Description:TECHNICAL FIELD
The present disclosure generally relates to a field of material science. Particularly, but not exclusively the present disclosure relates to a method of coating zinc substrates or zinc coated substrates. Further, embodiments of the present disclosure disclose a method for coating a nickel layer on a zinc substrate.

BACKGROUND OF THE DISCLOSURE
Zinc is widely used in variety of applications mainly due to its abundance availability, low cost, and environmental compatibility. Also, zinc may be coated as a protective layer on other materials such as but not limiting to steel. Zinc coating on the steel protects the steel from corrosion due to the sacrificial nature of the coating. The zinc coating on the steel surface gets oxidized, instead of the steel surface, thereby protecting the steel surface. Zinc may be reactive element and electronegative in nature. Hence, under corrosive environment, zinc substrate or zinc coated substrate may undergo severe corrosion. Zinc has low melting point of about 419.5 °C and hence lacks the thermal stability.

In order to supress the corrosion of zinc substrate or zinc coated substrate, attempts have been made to modify the surface of zinc substrate or zinc coated substrate. One such attempt is providing Alumina (Al2O3) thin film coating on zinc substrate in order to avoid hydrogen evolution reaction in alkaline media. However, Al2O3 coatings may be brittle in nature and tend to grow cracks on the surface of coating and hence subjecting the zinc substrate for corrosion. Furthermore, Al2O3 coating may be unstable in acidic environments. Hence, such coatings may not be suitable to protect the zinc substrate in acidic conditions. Organic polymer-based sol-gel coatings along with corrosion inhibitors may be employed for the protection of zinc substrates, but, such coatings may not suitable for high temperature operations and may not provide high temperature stability for the zinc substrate or zinc coated substrate. Chromium (IV) coatings may also employed for the protection of zinc surface. However, the usage of chromium (IV) may be mainly restricted due to its carcinogenic nature giving rise to health hazards. Further, thin layers of SiO2 has been tried as surface protection coating on zinc substrate. However, SiO2 coating process may not economically feasible due to the requirement of sophisticated equipment.

Nickel coating may be commonly applied to zinc substrate or zinc coated substrate to provide protection against corrosion, erosion, and abrasion. However, getting uniform, homogeneous nickel coating on zinc substrate may be still a challenging task due to uncontrolled dissolution of zinc from the substrate leading to irregular nickel coating.

The present disclosure is directed to overcome one or more limitations stated above, or any other limitations associated with the conventional coatings on zinc substrates or zinc coated substrates.

SUMMARY OF THE DISCLOSURE
One or more drawbacks of conventional methods for coating zinc substrate or zinc coated substrate are overcome. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be a part of the claimed disclosure.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

In one non-limiting embodiment of the present disclosure, there is provided a method for uniform deposition of nickel layer on a zinc substrate is disclosed. In the method, zinc substrate is dipped in a coating bath comprising a reduced total nickel salt concentration. The zinc substrate acts as cathode and nickel plates act as anode and the coating bath acts as electrolyte for electrodeposition. Live current is applied to the cathode for the electrodeposition of the nickel layer on the zinc substrate.

In an embodiment, coating of the nickel layer on the zinc substrate exhibits improved adhesion with uniform, homogenous and crack free morphology.

In an embodiment, the zinc substrate is at least one of pure zinc substrate and a zinc coated substrate. Further, the zinc coated substrate is at least one of electrogalvanized (EG) substrate and the galvanized (GI) substrate.

In an embodiment, density of the live current applied during the electrodeposition of the nickel layer ranges from about 600 A/m2 to about 800 A/m2.

In an embodiment, the reduced total nickel salt concentration in the coating bath ranges from about 25 g/l to about 200 g/l.

In an embodiment, the reduced total nickel salt concentration comprises nickel sulphate and nickel chloride salts in a ratio of 4:1.

In an embodiment, the coating bath employed for the coating of nickel layer optionally includes inert salt.

In an embodiment, the inert salt in the coating bath is at least one of ammonium chloride, sodium sulphate, boric acid and combination thereof.

In an embodiment, amount of ammonium chloride in the coating bath is about 30 g/l to 100 g/l.

In an embodiment, amount of sodium sulphate in the coating bath is about 0 g/l to 100 g/l.

In an embodiment, amount of boric acid in the coating bath is about 30 g/l to 50 g/l.

