The SCC Of 13Cr And Super 13Cr Stainless Steel In CO₂-saturated CaCl₂ Completion Brine

The stress corrosion crack (SCC) behavior of 13Cr and super13Cr in CO2-saturated CaCl₂ brine was investigated by four-point bend, U-bend test, surface analysis techniques and electrochemical measurements The effects of temperature, dissolved O2, acetic acid and different kind of inhibitor on SCC were considered in elastic zone; and the effects of temperature, brine concentration and completion fluid additive were considered in non–elastic zone.The results for 13Cr stainless steel showed that in non-elastic zone 33% CaCl₂ brine with no deoxidization, 13Cr stainless steel mainly suffered general corrosion and pitting corrosion both at 100℃and 150℃; however, in 33% CaCl₂ brine with deoxidization, 13Cr stainless steel mainly suffered general corrosion and cracks both at 100℃and 150℃. The adding of acetic acid could accelerate the pitting corrosion with no deoxidization, but the SCC was restrained by the adding of the acetic acid in 33% CaCl₂ brine with deoxidization. Sodium molybdate,Lauric acid,Sodium sulfocyanate can't prevent 13Cr from SCC. Potentiodynamic polarization result in non-elastic zone indicated that the corrosion rate increased with enhance of stress,temperature,brine concentration.The results for super 13Cr stainless steel in non-elastic zone showed that acetic acid increased the stress corrosion cracking susceptivity in 33wt% CaCl₂ under no deaerated condition, but it reduced the SCC susceptivity under deaerated condition. Sodium molybdate,Sodium sulfocyanate can't prevent super13Cr from SCC; the SCC was restrained by the adding of Lauric acid.Potentiodynamic polarization result indicated that the corrosion rate increased with enhance of stress, temperature, brine concentration in elastic zone .The four-point bend experiment show that: under the condition of 33% CaCl₂ brine, 70%YS, 150℃, SCC can occur.