摘要
通过极化曲线正交试验筛选出银缓蚀剂的复配组成,比较了该复合缓蚀剂在腐蚀介质中对银电极的腐蚀电流、腐蚀速度、缓蚀效率、交流阻抗膜电阻与膜电容等电化学参数的影响,得出最佳的银器防变色唑系复合缓蚀剂成膜处理的最佳工艺:复合缓蚀剂组分MBO:PMTA:MBI为1:2:3,成膜浓度为0.0189mol/L,pH值3.0,成膜时间为4h,预膜温度50℃。实验结果和实际应用效果表明,该种复合缓蚀剂具有较好的抗银腐蚀和变色的能力。
The technique of corrosion inhibitor treatment is one of the most effective ways for silver antitarnish-ing in accordance with Chinese conservation principles for ancient artifacts. In this paper,the principles and methods of corrosion electrochemical polarization curve and impedance spectrum are introduced which were used in the corrosion inhibitors screening for silver antitarnishing while orthogonal electrochemical experiment was designed for optimizing the formula of composite corrosion inhibitor, the effects of the components and their concentrations on the corrosion parameters, and the optimized silver anti - tarnishing formula was screened out which was composed with MBI (2 - mercaptobenzimidazole), MBO(2 - mer captobenzoxazole) and PMTA (1 - phenyl - 5 - mercapto - tetrazole). Test results showed that MBI concentration had the most obvious influence on silver tarnishing among the corrosion inhibitors of the composite formula in Na2S solution, the best ratio of composite corrosion inhibitors MBO: PMTA: MBI was 1: 2:3,and their total concentration was 0.0189 mol/L. The accelerated atmospheric corrosion tests in the sulfur sublimate and the vapor of mercapto - acetic acid proved that anti - tarnishing capability of the silver coupon treated with this composite corrosion inhibitor is improved obviously in different corrosive media.
Compared with the measurement results of polarization curves and impedance spectra, it can be concluded that the surface characteristics of silver electrode was changed after treated with corrosion inhibitors , the self-corrosion potential moved towards negative direction, the slope of cathodic polarization curve increased, that indicated corrosion cathodic process (dissolved oxygen diffusion) has been inhibited and reduced the corrosion current. The slope of anodic polarization curve increased obviously that indicat- ed the surface protective film isolated silver from the corrosive media to inhibit its tarnishing. When PM-TA,MBO and MBI were mixed to use as composite corrosion inhibitors, the inhibition on cathodic and anodic processes were further enhanced, the effectiveness of silver anti - tarnishing was improved in Na2S and mercaptoacetic acid solution. The electric resistance of silver surface protective film formed with composite was up to 343.5kΩ·cm2 and the film capacitance was down to 5.09 μF·cm-2,it showed that significant synergistic effect occurred among those constitutions of the composite inhibitors.
The ancient silver box excavated from the underground palace of Leifeng tower in Hangzhou, Qing Dynasty silver coins and many other silver artifacts treated with the composite corrosion inhibitors, these ancient silver artifacts surface have been kept clean and bright without appearance of any spot for more than one year so far and the anti-tarnishing capability of the silver antiques is improved obviously.
出处
《文物保护与考古科学》
2002年第B12期1-12,共12页
Sciences of Conservation and Archaeology
基金
国家文物局文物科研项目
编号:9920
关键词
银
抗变色
缓蚀剂
文物保护
Silver, Anti- tarnishing, Corrosion inhibitor, Antiquity conservation
