Electrochemical Behavior and Electrodeposition of Sn Coating from Choline Chloride–Urea Deep Eutectic Solvents

Xiaozhou Cao,Chao Wang,Yuanyuan Shi,Lulu Xu,Siyi Li,Xiangxin Xue,Fengguo Liu,Dong Wu

doi:10.3390/coatings10121154

Abstract

The electrochemical behavior and electrodeposition of Sn were investigated in choline chloride (ChCl)–urea deep eutectic solvents (DESs) containing SnCl2 by cyclic voltammetry (CV) and chronoamperometry techniques. The electrodeposition of Sn(II) was a quasi-reversible, single-step two-electron-transfer process. The average transfer coefficient and diffusion coefficient of 0.2 M Sn(II) in ChCl–urea at 323 K were 0.29 and 1.35 × 10−9 cm2∙s−1. The nucleation overpotential decreased with the increase in temperature and SnCl2 concentration. The results of the chronoamperometry indicated that the Sn deposition on tungsten electrode occurred by three-dimensional instantaneous nucleation and diffusion controlled growth using the Scharifker–Hills model. Scanning electron microscopy (SEM) showed that the morphology of the deposits is uniform, as a dense and compact film prepared by potentiostatic electrolysis on Cu substrate. X-ray diffraction (XRD) analysis revealed that the deposits were pure metallic Sn.

Highlights

Tin and its alloy coatings are widely used in various industrial fields because of its high corrosion resistance, non-toxicity and good soldering properties, which has an soldered coating for printed wiring boards, connectors, lead frames and transistor leads, protective coating to steel sheet from corrosion, tinplates for the food industry, coating on copper and aluminum bus-bars to ensure good contact at joints to carry high electrical currents [1,2].Tin and tin alloy can be electrodeposited in acidic or alkaline aqueous solution [3,4]
It can be clearly seen that the curves display a couple of well defined cathodic and anodic peaks, which is for a typical metal
That the curves display a couple of well defined cathodic and anodic peaks, which is for a typical metal deposition–stripping

Summary

Introduction

Tin and tin alloy can be electrodeposited in acidic or alkaline aqueous solution [3,4]. The hydrogen discharge secondary reaction during the electrolysis process and the relatively narrow potential windows in the aqueous solution, electrodeposition of metals or alloys from deep eutectic solvents, have attracted substantial interest in recent years [8]. Deep eutectic solvents (DESs) are a new class of ionic liquids, based on combinations of choline chloride with hydrogen bond donors, such as carboxylic acids, glycols and amides [9]

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Results

Conclusion