Key observations from Period 1 that drive the further advancement of this work include the following: although surface defects from polishing are visible at initial times (appearing as dark spots in optical image at = 0 s in Fig. ), they are not responsible for pit formation. This is evident from magnified images showing pit emerging from optically homogeneous regions, indicating that imperfections in the dynamically formed passive layer are the primary cause of pit formation. The normalized image at = 0.8 s in Fig. reveals heterogeneities, which can be attributed to these imperfections and linked to the locations of pit formation. In the next section, we delve deeper into this correlation using unsupervised ML approaches.