采用光学显微镜、扫描电镜、电子探针、X射线衍射、XPS等方法对银质纪念币在大气中放置出现的白斑的成份、结构进行了宏观和微观的分析检查, 并结合湿热加速试验及银币生产现场情况, 综合分析白斑的生成机理. 结果表明: 在湿润环境中, Cl-、O2、H2S是导致银币表面产生白斑的主要物质; 银币表面白斑腐蚀产物主要由AgCl、Ag2O和Ag2S构成, 腐蚀产物的颜色并不随腐蚀白斑长大而改变; 银币表面存在的供氧差异腐蚀电池是银币表面白斑形核、长大的主要诱因.
Morphology and chemical composition of the corrosion spots on the surface of souvenir silver coins were examined by optical microscope(OM), scanning electron microscope(SEM), electron microprobe (EMPA), X- ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). It was found that the silver was sensitive to the presence of Cl-、O2 and H2S in humid atmosphere. XPS and XRD analytical results showed that the white spots were consisted of AgCl、Ag2O and Ag2S. The white tarnished complex on the surface of silver was a series of electrochemical process that required the presence of chloride, oxygen and sulfur.
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