Analysis of‘Rusty Spots’ of Au999 Pure Gold Bar

Yuan Junping; Wang Chang

doi:10.15980/j.tzzz.2017.07.003

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Analysis of‘Rusty Spots’ of Au999 Pure Gold Bar
Vol. 37, Issue 7, Pages: 704-707(2017)
Published： 2017 ，
DOI： 10.15980/j.tzzz.2017.07.003

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[1]袁军平,王昶.Au999纯金条“锈斑”问题探讨[J].特种铸造及有色合金,2017,37(07):704-707.

Yuan Junping, Wang Chang. Analysis of‘Rusty Spots’ of Au999 Pure Gold Bar. [J]. Special Casting & Nonferrous Alloys 37(7):704-707(2017)
[1]袁军平,王昶.Au999纯金条“锈斑”问题探讨[J].特种铸造及有色合金,2017,37(07):704-707. DOI： 10.15980/j.tzzz.2017.07.003.

Yuan Junping, Wang Chang. Analysis of‘Rusty Spots’ of Au999 Pure Gold Bar. [J]. Special Casting & Nonferrous Alloys 37(7):704-707(2017) DOI： 10.15980/j.tzzz.2017.07.003.

摘要

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

S形式存在

是导致变色的根本原因

同时

它与微量的SiO

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。

Abstract

Au999has 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 investigation.The results indicate that the overall gold content of pure gold bars meets the standard requirements.However

the surface of the‘rusty spots’ area has amounts of Ag

S and O elements and trace of Cl

Si and Na elements.Ag and S exists in form of Ag

which is responsible for tarnish.Meanwhile

S and trace of SiO

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.