A microclimate model to simulate neutral salt spray testing for corrosion inhibitor evaluation and functional coating development

Abstract

A microclimate exposure model was developed to simulate the neutral salt spray test (NSS) environment which was used to estimate the pitting corrosion inside an artificial defect of a coating system, when it is exposed to a virtual microclimate. The model uses a dynamic process to simulate salt fog droplet formation, subsequent coalescence, and movement on a coated surface, to determine wet-dry cycles on realistic test samples. While the presented model is formulated to comply with standardised NSS tests, e.g. ASTM B117, the developed method can be tuned to simulate a variety of common cyclic environmental testing conditions, and has wide applicability for the virtual assessment of functional coatings. We will show that when validated against empirical data obtained from inhibitor and pitting studies, the developed model is able to predict the pit growth rate of an AA2024‐T3 aluminium alloy panel placed in a NSS test chamber. We will also explore the adaptation of the model to encompass the virtual assessment of functional coatings such as corrosion inhibiting coatings, and their impact on reducing pitting events and pit growth. This work demonstrates an effective approach for building models and establishing interrelationships with other corrosion models or empirical data to produce a predictive system that could ultimately lead to a rapid methodology for virtually screening new functional coatings and formulations, reducing labour costs and freeing up testing infrastructure for materials validation tasks.