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Critical Crevice Temperature of 2205 Duplex Stainless Steel in Fe(III)/Fe(II)-Buffered Acidic Chloride Solutions
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DOI：10.1149/1945-7111/ae62b1.png)
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Abstract
En 中文
The critical crevice temperature (CCT) of 2205 duplex stainless steel was evaluated in acidic chloride solutions representative of hydrometallurgical leach liquors (50 g & centerdot;l-1 H2SO4, 0-15 g & centerdot;l-1 Cl-) containing the Fe(III)/Fe(II) redox couple at ratios of 1:10, 1:1, and 1000:1. Conventional electrochemical CCT methods are unreliable in redox-buffered environments. Under potentiostatic control, bulk Fe(II) oxidation dominated the measured current, obscuring the crevice corrosion response. Open-circuit potential (OCP) ramping overestimated CCT by up to 45 degrees C relative to immersion testing. This discrepancy arises from temperature-dependent acceleration of Fe(III)/Fe(II) redox kinetics, which increases exchange current density and reduces mixed-potential sensitivity to localized attack. Immersion testing was therefore required to obtain meaningful CCT values. Within 1-10 g & centerdot;L-1 total Fe, CCT was insensitive to iron concentration at constant Fe(III)/Fe(II) ratio and chloride concentration, indicating that redox buffering-not total oxidant concentration-controls crevice stability. Increasing chloride decreased CCT from 98.7 degrees C to 39.9 degrees C, while increasing Fe(III)/Fe(II) further reduced CCT by 10 degrees C-20 degrees C. At 15 g & centerdot;L-1 Cl- and a 1000:1 ratio, crevice corrosion initiated at room temperature. These results show that redox buffering and chloride jointly destabilize passive films in confined geometries and that electrochemical techniques may misrepresent localized corrosion resistance in hydrometallurgical environments. Electrochemical CCT tests failed in Fe(III)/Fe(II) redox environments.Potentiostatic current was dominated by Fe(II) oxidation.OCP ramping overestimated CCT by up to 45 degrees C.Fe(III)/Fe(II) redox couples significantly reduced CCT of 2205 DSS in chloride solutions.At 15 g & centerdot;L-1 chloride and 1000:1 ratio, crevice corrosion occurred at room temperature.
Keywords:
duplex stainless steel
crevice corrosion temperature
redox-buffered environments
electrochemical techniques
immersion testing
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