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The survey of 10-century-old illuminations showed that the gold-like areas were made with the use of brass powder. Since this layer has been showing significant damage, it is vital to identify the degradation mechanisms to prevent the priceless manuscript from further deterioration. Degradation of the pseudo-gilded areas, such as darkening of the metal phase and disintegration of the binder, are well visible on the illuminations. The aim of the study was to compare the corrosivity of brass induced by binders using artificial aging tests modelling the conditions for the deposition of illuminated documents in the archives. Egg white, gum Arabic, isinglass and parchment glue were applied throughout the experiments. The samples on brass coupons and electrical resistance probes (ER-probes) were subjected to artificial aging at a high relative humidity and in the air containing acetic acid vapour and the effect of an increased relative humidity on the corrosion behaviour of brass was evaluated. Corrosion depth of the ER-probes versus time was evaluated as well. The results show that the presence of the binder layer on brass increases the corrosion rate of brass at an elevated relative humidity of ambient air. Proteinbased binders resulted in a higher corrosion rate of brass probes compared to that of polysaccharide-based binder -gum Arabic.

Electrochemical chloride extraction from a reinforced concrete structure may be accompanied with an electrochemical injection of healing agents if such agents are positively charged and are able to migrate towards the activated reinforcement. Positive charge carried by nanoparticles or cathionic corrosion inhibitors might be the proper choice. Organic substances with a positive charge and their salts are mostly such inhibitors. The essential conditions for successful application of such corrosion inhibitors are their sufficient corrosion inhibition efficiency that was studied and evaluated and their stability of positive charge in chloride containing concrete pore solution.

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