Bimetallic composite pipe consists of a corrosion resistance alloy (CRA) layer for corrosion resistance and carbon steel for mechanical properties, which shows a promising prospect of gathering pipeline with its effective-cost and reliable corrosion resistance. However, the corrosion resistance of composite pipe is determined by the quality of its welding gap. This paper aims to investigate the TIG welding gap corrosion resistance of X52/825 metallurgical clad pipe in H2S/CO2 environment.
Corrosion tests of X52/825 welding gap were performed in a stimulated gas field solution containing both 1 MPa CO2 and 1.5 MPa H2S at 70°C for 720 h in a self-designed high temperature and high pressure autoclave. The anti-stress corrosion cracking (SCC) performance of X52/825 clad pipe ring root welding gap was investigated in both NACE A solution and the stimulant gas field solution by four point bending testing and constant load test. Then the experiments were rerun in XX high sour gas well. In addition, the alloy diffusion and microstructure characteristics of TIG welding gap were analyzed through scanning electron microscopy and energy dispersive X-ray spectroscopy technologies.
The results reveal that the root welding gap is almost not corroded in the stimulant gas field solution, and no micro-cracks were observed by electron microscope. Anti-SCC test results show the root welding gap does not break, indicating a good resistance to environmental-cracking in H2S/CO2 environment. The transition layer can be obviously observed in the root welding zone, and the alloy content of transition layer is diluted. However, the transition layer does not penetrate into the inner of CRA layer, which illustrates its good anti-corrosion performance. Therefore, TIG welding technology can be well used in the welding process of composite pipe.
This paper may provide theoretical reference for manufacturing and application of clad pipe.
Corrigendum: It has come to the attention of the publisher that the article Naiyan Zhang and Dezhi Zeng “Research on TIG welding gap corrosion resistance of X52/825 metallurgical clad pipe in H2S/CO2 environment” published in Anti-Corrosion Methods and Materials incorrectly listed the author order and funding information. The order has now been corrected to Naiyan Zhang and Dezhi Zeng and the acknowledgment not correctly lists all funders of the research.
The authors acknowledge the financial support by the National Natural Science Foundation of China (No. 51374177) and the youth backbone teachers support program of Southwest Petroleum University, and the China Scholarship Council for covering part of the testing costs. Without their support, this work would not have been possible.
Zhang, N. and Zeng, D. (2019), "Research on TIG welding gap corrosion resistance of X52/825 metallurgical clad pipein H2S/CO2 environment", Anti-Corrosion Methods and Materials, Vol. 66 No. 4, pp. 412-417. https://doi.org/10.1108/ACMM-09-2017-1846
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