In an embodiment, pH of the coating bath is maintained in the range of 3 to 4.5.

In an embodiment, time duration required for the coating of nickel layer is at most 10 minutes.

In an embodiment, total thickness of the nickel layer on the zinc substrate is about 8 µm to about 10 µm.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Figure 1 illustrates process for deposition of nickel layer on a zinc substrate, in accordance with an embodiment of the present disclosure.

Figure 2 illustrates process of electroplating of zinc layer on a steel substrate, in accordance with an embodiment of the present disclosure.

Figure 3 illustrates micrographic view of a steel substrate coated with Zinc layer, in accordance with an embodiment of the present disclosure.

Figure 4 illustrates micrographic view of nickel layer deposited on a zinc coated substrate using conventional coating bath and by applying direct current.

Figure 5 illustrates micrographic view of nickel layer deposited on a zinc coated substrate using conventional coating bath and by applying live current.

Figures 6a, 6b and 6c illustrate micrographic views of nickel layer deposited on the zinc substrate using reduced nickel salt coating bath and by applying live current, in accordance with various embodiments of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAILED DESCRIPTION
The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent methods do not depart from the scope of the disclosure. The novel features which are believed to be characteristic of the disclosure, as to method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.

Conventionally, electrodeposition technique has been employed for coating of nickel on zinc substrate or zinc coated substrate. Such conventional process may not commercially viable due to the dissolution of zinc from the coating into the nickel coating bath. While nickel layer may form on a zinc substrate, Zn from the substrate dissolves into solution in the form of Zn2+ ions. Hence, the nickel present in the coating bath may be uncontrollably deposited on the zinc substance or zinc coated substrate giving rise to inhomogeneous, nonuniform coating structure. In addition to this, due to very high nickel concentration in the conventional nickel-plating bath, initial nickel deposition by taking up electron from the zinc surface may be uncontrollable. This situation may result in poor adhesion of nickel layer on the zinc substrate. Furthermore, the conventional nickel-plating baths employed for electroplating of a zinc substrate or a zinc coated substrates may become unstable due to rapid change in bath pH leading to deposit precipitation leading to bath turbidity and thereby inhomogeneous nickel layer coating on the zinc substrate.

From the discussion of prior arts, it is evident that obtaining uniform, homogenous and crack free nickel coating on zinc substrate is still a challenge. Hence, a single coating method to coat nickel layer on the zinc substrate with all these required properties may be of prime importance in order to enhance properties such as but not limited to corrosion resistance, high temperature thermal stability, weldability. Herein, the present invention provides a method for uniform deposition of nickel layer on a zinc substrate.

The present disclosure provides a method for uniform deposition of nickel layer on a zinc substrate. In the method of the present disclosure, zinc substrate may be dipped in a coating bath comprising a reduced total nickel salt concentration. The zinc substrate acts as cathode and the nickel plates acts as anode and the coating bath acts as the electrolyte for electrodeposition. Live current is applied to the cathode for the electrodeposition of the nickel layer on the zinc substrate. The coating of the nickel layer on the zinc substrate exhibits improved adhesion with uniform, homogenous and crack free morphology.

In an embodiment, the zinc substrate is at least one of pure zinc substrate and a zinc coated substrate. Further, zinc coated substrate is at least one of electrogalvanized (EG) substrate and the galvanized (GI) substrate.

In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

The present disclosure discloses a method for uniform deposition of nickel layer on a zinc substrate is explained with the help of figures. However, such exemplary embodiments should not be construed as limitations of the present disclosure, since the method may be used for other types of coating on a zinc substrate or nickel layer coating on any substrate other than zinc. A person skilled in the art may envisage various such embodiments without deviating from scope of the present disclosure.

