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Abdolalizadeh M, Mohammadi Achachluei M, Oudbashi O. Studying the Products and Factors Involved in Corrosion of Brass Alloy in Four Qajar Era Manuscripts. JRA 2024; 10 (1) :167-188
URL: http://jra-tabriziau.ir/article-1-397-en.html

Copper and its alloys are prone to corrosion influenced by environmental factors. Corrosion can influence a lot of characteristics of historical artifacts, such as their apparent features and their visual appeal. It is common to observe proximity of metal and organic materials in historical artifacts, particularly in gilded manuscripts, where metal deterioration occurs from corrosive agents such as carboxylic acids, leading to greenish corrosion byproducts. This study examines four manuscripts from the Qajar era featuring metal decorations to identify the factors involved in corrosion of the metal areas. In the analyses conducted in this research FESEM-EDS, ATR-FTIR, Raman and pH measurement methods were used. The study identified a type of copper alloy in all four historical artifacts, which resembles brass. Based on samples derived from all four historical manuscripts, the adhesive agent that attached metal to the paper substrate was identified to be Arabic gum. The corrosion products were recognized as metal carboxylates, including copper and zinc carboxylates. Formates and acetates were also detected within the structure of the greenish corrosion byproducts. Areas with oily stains which were found in two of the samples, exhibited more pronounced corrosion, emphasizing the destructive impact of oil in formation of metal soaps, as also noted in the research literature. The corrosion byproducts in the metal areas have diminished the golden appearance of the decorations and penetrated the paper fibers. The acidity test revealed that the pH levels in the corroded areas were around one unit lower than in areas without metal presence. This difference is a significant factor in deteriorating the cellulose substrate through acid hydrolysis.