The anodization of aluminium in a microwave excited O2 plasma has been studied at temperatures less than 100 °C. Thirty nanometers of oxide were grown in times substantially less than one hour. The growth kinetics follow those expected using the constant current growth mode. X-ray diffraction, Fourier transform infrared absorption, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and electrical studies were carried out. The oxide is amorphous and stoichiometric, the as-grown films have high electrical conductivity. The method may be well suited for the formation of protective coatings.