اهميت تحليل لايه هاي خوردگي در مطالعه فني آثار فلزي تاريخي

The Importance of Scientific Investigation on the Corrosion Layers in Technical Studies of the Historical Metal Objects

در مطالعه آثار فلزي تاريخي، لايه هاي خوردگي چگال به دليل ارزش‌هاي فني نهفته در آن ها از اهميت خاص برخوردارند. در مقاله ذيل با هدف تأكيد بر امكان دستيابي به شواهد مؤثر در روند تحليل مطالعات ريزساختار و رفتار خوردگي آثار، با استناد به مطالعات خوردگي پيشين انجام شده با استفاده از ميكروسكوپ‌هاي نوري (PLM) و الكترون روبشي( SEM) و روش هاي تجزيه (EDX و XRD)، روي نمونه آثار فلزي مكشوفه از محوطه‌هاي صرم، مارليك، گوهر تپه، بم، زيويه، قلي درويش، لرستان و لفورك، به شواهدي چون ريزساختار فسيلي باقيمانده از دانه‌بندي در حلقه مكشوفه از صرم، مغزه بندي در پيكرك مارليك، ساختار فريتي-پرليتي در دسته خنجر فولادي زيويه، توزيع آخال سرب در قطعه مكشوفه از بم، جهت‌گيري آخال‌ها در پيكان برنزي گوهر تپه، شيب كربن در بازوبند فولادي لرستان، ترسيب دوره‌اي در كلاه‌خود اورارتو، برگشت لايه قلع در كمربند منسوب به لرستان، تبلور نمك در قطعه مطالعاتي قلي درويش و تصوير الياف پشم در سگك مكشوفه از لفورك، مستندات مؤثري در تحليل فرايند ساخت و رفتار خوردگي اين آثار هستند. لذا مطالعه لايه‌هاي خوردگي در ايجاد رويكرد علمي حفاظت آثار اهميت داشته و قبل از هرگونه مداخله‌اي بايد چارچوبي صحيح براي بررسي فرآيندهاي خوردگي تعريف شود.

in many cases it may be thought that corrosion products cover the unique characteristics of ancient metal objects that are desirable to display. While from 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 their substantial 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. Decuprificatio 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