Molecular dynamics simulations have been used to study the behaviour of a liquid mixture of octacosane and heptane between two planar hematite surfaces; one of the surfaces was coated by a monolayer of an imidazoline-based corrosion inhibitor (CI). It was found that the octacosane could be inserted into the CI monolayer when it was aligned with the alkyl tails of the CIs, but the rate for such an insertion was slow. Potential of mean force calculations confirmed that there is a free energy barrier to insertion of octacosane into the CI film, and identified a secondary minimum about 13 Å from the surface as a metastable intermediate for insertion. A much more rapid process was adsorption of the octacosane onto the exposed hematite (102) surface, forming multiple layers and with a packing that was reminiscent of the octacosane crystal structure but with an orientation that matched the topology of the haematite surface.