EIS MODELING OF FILMS OF BIS-TRI-ETHOXYSILYLPROPYLTETRASUL-FIDE ON AI 2024-T3 SUBSTRATES

摘要

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 non-corrosive electrolyte 0.5 M K{sub}2SO{sub}4. The effects of continuous immersion of the films in this electrolyte and curing the films at room temperature or at 100 C in air were studied. An equivalent circuit is proposed that fits the experimental data very well. It is demonstrated that by this approach the hydrolysis of the ester groups to silanol groups and condensation of the latter to siloxane units in the film can be observed. Evidence is presented for the formation of an interfacial film between the crosslinked silane film and the aluminum oxide. It is concluded that EIS in a non-corrosive electrolyte is a useful method for studying the stability of silane films formed on metals and can contribute to determining the optimum conditions for depositing silane films on metals for corrosion protection.