fa ارزیابی تأثیر آهن بر فرایند تخریب ساختاری چرم کروم در شرایط مدفون، بر اساس شاخص‌های تخریب در طیف‌های FTIR دانش حفاظت Conservation Science پژوهشي Original Research آهن و محصولات خوردگی آن از جمله عوامل موثر در فرایند تخریب آثار چرمی، به‌ویژه نمونه‌های مدفون هستند. بر این اساس هدف از این مطالعه، ارزیابی تأثیرات محصولات خوردگی آهن در شدت تخریب چرم است. در این راستا یک نمونه چرمی حاصل از خاک‌برداری محوطه کارخانه چرم خسروی تبریز (دانشگاه هنر اسلامی تبریز) مورد مطالعه قرار گرفت. بر اساس خصوصیات ظاهری، این چرم در شرایط تدفین در مجاورت آهن و محصولات خوردگی آن قرار داشته است. جهت ارزیابی ساختاری بخش‌های مختلف چرم و شدت تخریب آنها، از آزمون نقطه‌ای شناسایی آهن، اندازه گیری میزان خاکستر چرم، <span dir="LTR">&micro;-XRF</span>، طیف سنجی <span dir="LTR">UV-Vis</span> و <span dir="LTR">FTIR</span> و بررسی میکروسکوپی استفاده شد. همچنین طیف‌های <span dir="LTR">FTIR</span> بر اساس تابع گوسی برازش شد و مورد بررسی قرار گرفت. نتایج حاصل نشان داد که این نمونه با استفاده از نمک‌های کروم دباغی شده و احتمالاً از آهک جهت موزدایی آن استفاده شده است. بررسی چهار نقطه از این نمونه، حضور آهن با میزان متفاوت را در بخش‌های مختلف چرم نشان داد، به عبارتی بخشی از چرم در تماس مستقیم با آهن قرار داشته است و به مرور محصولات خوردگی به ساختار چرم نفوذ کرده و موجب اختلاف در میزان آهن در بخش‌های مختلف آن شده‌اند. بررسی خصوصیات ساختاری این نواحی نشان داد که با افزایش آهن، تغییر در یکپارچگی ساختار مارپیچ سه جزئی کلاژن و هیدرولیز آن افزایش یافته و از طرفی تشدید اکسایش کلاژن را نیز به‌همراه داشته است.<br> &nbsp; As leather production is an ancient industrial activity, historical leathers represent an important part of any society&rsquo;s cultural materials. However, since leather is made from collagen fibers that are susceptible to many degradation factors, leather artifacts have been remained less often than other historical materials. Wide variety application of leather, imposes a particular set of conditions, which can bring about deterioration in the leather. In general, deterioration of leather is a chemical process in which there are a great number of contributing factors. Iron and its corrosion products are among the effective factors in the degradation of leathers, especially in buried specimens. This factor, in combination with the leather and tanning chemistry, leads to very diverse and complex degradation mechanisms. Therefore, the aim of this study is to evaluate the effects of iron corrosion products on leather deterioration. Accordingly, a buried leather sample obtained from historic &ldquo;Khosravi&rdquo; Leather Factory, Tabriz Islamic Art University, was examined. Based on appearance, the leather was buried in the vicinity of the iron and its corrosion products. Different parts of leather show the possibility of penetration of different amounts of iron or its corrosion products. Structural evaluation of different parts of the leather and their deterioration was performed by spot test of iron (using potassium&nbsp;ferrocyanide), leather ash measurement, Micro x-ray fluorescence (&micro;XRF), Ultraviolet&ndash;visible (UV-Vis) and Fourier-transform infrared (FTIR) spectroscopy and microscopic examination. FTIR spectra were also fitted to the Gaussian function. The results showed that this sample was tanned with chromium salts and, probably, lime was used for dehairing. Examination of leather showed that the amount of iron varied in different parts of leather. In other words, a part of the leather has been in direct contact with iron and, over time, corrosion products have penetrated the leather structure. This has led to differences in the amount of iron in different parts of leather. Structural changes in different parts of leather were investigated using degradation indices in FTIR spectra. The hydrolysis degree of the polypeptide chains can be semiquantified using the amide I/amide II band intensity ratio (I_AI/ I_AII), which is about 1.25 - 1.30 for new leathers and increases with deterioration. The triple helical structure integrity can be also evaluated by peak absorbance ratio of amide III and 1450 cm^-1, which is equal to or higher than 1 for the intact collagen triple helix and around 0.5 for denatured collagen. Moreover, the relative position of amide I and amide II bands (&Delta;ѵ=ѵ_AI-ѵ_AII) is corresponding to the collagen gelatinization process, and the value is around 90-100 cm-1 for new leathers. The carbonyl&nbsp;index at 1740cm^-1&nbsp;also shows the&nbsp;oxidation&nbsp;of collagen. Accordingly, examination of the structural properties of different parts of the leather showed that as the amount of iron in the leather increased, the integrity of triple-helical structure of collagen collapsed (decrease in I_AIII/I₁₄₅₀) and its hydrolysis increased (increase in I_AI/I_AII). And it also has increased collagen oxidation (increase in I₁₇₄₀/I_AI). However, the results did not show a significant change in the index of collagen gelatinization (&Delta;ѵ).<br> &nbsp; چرم, کلاژن, دباغی کروم, تخریب چرم, آهن, FTIR Leather, Collagen, Chromium tanning, Degradation of leather, Iron, FTIR 91 104 http://jra-tabriziau.ir/browse.php?a_code=A-10-370-1&slc_lang=fa&sid=1 Alireza Koochakzaei علیرضا کوچکزایی alireza.k.1989@gmail.com 10031947532846004919 10031947532846004919 Yes Tabriz Islamic Art University دانشگاه هنر اسلامی تبریز Mahsa Saidi Mehrabad مهسا سعیدی مهرآباد saidimahsa98@gmail.com 10031947532846004920 10031947532846004920 No Tabriz Islamic Art University دانشگاه هنر اسلامی تبریز