Effect of grain boundary constitution on corrosion behaviour in cobalt-carbon nanotube composite coatings

Kumar, GM and Jyotheender, KS and Srivastava, C (2022) Effect of grain boundary constitution on corrosion behaviour in cobalt-carbon nanotube composite coatings. In: Materialia, 24 .

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Abstract

Corrosion behavior and micro-texture of electrodeposited cobalt coatings containing different volume fractions of carbon nanotubes (CNTs) were investigated and correlated. For lower CNT volume fractions, a compact and smoother coating morphology were observed. The morphology however, became coarser for higher CNT volume fractions. Corrosion properties of the coatings were determined using the electrochemical impedance spectroscopy and Tafel polarization techniques. Pristine cobalt coating showed corrosion potential (Ecorr), corrosion current density (icorr), and polarization resistance (Rp) values of -0.574 V, 21.48µA/cm2 and 2071 ohms.cm2 respectively. With the incorporation of CNTs, the coating corrosion resistance increased up to Co-CNT3 coating (produced by 20mg/L of CNT dispersion). Co-CNT3 coating showed Ecorr, icorr and Rp values of -0.521V, 5.33µA/cm2 and 3525 ohms.cm2 respectively. However, for higher volume fractions of CNTs, the coating corrosion resistance dropped to values lower than pristine cobalt coating. For Co-CNT6 coating (produced from 80 mg/L of CNT dispersion) the Ecorr, icorr and Rp values were -0.581V, 23.45µA/cm2 and 1409 ohms.cm2 respectively. Micro-texture analysis was conducted for pristine Co and Co-CNT3 coatings to investigate the correlation between the observed corrosion behavior and coating micro-texture. Both the coatings showed strong 211¯0 texture along the coating growth direction. When compared to printine Co coating, the Co-CNT3 coating showed lesser fraction of high angle grain boundaries as well as higher fraction of low energy special boundaries like STGBs (32°/ 211¯0, 62°/ 211¯0 angle axis pair) leading to better corrosion resistance performance for Co-CNT3 coatings.

Item Type:	Journal Article
Publication:	Materialia
Publisher:	Elsevier B.V.
Additional Information:	The copyright for this article belongs to the Elsevier B.V.
Keywords:	Carbon nanotubes; Cobalt; Cobalt alloys; Composite coatings; Corrosion resistance; Corrosion resistant coatings; Corrosive effects; Dispersions; Electrochemical corrosion; Electrochemical impedance spectroscopy; Electrodeposition; Electrodes; Grain boundaries; Morphology; Polarization; Volume fraction, Carbon nanotubes composites; Carbon nanotubes dispersion; Cobalt coating; Composites coating; Corrosion behaviour; Electrodeposited cobalt; Grain-boundaries; Low carbon; Micro-texture; Obalt coating, Textures
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	20 Jul 2022 11:42
Last Modified:	20 Jul 2022 11:42
URI:	https://eprints.iisc.ac.in/id/eprint/74935

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