The formation of self-assembling membrane of hexadecane-thiol on silver to prevent the tarnishing
The formation of self-assembling membrane of hexadecane-thiol on silver to prevent the tarnishing
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DOI：
10.1016/j.electacta.2004.01.052
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发表时间：
2004-07-30
影响因子：
6.6
通讯作者：
Takenouti, H
中科院分区：
文献类型：
--
作者：
Evesque, M;Keddam, M;Takenouti, H
银制品暴露在硫化物污染的大气中时会失去光泽。我们找到了在含10 mM Na（2）S的0.5 M NaCl溶液中，在银表面形成一层有效的、不可见的保护膜的最佳条件。该溶液不仅由于两种腐蚀剂的偶联，而且由于高浓度的S（2-）（320 ppm），因而是一种高腐蚀性的介质。银表面首先通过在三种有机溶剂（乙醇、丙酮和己烷）中连续剪切来仔细脱脂，然后在硫酸溶液中轻微表面活化。然后，将银样品在30 ℃下浸入含有0.15 M C16 H33 SH的异丙醇溶液中1小时。失泽的动力学跟踪反射率，石英微天平测量，和电化学阻抗谱。十六烷硫醇的保护在反射率方面达到90%，在1小时的腐蚀试验后，即通过目视检查没有改变。结果表明，硫醇膜具有双层结构，内层为一层或两层单层自组装膜，外层为几十微米。该表面膜显著地限制了溶解氧向电极表面的扩散，从而减慢了硫化银（Ag 2 S）形成的速率。(C)2004爱思唯尔有限公司保留所有权利。
Artefacts in silver suffer from tarnishing when exposed to atmospheres polluted by sulphide. We have found the optimum conditions to form an efficient, invisible and protective film against the tarnishing appearance on silver in 0.5 M NaCl solution containing 10 mM Na(2)SThis solution corresponds to a highly aggressive medium not only by the coupling of two aggressive agents, but also by a high concentration of S2- (320ppm). The silver surface was first degreased carefully by successive clippings in three organic solvents, ethanol, acetone and hexane, followed by a slight surface activation in sulphuric acid solution. Then, a silver specimen was immersed in an isopropanol solution with 0.15 M C16H33SH during 1 h at 30degreesC. The kinetics of tarnishing was tracked by reflectance, quartz-micro balance measurements, and electrochemical impedance spectroscopy. The protection of hexadecane-thiol reaches 90% in terms of reflectance, after I h of corrosion test, that is, no alteration by visual inspection. It was deduced that the thiol film has a double structure, an inner self-assembling membrane of one or two monolayers and an outer-layer with some tenths micrometers. This surface film limits markedly the diffusion of dissolved oxygen to the electrode surface, thus slows down the rate of silver sulphide (Ag2S) formation. (C) 2004 Elsevier Ltd. All rights reserved.