodeposition of the electroplating composition exhibits a corrosion current density (Icorr) of about 1.5 µA/cm2 to 14 µA/cm2, including all the values in the range, for instance 1.6 µA/cm2, 1.7 µA/cm2, 1.8 µA/cm2, 1.9 µA/cm2 and so on and so forth. The inventors have found that the Zn based electroplating composition of the present disclosure without any additive and/or surfactant component lowers the corrosion current values of the coating substantially.

In some embodiments of the present, the coating on the substrate provided by the DC electrodeposition of the electroplating composition exhibits a corrosion current density (Icorr) of about 1.5 µA/cm2 to 3 µA/cm2, including all the values in the range, for instance, 1.6 µA/cm2, 1.7 µA/cm2, 1.8 µA/cm2, 1.9 µA/cm2 and so on and so forth.

In some embodiments of the present disclosure, the pulsed electrodeposition of the Zn based electroplating composition on a substrate, such as steel is carried out by- a) depositing the electroplating composition on the steel substrate by employing a pulsed current with an average current density of about 170 mA/cm2 to 190 mA/cm2, a peak current density of about 240 mA/cm2 to 720 mA/cm2, duty cycle of about 25% to 75%, and a frequency of about 25 Hz to 200 Hz, wherein the electroplating composition is stirred at a rate of about 250 to 350 rpm during deposition to provide a substrate comprising coating of the Zn based electroplating composition.

In some embodiments of the present disclosure, the average current density employed in the pulsed electrodeposition is about 170 mA/cm2, about 175 mA/cm2, about 180 mA/cm2, about 185 mA/cm2, or about 190 mA/cm2, including values and ranges thereof. In some embodiments, the average current density employed in the pulsed method of deposition is about 175 mA/cm2 to 185 mA/cm2, including values and ranges thereof. In an exemplary embodiment, the average current density for the pulsed deposition is about 180 mA/cm2.

In some embodiments of the present disclosure, the peak current density employed in the pulsed electrodeposition is about 240 mA/cm2 to 720 mA/cm2, including values in the range, for instance, 241 mA/cm2, 242 mA/cm2, 243 mA/cm2, 244 mA/cm2 and so on and so forth.

In some embodiments of the present disclosure, the duty cycle of the pulsed current during pulsed electrodeposition varies from about 25% to 75%, including all the values in the range, for instance, 26%, 27%, 28%, 29% and so on and so forth.

In some embodiments of the present disclosure, the frequency of the pulsed current during pulsed electrodeposition is ranging from about 25 Hz to 200 Hz, including all the values in the range, for instance, 26 Hz, 27 Hz, 28 Hz, 29 Hz and so on and so forth.

In some embodiments of the present disclosure, the coating on the substrate provided by the pulsed electrodeposition of the electroplating composition exhibits a corrosion current density (Icorr) of about 0.6 µA/cm2 to 23 µA/cm2, including all the values in the range, for instance, 0.7 µA/cm2, 0.8 µA/cm2, 0.9 µA/cm2, 1.0 µA/cm2 and so on and so forth. The inventors have found that the Zn based electroplating composition of the present disclosure without any additive and/or surfactant component lowers the corrosion current values of the coating substantially.

In some embodiments of the present disclosure, the coating on the substrate provided by the pulsed electrodeposition of the electroplating composition exhibits a corrosion current density (Icorr) of about 0.6 µA/cm2 to 3 µA/cm2, including all the values in the range, for instance, 0.7 µA/cm2, 0.8 µA/cm2, 0.9 µA/cm2, 1.0 µA/cm2 and so on and so forth.

The Zn based electroplating composition comprising metallic nanoparticle, such as Al nanoparticle and the method of preparing the composition disclosed herein provides for many advantages-
- the Zn based electroplating composition provides for improved corrosion properties without presence of any additive and/or any surfactant in the composition.
- the inventors have particularly found that during preparation of the electroplating composition, dividing the Zn electrolyte solution into two batches and then dispersing the metallic nanoparticle, such as Al nanoparticle in first batch of the electrolyte solution to obtain an emulsion and then mixing the emulsion in second batch of the electrolyte solution provides for improved dispersion of the metallic nanoparticle in the composition. As a result, it was noted that effective deposition of the composition on a substrate is achieved with higher content of metallic nanoparticle, such as Al nanoparticle in the coating on a substrate.

