No abstract

The application of characterization methods with high spatial resolution to the analysis of buried coating/metal interfaces requires the design and use of model systems. Herein, an epoxy‐like thin film is used as a model coating resembling the epoxy‐based coatings and adhesives widely used in technical applications. Spin coating is used for the deposition of a 30 nm‐thin bilayer (BL) composed of poly‐(ethylenimine) (PEI) and poly[(o‐cresyl glycidyl ether)‐co‐formaldehyde] (CNER). Fourier‐transform infrared spectroscopy (FTIR) results confirm that the exposure of coated AA2024‐T3 (AA) samples to the corrosive electrolyte solution does not cause the degradation of the polymer layer. In situ atomic force microscopy (AFM) studies are performed to monitor local corrosion processes at the buried interface of the epoxy‐like film and the AA2024‐T3 aluminum alloy surface in an aqueous electrolyte solution. Hydrogen evolution due to the reduction of water as the cathodic corrosion reaction leads to local blister formation. Based on the results of the complementary energy‐dispersive X‐ray spectroscopy (EDX) analysis performed at the same region of interest, most of the hydrogen evolved originates at the vicinity of Mg‐containing intermetallic particles.

The aim of this study is to develop nanometer‐thin epoxy‐based films on aluminium alloy AA2024‐T3 as a model coating system for high resolution corrosion studies. Spin coating was used for the layer‐by‐layer (LbL) deposition of poly‐(ethylenimine) (PEI) and poly([o‐cresyl glycidyl ether]‐co‐formaldehyde) (CNER) bilayers. The film chemistry and the cross‐linking process were characterized by means of Fourier‐transform infrared spectroscopy (FTIR). Ellipsometric data confirmed the linear increase of film thickness. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicate the improvement of the film barrier properties with increasing film thickness. Mapping of the topography and the volta potential was performed by means of scanning Kelvin probe force microscopy (SKPFM). The results indicate the presence of a homogeneous film structure, while the intermetallic phases can still be identified below the coating. The SKPFM analysis confirmed that the model films are suitable for investigation of corrosion processes at the coating/metal interface.