Microstructure–Electrochemical Correlation of Corrosion Behavior in AISI 316 and Duplex 2205 Stainless Steels in 3.5 wt.% NaCl Solution

Abstract

The increasing demand for corrosion-resistant materials in desalination systems requires a deeper understanding of passive film stability in chloride-rich environments [1]. This study analyzes the microstructure-electrochemical correlation between AISI 316 and duplex 2205 stainless steels in a 3.5 wt.% NaCl solution using microstructural characterization, Vickers microhardness, and electrochemical techniques (OCP, polarization, and EIS). Results show that duplex 2205 exhibits higher hardness due to its ferrite-austenite structure, resulting in enhanced passive film stability. It presents more noble corrosion potentials, lower corrosion current densities, and higher charge-transfer resistance, indicating superior corrosion resistance. In contrast, AISI 316 shows localized degradation after polarization. This improved performance is attributed to the optimized duplex microstructure and the formation of a more stable and protective passive film. These results provide valuable insight into the structure-property relationship governing corrosion resistance, supporting the selection of duplex 2205 for desalination applications.