Chemical-physical characterisation of 5-Phenyl-1H-tetrazole inhibitive behaviour: a new non-toxic compound for a sustainable protection of Cu-alloys

The inhibitive effect against copper-alloy corrosion in NaCl 3 wt% of a non-toxic compound, namely 5-Phenyl-1H-tetrazole (PT), is probed and compared with the performance of the most used and toxic 1H-Benzotriazole (BTA), by using a multi-technique approach. Electrochemical impedance spectroscopy and potentiodynamic polarisation measurements, at different inhibitors concentrations, are performed in order to evaluate the best inhibition efficiency (IE%) and the optimum concentration of the inhibitors. The inhibition efficiencies of PT (IE = 94.7–96.1%) and BTA (IE = 99.5–99.9%) are comparable, with the advantage that PT acts at a much lower concentration (1 mM respect to 10 mM). To shed light on the inhibition mechanism at the early stage of the corrosion (2 h), we investigate the samples surfaces composition and morphology by X-ray photoelectron spectroscopy, micro-Raman spectroscopy and atomic force microscopy. Different inhibition mechanism and patina composition are observed and commented for the two inhibitors. The reported experimental tests suggest PT as a promising candidate for replacing toxic BTA in the prevention of bronze archaeological and artistic objects corrosion. Graphical Abstract