Electrochemical anticorrosion performance evaluation of Al2O3 coatings deposited by MOCVD on an industrial brass substrate |
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Authors: | Francesca Guidi Giovanni Carta Gilberto Rossetto Guido Salmaso |
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Affiliation: | a Ca’ Foscari University of Venice, Department of Chemistry, D.D.S. Marta 2137, 30123 Venezia, Italy b CNR-ICIS, Corso Stati Uniti 4, 35127 Padova, Italy c INFN Laboratori Nazionali di Legnaro, 35020 Legnaro, PD, Italy |
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Abstract: | Alumina (Al2O3) coatings of different thickness were deposited on OT59 brass substrate (BS) using the metal organic chemical vapour deposition (MOCVD) technique to evaluate the corrosion performance by EIS measurements. The used precursor was dimethyl-aluminium-isopropoxide. Electrochemical characterizations of the deposited films were performed in a standard very aggressive acidic solution (aerated 1N H2SO4 at 25 °C up to 168 h of immersion time) by means of direct current method (Tafel curves) and electrochemical impedance spectroscopy (EIS). The Rutherford backscattering spectroscopy (RBS) indicated that the films are very pure with the correct Al2O3 stoichiometry, while the IR absorption spectra showed that the films did not contain any OH groups. The surface film morphology was investigated by atomic force microscopy (AFM) and displayed a globular texture. The films were very smooth, with a maximum root mean square roughness, for example, of 14 nm for a 0.96 μm thick coating. The EIS data confirmed, as expected, that a 2.40 μm Al2O3 layer ensures the best corrosion protection after 168 h of immersion in the very acidic environment used. |
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Keywords: | Al2O3 anticorrosion layers MOCVD OT59 brass Electrochemical impedance spectroscopy (EIS) long time measurements |
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