Adsorption of self-assembled monolayer (SAM) of different imidazolines derivatives was investigated on Fe2O3 (0 0 01) surface with DFT calculations to understand their corrosion inhibition mechanism. Quantum chemistry calculations enable us acquiring a better insight on the nature of imidazoline/surface interactions, i.e. partly covalent bonds, and self-organization of imidazoline ring on the surface than the previous force field-based studies. The SAM is composed of a network of H-bonded inhibitors. The influence of the alkyl chain length of imidazoline derivatives, which form a hydrophobic barrier above the surface, on the energetic and structural properties of the SAM was evaluated.