Influence of Microstructure on Tendency to Pitting Corrosion of G3 Alloy

The influence of microstructure on the tendency to pitting of G3 alloy used for casing was studied by potentiodynamic scan and modern microscopic analysis methods. The results show that the γ phase was obtained by treatment of 1170 ℃×60 min (water), which made the microstructure homogeneous and thus improved the pitting resistance of G3 alloy. Pitting occured at the grain boundaries, inclusions and matrix precipitates easily. The occluded cells generated at the pitting bottom made Fe, Cr, Ni dissolved and group-like compounds generated.