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Correlation between morphology and electrochemical behavior of chromium-free conversion coatings for aluminum alloys corrosion protection

Boyer, Quentin and Ortega Vega, Maria Rita and de Fraga Malfatti, Célia and Duluard, Sandrine Nathalie and Ansart, Florence Correlation between morphology and electrochemical behavior of chromium-free conversion coatings for aluminum alloys corrosion protection. (2018) Surface and Coatings Technology, 351. 115-127. ISSN 0257-8972

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Official URL: https://doi.org/10.1016/j.surfcoat.2018.07.068

Abstract

Chromium(III)-based, tungstate-based and cerium(III)-based conversion coatings on AA2024-T3 are compared in terms of morphology and electrochemical behavior. The durability of coatings is studied under neutral salt spray conditions and in a weakly aggressive electrolyte composed of 0.1 mol/L Na2SO4 and 10−3 mol/L NaCl. The use of both microscopic and electrochemical analyses such as fitting of electrochemical impedance spectroscopy diagrams allows one to have a better insight into the influence of the interfacial and conversion layers on the degradation phenomena. The role of the remaining native interfacial oxide layer is particularly highlighted, its resistance being the highest at the beginning of the exposure. The degradation of the barrier effect of this interfacial layer is demonstrated to be closely related to the performances of the conversion layer both in terms of passive protection and a reservoir of corrosion inhibitor. Finally, coupled analyses from EIS fitting and microscopic observations allow one to reach a precise interpretation of the strengths and weak points of such system. This diagnostic is an important step towards the optimization of the chromium-free systems.

Item Type:Article
HAL Id:hal-02134714
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Other partners > Universidade Federal do Rio Grande do Sul - UFRGS (BRAZIL)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Laboratory name:
Funders:
European Commission - French Ministry of Economy and Industry - (FRANCE) - Région Occitanie/Pyrénées-Méditerranée - (FRANCE)
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Deposited By: cirimat webmestre
Deposited On:29 Apr 2019 10:03

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