Eco-friendly extract of Brassica campestris for a sustainable inhibition of Cor-Ten corrosion

Summary In this work the natural extract of Brassica campestris was investigated as corrosion inhibitor of Cor-Ten steel in different environments. Cor-Ten is a "weathering steel", used in modern and contemporary art and also for infrastructures and buildings for its good mechanical properties and good resistance to atmospheric corrosion, due to the formation of a protective and uniform oxides layer on the surface. However, in the presence of chlorides (marine environment) or acidic rain water (polluted urban environment), Cor-Ten suffers high corrosion rates and the protective patina degenerates into severe corrosion products. Brassica campestris is a widespread, easily available and commonly cultivated plant, to the best of our knowledge never tested for such application so far. Motivation Environmental and safety issues represent a global concern for the use of corrosion inhibitors in the Conservation of Cultural Heritage. The applications of non-toxic and natural products as "green" corrosion inhibitors recently gained increasing importance because of the advantages of their eco-friendly and biodegradable nature, readily availability, renewable sources and low cost processing. Results Electrochemical Impedance Spectroscopy and Dynamic Polarization experiments were performed as a function of the concentration of Brassica campestris extract at room temperature. The surface chemical composition of Cor-ten steels was investigated by X-Ray Photoelectron Spectroscopy, both before and after the corrosion attacks. The electrochemical results demonstrated that a very small concentration of Brassica campestris extract could inhibit Cor-Ten corrosion in chlorides solutions up to 80-84% inhibition efficiency. Surface analysis confirmed the good protective effect of the addition of 80 ppm of the plant extract to the corrosive medium on the surface of the Cor-ten steel substrates. The performance of the Brassica campestris extracts in the acidic medium gave no such positive results. Acknowledgements. This work was financially supported by the PON03PE_00214_1 TECLA Project: "Nanotecnologie e nanomateriali per i Beni Culturali", Distretto di Alta Tecnologia per l'Innovazione nel settore dei Beni Culturali della Regione Sicilia.