Application of atomic force microscopy (AFM) for in situ corrosion studies of thin film covered AA2024-T3 aluminium alloy surface

摘要

The performance of functional coatings and adhesively joined hybrid components relies strongly onthe stability of the polymer-metal interface. With the increasing utilization of multi-materialstructures in the automotive and aerospace industry, it is of great scientific and technical interestto understand the processes leading to interface degradation and to develop novel strategies toincrease corrosion and delamination resistance.The aim of this project is to develop thin epoxy-based films and their carbon nanofiller loadedcomposites on aluminium alloy AA2024-T3 as a model system and to investigate their interfacialstability under corrosive and coupled corrosive-mechanical load. Spin coating was used for thelayer-by-layer deposition of poly[(o-cresyl glycidyl ether)-co-formaldehyde] and poly-(ethylenimine)bi-layers. Atomic force microscopy (AFM) results indicate a very homogeneous and dense filmwith low surface roughness. Carbon nanofillers were introduced either by mixing into the coatingcomponents or in between individual layers to control the separation between the carbon nanofillersand alloy surface. The film chemistry and barrier properties were characterized by means ofspectroscopic and electrochemical methods, respectively. The degradation and delaminationbehavior of the epoxy-based films was characterized by means of in situ AFM corrosionexperiments. The quantitative imaging (QI) mode allowed the observation of hydrogen-generationinduced blister formation during exposure to corrosive electrolyte and how the local corrosionprocesses evolved with exposure time. Complementary energy dispersive X-ray spectroscopy(EDX) analysis was performed to correlate the corrosion behavior with the different intermetallicparticle chemistries and distributions. The presentation will summarize our results on the effect ofinterface chemistry and carbon nanofiller – alloy separation on the initiation of local corrosionprocesses on thin film covered AA2024-T3 aluminium alloys.