Laboratory-scale testing of the anti-corrosion effectiveness of a primer coating on a bare AA2024 surface

In this study, the behaviour of a cut-edge electrode machined from a coated AA2024-T3 plate, designed for an aircraft structure, has been used to mimic the electrochemical response occurring after a mechanical scratch on a coated structure. In situ pH imaging with an ion-selective microprobe was used to confirm the competition between the effect of the inhibitor release and local corrosion activity around intermetallic (IM) particles. In this work, the validation of the described method is based on conventional chromate/dichromate inhibitors, assumed to be cathodic inhibitors. An experimental method, supported by mass transport modelling, was defined to characterize the competition between the triggering of localized microstructural corrosion and the passivation of a bare metal surface. Copyright (C) 2016 John Wiley & Sons, Ltd.