Corrosion protection of aluminium by ultra-thin atomic layer deposited alumina coatings

Electrochemical and surface analyses were applied to study the corrosion mechanisms of aluminium protected by ultra-thin (≤50 nm) alumina coatings grown by atomic layer deposition. Corrosion takes place via residual channel defects connecting the substrate to the electrolyte through the insulating coating. The data evidence the growth of a spurious aluminium oxide film at the substrate/coating interface in the reactor, that is beneficial to the sealing performance of the thinner films (10 nm). The resistance to the initiation of localized corrosion by pitting is increased with thicker films (20 and 50 nm) owing to improved sealing and barrier properties.