Au999纯金条“锈斑”问题探讨

Analysis of‘Rusty Spots' of Au999 Pure Gold Bar

Au999具有优异的化学稳定性,但用其生产的产品有时出现"锈斑"现象。采用扫描电镜、微区能谱分析仪、XRF、化学分析、XPS等方法对"锈斑"进行了研究。结果表明,纯金条的含金量满足标准要求,但在"锈斑"区表面存在大量的Ag、S、O元素,以及微量的Cl、Si、Na元素。Ag与S以Ag_2S形式存在,是导致变色的根本原因,同时,它与微量的SiO_2杂质经炸酸处理后被腐蚀消耗,导致了"锈斑"区的显微孔洞。这些杂质元素的来源主要是生产管理不当,解决"锈斑"问题,必须改进生产现场管理,优化工艺流程。

Au999 has excellent chemical stability, however, the products made of Au999 sometimes form ＇rusty spots＇. Rusty spots of Au999 pure gold bars were investigated by scanning electron microscope （SEM）, micro-area energy dispersive spectrometer, XRF, chemical analysis, XPS and field investiga- tion . The results indicate that the overall gold content of pure gold bars meets the standard require- ments. However, the surface of the ＇rusty spots＇ area has amounts of Ag, S and O elements and trace of C1, Si and Na elements. Ag and S exists in form of Ag2S, which is responsible for tarnish. Mean- while, Ag2S and trace of SiO2 are corroded and consumed after acid treatment, resulting in micro cavities on the ＇rusty spots＇ area. These impurity elements are caused by improper production management. Thus, to solve the ＇rusty spots＇ of pure gold bars, it must improve management of the production site and optimize the production process and technical process as well as keeping the worksite clean and strengthening the inspection and control procedure.