Influence of self-assembling adhesion promoter on the properties of the epoxy/aluminium interphase

The paper considers the influence of an adhesion promoter on the electrochemical behaviour and on the glass transition in adhesive joints of an epoxy coat on aluminium AlMg3 as a function of the surface pre-treatment. The adsorption of phosphoric acid mono alkyl ester as adhesion promoter (AP) on aluminium samples and the influence of the AP on the polymer network in the epoxy/aluminium interphase has been studied by means of electrochemical impedance spectroscopy (EIS). The results reveal that the coupling layer has been well formed and it has promoted formation of a durable interphase, such as the higher cross-linking density in the epoxy network, indicated by the increased glass transition temperature and the increased corrosion performance of the coated aluminium sample, indicated by the result from the corrosion test. The combination of phosphoric acid anodic oxidation (PAA) and application of AP could be proposed as alternatives to chromium-based pre-treatments for aluminium.