Passivation Film Characteristics of 2205 Duplex Stainless Steel in Reboiler Tubes Under the Combined Effects of Dissolved Oxygen and Applied Stress

In the normal operational environment, reboiler tubes are exposed to high temperatures, high saline contents, and dissolved oxygen, making them susceptible to stress corrosion cracking (SCC), which can lead to premature failure. To explore the SCC mechanisms in reboiler tubes, C-ring samples were prepared for a series of experiments, which include electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and cyclic voltammetry, to assess the SCC behavior of 2205 duplex stainless steel (DSS). An increase in both dissolved oxygen and applied stress contributes to a reduction in impedance values, facilitating chloride ion transport across the metal–electrolyte interface double layer and subsequently promoting passive film degradation. This degradation significantly impairs the passive film integrity; chloride ions reside at anionic sites in the passivation film's metal oxide. Furthermore, stress-induced dislocations augment the migration of cation vacancies within the passive film/2205DSS matrix, culminating in passive film rupture.