Intergranular Corrosion Resistance of Σ3 Grain Boundaries in Alloy 22

Alloy 22 electrodes crevice corroded under constant current conditions in 5 M NaCl at accumulated damage predominantly in the form of intergranular corrosion. Electron backscatter diffraction was used to determine the relationship between the location of damage and the crystallographic features of the grains and grain boundaries. The alloy possessed an exceptionally high number of "special" grain boundaries, and an intergranular attack was observed on random grain boundaries not exhibiting this special grain boundary character. The high percentage of special boundaries offers one reason for the excellent crevice corrosion resistance of this alloy.