Corrosion Behavior of UNS S32205 Duplex Stainless Steel with Different Austenite Domain Sizes in Aqueous Chloride Solutions

Abstract

This study investigates the role of austenite domain size in governing the electrochemical corrosion behavior of UNS S32205 duplex stainless steel. Specimens with a quantified range of austenite domain sizes were subjected to electrochemical testing in 0.1 - 1.0 M NaCl solutions, complemented by analyses of post-corrosion morphology and surface composition. The results demonstrate that microstructures with finer austenite domains exhibit systematically superior corrosion resistance across all tested conditions. This is evidenced by a higher charge transfer resistance, a lower corrosion current density, and a more stable passive film compared to their coarse-structured counterparts. The enhancement is attributed to accelerated repassivation kinetics and the geometric confinement of corrosive attack within the refined dual-phase network, which effectively suppresses stable pit growth within the less-connected ferrite phase. This work establishes austenite domain size as a master microstructural variable for controlling localized corrosion in 2205 DSS, providing a scientific basis for optimizing the alloy's durability through microstructural refinement strategies during thermo-mechanical processing.