In an embodiment of the present disclosure, Figures 1 and 2 provides characterization of the Al nanoparticle and Si nanoparticle, respectively through TEM and XRD analysis. The XRD analysis of the Al nanoparticle shows that the Al nanoparticles have a crystalline rutile structure. The XRD analysis of the Si nanoparticle shows that Si nanoparticles have an amorphous structure.

In an embodiment of the present disclosure, Figure 6 illustrates corrosion properties of the coating obtained from the Zn based electroplating composition comprising Al nanoparticles. The coating was obtained through DC electrodeposition and Pulsed electrodeposition. The pulsed electrodeposition was carried out by- i. 50% duty cycle with 200 Hz frequency (P1); and ii. 75% duty cycle with 25 Hz frequency (P2). The plot depicts that- lower concentrations of 1 g/L Al nanoparticles in the composition with pulsed deposition parameters of higher duty cycle with low frequency (P2) show very low Icorr of 0.62 µA/cm2 when compared to Icorr of benchmark (commercially available passivated Zn-Ni electroplated product) data. From the data in the plot of Figure 6, it can be understood that the electroplating composition of the present disclosure without any additive and/or any secondary coatings were able to improve corrosion properties, particularly, better than the benchmark data.

In an embodiment of the present disclosure, Figure 7 provides the image of Top surface morphology data of the coating of the Zn based electroplating composition having Al nanoparticles in an amount of 1 g/L, 2.5 g/L, 5 g/L and 10 g/L, respectively. No difference in the morphologies were observed in the coatings under DC electrodeposition and pulsed electrodeposition (both P1 and P2) at the mentioned varied concentration of Al nanoparticles in the composition, respectively.

In an embodiment of the present disclosure, Figure 8 provides a plot depicting the corrosion properties of the Zn based electroplating composition comprising Si nanoparticle (comparative composition). The Icorr values are significantly higher when compared the Icorr values noted in the Figure 6 for the coating obtained from the composition of the present disclosure (Zn-based electroplating composition comprising Al nanoparticle).

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: Preparation of the Zn based electroplating composition comprising Al nanoparticle
To about 500 ml of demineralized water, about 125 g of Zinc sulphate, about 3 g of Zinc chloride and 15 g of boric acid were added and stirred for about 1 to 1.5 hours to obtain an electrolyte solution. The pH of the solution was adjusted to 3 to 3.5. About 250 ml of the electrolyte solution was taken (first batch electrolyte solution), to which 0.5 to 5 g amount of Al nanoparticles was added and pH was adjusted to 3 to 3.5 and the solution was stirred for about 15 minutes to 20 minutes and ultrasonicated for about 1 hour to obtain an emulsion. The emulsion was added to remaining 250 ml of the electrolyte solution (second batch electrolyte solution) and stirred overnight (about 8 hours to 12 hours) and the solution was ultrasonicated for about 30 minutes to obtain the electroplating composition.
Figure 4 provides a flow chart depicting the process of preparation of the electroplating composition.

Example 2: Preparation of the Zn based electroplating composition comprising Si nanoparticle- Comparative composition
To about 500 ml of demineralized water, about 125 g of Zinc sulphate, about 3 g of Zinc chloride and 15 g of boric acid were added and stirred for about 1 to 1.5 hours to obtain electrolyte solution. The pH of the solution was adjusted to 3 to 3.5. About 250 ml of the electrolyte solution was taken (first batch electrolyte solution), to which 0.5 to 5 g amount of Si nanoparticles was added and pH was adjusted to 3 to 3.5 and the solution was stirred for about 15 minutes to 20 minutes and ultrasonicated for about 1 hour to obtain an emulsion. The emulsion was added to remaining 250 ml of the electrolyte solution (second batch electrolyte solution) and stirred overnight (about 8 hours to 12 hours) and the solution was ultrasonicated for about 30 minutes to obtain the electroplating composition.

