Spatiotemporally resolved corrosion protection of AA2024-T3 by a lithium-based conversion layer
Ziyu Li (TU Delft - Team Arjan Mol)
A. M. Homborg (TU Delft - Team Arjan Mol, Netherlands Defence Academy)
P. Visser (Akzo Nobel)
Yaiza Gonzalez Gonzalez-Garcia (TU Delft - Team Yaiza Gonzalez Garcia)
JMC Mol (TU Delft - Team Arjan Mol)
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Abstract
In this work, the corrosion mechanism of AA2024-T3 covered by a lithium-based conversion layer is studied with high spatial and temporal resolution. Although the aluminium alloy surface is protected by a multi-layered conversion layer, areas around intermetallic phases (IMPs) represent weak spots due to an insufficient generation of a protective inner dense layer. For the freshly formed conversion layer, both the top and the inner layer undergo a gradual dissolution upon exposure to relatively dilute NaCl solution within 2 h due to their chemical instability. For the ambiently-aged conversion layer, most corrosion activity around IMPs is related to the S-phase and large constituent phases, due to their active nature and the lower local conversion layer quality, respectively. Moreover, S-phase-related corrosion activity lasts approximately 8 h due to fast dissolution whereas reactions induced by large constituent particles remain active over the entire re-immersion period of 12 h.
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