Time of flight secondary ion mass spectrometry (ToF-SIMS) spectra of aluminium hydroxide powders and thin films suggest that fragments of largely intact hydroxide layers are cleaved from the surface during ion bombardment. This leads to the presence of large repeating clusters of aluminium oxide dominated fragments up to 3000 Da in the SIMS spectra. The more intense repeating fragments of aluminium species appear to enhance the sputter rate on Al2O3. In the case of oxide films on the surface of aluminium alloy with 13 wt.% Si, there were no detectable higher mass repeating fragments for silicon species. The difference is linked both to the limited observations of these very large fragments in the absence of a layered crystal structure and the initially higher removal rate of aluminium species compared with silicon species on the surface of this alloy. This latter observation, confirmed by SIMS imaging during profiling, is at odds with typical observations reported in the literature. Copyright © 2012 John Wiley & Sons, Ltd.