Seamless X60QOS and X65QOS line pipes are widely used for offshore and onshore Sour Service applications. Sour Service refers to the risk of hydrogen related cracking as Sulfide Stress Cracking (SSC). The International standard (NACE MR0175 / ISO 15156) provides requirements for assessing the resistance to SSC, specifically on how to qualify for use in region 3 of the environmental severity diagram (Figure 1 in paragraph 7.2.1.2 of part 2). It is requested to expose materials in an acid solution saturated by 1 bar of H2S (NACE TM0177 Solution A) and to apply a tensile stress above 80% AYS by means of different methods: uniaxial tensile, C-ring or Four-Points Bend. However, for very sour fields presenting H2S partial pressures much higher than 1 bar, the preservation of the SSC resistance might be questioned and is presently a major concern for the O&G industry.
The present paper is dedicated to the evaluation of the SSC resistance of seamless quenched and tempered X65 grades, including the girth weld in the standard NACE TM0177 Solution A up to 15 bar of H2S partial pressure. Corrosion tests consisted of four-point bend tests performed in autoclave vessels. Different test configurations were investigated as specimen sampling locations through the wall thickness and surface state preparation.

Seamless X60QOS and X65QOS linepipes are widely used for Sour Service offshore and onshore applications. Sour Service refers to the risk of hydrogen related cracking, such as by Sulfide Stress Cracking (SSC). The International standard NACE MR0175 / ISO 15156 provides requirements for assessing the resistance to SSC, specifically on how to qualify for use in region 3 of the environmental severity diagram (Figure 1 in paragraph 7.2.1.2 of part 2). Qualification requires exposing materials in an acid solution saturated by 1 bar of H2S (NACE TM0177 Solution A) and to apply a tensile stress above 80% AYS by means of different methods: uniaxial tensile, C-ring or Four-Point Bend. However, for very sour fields presenting H2S partial pressures much greater than 1 bar, the preservation of the SSC resistance might be questioned and is presently a major concern for the O&G industry.