Synergistic inhibition effect of Chitosan and L-Cysteine for corrosion protection of copper-based alloys

The development of active materials for the protection of metallic substrates from corrosion is a task of primary importance for many applications. Several organic compounds were studied to investigate their corrosion inhibition potential in order to replace hazardous compounds [1-2]. The purpose of this research has been the investigation of the efficiency of a new environmental-friendly anticorrosive coating that takes advantage from the synergist effect of a biopolymer matrix combined with amino acids. The inhibition of the corrosion of the copper-based alloys has been studied using Chitosan (CH) as a biopolymer and L-Cysteine (Cy) as amino acid. The latter was selected since, in addition to the amino group, Cy also contains the -SH groups which have a strong affinity with copper. The CH/Cy coatings were optimized paying particular attention to the requirements necessary for their application in the field of cultural heritage. To evaluate the protective efficacy of the coatings, accelerated corrosion tests, purposely tailored, were carried out on bare and coated metal disks. Our tests reveal that the efficiency in the corrosion inhibition increases with a minimum amount of Cy (0.5 mg/ml). The nature of the protective film formed on the copper-based alloy surface was analysed by FTIR spectroscopy 42 whereas the surface modifications due to the corrosion treatments were characterized by Optical Microscopy. The experimental data show that the CH/Cy coatings have a protective action onto the copper-based alloy surface with a consequent inhibition of the corrosion process. [1] G. Giuliani, M. Pascucci, C. Riccucci, E. Messina, M. Salzano de Luna, M. Lavorgna, G.M. Ingo, and G. Di Carlo, Progress in Organic Coatings, 122, 138-146 (2018). [2] M.A. Amin, K.F. Klaled, Q. Mohsen and H.A. Arida, Corrosion Science 52, 1684-1699 (2010).