Electropolishing of nickel and cobalt in deep eutectic solvents

Abstract

Electropolishing is a common method for decreasing surface roughness and removing surface irregularities. In this paper the electropolishing of nickel and cobalt are successfully demonstrated in a deep eutectic solvent, comprising a 2: 1 molar mixture of ethylene glycol (EG) and choline chloride. Voltammetric and electrochemical impedance studies were used to characterise the polishing mechanism and show that film formation occurs prior to polishing. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterise the morphology before and after polishing and 3D optical microscopy was used in-situ to observe film formation during polishing. This study shows that the impact of film formation and subsequently mass transport factor are responsible for electropolishing of both metals in the choline chloride-based ionic liquid.

Strong Microheterogeneity in Novel Deep Eutectic Solvents

“…[1][2][3] DESs are mostly made of cheap, readily available and rather safe starting compounds. [2] Their applications are widespread, for example in metal processing [15,16] and synthesis or biomass processing and catalysis as well as extraction, [17] but many more applications can be found and will be discovered in the future. [2,3,[18][19][20] Calculations on DESs are rather sparse compared to experiments and often concentrate on the understanding of the hydrogen bonding behavior since a plethora of hydrogen bonds are available, examples are Refs.…”

Novel Electropolishing of Pure Metallic Titanium in Choline Chloride-Based Various Organic Solvents

“…electrolyte. 10 This can be ascribed to the presence of methanol and ethanol that provide a proper viscos layer over metallic titanium electrode that facilitates mass transport through it. In earlier study, the electropolished titanium surface possesses an average roughness of 5.7 nm which is higher than that of current results by almost 10 times.…”

“…[6][7][8][9] It is also a few work on titanium, nickel and cobalt surface finishing were documented using ionic liquids. 3,10 Abbott et al is one of the pioneers that has own perspective regarding usage of deep eutectic solvents. 11,12 The majority of electropolishing of titanium were conducted in aqueous media based on perchloric acid, such as perchloric acid/ acetic acid and perchloric acid/methanol/ethylene glycol and perchloric acid-free electrolyte, for instance methanol/sulfuric acid.…”

Advantages of Electrochemical Polishing of Metals and Alloys in Ionic Liquids

“…The data on electropolishing of nickel were obtained in a mixture of choline chloride with ethylene glycol (1:2) [56][57][58][59][60][61][62][63]. The nickel finishing was conducted at the optimum voltage of 3.75 V for 900 s at 70 • C. The average roughness of nickel was found to decrease from 138.408 to 28.640 nm to form a smoothed surface of the sample in ethaline [56].…”