THE REMOVAL OF CORROSION PRODUCTS ON EXCAVATED METAL ARTIFACTS USING CHELATING AGENT

1、螯合剂的选择首先对市场上广泛使用的EDTA-3Na和NTA-2Na进行了比较。两种溶液几乎呈中性，对于去除铜合金物体上的腐蚀产物具有相同的效果。我们选择EDTA-3Na，因为NTA-2Na溶液对皮肤有轻微刺激，并继续我们的研究。2．从处理过的物体上去除螯合剂用静置和流动的蒸馏水洗涤几次后，通过紫外光谱法检测不到螯合剂。但在少数情况下，处理过的表面上会出现新的腐蚀产物。我们认为处理后它们变得敏感，并试图稳定腐蚀。3．足量的螯合剂处理过程中，我们通过紫外光谱在测量限度内测量溶液的反应程度。当调节溶液每摩尔EDTA-3Na反应0.3至0.5摩尔铜离子时，我们快速且经济地处理它们。 4．被处理物体表面的稳定化。一般来说，经螯合剂处理的青铜物体上的新腐蚀产物大多是通过苯并三唑（BTA）来稳定的。如果它不起作用，我们在高湿度条件下检查了用氟烯烃丙烯酸共聚物浸渍和涂覆的物体。该树脂具有高效的阻隔氧气和水蒸气的能力，且处理后易被溶剂溶解。5．去除铁质物体上的腐蚀产物。我们将上述药剂应用于铁质物体。已经很脆弱的腐蚀产物层很容易通过机械方法去除。螯合剂并没有比通常的机械去除方法有多大帮助。

1. Selection of Chelating agentWe had first compared EDTA-3Na and NTA-2Na on the market of wide use. Both solution are almost neutral and have the same effect of removing corrosion products on copper alloy objects. We chose EDTA-3Na, because the solution of NTA-2Na slightly stimulated the skin, and continued our study.2. Removal of chelating agent from treated objectsAfter several time of washing with standing and flowing distillled water, the agent was not detectable by ultra-violet spectroscopy. But in a few cases new corrosion products appeared on the treated surface. We thought they were changed sensitive by the treatment and tried to stabilize the corrosion.3. Adequate quantity of chelating agentDuring treatment, we measured solution within the measurement limits by UV spectroscopy showed the degree of reaction. When the solution was regulated to react 0.3 to 0.5 mol of copper ion per mol of EDTA-3Na, we treated them quickly and economically.4. Stabilization of the surface of treated objects.Generally most of new corrosion products on the bronze objects treated by chelating agent are stabilized by benzotriazole (BTA).In case that it should not work, we examined the objects impregnated and coated with fluorolefin acryl copolymer under high humidity conditions. This resin has high effectiveness to shut off oxygen and vapor, and yet is easily solved by solvent after treatment.5. Removal of corrosion products from iron objects.We applied above agent to iron objects. The layr of corrosion products which is already fragile is easily removed by mechanical methods. Chelating agent does not help much than the usual mechanical removal methods.