A novel approach based on Greenwood-Williamson theory for the estimation of tribocorrosive wear

Tribocorrosion is defined as the event involving the synergistic action of mechanical wear and corrosion. It is particularly diffused in engineering fields such as biomedical, transportation and marine. In this regard, the presence of oxygen and oxidizing species coupled with friction boosts the material loss more than the simple sum of both. In any case, that synergy can act positively or negatively, determining in the last occurrence a beneficial effect. The topic is constantly investigated from scientific community. Experimentally speaking, via sophisticated electrochemical techniques like voltammetry and impedance spectroscopy. Numerically, instead, by analytical models, most of them at macroscopic level. Indeed, the massive number of factors affecting tribocorrosion makes the theoretical dissertation complex, pushing the researchers towards empirical formula. In this regard, the work aims to propose a model based on the concept of the real contact area (RCA). More in details, the approach adopts the common theory provided by Greenwood-Williamson, inserted thus into tribocorrosion framework. Consequently, the kinetics of repassivation of oxide layer was also taken into account. Moreover, the topography was updated at each sliding cycle in agreement with the real scenario. Successively, for the validation phase, experimental trials were performed on the coupling stainless steel 316L- alumina immersed into a solution composed of 3.8 % of sodium chloride for three values of sliding velocity. The tribological conditions and the kind of electrolyte were chosen respect to specific marine applications. The in-situ apparatus is equipped with linear reciprocating tribometer and potentiostat, whereas the numerical simulations were conducted by MATLAB R2024b tool. Lastly, the surface analysis was achieved through an optical laser microscope paired with an high performance post- processing software . The results confirmed the relevant impact of frequency on tribocorrosive variables such as potential and current. In addition, the synergy was found to be both positive and negative (antagonistic role). On the whole the modelling was coherent with the tests but future improvements are surely required, trying to yield accurate and universal laws.