Inclusion of 5-Mercapto-1-Phenyl-Tetrazole into β-Cyclodextrin for Entrapment in Silane Coatings: An Improvement in Bronze Corrosion Protection

The corrosion protection of coatings can be reinforced by the addition of entrapped corrosion inhibitors. β-cyclodextrin (β-CD) can form inclusion complexes with small inhibiting organic molecules that, when entrapped in coatings, allow the inhibitor release and adsorption at corrosion initiation sites. In this paper, several Nuclear Magnetic Resonance (NMR)-based experiments (e.g., Complexation-Induced Shifts (CIS), NMR titration, Diffusion-Ordered Spectroscopy (DOSY)) were performed to study the stability and geometry of a complex formed by β-cyclodextrin with 5-mercapto-1-phenyl-tetrazole (MPT). The complex was also detected by Electrospray Ionization (ESI) mass spectrometry and characterized by Fourier Transform Infrared (FTIR) spectra. Its influence on the protectiveness of a silane coating against bronze corrosion was evaluated in plain (AR) and concentrated (ARX10) synthetic acid rain, under different exposure conditions. In particular, the time evolution of the polarization resistance values during 20 days in ARX10 and the polarization curves recorded at the end of the immersions evidenced a higher protectiveness of the coating with the β-CD–MPT complex in comparison to that containing only MPT or only β-CD. The cyclic AR spray test carried out on coated bronze coupons with cross-cut scratches evidenced the absence of underfilm corrosion starting from the scratches only in the complex-containing coating.

Research Progress on Ancient Bronze Corrosion in Different Environments and Using Different Conservation Techniques: A Review

ABSTRACTAncient Chinese bronzes are precious cultural relics. Their surfaces are often severely damaged by dynamic changes in the external environment, both before and after they are unearthed. Therefore, scientific research has been required to preserve these treasures. In recent years, along with the development of modern science and technology, innovative instrumental analytical techniques have become indispensable tools to study corrosion phenomena as well as to evaluate post-excavation conservation techniques. In this paper, we present an overview of bronze corrosion processes in various environments, including analysis of the types of corrosion, mechanisms of formation and factors that influence bronze corrosion products. In addition, we compare the characteristics of corrosion products that have formed on archaeological sites, in tombs, and in museums. Lastly, we introduce some novel techniques for bronze protection, and we propose the focus for future research. Our expectation is that this review will provide a scientific basis for bronze preservation.