Example 3: Coating the Zn based electroplating composition comprising Al Nanoparticle on a substrate through DC electrodeposition and Pulsed Electrodeposition.
i. DC electrodeposition
About 20 cm2 of the substrate was subjected to DC electrodeposition with 500 ml of the Zn based electroplating composition comprising Al nanoparticles. Electrodeposition was carried out with current density of about 180 mA/cm2 and with stirring rate of about 300 rpm and a stirrer bid of size about 3 cm length and about 0.5 cm diameter.
ii. Pulsed electrodeposition
i. P1: About 20 cm2 of the substrate was subjected to pulsed electrodeposition with 500 ml of the Zn based electroplating composition comprising Al nanoparticles. The parameters employed were- current density of about 180 mA/cm2; peak current density of about 240 mA/cm2; duty cycle of about 50%; frequency of about 200 Hz; stirring rate of about 300 rpm; and stirrer bid of size about 3 cm length and about 0.5 cm diameter.
ii. P2: About 20 cm2 of the substrate was subjected to pulsed electrodeposition with 500 ml of the Zn based electroplating composition comprising Al nanoparticles. The parameters employed were- current density of about 180 mA/cm2; peak current density of about 240 mA/cm2; duty cycle of about 75%; frequency of about 25 Hz; stirring rate of about 300 rpm; and stirrer bid of size about 3 cm length and about 0.5 cm diameter.

Figure 6 illustrates the corrosion properties (Icorr) of the coating of Zn based electroplating composition comprising Al nanoparticle on a substrate in comparison with the corrosion properties of commercially available Zn-Ni sample (benchmark) and pure zinc coating (Zn (pr)) and Zinc coating comprising additive (Zn (additive)).

Example 4: Comparative Experiment- Coating the Zn based electroplating composition comprising Si nanoparticle on a substrate through pulsed electrodeposition
i. DC electrodeposition
About 20 cm2 of the substrate was subjected to DC electrodeposition with 500 ml of the Zn based electroplating composition comprising Si nanoparticles. Electrodeposition was carried out with current density of about 180 mA/cm2 and with stirring rate of about 300 rpm and a stirrer bid of size about 3 cm length and about 0.5 cm diameter.
ii. Pulsed electrodeposition
i. P1: About 20 cm2 of the substrate was subjected to pulsed electrodeposition with 500 ml of the Zn based electroplating composition comprising Si nanoparticles. The parameters employed were- current density of about 180 mA/cm2; peak current density of about 240 mA/cm2; duty cycle of about 50%; frequency of about 200 Hz; stirring rate of about 300 rpm; and stirrer bid of size about 3 cm length and about 0.5 cm diameter.
ii. P2: About 20 cm2 of the substrate was subjected to pulsed electrodeposition with 500 ml of the Zn based electroplating composition comprising Si nanoparticles. The parameters employed were- current density of about 180 mA/cm2; peak current density of about 240 mA/cm2; duty cycle of about 75%; frequency of about 25 Hz; stirring rate of about 300 rpm; and stirrer bid of size about 3 cm length and about 0.5 cm diameter.

Figure 8 illustrates the corrosion properties (Icorr) of the coating of Zn based electroplating composition comprising Si Nanoparticle on a substrate in comparison with the corrosion properties of commercially available Zn-Ni sample (benchmark) and pure zinc coating (Zn (pr)) and Zinc coating comprising additive (Zn (additive)).

Figure 10 provides a plot depicting corrosion properties (Icorr) of a substrate coated with Zn based electroplating composition comprising Al nanoparticles (composition of the present disclosure) and Zn based electroplating composition comprising Si nanoparticles (comparative composition) in relation to benchmark data (commercially available Zn-Ni sample), coating having pure zinc (Zn (pr)), and the coating having zinc and additive (Zn (additive)). The data in the Figure 10 explicitly demonstrates that the coating obtained from the Zn based electroplating composition comprising Al nanoparticles has improved corrosion properties, i.e., low Icorr when compared to coating obtained from the Zn based electroplating composition comprising Si nanoparticles.

The foregoing description of the specific embodiments reveal 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.

