Electrochemical Impedance Spectroscopy of Bis-[Triethoxysilypropyl]Tetrasulfide on Al 2024-T3 Substrates
- 1 May 2001
- journal article
- Published by Association for Materials Protection and Performance (AMPP) in Corrosion
- Vol. 57 (5) , 413-427
- https://doi.org/10.5006/1.3290365
Abstract
Thin films of the hydrolyzed silane bis-[triethoxysilylpropyl]-tetrasulfide (sulfane) were deposited on alkaline-cleaned Al 2024-T3 panels and investigated by electrochemical impedance spectroscopy (EIS) using the noncorrosive electrolyte 0.5 M potassium sulfate (K2SO4) aqueous solution. The effects of continuously immersing the films in this electrolyte and curing the films at room temperature or at 100°C in air were studied. Three equivalent circuits were proposed that fit the experimental data very well. A continuous increase of impedance and the appearance of an additional time constant with respect to time in EIS spectra during immersion, curing, and aging processes were explained by the hydrolysis of the ester groups to silanol groups and condensation of the latter to siloxane bonds in the film, and by the formation of an unknown interfacial phase between the cross-linked silane film and the aluminum oxide (Al2O3). Reflection absorption Fourier transform infrared spectroscopy (RAIR) was use...Keywords
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