CREVICE CORROSION SUSCEPTIBILITY OF ALLOY 22 IN FLUORIDE AND CHLORIDE CONTAINING ENVIRONMENTS

摘要

Alloy 22 (N06022) is highly resistant to crevice corrosion in pure chloride (Cl~-)solutions. Little research has been conducted to explore the resistance of this alloy to other halides such as fluoride (F~-) and bromide (Br~-).Even less information is available exploring the behavior of localized corrosion for Alloy 22 in mixtures of the halide ions. Standard electrochemical tests such as polarization resistance andcyclic potentiodynamic polarization (CPP), were conducted to explore the resistance to corrosion of Alloy 22 in deaerated aqueous solutions of 1 M NaCl, 1 M NaF and 0.5 M NaCl + 0.5 M NaF solutions at 60 deg C and 90 deg C. Results show that the general corrosion rate was the lowest in the mixed halide solution and the highest in the pure fluoride solution. Alloy 22 was not susceptible to localized corrosion in the pure fluoride solution. In 1 M NaCl solution, Alloy 22 was susceptible to crevice corrosion at 90 deg C. In the mixed halide solution Alloy 22 was susceptible to crevice corrosion both at 60 deg C and 90 deg C.