The 316L-grade SS plates provided by Aperam industry (France) were cut into rectangles, each measuring approximately 10 mm by 10 mm. The composition and microstructure of the sample were identical with those described in . The sample contains, in addition to Fe, approximately 17% Cr, 10% Ni, 10% Mo and some trace elements like Cu, Mn, Si etc. The cut samples were subjected to a series of progressive polishing stages, starting with 320-grit silicon carbide (SiC) and proceeding through 400, 600, and 1200 grit, all of which were cooled with tap water. The samples received their final polish with a 1-micron diamond suspension applied to a Presi TM cloth, resulting in a mirror-smooth surface finish. AFM measurements revealed a surface roughness of around 10-20 nm, with further details provided in the following section (SI-2). The sample was subsequently cleaned with ethanol and deionized water, gently dried with argon, and then placed in the opto-electrochemical cell. Importanly, the surface of the samples exhibited scratches and inclusions after polishing, visible as dark contrasted spots in optical images at 𝑡=0 s, prior to pit initiation; however, these areas did not serve as initiation sites for pits (vide infra). All experiments were conducted in aqueous solutions of 5 mM-100 mM NaCl (analytical grade, VWR Prolabo), prepared using water purified by Millipore TM system (18 MOhm×cm).