Low-temperature atomic layer deposition of Al2O3 thin coatings for corrosion protection of steel: Surface and electrochemical analysis

ToF-SIMS, XPS, voltammetry and EIS investigation of the anti-corrosion properties of thin (10, 50 and 100 nm) alumina coatings grown by atomic layer deposition at 160 °C on steel is reported. Surface analysis shows a thickness-independent Al2O3 stoichiometry of the coating and trace contamination by the growth precursors. The buried coating/alloy interface has iron oxide formed in ambient air and/or resulting from the growth of spurious traces in the initial stages of deposition. Electrochemical analysis yields an exponential decay of the coating porosity over four orders of magnitude with increasing thickness, achieved by sealing of the more defective first deposited 10 nm.

► 10–100 nm Alumina coatings grown by ALD at 160 °C for protection of steel.
► Al2O3 stoichiometry of the coating and trace contamination by growth precursors.
► Iron oxide and siloxane presence at the buried coating/steel interface.
► Exponential decay of coating porosity over four orders of magnitude with thickness increase.
► Coating thickness increase required to seal the defective first deposited 10 nm.