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International audience; As part of an M-ERA.NET project called B-IMPACT some polidentate Schiff bases were synthesized and tested as corrosion inhibitors of bronze. The tests consisted of exposures of bronze specimens to a concentrated artificial acid rain solution, containing or not containing the studied substances added under saturation conditions (< 10(3) M). Their inhibiting effect was evaluated during 20 day immersions by means of non-destructive electrochemical tests (Electrochemical Impedance Spectroscopy) and by finally recording the polarization curves. Observations by a scanning electron microscope coupled with Energy Dispersive X-ray Spectroscopy allowed comparing the morphology of corrosion attack in the absence and presence of inhibitors. The best inhibiting properties were achieved in the presence of 2-(salicylideneimino)thiophenol (SITP). The addition of phosphate ions to SITP induced the formation of a surface film particularly resistant against localized corrosion phenomena. Raman and XPS spectroscopy were applied in order to investigate the inhibition mechanism of sire without and with the presence of phosphate ions.; Nell’ambito di un progetto M-ErA.NET denominato B-IMPACT, sono state sintetizzate alcune basi di schiff polidentate che sono state usate come inibitori della corrosione del bronzo. Le prove consistevano in esposizioni ad una soluzione di pioggia acida artificiale con-centrata, in cui le sostanze erano presenti in concentrazioni di saturazione (< 10-3 M). Il loro effetto inibitore è stato valutato durante 20 giorni di immersione tramite prove elettrochimiche non distruttive (spettroscopia di Impedenza Elettrochimica) e attraverso la regi-strazione di curve di polarizzazione. Osservazioni al microscopio elettronico a scansione accoppiato ad una microsonda a dispersione di energia hanno permesso di confrontare la morfologia dell’attacco corrosivo in assenza e in presenza di inibitori. Le migliori proprietà inibitrici sono state rilevate in presenza di 2-salicilideneimmino tiofenolo (sITP). L’aggiunta di ioni fosfato al sITP induce la formazione di film superficiali particolarmente resistenti nei confronti di fenomeni di corrosione localizzata. sono inoltre state applicate la spettro-scopia raman ed XPs per meglio investigare il meccanismo di inibizione del sITP, sia in assenza che in presenza di ioni fosfato.

International audience; Bronze statues exposed to an urban area suffer corrosion processes induced by acid rainwater. Use of corrosion inhibitors is one of the most convenient and cost-effective techniques to mitigate it. In a previous work, it was found that 4-methyl-1-p-tolylimidazole (MTI) is non-toxic and efficient inhibitor of copper, and thus we will examine the anticorrosive effect of this substance to copper-tin bronze. First, with bare Cu-6Sn (wt%) bronze, inhibiting efficiency in artificial acid rainwater in urban environment was evaluated by Tafel extrapolation, polarization resistance, and electrochemical impedance spectroscopy (EIS) methods. This study showed that all three methods supply similar inhibiting efficiency validating thus the use of EIS, the least invasive method. This study was followed by the evaluation of inhibiting effect on patinated bronze in sulphate medium. A quntitative study about the inhibiting effect on patinated bronze is scarcely reported in the literature. EIS data revealed three capacitive loops. Comparison with EIS obtained in bare specimens allowed attributing the additional capacitive loop located at the highest frequency domain to the dielectric property of the patina layer. The impedance modulus determined in presence of MTI increased markedly with immersion time, revealing a protective effect of this non-toxic corrosion inhibitor.