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ATR-FTIR Kretschmann spectroscopy for interfacial studies of a hidden aluminum surface coated with a silane film and epoxy II. Analysis by integrated ATR-FTIR and EIS during exposure to electrolyte with complementary studies by in situ ATR-FTIR and in situ IRRAS



The destabilization of the interface between a polymer and a metal surface is of considerable interest in several application areas, including the ongoing research on environmentally friendly pretreatments as a replacement for the Cr(VI)-containing systems where the understanding of mechanisms and performance of a confined metal/polymer interface is of utmost importance. Processes at hidden interfaces are, however, difficult to analyze in detail and at relevant climatic conditions. This study has been divided in two parts, where the subject of Part I is the surface characterization by ATR-FTIR Kretschmann and IRRAS spectroscopy of aluminum coated with an amino-functional silane, and the interfacial analysis by ATR-FTIR Kretschmann after further application of an epoxy film. This second part describes the interaction between the coated sample and an electrolyte. The analysis is performed by integrated in situ ATR-FTIR Kretschmann and EIS, which requires model systems with evaporated metal films on an internal reflection element. Complementary analyses were also conducted on substrates in the absence of the metal film, and or in the absence of an epoxy top-coat, respectively. Changes in the interfacial region were observed and assigned to the water uptake including swelling of the epoxy, and the formation of aluminium oxidation and hydration products. Complementary studies allowed the distinction between water uptake in the silane film and the epoxy, respectively, as well as reformations of the siloxane network. Copyright © 2011 John Wiley & Sons, Ltd.