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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, but “rust spots” sometimes appear on the products it is made of. The “rust spots” were studied by scanning electron microscopy, energy dispersive spectroscopy, XRF, chemical analysis and XPS. The results show that the gold content of pure gold bars meets the standard requirements, but a large amount of Ag, S, O elements and trace elements of Cl, Si and Na exist on the surface of the “rust spots” area. Ag and S exist in the form of Ag_2S, which is the fundamental cause of discoloration. At the same time, it is corroded and consumed by a small amount of SiO_2 impurities by the acid treatment, resulting in micropores in the “rust spots”. The main source of these impurity elements is improper production management, to solve the “rust” problem, we must improve production site management, optimize the process.