This observation represents the main outcome of this work, enabling reliable predictions about the locations where pits are most likely to appear based solely on clustering of the evolution of normalized intensities during passive film formation. While not all blue-clustered areas will develop into pitting sites, it can be concluded with 100 % accuracy that white-clustered areas in Fig. and all other sets of data available in SI are not susceptible to pitting corrosion. At this stage, the conclusion remains purely phenomenological and calls for a physically grounded explanation, which will be provided in the next section. In these simulations, we first calculated the total charge from current vs. time curves recorded during Period 1 across the entire dataset and plotted it as a function of averaged normalized reflectivity over the whole surface at the end of Period 1, shown as dots in Fig. . Using Faraday's law, we determined the total thickness of the passive layer, assuming a 1:1 thickness ratio for Cr 2 O 3 and Fe 2 O 3 during SS oxidation. Simultaneously, Fresnel's law was applied to calculate the thickness of the Cr 2 O 3 /Fe 2 O 3 passive layer based on normalized intensity values. Details of these calculations are provided in the SI.