Corrosion Evaluation of Recycling Pipe Section from a Subsea Gas Pipeline

Macroscopic analysis, X-ray diffraction (XRD), chemical composition analysis, mechanical property test, metallographic analysis and hardness test were used to investigate the recycling pipe section from a submarine gas transmission pipeline of high frequency resistance welded X70 steel pipe. Based on site environmental conditions, internal corrosion simulation experiments were performed to find the corrosion reasons, and to predict the residual strength and residual lifespan of the pipeline. The results show that the inner-wall of the pipe corroded seriously. According to the calculation, the residual strength was 33.24 MPa and residual lifespan of the pipeline was at least 7.06 years. In addition, some improvements and suggestions are proposed in detail.