Figure 1 illustrates a flow chart of a method for uniform deposition nickel layer (203) on a zinc substrate (200) using a coating bath containing reduced total nickel salt concentration and live current. Substrate used for nickel layer (203) deposition may be a zinc substrate (200). The zinc substrate (200) is at least one of pure zinc substrate and a zinc coated substrate. Further, the zinc coated substrate is at least one of electrogalvanized (EG) substrate and the galvanized (GI) substrate. For depositing the nickel layer (203) on the zinc substrate (200), a coating bath containing reduced total nickel salt concentration of about 25 g/l to about 200 g/l nickel sulphate and nickel chloride salt in the ratio of about 4:1, ammonium chloride of about 30 g/l to about 100 g/l, sodium sulphate of about 0 g/l to 100 g/l and boric acid of about 30 g/l to about 50 g/l may be prepared. The coating bath may be maintained at pH of about 3 to 4. Zinc substrate (200) may be dipped in the coating bath (step 102) for at most 10 minutes for electrodeposition. The zinc substrate (200) acts as cathode and the nickel plates acts as anode and the coating bath acts as electrolyte. During electrodeposition process, live current density of about 600 A/m2 to about 800 A/m2 may be applied to cathode (step 103) for the deposition of nickel layer (203) on the zinc substrate (200), such that total thickness of the nickel layer (203) on the zinc substrate (200) is about 8 µm to about 10 µm.

EXAMPLES:

In an embodiment of the present disclosure, a zinc coated steel substrate may be considered as a zinc substrate (200) for the exemplary explanation. Coating of zinc on the steel substrate (201) may be performed using the method as shown in figure.2. A steel substrate (201), having a composition comprising of Carbon 0.2 wt.% to 0.25 wt.%; Manganese 1.15 wt. % to 1.4 wt. %; Sulphur less than 0.01 wt. %; Phosphorus less than 0.05 wt. %; Silicon 0.2 wt. % to 0.35 wt.%; Aluminium less than wt.0.1 %; Copper less than 0.05 wt.%; Chromium wt.0.15 % to about 0.35 wt. %; Nickel less than wt.0.1 %; Molybdenum less than wt.0.01 %; Vanadium less than 0.01 wt.%; Niobium less than 0.01 wt.%; Titanium 0.02 wt. % to 0.05 wt.%; Nitrogen less than 50 ppm; Boron 0.002 wt.% to 0.005 wt.%; and the balance being iron optionally along with incidental elements may be used. The steel substrate (201) may be subjected for degreasing to remove oil contaminants, grease residue, corrosion or any other foreign deposits on the surface followed by water rinsing. In the cleaning process, the steel substrate (201) may be subjected for acid pickling at a temperature ranging from about 50 °C to about 70 °C in 15 wt. % HCl solution, and the time ranging from 5 minutes to 10 minutes. The steel substrate (201) may then be water rinsed to clean carry overs of the caustic solution on the surface of the steel substrate (201) during washing. Anodic cleaning may be carried out at about 75 °C to about 90 °C by applying voltage of about 4 V to 6 V. Subsequent to anodic cleaning, the steel substrate (201) may be subjected to caustic dipping NaOH solution to neutralise the steel surface. Electroplating of zinc layer (202) may be carried out from a coating bath containing zinc salt and brighteners at a pH of about 9 to 10, current density of about 100 A/m2 to about 300 A/m2 for about 3 minutes to about 20 minutes and finally subjected to water rinsing to obtain zinc layer (202) on steel substrate (201) [shown in figure 3]. Zinc electroplated surface may be further polished mechanically. Figure 3 illustrates the surface morphology of zinc coated substrate. The total thickness of zinc layer (202) is about 2 µm to about 15 µm. The zinc coated steel substrate may be used as electrogalvanized (EG) substrate or may be subjected to an annealing process to yield galvanised (GI) substrate and employed in subsequent nickel layer (203) deposition

For the purpose of experimental comparison, a nickel layer (203) deposited on the zinc substrate (200) by employing conventional electrodeposition technique is shown in figure 4. A conventional coating bath having 300 g/l of NiSO4.6H2O, 60 g/l of NiCl2.6H2O, 40 g/m of boric acid may be employed for the nickel layer (203) deposition and the coating bath may be maintained at pH of about 3 to 4. A direct current (DC) density of about 100 A/m2 to about 400 A/m2 may be applied during nickel layer (203) deposition process. As evident from figure 4, zinc dislocation during coating process may lead to uncoated regions and gives rise to inhomogeneous nickel layer (203) on the zinc substrate (200).

Conventional nickel coating bath with live current:
The major reason(s) for discontinuous nickel plating on zinc may be multifold. The electroplated zinc, being a less noble element it may tend to dissolve in the solution and the nickel, present in the solution may be deposited uncontrollably in the zinc plated surface as given in the following equations)
Zn surface ? Zn2+solution + 2e --------(1)
(L) (R)

Ni2+solution + 2e ? Nisurface ----------- (2)

Hence, giving rise to inhomogeneous coating structure. There may be requirement of extra electron to shift the first reaction to left side in order to stop the dissolution of zinc. In order to overcome zinc dissolution problem, a ‘live current’ may be applied to the zinc substrate, i.e. the there is a negative bias given on the zinc plated steel substrate before dipping the material in the coating bath to ensure the complete stoppage of dissolution of zinc from the substrate.

