SUSCEPTIBILITY OF IRON-BASED ALLOYS TO LOCALIZED (PITTING) CORROSION

Localized corrosion, particularly pitting corrosion, represents one of the most critical degradation mechanisms affecting iron-based alloys. Unlike uniform corrosion, pitting leads to the formation of small, deep cavities that can cause catastrophic failure with minimal overall material loss. This paper investigates the susceptibility of iron-based alloys—including carbon steels, low-alloy steels, and stainless steels—to pitting corrosion. The study explores the influence of environmental factors such as chloride concentration, pH, and temperature, as well as metallurgical parameters including microstructure, alloying composition, and surface condition. Experimental electrochemical testing methods, including potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), are analyzed alongside microscopic characterization techniques such as scanning electron microscopy (SEM). The results demonstrate that alloying elements such as chromium, molybdenum, and nickel significantly improve resistance to pitting by stabilizing passive films. However, defects in the passive layer, inclusions, and aggressive ions can initiate pit formation. The study concludes with recommendations for improving corrosion resistance through alloy design, surface treatment, and environmental control strategies [1].