Corrosion and Tarnish Behaviour of 925Ag75Cu and 925Ag40Cu35Zn Alloys in Synthetic Sweat and H₂S Atmosphere

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• 作者：Yang Qingqing ; Xiong Weihao ; Yang Zhen ; Shen Dingjie ; Wang Ronghui
• 关键词：925Ag alloys ; corrosion ; tarnish ; synthetic sweat ; H₂S atmosphere
• 刊名：Rare Metal Materials and Engineering
• 出版年：2010
• 出版时间：April 2010
• 年：2010
• 卷：39
• 期：4
• 页码：578-581
• 全文大小：379 K

文摘

The purpose of this paper is to investigate the corrosion and the tarnish behaviour of 925Ag75Cu and 925Ag40Cu35Zn alloys in synthetic sweat at 37 °C and H₂S atmosphere at room temperature. The alloys were in two hardening states, viz., aging at 250 °C for 4 h and 70 % cold rolling + aging at 200 °C for 4 h, and tested by means of static corrosion, examined by XRD, SEM, EDS and XPS. The results show the corrosion and the tarnish in synthetic sweat at 37 °C of these two 925Ag alloys are induced by Cl⁻ and OH⁻ anions. The tarnish of 925Ag40Cu35Zn alloy is much slower than that of 925Ag75Cu alloy, and the white AgCl and the grayish black Ag₂O produced by corrosion are difficult to deposit on the surface of 925Ag40Cu35Zn alloy resulting in grayish black corrosion film. The corrosion and the tarnish in H₂S atmosphere at room temperature of these two 925Ag alloys are induced by S²⁻ anion. The corrosion and the tarnish of 925Ag40Cu35Zn alloy are much slower than 925Ag75Cu alloy. This is because Zn in 925Ag40Cu35Zn alloy reacts earliest with H₂S to form white ZnS, which significantly retards the reaction between Ag or/and Cu and H₂S to form grayish black Ag₂S and black Cu₂S.