The conventional coating bath having 300 g/l of NiSO4.6H2O, 60 g/l of NiCl2.6H2O, 40 g/m of boric acid may be employed for the deposition of nickel layer (203) and the coating bath may be maintained at pH of about 3 to 4. However, instead of direct current, a live current density of about 200 A/m2 to about 1200 A/m2 may be applied to the zinc substrate (200) which acts as cathode. The very high nickel iron concentration in the coating bath may take up electron from the zinc surface in an uncontrolled fashion and may lead to poor adhesion the interface. Figure 5 indicates the poor adhesion of nickel layer (203) coating on zinc substrate (200). Furthermore, increasing the current density beyond 800 A/m2 may not be industrially feasible even it though has advantages in avoiding zinc dissolution.

Following paragraphs now enumerates examples of the nickel coating on the zinc substrate using a method of the present disclosure:

Reduced nickel salt concentration in coating bath with live current.

Case 1:
In an embodiment, a coating bath containing total nickel salt concentration of 200 g/l, nickel sulphate and nickel chloride salt in the ratio of about 4:1, boric acid of about 30 g/l to about 50 g/l may be employed for the nickel layer (203) deposition. The coating bath may be maintained at pH of about 3 to 4. During the electrodeposition, zinc substrate (200) may be used as cathode and the nickel plates act as anode and the coating bath may act as electrolyte. A live current of about 600 A/m2 to about 800 A/m2 may be applied to zinc substrate (200) i.e. cathode in order to create a negative bias during electrodeposition of nickel layer (203) on zinc substrate (200). Coating process may be carried at 35 °C to about 50 °C for almost to 10 minutes. Coating bath may be transparent, free from coagulations even after completion of the nickel coating process as depicted in figure 6. It clearly seen that coating bath with reduced nickel salt concentration may not leading to any hydrogen reduction reaction and precipitation. The reduced total nickel salt concentration in the coating bath paired with live current density leads to the formation of crack free, homogeneous, improved adhesion nickel layer (203) on zinc substrate (200) as shown in figure 6a.

Case 2:
In an embodiment, a coating bath containing reduced total nickel iron concentration of 100 g/l (half the amount of nickel as compared to case 1), nickel sulphate and nickel chloride salt in the ratio of about 4 to 1, ammonium chloride of about 30 g/l, sodium sulphate of 100 g/l and boric acid of about 50 g/l may be employed for the nickel layer (203) deposition. The coating bath may be maintained at pH of about 3 to 4. Ammonium chloride may be added to enhance lowered electron conductivity that might be caused due to reduced total nickel salt concentration in the coating bath. These salts may not participate in the electroplating reaction but may only help to maintain the bath conductivity creating sufficient ions migration. Zinc substrate (200) may be used as cathode. A live current of about 600 A/m2 to about 800 A/m2 may be applied to zinc substrate (200) cathode in order to create a negative bias. Coating process may be carried at 35 °C to about 50 °C for almost 10 minutes. The reduced total nickel salt concentration in the coating bath due to reduced nickel salt concentration may be compensated with addition of ammonium chloride. Figure 6b indicates the formation of crack free, homogeneous, improved adhesion nickel layer (203) on zinc substrate (200).

Case 3:
In an embodiment, a coating bath containing reduced total nickel iron concentration of about 50 to about 100 g/l (half the amount of nickel as compared to case 2), nickel sulphate and nickel chloride salt in the ratio of about 4 to 1, ammonium chloride of about 100 g/l, boric acid of about 30 g/l may be employed for the nickel layer (203) deposition. Increased amount of ammonium chloride not only enhance the ionic conductivity, but also enhance the stability of coating bath during electrodeposition process. The coating may be maintained at pH of about 3 to 4. Zinc substrate (200) may be used as cathode. A live current of about 600 A/m2 to about 800 A/m2 may be applied to zinc substrate (200) cathode in order to create a negative bias. Coating process may be carried almost to 10 minutes. The reduced ionic conductivity in the coating bath due to reduced nickel salt concentration may be compensated with addition of ammonium chloride. Figure 6c indicates the formation of crack free, homogeneous, improved adhesion nickel layer (203) on zinc substrate (200).

