Evaluating the Electrochemical Behavior of Ni Free Lean Duplex Stainless Steels in Simulated Body Fluid

This study investigates the electrochemical performance of three in-house developed Ni free lean duplex stainless steel alloys was investigated at 20 and 37 °C after different immersion times (1, 12, 24 h) in simulated body fluid (SBF) and results were compared with that of conventional 304 SS alloy. The objective was to develop cost effective SS with comparable properties to that of 304 SS in SBF solution. SEM analysis confirmed that the designed alloys have a dual microstructure, composed of ferrite and austenite phases. Different electrochemical techniques were employed to quantify corrosion performance of the alloys in terms of pitting potential (E_pit), passive current density (i_pass), and charge transfer resistance (R_ct), respectively. Among the designed alloys, alloy 2 and 3 exhibited excellent corrosion resistance in SBF comparable to that of 304 SS. E_pit values at 37 °C were found to be; 236 mV_SCE for 304 > 235 mV_SCE for alloy 2 > 225 mV_SCE for alloy 3 > 198 mV_SCE for alloy. While at 20 °C/1 hr. immersion, pitting potentials were; 357 mV_SCE > 331 mV_SCE > 324 mV_SCE > 167 mV_SCE for alloys 304, alloy 2, alloy 3 and alloy 1, respectively.