Electroplating composite coating is an effective method to prepare composite coating through the codeposition of metallic, nonmetallic, or polymer particles with metal to improve properties such as corrosion resistance, hardness, and wear performance. This paper reports the synthesis of a novel Ni-BaFe12O19 magnetic nanocomposite coating exhibiting improved corrosion resistance. In the present paper, BaFe12O19 particles were synthesized by a single-step solution combustion method and characterized for phase, particle size, and morphology. These particles were incorporated in a nickel metal matrix, and the properties of the coatings like nanohardness and corrosion resistance were investigated. The coating microstructure was also studied using field emission scanning electron microscope. A Vickers hardness of 777 HV was exhibited by Ni-BaFe12O19, and plain Ni coating exhibited a hardness of 517 HV. The Ni-BaFe12O19 composite coating exhibited improved corrosion resistance compared to plain Ni coating with an
In recent years, there is an increased interest in the synthesis and properties of particle reinforced metal matrix nanocomposite coatings with grain size of both matrix and dispersed particles less than 100 nm [
The solution combustion method is a very versatile technique that has been used for the preparation of magnetic oxides and in particular ferrites [
Photographs showing combustion synthesized BaFe12O19 powder (a) after crushing and (b) attracted to magnetic stirring bar.
Assuming complete combustion, the theoretical equation for the formation of barium ferrite using ODH can be written as follows:
Nickel sulfamate plating bath was prepared by mixing 300 g L−1 of nickel sulfamate solution (50 g of nickel per liter), 10 g L−1 of nickel chloride, 30 g L−1 boric acid, and 0.2 g L−1 of sodium lauryl sulfate. The Ni-sulfamate plating bath (approximately 200 mL) containing BaFe12O19 particles (5 g/L) was taken in a glass beaker and was mechanically stirred overnight. For higher bath loadings, the electrolyte bath was saturated with powders because of its very fine nature, and there was no coating formation, and hence 5 g/L of barium hexaferrite particles was chosen. During electrodeposition, the bath was held at room temperature, and its pH was maintained at 4 by the addition of sulfamic acid and basic nickel carbonate. A pure nickel sheet (
The XRD patterns of plain Ni and Ni-BaFe12O19 composite coatings electrodeposited at 1.55 A dm−2 were also recorded. The metallographic specimens for cross-sectional studies were prepared by sandwiching electrodeposited Ni-BaFe12O19 brass coupons with a copper backup in a Bakelite matrix followed by mechanical grinding and polishing with
Corrosion behavior of Ni and Ni-BaFe12O19 composite coatings electrodeposited at 1.55 A dm−2 for 45 min on mild steel coupons was conducted using CHI 604 2D electrochemical workstation. The test was carried out in deaerated 3.5 wt% (0.6 M) NaCl solution (
The corrosion potential
Corrosion rates (CR) were calculated by the following equation:
The as-prepared BaFe12O19 powder was poorly crystalline as seen from the XRD pattern (Figure
Powder XRD pattern of as-prepared BaFe12O19 powder.
And hence it was not possible to determine the crystallite size. However, the phase purity of the sample was indirectly evident from the strong magnetic behavior of the as-prepared BaFe12O19 powder (Figure
The powder morphology of the combustion synthesized barium ferrite powder was analyzed by field emission scanning electron microscopy (FESEM) (Figure
Field emission scanning electron microscope image of as-prepared barium ferrite particles.
The particle size analysis of BaFe12O19 powder prepared by solution combustion method is shown in Figure
Particle size distribution of as-prepared BaFe12O19 powder.
The XRD patterns of Ni and Ni-BaFe12O19 electrocomposite coatings are shown in Figure
XRD patterns of electrodeposited (a) Ni and (b) Ni-BaFe12O19 composite coatings.
FESEM images of electrodeposited plain Ni and Ni- BaFe12O19 composite coating surfaces are shown in Figure
Surface FESEM images of electrodeposited (a-b) Ni and (c-d) Ni-BaFe12O19 composite coatings.
The energy dispersive X-ray analysis (EDAX) spectra recorded on the surface of the coatings confirmed the incorporation of barium hexaferrite particles in the coating (Figure
EDAX spectra recorded on the surface of electrodeposited Ni-BaFe12O19 composite coating.
The nanohardness values obtained from Oliver Pharr method on the cross-sections of the electrodeposited (1.55 A dm−2) Ni and Ni-BaFe12O19 coating surface
The Tafel plots obtained for Ni and Ni-BaFe12O19 coatings in 3.5 wt% NaCl are shown in Figure
Corrosion potential, corrosion rates, and Tafel slopes calculated from potentiodynamic diagrams for mild steel, pure Ni, and Ni-BaFe12O19.
Coating |
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( |
(V) | (V/dec) | (V/dec) | (k |
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Ni | 3.61 | −0.551 | 0.031 | 0.114 | 8.29 |
Ni-BaFe12O19 | 0.034 | −0.279 | 0.2615 | 0.1262 | 1087.67 |
Tafel plots of electrodeposited (a) plain Ni and (b) Ni-BaFe12O19 coatings.
The Nyquist impedance plots for Ni and Ni-BaFe12O19 obtained in free-air (nonaerated) condition in 3.5% NaCl solution are shown in Figure
Nyquist plots of electrodeposited plain Ni (inset) and Ni-BaFe12O19 coatings.
The Bode plot of Ni showed a distinct single peak corresponding to the electrode/electrolyte interface compared to Ni-BaFe12O19 (Figure
Bode plots of electrodeposited (a) Ni and (b) Ni-BaFe12O19 coatings.
The phase angle versus log (frequency) shows that phase angle of both Ni and Ni-BaFe12O19 coatings was less than
The equivalent circuit shown in Figure
Electrochemical impedance analysis data.
Sample |
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( |
( |
(k |
( | ||
Ni | 1.05 | 226.1 | 0.83 | 7.03 | — |
Ni-BaFe12O19 | 1.12 | 2.74 | 0.37 | 1081 | 9.9 |
(a): Equivalent circuit used to fit the parameters of nickel (
Barium hexaferrite particles having magnetic property prepared by the solution combustion method were incorporated in the Ni-metal matrix. The bath loading beyond 5 g/L was not possible due to the very fine nature of the combustion synthesized powder. It was gratifying to note that the anticorrosion properties of the Ni matrix could be further improved by the incorporation of hard BaFe12O19 particles in the Ni matrix. Corrosion potential and corrosion current were lower for Ni-BaFe12O19 when compared to Ni. There was an increase in the nanohardness of the Ni-composite coating with the incorporation of BaFe12O19 particles. The
The authors thank the Director of CSIR-NAL for his encouragement and SIP-SED-02 project for the funding. The authors thank Mr. Siju and Mr. Praveen for the FESEM and nanohardness measurements.