Study on Corrosion Behaviors of 120 and 125 ksi Drill Pipes in NACE Solution

The modified 27CrMo steel is turned into the 120 and 125 ksi drill pipes via the heat treatment process.The corrosion properties of the said two drill pipes are compared and analyzed by means of the electrochemical technology test tests, the immersion test and the sulfide stress corrosion test.The results show that the 120 ksi drill pipe develops oval corrosion pits, while the 125 ksi drill pipe develops thin an long corrosion pits the depth of which is two times that of the former, and at the bottom of which corrosive fractures are found.The 120 ksi drill pipe has passed the SSC test as per NACE TM 0177, Method A, Solution D, whereas the 125 ksi drill pipe has fractures in mode of intergranular fracture, which means that its anti-SSC property is poor.