Scanning electrochemical microscopy studies for the characterization of localized corrosion reactions at cut edges of coil-coated steel

The study presents the local distribution of anodic and cathodic sites in a corroding cut edge of coil-coated steel using scanning electrochemical microscopy (SECM). The objective was to analyze the localized corrosion reactions efficiently. Methodologically, platinum and antimony microdiscs were utilized as tips for advanced amperometric/potentiometric operation, allowing for in situ imaging of local changes in electrochemical activity, oxygen concentration, and pH distribution in relation to localized anodes and cathodes. Results indicated that local alkalization and oxygen consumption linked to cathodic activity were detected atop the zinc layer covered with thinner polymeric coating, providing direct evidence of a differential aeration process at the asymmetrical cut edge, alongside the galvanic coupling of aluzinc and steel. Anodic activity, resulting in local acidification, was observed at the other aluzinc layer throughout all exposure durations.