Alloy 22, a nickel based alloy rich in chromium and molybdenum, shows an outstanding corrosion resistance in
most environments. Studies carried out in chloride solutions under aggressive environmental conditions, reported
crevice corrosion behavior of this alloy and also inhibition effect of several oxyanions, such as nitrate, sulfate,
carbonate and bicarbonate. Since there is little information regarding phosphate effect, the objective of this work
is to study its effect on the corrosion behavior of Alloy 22.
Electrochemical tests were performed to study uniform and localized corrosion of Alloy 22 in deaerated aqueous
solution of 1M NaCl and 1M NaCl with different phosphate additions at 90oC and pH near neutral. The anodic
films obtained were studied by SEM/EDS. Comparison of the results indicates that the passivity potential range
depend on phosphate presence and might be related with the incorporation of the anion in the passive film.
Results of the tests performed with PCA specimens showed a strong inhibitory effect of phosphate ions on
chloride induced crevice corrosion of Alloy 22.
Keywords: Localized corrosion, N06022, repassivation potential, inhibition, phosphates