Impedance evaluation of permeability and corrosion of Al-2024 aluminum alloy coated with a chromate free primer

A Foyet, T.H. Wu, A. Kodentsov, L.G.J. Ven, van der, G. With, de, R.A.T.M. Benthem, van

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7 Citations (Scopus)

Abstract

The corrosion of AA-2024 aluminum alloy protected with a chromate free primer is investigated afterimmersion in a 0.5MNaCl aqueous solution. Thewater uptake by the coating increases continuouslywhenthe film, applied on an aluminum AA-2024 substrate, is placed in the 0.5MNaCl solution. This increase isattributed to corrosion reactions taking place at the alloy/coating interface when water molecules reachthe interface. The maximum water volume fraction absorbed by a similar coating applied on platinumsubstrate is 3.5 vol% and the permeability is 7.6¿0−12m2 s−1. After 72 h immersion in the 0.5M NaClsolution, the Nyquist representation of impedance data shows transmission line behavior that can beassigned to percolation pathway along the filler particles afterwater uptake. Charge transfer and diffusionof corrosion reactants and products occur, but no delamination was observed for immersion longer than172 h. Furthermore, the coating resistance is still close to 108 ??cm−2 after this immersion time. Thisaccounts for the good protective performance of the coating.
Original languageEnglish
Pages (from-to)257-262
JournalProgress in Organic Coatings
Volume65
Issue number2
DOIs
Publication statusPublished - 2009

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