Combined Kelvin probe force microscopy and secondary ion mass spectrometry for hydrogen detection in corroded 2024 aluminium alloy

The capability of Kelvin probe force microscopy (KFM) to detect and locate hydrogen in corroded 2024 aluminium alloy was demonstrated. Hydrogen was introduced inside the 2024 alloy following a cyclic corrosion test consisting of cycles of immersion in 1 M NaCl solution followed by exposure to air at -20 °C. The combination of scanning electron microscopy, secondary ion mass spectrometry and KFM demonstrated that the grain and subgrain boundaries were preferential pathways for the short-circuit diffusion of hydrogen but also acted as a source of hydrogen diffusion in the lattice over distances of up to ten microns with non-negligible desorption when exposed to air at room temperature for 24 h.