بررسی روند تشکیل ترکیبات اکسیدی در آثار برنزی با استناد به مطالعات میکروسکوپی

Due to the complex corrosion mechanism of the bronze objects, explaining the structure of different layers of corrosion in these objects at microscopic levels is possible. Typically copper oxide(I) is the first corrosion layer on surface of bronze objects that are excavated of historical sites. However, depending on the environmental conditions، various forms of corrosion layer of tin or copper-rich oxide are formed that are effective in corrosion resistance of objects. Identification of tin oxides or copper-tin corrosion products is not simple by using of routine methods of instrumental analysis.However in this research the formation process of copper and tin oxides of some of historical bronze objects of Iran were studied by using the optical microscope with polarized light that show colored corrosion products and in some cases the method of scanning electron microscopy equipped with elemental analysis (SEM-EDX) was used to complete the identification process of oxide layers. According to the results, identify of evidence of differences in distribution of copper and tin in the microstructure that is result of macroscopic and microscopic segregation, formation of a solid solution of copper besides the copper-copper oxide eutectic mixture during the solidification process, the appearance of copper oxide inclusions in the microstructure of metal, moving The tin-rich layer of copper oxide layer to the outside, formation of copper oxide-tin oxide sandwiching layers, selective dissolution of tin in the outer layers, decuprification phenomenon in corrosion layers  and condensation of tin oxides in the center of sample and finally the usual formation or degradation of copper oxide layer under certain conditions have been studied with microscopic imagesof selected samples of bronze objects which confirmed the ability of microscopic techniques in the study of oxide layers of bronze objects.