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

Abstract

In this report we present a straightforward and efficient electropolishing methodology of pure metallic titanium in two different electrolytic baths; choline chloride-ethanol (ChCl-eth.) and choline chloride-methanol-butanol (ChCl-meth.-but.) in molar ratios of 1 : 4 and 1 : 6 : 2, respectively at 20°C. The electrolytic baths under study possess relatively low-cost and environmentally benign. In the electropolishing processes, potentiostatic technique was applied. For the surface characterizations both atomic force microscope (AFM) and scanning electron microscopy (SEM) were used. The results showed that titanium surface was polished electrochemically at nanoscale and relatively free from defects. The working voltages of 2 and 1.2 V were applied in ChCl-eth. and ChCl-meth.-but., respectively within a time scale of 40 minutes in the present electrolytic baths. The roughness of pure metallic titanium (ca. 120.5 nm) was reduced to 0.10 nm in ChCl-eth. and 0.66 nm in ChCl-meth.-but.

Advantages of Electrochemical Polishing of Metals and Alloys in Ionic Liquids

“…According to the SEM and AFM data, nanoscale polishing of pure titanium was achieved for 40 min, the initial roughness of the sample (120.5 nm) being reduced to 0.10 and 0.66 nm in choline chloride-ethanol and choline chloride-methanol-butanol mixtures, respectively [43]. No anodic gas evolution occurred when butanol was added to IL.…”

“…A great number of publications have been dedicated to electrochemical finishing of titanium and its alloys [38][39][40][41][42][43][44]. These materials attract attention as objects for electropolishing to obtain the high-quality surface required for medicine and related areas.…”

“…The mixtures of choline chloride (ChCl) with ethanol (1:4 molar ratio) and choline chloride with methanol-butanol (1:6:2 molar ratio) also were successively used for electrochemical polishing of Ti under potentiostatic conditions (2 and 1.2 V, respectively) [43]. The state of the metallic titanium surface before and after electropolishing in choline chloride mixtures with alcohols is illustrated in Figure 5.…”

“…The authors of [43] supposed that the low onset voltage in choline chloride mixtures with alcohols compared with ethylene glycol can be explained by the low viscosity of the electrolyte solution. The importance of the electrolyte viscosity in electropolishing was proved also for Ag, Au, Co, Cu, Fe, Ni, Pb, Sn, and Zn [2] in ethaline and 1-butyl-3methylimidazolium chloride (16 and 142 cP at 70 • C, respectively).…”

Electropolishing of Pure Metallic Nickel and Cobalt in Choline Chloride-propylene Glycol Eutectic Liquid: An Electrochemical Study Using AFM and SEM

“…[7][8][9][10][11] Nowadays, new electrolytic baths known as deep eutectic solvents (DESs) have attracted the attention of scientists to utilize them as electrolytic baths for electropolishing. [12][13][14] The DES can compete with the aqueous counterparts in many aspects. For example, the less gas evolution during under controlling of dissolution of metals and alloys electrochemically, relatively high-quality electropolished surfaces, as well as benign nature of the DESs.…”