Faculty Publications

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Electrochemical studies on the corrosion resistance of Zn–Ni–Co coating from acid chloride bath
(Springer, 2020) Bhat, R.S.; Manjunatha, K.B.; Prasanna Shankara, R.; Venkatakrishna, K.; Hegde, A.C.
Anticorrosive deposits are a valuable approach to defending against corrosion from mild steel structures/machinery equipment. The Zn–Ni–Co coating has been deposited on low carbon steel surfaces using environment friendly optimized acidic chloride bath with ZnCl2·6H2O, NiCl2·6H2O, CoCl2·6H2O, sulphanilic acid (C6H7NO3S) and gelatin (C6H8O6). The standard Hull cell technique has been adopted for the optimization of bath components and experimental conditions, for the superior corrosion resistant coating. The corrosion test with potentiodynamic polarization method was performed to investigate the role of pH on the film quality and corrosion performances of the films. Further, the effect of current densities on corrosion resistance, thickness and hardness, have been investigated. Cyclic voltammetry technique has been used to test the electrochemical properties of the Zn–Ni–Co coating in acidic solutions. The results revealed that the increase in the current density favoured the increase in Ni and Co content in the deposit, showed higher corrosion resistance and higher cathodic current efficiency. The structural and morphological characteristics of the alloy coating have been obtained through scanning electron microscopy and X-ray diffraction techniques. The atomic force microscope was used to examine the topographic structure of the coating. X-ray Photoelectron spectroscopy was used to determine the chemical composition of alloy coatings and verified by energy dispersive X-ray analysis. The results indicate that a new and low-cost chloride bath for Zn–Ni–Co coating exhibit superior corrosion resistance properties and can be implement in various industrial applications such as automobiles, machine tools etc.[Figure not available: see fulltext.]. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Electrodeposition of Zn–Co Coating and its Electrochemical Performance
(Pleiades journals, 2022) Bhat, R.S.; Manjunatha, K.B.; Venkatakrishna, K.; Hegde, A.C.
Abstract: We report the acid chloride bath based electroplating of Zn–Co alloy on low carbon steel (LCS). As additives, the sulphanilic acid (SA) and gelatin were used for electroplating. The bath exhibited an anomalous co-deposition with a higher deposition of Zn over nobler Co. The role of bath composition, current density, partial current density, pH, and temperature on thickness, hardness, and corrosion resistance of deposit was studied. The corrosion behavior in 3.5 wt % sodium chloride solution and electrochemical behavior in acid chloride solutions of Zn–Co alloy coatings were studied using the potentiodynamic polarization method and cyclic voltammetry technique respectively. Mott–Schottky plot with positive slope confirms the development of n-type semiconductor layer at the interface of substrate and coating, which results in superior corrosion resistance of coatings. The colorimetric method has been used to estimate the composition of the deposit and further verified by energy dispersive X-ray spectroscopy (EDX) technique. The surface features and the topographical structure of the alloy film were obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The results indicate that the Zn–Co alloy films exhibited superior corrosion resistance with the lowest corrosion rate (138 µm y–1). Hence this alloy coating will find suitable applications in automobile and aerospace industries. © 2022, Pleiades Publishing, Ltd.
Electrochemical Studies of Zn-Ni-Fe Alloy Coatings for Better Corrosion Resistance Applications
(Springer, 2022) Bhat, R.S.; Munjunatha, K.B.; Bhat, S.I.; Venkatakrishna, K.; Hegde, A.C.
Anti-corrosive alloy coatings are a valuable solution to the protection of low carbon steel structures/equipment against corrosion. The Zn-Ni-Fe coatings have been deposited galvanostatically on low carbon steel from an acid chloride bath. Sulfanilic acid and gelatin were used as additives for the homogeneity of the deposit. The Hull cell method has been used to optimize both bath constituents and plating conditions. The corrosion behavior of the coating films was examined with potentiodynamic polarization and the electrochemical impedance spectroscopy methods. The effects of current density, pH, and temperature on deposit properties like hardness, thickness, and corrosion rates were examined. The electrochemical characteristics of the Zn-Ni-Fe have been studied by the cyclic voltammetry technique. The morphology of the deposit was investigated with scanning electron microscopy and the surface roughness of the coating film was analyzed by atomic force microscopy. The Ni and Fe contents in the deposit were analyzed by colorimetric technique and cross-checked with energy-dispersive x-ray analysis. The capacitive reactance at the interface is attributed to the excellent corrosion resistance at optimal current density (40 mA cm−2) as indicated by the Nyquist plot with large polarization resistance. Furthermore, the positive slope of Mott-Schottky revealed that the semiconductor film at the interface is n-type. The results show that a new Zn-Ni-Fe alloy coating film exhibits better corrosion resistance properties and can be executed in industrial applications such as machine tools, bolts, and nuts in the automobile for corrosion protection, etc. © 2022, ASM International.

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