When exposed to air, steel forms passivating iron oxide surfaces, such as hematite (α-Fe 2 O 3 ). Two slabs of α-Fe 2 O 3 with dimensions (xyz) of approximately 55 Å × 55 Å × 12 Å were used as the substrates, with the (010) plane exposed to the liquid phase. Periodic boundary conditions were imposed in the x-and y-directions. Initially, the two hematite slabs were separated by 120 Å of vacuum space. For the adsorption calculations, a single OFM molecule was placed at the centre of the simulation cell, and either 700 n-hexadecane or 373 PAO molecules were randomly distributed between the slabs using the amorphous builder plugin in MAPS, see Figure . This gave a similar total number of C atoms (∼ 11200) for both systems. Two systems were used for the hard-disk area calculations (see Supporting Information). In the first set-up (dimerisation simulations), two OFM molecules were placed close to the surface of one of the hematite slabs, using the same system size and number of solvent molecules as in the adsorption calculations. In the second set-up (annealing simulations), one hematite slab was covered a with pre-formed monolayer of OFM molecules with different surface coverages. The number of OFM molecules included varied from 106 to 198 and the system size was approximately 55 Å × 55 Å × 100 Å. This yields initial surface coverages, Γ = 3.5-6.5 nm -2