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2010-06-06 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Romano Anne-Pascale , Fedel M., Deflorian F., Olivier Marie-Georges , "Influence of silane pretreatment on the development of filiform corrosion of AA 6016" in EIS 2010, Algarve, Portugal, 2010

  • Codes CREF : Corrosion des matériaux (DI2114)
  • Unités de recherche UMONS : Science des Matériaux (F502)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Ingénierie des matériaux (CRIM)

Abstract(s) :

(Anglais) Aluminium alloys are known to be particularity sensitive to filiform corrosion. The aim of this work is to compare the filiform corrosion resistance of Al 6016 substrates without pretreatment (simply etched with a commercial acid etching product) and with a silane pretreatment. Al 6016 samples, with or without silane, were covered with an epoxy cataphoretic primer (PPG Industries France). The curing of the coating was performed at different temperatures (195°C, 185°C, 175°C, 165°C and 155°C) in order to modify its mechanical properties. The corrosion protection of the coating was evaluated by a normalized filiform corrosion test (ISO/DIS 4623: painted and scratched samples were inoculated 1 h in HCl and exposed in a constant humidity chamber at 40°C and 82% RH for 21 days) and by electrochemical impedance spectroscopy on scratched samples. On intact coatings, EIS measurements were used to follow the evolution of the water uptake and the barrier properties. In addition, EIS was applied to determine the performances of the systems as a result of exposure to HCl vapors. Al 6016 samples were placed under the same operating conditions as the normalized filiform corrosion test. Four series of Al samples were analysed by EIS. Samples A were analysed after painting. Samples B and C were placed in HCl vapours for 1 hour in order to simulate the conditions used to initiate filiform corrosion. EIS measurements were carried out on samples of series B after this first step. Serie C were placed for 21 days in climatic chamber (40°C and 82%RH) before measuring, in order to simulate the conditions under which filiform corrosion takes place. Samples D were placed for 21 days at room temperature (25°C and 40%RH) as reference. This study showed that HCl vapours induce not only filiform corrosion but also a modification of barrier properties and water uptake of coatings. The silane layer improves the filiform corrosion performances by improving adhesion and barrier properties of the film. This study emphasized the combined effect of the silane layer and mechanical properties of the cataphoretic coating on the corrosion filiform performances and resistance to initiation by HCl vapours.