• Correlation of Pre-Pitting Film Properties with Pit Locations After clustering the pre-pitting arrays, we reconstructed the K-Means labels into a binary image corresponding to the original microscopy frames. A statistical analysis was then conducted to determine whether pits preferentially formed in specific pre-pitting clusters. The results demonstrated a strong correlation: the vast majority of pits appeared within a single cluster, indicating that certain regions of the passive film were more susceptible to breakdown. This finding suggests that the passive film exhibited spatial heterogeneity before pitting initiation, with one region displaying characteristics that made it more prone to localized failure. The details of the statistical analysis are provided in the next section.