The present study concerns the corrosion protection of the aluminium alloy (AA) 2024 by sodium decanoate (a long-carbon-chain carboxylate). This compound-type is known to form hydrophobic films on the metal surface. The characterization of the inhibition mechanisms was studied for different experimental conditions (pH. NaCl concentrations) by using electrochemical techniques. Special attention was paid to the action of the carboxylate on the intermetallic particles by performing local electrochemical impedance measurements on a model system (Al/Cu couple). The decanoate afforded high protection to the AA2024 both by preventing chloride ion attack of the oxide layer and by limiting galvanic coupling between the intermetallic particles and the surrounding matrix. A passivation effect of the compound was also shown. (C) 2009 Elsevier Ltd. All rights reserved.