Synergistic effects of composition and natural aging on localized corrosion in Al–W thin films

This study investigates the role of tungsten in localized corrosion and pit growth kinetics in Al–W thin film coatings using a two-dimensional (2D) pit growth framework. Pure aluminum and Al–W thin films containing 2.8 wt% and 5.2 wt% tungsten were examined using electrochemical measurements with in situ optical imaging and cross-sectional STEM-EDS after approximately 34 years of natural aging in laboratory or office conditions. A higher tungsten content lowers the anodic pit current density, and facilitates the development of a thicker, more robust passive film. The anodic dissolution kinetics exhibit distinct potential-dependent regimes governed by ohmic resistance and mass transport limitations. Long-term aging enhances the atomic ratio of oxygen to metal within the metal film and the pitting resistance, highlighting the beneficial role of tungsten in stabilizing passive films and improving corrosion durability of thin-film aluminum coatings.