Effects of temperature and pH on uniform and pitting corrosion of aluminium alloy 6061-T6 and characterisation of the hydroxide layers

Effet de la température et du pH sur la corrosion de l'alliage d'Al 6061-T6 et caractérisation des couches d'oxydes

Sarah L’haridon-Quaireau (1) , Mathilde Laot (1) , Kimberly Colas (1) , Bénédicte Kapusta (1) , Sylvie Delpech (2) , Dominique Gosset (3)

1 SEMI - Service d'Etudes des Matériaux Irradiés
2 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
3 SRMA - Service des Recherches Métallurgiques Appliquées

During operation in material testing reactors (MTR), the AA-6061-T6 alloy used for core components is covered by aluminium hydroxide. In this work we investigate the effects of parameters on pitting and uniform corrosion of the aluminium alloy 6061-T6 in the conditions found in MTR for the core structures: temperature (70e100 C) and pH (5 and 7.5). After corrosion experiments, characterisation techniques are used to observe the formed hydroxide, its composition and crystallographic structure (TEM, SEM, EDX, XRD, m-Raman spectroscopy and electron diffraction) and formulate hypotheses on the mechanisms of corrosion at play. At low temperature (70 C), the film is composed of two layers of different aluminium hydroxide phases. These two phases have different corrosion behaviours depending on the pH. The pH has a strong impact of the outer layer but not on the inner layer. PH increase is observed in deaerated medium, this pH variation is due to oxidation of magnesium of the alloy. In addition, corrosion models are used to predict the hydroxide thickness in MTR for a safe and efficient operation. These models are based on empirical correlations. The data obtained from this study allows to discuss the application of these models at low temperature (70 C).

Mots clés: pH; Microstructure; Corrosion; Aluminium hydroxide

Domaines: Matériaux

Sarah L’haridon-Quaireau, Mathilde Laot, Kimberly Colas, Bénédicte Kapusta, Sylvie Delpech, et al.. Effects of temperature and pH on uniform and pitting corrosion of aluminium alloy 6061-T6 and characterisation of the hydroxide layers. Journal of Alloys and Compounds, 2020, 833, pp.155146. ⟨10.1016/j.jallcom.2020.155146⟩. ⟨hal-03037512⟩