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Influence of the alloy microstructure and surface state on the protective properties of trivalent chromium coatings grown on a 2024 aluminium alloy

Verdalet-Guardiola, Xavier and Bonino, Jean-Pierre and Duluard, Sandrine Nathalie and Fori, Benoit and Blanc, Christine Influence of the alloy microstructure and surface state on the protective properties of trivalent chromium coatings grown on a 2024 aluminium alloy. (2018) Surface and Coatings Technology, 344. 276-287. ISSN 0257-8972

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Official URL: https://doi.org/10.1016/j.surfcoat.2018.03.046

Abstract

The protective properties of trivalent chromium process (TCP) coatings grown on a 2024-T3 aluminium alloy were studied on the basis of electrochemical measurements performed both in sulphate and chloride solutions and neutral salt spray tests. The influence of the alloy microstructure and surface state was studied: two batches, each one characterized by its own coarse intermetallic particle distribution, and two surface states, i.e. laminated and polished, were considered. Results showed that in 0.1 M Na2SO4, the protective properties of the TCP coatings decreased when the roughness of the initial surface increased. Furthermore, improved protective properties were observed for a TCP coating grown on a surface containing a lower amount of Al-Cu-Mg IMCs in the initial microstructure. The most plausible explanation is that a fast kinetics of coating growth, either associated to strong initial roughness or a great surface copper coverage, was detrimental for the protective properties of the coatings. In more aggressive solutions, i.e. 0.5 M NaCl solution or for neutral salt spray tests, the differences are not significant. The findings are highly relevant for industrial applications: the results showed that variations in batches, for a same type of alloy, or in initial surface state should not be detrimental for the corrosion resistance of the TCP coated samples. However, the conversion process had to be adapted for different types of alloys, characterized by their own microstructure.

Item Type:Article
HAL Id:hal-01989083
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 > MÉCAPROTEC Industries (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Laboratory name:
Funders:
French National Research Agency (ANR)
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Deposited By: cirimat webmestre
Deposited On:22 Jan 2019 10:23

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