拉曼光谱分析青铜器本体中锈蚀产物

青铜器锈蚀研究能够揭示出青铜器腐蚀机理，为制定科学的保护措施提供重要的参考资料。目前，青铜器锈蚀研究主要从其外部锈蚀产物入手，通过锈蚀组成结构分析，探讨其腐蚀机理。本文选择了保存较好青铜器本体样品进行了内部锈蚀情况研究。首先采用金相制备技术，通过打磨、抛光和超声清洗处理后，制备了断面相组织形态清晰的24件秦早期青铜器青铜本体样品。然后利用共聚焦显微拉曼光谱仪对样品夹杂物进行了光谱学研究，发现其物相为PbCO₃和PbO及Cu₂O，都属于常见的青铜合金腐蚀产物。样品金相组织中圆形或者大面积无规则亮灰色区域为Cu₂O，反映出青铜器表面不仅易于形成一定厚度Cu₂O锈蚀层，在相界之间也容易发生氧化反应生成Cu₂O，存在合金内部和外部同时发生腐蚀生成赤铜矿锈蚀的情况。此外，拉曼光谱分析显示黑灰色物质主要为铅腐蚀产物——PbCO₃和PbO，反映出铅元素的腐蚀过程：Pb→PbO→PbCO₃。在铸造态青铜合金组织中，铅一般呈近圆形颗粒状态分布在相界之间。青铜器内部分布的铅颗粒在土壤埋藏环境中会发生氧化反应生成PbO，再与地下水中溶解的CO2-₃发生化学反应生成比较稳定的PbCO₃。结果表明：外界腐蚀因素(水、溶解氧和碳酸根等)能够通过合金中相界间通道进入青铜器内部，在相界表面逐步发生反应形成以金属氧化物为主的腐蚀产物。

Using Raman Spectrum Analysis to Research Corrosive Productions Occurring in Alloy of Ancient Bronze Wares

The present paper analyzes the interior rust that occurred in bronze alloy sample from 24 pieces of Early Qin bronze wares. Firstly, samples were processed by grinding, polishing and ultrasonic cleaning to make a mirror surface. Then, a confocal micro-Raman spectrometer was employed to carry out spectroscopic study on the inclusions in samples. The conclusion indicated that corrosive phases are PbCO₃, PbO and Cu₂O, which are common rusting production on bronze alloy. The light-colored circular or massive irregular areas in metallographic structure of samples are proved as Cu₂O, showing that bronze wares are not only easy to be covered with red Cu₂O rusting layer, but also their alloy is easy to be eroded by atomic oxygen. In other words, the rust Cu₂O takes place in both the interior and exterior parts of the bronze alloy. In addition, Raman spectrum analysis shows that the dark grey materials are lead corrosive products——PbCO₃ and PbO, showing the corroding process of lead element as Pb→PbO→PbCO₃. In the texture of cast state of bronze alloy, lead is usually distributed as independent particles between the different alloy phases. The lead particles in bronze alloy would have oxidation reaction and generate PbO when buried in the soil, and then have chemical reaction with CO2-₃ dissolved in the underground water to generate PbCO₃, which is a rather stable lead corrosive production. A conclusion can be drawn that the external corrosive factors (water, dissolved oxygen and carbonate, etc) can enter the bronze ware interior through the passageway between different phases and make the alloy to corrode gradually.