In some cases, a subsequent C-O bond dissociation in the cresol molecule led to the formation of toluene. We also investigate the early stages of polyphosphate tribofilm growth. Despite the fact that P-O bond formation is accelerated on the more reac-tive surfaces, the rate of P-O bond cleavage is also increased by a similar amount, meaning that the total number of P-O bonds is comparable between the three surfaces. The polyphosphate chain length is also similar between the surfaces, with a skew in the distribution to higher chain lengths (up to octomers) for the more reactive iron surfaces. The rate of TCP decomposition increases exponentially with temperature and shear stress, indicating that this is a SATA process. 3D fits to the Bell model lead to activation energies and pre-exponential factors both increasing in the order: Fe 3 O 4 (100) < Fe 3 C(010) ∼ α-Fe(110). This implies that, although the energy barrier is smaller for the less reactive oxide surfaces, the fraction of successful collisions is also much lower. This trend may be due to the decreased availability of iron atoms on the surface, which are essential to promoting the decomposition reactions. The activation volume increases in the order: Fe 3 O 4 (100) < Fe 3 C(010) < α-Fe(110), which suggests that higher surface energy causes the TCP molecules to be anchored to the surface, leading to more efficient transmission of shear stress. An additional contribution to the larger activation energy for α-Fe(110) surfaces could be the reduced contact stiffness. We have shown that surface chemistry plays a central role in the mechanochemical decomposition of an industrially important lubricant additive. The differences between the three ferrous surfaces can be rationalised through parameters from the Bell model. Future simulations could consider the impact of heterogeneous surfaces, such as steel on mechanochemical reactions. Experiments could consider using more controllable surfaces, such as specific iron oxides, for optimal comparison with molecular simulations of nanoscale contacts.