Engineering the Protective Oxide Chemistry for Enhanced Corrosion Protection Performance of FeCuCrNiCo-CNT Composite Coatings in 3.5 M NaCl Solution Corrosive Media

Singh, S and Srivastava, C (2023) Engineering the Protective Oxide Chemistry for Enhanced Corrosion Protection Performance of FeCuCrNiCo-CNT Composite Coatings in 3.5 M NaCl Solution Corrosive Media. In: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science .

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Abstract

Direct electrodeposition method was used to co-electrodeposit different volume fractions of carbon nanotubes in FeCuCrNiCo high entropy alloy matrix. Phase constitution, morphology, wettability, protective oxide film chemistry, and corrosion behavior of the composite coatings were studied as a function of volume fraction of carbon nanotubes (CNTs). Pristine HEA coating contained mixture of body-centered cubic (bcc) and face-centered cubic (fcc) phases which transformed into nearly single-phase body-centered cubic microstructure with the incorporation of CNTs upto a certain optimum volume fraction. The phase heterogeneity, however, re-appeared for higher CNT additions. The coating morphology showed a transition from one containing mixture of dendritic and granular features to a more compact, smooth, and fine-grained globular matrix with CNT incorporation. A monotonic increase in the water contact angle was also observed with increasing CNT content in the composite coating. Weight loss and potentiodynamic polarization techniques employed for coating corrosion analysis showed that the corrosion behavior of pristine coating was highly sensitive to the amount of reinforced CNTs. Addition of an optimum CNT amount in HEA coating (produced from an electrolyte with 12.5 mg/L of dispersed CNTs) led to a considerable decrease (85.6 pct) in the corrosion rate (compared to the pristine HEA coating). In addition to improved morphology, phase homogenization, and increased contact angle, the reason for this significant improvement was also attributed to the evolution of protective oxides like Cr2O3 and NiO in case of HEA-CNT composite with optimum CNT concentration. For higher CNT additions, a drastic decrease in the protection efficiency was observed because of re-appearance of phase heterogeneity. This promoted galvanic coupling and due to the presence of surface defects in forms of cracks arising due to the presence of agglomerated CNTs in the electrodeposited coatings. © 2023, The Minerals, Metals & Materials Society and ASM International.

Item Type:	Journal Article
Publication:	Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Publisher:	Springer
Additional Information:	The copyright of this article belongs to Springer.
Keywords:	Chromium alloys; Chromium compounds; Cobalt alloys; Composite coatings; Contact angle; Corrosion rate; Corrosion resistant coatings; Corrosive effects; Electrodeposition; Electrodes; Electrolytes; Iron alloys; Metallic matrix composites; Morphology; Nickel alloys; Nickel oxide; Oxide films; Sodium chloride; Surface defects; Volume fraction; Body-centred cubic; Carbon nanotubes composites; Composites coating; Corrosion behaviour; Corrosion protection performance; Corrosive media; Electrodeposition methods; High carbons; NaCl solution; Protective oxides; Carbon nanotubes
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	10 Mar 2023 10:42
Last Modified:	10 Mar 2023 10:42
URI:	https://eprints.iisc.ac.in/id/eprint/80956

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