Parameter Optimized Range
Total nickel salt concentration 25-200 g/l
Ratio of nickel sulfate and nickel chloride 4:1
Additional salt for bath conductivity (i) Ammonium Chloride 30-100 g/l
(ii) Sodium sulfate, 0-100 g/l
Additional chemical for pH balance Boric acid: 30-50 g/l
Working pH 3- 4.5
Current density 600-800 A/m2
Current type Live, DC
Time of plating At most 10-minuts
Nickel layer thickness 8 µm -10 µm.

Table-1

Table 1 summaries the coating parameters employed for the deposition of nickel layer (203) on zinc substrate (203) as disclosed in example 3.

In an embodiment, comparison has been made between nickel layer (203) obtained by conventional process and nickel layer (203) obtained using combination of bath containing reduced nickel salt concentration by applying live current. It is evident that, nickel layer (203) deposited by conventional method leads to irregular inhomogeneous coating on zinc substrate (200) as shown in figure 4; whereas the nickel layer (203) deposited by the method of the present disclosure exhibits improved adhesion with uniform, homogenous and crack free morphology as shown in figures 6a, 6b and 6c.

In an embodiment adhesive, uniform, homogenous and crack free nickel layer on the zinc substrate may provide improved corrosion resistance, high temperature oxidation resistance, abrasion resistance and thermal resistance during subsequent real time operations. The present disclosure may be thus successful in providing a simple and efficient method for uniform deposition of nickel layer on zinc substrate.

Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals

Referral Numerals Description
101-103 Flowchart blocks for nickel layer deposition
101 Zinc layer coating
102 Zinc substrate dipping
103 Live current apply
201 Steel substrate
202 Zinc layer
203 Nickel layer
200 Zinc substrate/cathode

Claims:
1. A method for uniform deposition of nickel layer (203) on a zinc substrate (200), the method comprising:
dipping the zinc substrate (200) in a coating bath, wherein the coating bath comprises a reduced total nickel salt concentration, and wherein, the zinc substrate (200) act as cathode and nickel plates act as anode and the coating bath acts as electrolyte for electrodeposition; and
applying live current to the cathode (200) for electrodeposition of the nickel layer (203) on the zinc substrate (200).

2. The method as claimed in claim 1, wherein coating of the nickel layer (203) on the zinc substrate (200) exhibits improved adhesion with uniform, homogenous and crack free morphology.

3. The method as claimed in claim 1, wherein the zinc substrate (200) is at least one of pure zinc substrate and a zinc coated substrate.

4. The method as claimed in claim 3, wherein the zinc coated substrate is at least one of electrogalvanized (EG) substrate and the galvanized (GI) substrate.

5. The method as claimed in claim 1, wherein density of the live current applied during the electrodeposition of the nickel layer (203) ranges from about 600 A/m2 to about 800 A/m2.

6. The method as claimed in claim 1, wherein the reduced total nickel salt concentration in the coating bath ranges from about 25 g/l to about 200 g/l.

7. The method as claimed in claim 1, wherein the reduced total nickel salt concentration comprises nickel sulphate and nickel chloride salts in a ratio of 4:1.

8. The method as claimed in claim 1, wherein the coating bath employed for the coating of nickel layer (203) optionally includes inert salt.

9. The method as claimed in claim 8, wherein the inert salt in the coating bath is at least one of ammonium chloride, sodium sulphate, boric acid and combination thereof.

10. The method as claimed in claim 9, wherein amount of ammonium chloride in the coating bath is about 30 g/l to 100 g/l.

11. The method as claimed in claim 9, wherein amount of sodium sulphate in the coating bath is about 0 g/l to 100 g/l.

12. The method as claimed in claim 9, wherein amount of boric acid in the coating bath is about 30 g/l to 50 g/l.

13. The method as claimed in claim 1, wherein pH of the coating bath is maintained in the range of 3 to 4.5.

14. The method as claimed in claim 1, wherein time duration required for the coating of nickel layer (203) is at most 10 minutes.

15. The method as claimed in claim 1, wherein total thickness of the nickel layer (203) on the zinc substrate (200) is about 8 µm to about 10 µm.