Among all the mineral reducing acids, sulphuric acid is the most aggressive towards CP titanium. Thanks to the strong complexing ability of sulphates with Ti4+, it acts promoting uniform attacks over the entire exposed surface, generating corrosion rates of about 7.7 mm/y. Plasma electrolytic oxidation (PEO) on titanium allows the formation of a thick crystalline oxide. The layer is able to protect the substrate until the corrosion potential (E-corr) remains nobler than the hydrogen reduction reaction, which could be considered as a reasonable threshold for oxide passivity, below which proton intercalation and cation reduction to Ti3+ can occur. In the following research, impedance measurements (EIS) has been performed at different cathodic potentials, with the aim of providing a scientific interpretation of the oxide delamination in concentrated hot reducing environment. The formation of a hydrogen bubble at the metal-oxide interface is the necessary condition for oxide failure.

Studio sulla delaminazione di ossidi PEO immersi in acido solforico mediante spettroscopia elettrochimica ad impedenza

L. Casanova;M. Gruarin;M. Pedeferri;M. Ormellese
2021

Abstract

Among all the mineral reducing acids, sulphuric acid is the most aggressive towards CP titanium. Thanks to the strong complexing ability of sulphates with Ti4+, it acts promoting uniform attacks over the entire exposed surface, generating corrosion rates of about 7.7 mm/y. Plasma electrolytic oxidation (PEO) on titanium allows the formation of a thick crystalline oxide. The layer is able to protect the substrate until the corrosion potential (E-corr) remains nobler than the hydrogen reduction reaction, which could be considered as a reasonable threshold for oxide passivity, below which proton intercalation and cation reduction to Ti3+ can occur. In the following research, impedance measurements (EIS) has been performed at different cathodic potentials, with the aim of providing a scientific interpretation of the oxide delamination in concentrated hot reducing environment. The formation of a hydrogen bubble at the metal-oxide interface is the necessary condition for oxide failure.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/1196606
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