Electropolishing of gold and gold alloys in HCl-glycerol-ethanol electrolytes

IF 7.5 Q1 CHEMISTRY, PHYSICAL
Julymar Rodriguez, Marie-Laure Doche, Jean-Yves Hihn
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Abstract

Electropolishing or electrochemical polishing (EP) is an ultrafinishing process that improves esthetic, technical and functional properties of metallic surfaces by reducing their roughness. This process is based on anodic dissolution of the workpiece through an oxidation reaction. For many years, cyanide-based electrolytes were used to electropolish precious metals like gold and its alloys. The need for safer working conditions encouraged the replacement of cyanide by other complexing agents, mainly thiourea. However, the latter is also harmful. Therefore, the aim of this work is to electropolish pure gold and 18k jewelry gold alloys (yellow, rose, red and gray) in a cyanide-free electrolyte, to evaluate the electrochemical behavior and the influence of different parameters. For this purpose, a previously reported solution based on hydrochloric acid and glycerol was used. In the first part of the study, the influence of chloride concentration on pure gold EP was determined by electrochemical techniques and surface properties analysis. The effects of adding ethanol to electrolyte composition and of variating rotation speed were also evaluated. The best results were obtained for a HCl 50% vol. - Glycerol 25 % vol. - Ethanol 25 % vol. electrolyte at a rotation speed of 1000 rpm. In the second part of the study, this solution was used to electropolish 18 K gold alloys. Silver-containing alloys were not uniformly polished due to the formation of an AgCl film on the surface that partially masks the substrates.

在 HCl-甘油-乙醇电解质中电解金和金合金
电抛光或电化学抛光(EP)是一种超精加工工艺,可通过降低金属表面的粗糙度来改善其美观、技术和功能特性。该工艺的基础是通过氧化反应对工件进行阳极溶解。多年来,人们一直使用氰化物电解液对黄金及其合金等贵金属进行电解抛光。由于需要更安全的工作条件,人们开始用其他络合剂(主要是硫脲)取代氰化物。然而,后者也是有害的。因此,这项工作的目的是在无氰电解液中对纯金和 18K 首饰金合金(黄色、玫瑰色、红色和灰色)进行电解抛光,以评估电化学行为和不同参数的影响。为此,我们使用了之前报道过的基于盐酸和甘油的溶液。在研究的第一部分,通过电化学技术和表面特性分析确定了氯化物浓度对纯金 EP 的影响。此外,还评估了在电解液成分中添加乙醇和改变旋转速度的影响。在转速为 1000 rpm 时,盐酸 50% vol. - 甘油 25 % vol. - 乙醇 25 % vol. 的电解液获得了最佳结果。在研究的第二部分,该溶液用于电解 18 K 金合金。含银合金的抛光并不均匀,这是因为表面形成了一层 AgCl 膜,部分遮盖了基底。
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来源期刊
CiteScore
8.10
自引率
1.60%
发文量
128
审稿时长
66 days
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