Electrochemical Characteristics of Cathodically Protected 2205 Duplex Stainless Steel in Saline Environment

Abstract

This study focuses on the electrochemical behavior of 2205 duplex stainless steel in 1 and 3.5% NaCl solutions using impressed current from external source. Simulated saline soil solutions of 1 and 3.5% NaCl were used as electrolytes. 10 × 10 mm specimens of 2205 duplex stainless steel were cold-mounted except for the exposed surface area of 10 mm2. Electrochemical corrosion measurements (open-circuit potential, polarization and chronoamperometry) were carried out using the electrochemical cell. All the measurements were conducted at room temperature (± 25°C). Characterization of the as-received 2205 duplex stainless steel before and after corrosion test works was conducted using SEM and optical microscope. Open-circuit potential was conducted on 2205 duplex stainless steel specimens to measure the free potential with respect to the reference electrode when no current was applied. Chronoamperometry measurements were conducted to study the current response with time when potentials of − 1.3, − 0.8 and − 0.3 V and − 1.2, − 1.4 and − 1.6 V were applied to 2205 duplex stainless steel. The results obtained have shown that 2205 duplex stainless steel immersed in 1% NaCl solution stabilized at higher potentials of 0.7 V, whereas when immersed in 3.5% NaCl solution it stabilized at lower potentials of 0.1 V signifying that 2205 duplex stainless steel in 3.5% NaCl solution has higher tendency to corrode in comparison with when immersed in 1% NaCl solution. High corrosion rates were observed for 2205 duplex stainless steel in 3.5% NaCl than in 1% NaCl. Increasing the concentration of NaCl increased the corrosion current densities (Icorr) and decreased the corrosion resistance. Furthermore, applying a more negative potential produced high current densities with time which accelerated the pitting corrosion on the surface of 2205 duplex stainless steel.