Throughout this specification, the term ‘combinations thereof’ or ‘any combination thereof’ or ‘any combinations thereof’ are used interchangeably and are intended to have the same meaning, as regularly known in the field of patents disclosures.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

Claims:We Claim:

1. A zinc based electroplating composition comprising metallic nanoparticle.
2. The composition as claimed in claim 1, wherein the metallic nanoparticle is aluminum.
3. The composition as claimed in claim 1, wherein the metallic nanoparticle is in an amount ranging from about 1 g/L to 10 g/L.
4. The composition as claimed in claim 1, wherein the metallic nanoparticle has particle size ranging from about 30 nm to 50 nm.
5. The composition as claimed in claim 2, wherein the aluminum has zeta potential ranging from about 42 mV to 48 mV.
6. A method of preparing the zinc based electroplating composition as claimed in claim 1, said method comprises-
- preparing a zinc-based electrolyte solution; and
- dispersing the metallic nanoparticle into the electrolyte solution to obtain the Zinc based electroplating composition.
7. The method as claimed in claim 6, wherein preparing the zinc-based electrolyte solution comprises mixing zinc sulphate, zinc chloride and boric acid with demineralized water, followed by adjusting pH of the solution to a range of about 3 to 4.5.
8. The method as claimed in claim 7, wherein the zinc sulphate is in an amount ranging from about 200 g/L to 300 g/L, the zinc chloride is in an amount ranging from about 5 g/L to 8 g/L and the boric acid is in an amount ranging from about 22 g/L to 35 g/L.
9. The method as claimed in claim 6, wherein the metallic nanoparticle is dispersed into the electrolyte solution by:
a) dividing the zinc based electrolyte solution into two batches;
b) adding the metallic nanoparticle to first batch of the electrolyte solution, followed by stirring and sonication to obtain an emulsion; and
c) adding the emulsion to second batch of the electrolyte solution, followed by stirring and sonication to obtain Zinc based electroplating composition.
10. The method as claimed in claimed in claim 9, wherein pH of the emulsion is adjusted to a range of about 3 to 4.5.
11. The method as claimed in claim 9, wherein in the step b), the stirring is carried out for a duration ranging from about 15 minutes to 20 minutes; and the sonication is ultrasonication carried out for a duration ranging from about 20 minutes to 40 minutes.
12. The method as claimed in claim 9, wherein in the step c), the stirring is carried out for a duration ranging from 8 hours to 12 hours; and the sonication is ultrasonication carried out for a duration ranging from about 20 minutes to 40 minutes.
13. The method as claimed in claim 9, wherein hydrodynamic particle size of the dispersed metallic nanoparticle in the step b) is ranging from about 10 microns to 20 microns.
14. The method as claimed in claim 9, wherein hydrodynamic particle size of the dispersed metallic nanoparticle in the step c) is ranging from about 1 µm to 2 µm.
15. A substrate comprising coating of the zinc based electroplating composition as claimed in claim 1.
16. The substrate as claimed in claim 16, wherein the metallic nanoparticle content in the coating is ranging from about 1 wt% to 4 wt%.
17. The substrate as claimed in 15, wherein the coating has corrosion potential ranging from about -1.03 to -1.1; the coating has deposition kinetics ranging from about 2 to 4 micron /minute; and the coating has corrosion current ranging from about 0.5 µA/cm2 to 19 µA/cm2.
18. The substrate as claimed in claim 15, wherein the substrate is selected from a group comprising Interstitial Free steel (IF Steel) and cold rolled close annealed (CRCA Steel).
19. A method of preparing the substrate as claimed in claim 16, said method comprising, electrodepositing the composition as claimed in claim 1 on a substrate.
20. The method as claimed in claim 19, wherein the electrodepositing is carried out by technique selected from a group comprising direct current (DC) electrodeposition and pulsed electrodeposition.
21. The method as claimed in claim 20, wherein the pulsed electrodeposition is carried out with average current density ranging from about 175 mA/cm2 to 190 mA/cm2, peak current density ranging from about 240 mA/cm2 to 720 mA/cm2, duty cycle ranging from about 25% to 25% and frequency ranging from about 25 Hz to 200 Hz.
22. The method as claimed in claim 20, wherein the DC electrodeposition is carried out with current density ranging from about 170 mA/cm2 to 190 mA/cm2; and at a stirring rate ranging from about 250 rpm to 350 rpm.