The Application of Nicotiana Tabacum Extract as an Herbal Corrosion Inhibitor to Control the Bronze Disease in Copper Historical Artifacts

Most corrosion inhibitors are toxic and can cause damage to conservators. The aim of this research is to achieve a non-toxic corrosion inhibitor which has good efficacy، is effective and inexpensive، and does not create structural changes، discoloration and deformation on the historical artifact. Nicotiana Tabacum (tobacco) extract consists of alkaloid components and these materials have an important role in controlling corrosion. In this paper، tobacco was selected and extracted، and its function in sodium chloride، 0. 5 M as the corrosion inhibitor was evaluated in historical copper artifacts. Review of literature shows that this compound has not been used in the field of restoration. Electrochemical potentiodynamic tests were used to assess the function of this extract. Using this method، some information such as the potential and rate of corrosion، the slope coefficient of cathodic-anodic polarization and resistance at the concentration of the extract was obtained. Further، weight loss tests were carried out. In these tests، copper coupons were prepared and، after artificial aging by the inhibitor، their performance was controlled. Fail/Pass test was used through Rosenberg test to evaluate efficiency of the inhibitor for controlling the bronze disease on historical samples and the distribution of such disease on the samples was evaluated. Accordingly، optical microscope (OM) and electron microscope (SEM-EDAX) were used and the effectiveness of the inhibitor was evaluated with the help of several indicators. Moreover، for evaluating the rate of glaring and glittering of the surface after using tobacco extract the optical density-measuring was used، and colorimetry method was used for studying the changes in color، brightness and overall patina color of historical artifacts after using tobacco. The results of experiments and studies imply the good performance of tobacco extract against corrosion and it can be argued that this herbal extract is a very good option due to its high effectiveness and the least amount of changes on the chloride patina.