اهمیت تحلیل لایه های خوردگی در مطالعه فنی آثار فلزی تاریخی

In many cases it may be thought, corrosion products cover the unique characteristics of ancient metal objects that are desirable to display. While the scientific point of view, the corrosion products as well as metal substrates are important and maintain the original topography of metal that have been replaced. In technical studies of the historical metal objects, the dense layers of corrosion products are of particular interest due to technical values inherent in them. In the present research, a few metal objects from different historical sites of Iran are studied with the main aim of finding technical evidences recorded in the corrosion layers. For this purpose optical and scanning electron microscopy techniques and instrumental methods of analysis were used. Decuprification  phenomenon  and the fossilized structure, recorded in the corrosion layers, remaining metallic and non-metallic inclusions and evidence of the occurrence of Microscopic segregation or coring phenomenon, evidence of the occurrence of annealing twin lines, cyclical deposition of copper oxide and secondary copper corrosion products and A similar layer structure of copper and tin oxides as Unusual phenomenon, crystallized salts, a shift of the initial tin-enriched layer, Evidence of the occurrence of ferrite-pearlite structure in magnetite corrosion product of steel objects and carbon content gradient in ferrous alloys were the results of the studies. According to this, scientific study of corrosion layers of metal objects is very important in the analysis of Corrosion behavior of objects and study of their microstructure and method of production. So this scientific information is important in archaeometry studies. There are many signs, determine the position of original surface of objects. Evaluation of corrosion layers to identify the symptoms and distribution of them before cleaning of objects is necessary. In conclusion, emphasis is made on the need for designing a model for the study of corrosion processes at the archaeological sites. A correct policy is necessary to consider the information obtained from archeological studies, conservation and related sciences and to provide objectives and different priorities for future researchers in their research or conservation programs.