Electrochemical studies using cyclic potentiodynamic polarization (CPP) and electrochemical impedance
spectroscopy (EIS) were performed to determine the corrosion behavior of Alloy 22 (N06022)
in 1M NaCl solutions at various pH values from acidic to neutral at 90ºC. All the tested material was
wrought Mill Annealed (MA). Tests were also performed in NaCl solutions containing weak organic
acids such as oxalic, acetic, citric and picric acids.
Results show that the corrosion rate of Alloy 22 was significantly higher in solutions containing oxalic
acid than in solutions of pure NaCl at the same pH. Citric and Picric acids showed a slightly higher
corrosion rate, and Acetic acid maintained the corrosion rate of pure chloride solutions at the same pH.
Organic acids revealed to be weak inhibitors for crevice corrosion. Higher concentration ratios, compared
to nitrate ions, were needed to completely inhibit crevice corrosion in chloride solutions.
Results are discussed considering acid dissociation constants, buffer capacity and complex formation
constants of the different weak acids.