Steel catenary risers, subsea flowlines and pipelines that are used to transport oil and gas products are susceptible to corrosion fatigue in environments containing CO₂ or H₂S, termed sweet and sour respectively. Fatigue crack growth rates (FCGRs) in such environments are generally enhanced compared to that in air due to crack tip dissolution or the embrittling effect of ingressed hydrogen generated from the corrosion process. Several factors influence the FCGR including partial pressure of CO₂ or H₂S, pH value, microstructure, temperature and loading frequency. Although there are reports in the literature on the effect of each of the parameters on FCGRs, data on the combined effects, for example, frequency and temperature are not well documented. The work conducted in this study focussed on the effects of temperature and loading frequency on FCGR of X65 pipeline steel welds in sweet and mildly sour environments. The results demonstrate the importance of the selection of the appropriate test temperature and loading frequency in FCGR laboratory tests in order to avoid use of non-conservative or unduly conservative results in engineering critical assessment (ECA). Furthermore, the influence of low concentrations of H₂S and the presence of corrosion inhibitor on FCGRs of carbon steels was investigated. The dominant corrosion processes under specific testing conditions are proposed.

_{用于运输石油和天然气产品的钢悬链线立管、海底输油管和管道在含有 CO 2}或 H ₂ S（分别称为甜酸和酸）的环境中易受腐蚀疲劳的影响。由于裂纹尖端溶解或腐蚀过程中产生的进入氢的脆化效应，这种环境中的疲劳裂纹扩展速率 (FCGR) 通常比空气中的更高。影响 FCGR 的几个因素包括 CO ₂或 H _2的分压S，pH值，微观结构，温度和加载频率。尽管文献中有关于每个参数对 FCGRs 影响的报道，但关于综合影响的数据，例如频率和温度，并没有得到很好的记录。本研究的工作重点是温度和加载频率对甜味和微酸环境中 X65 管线钢焊缝 FCGR 的影响。结果证明了在 FCGR 实验室测试中选择适当的测试温度和加载频率的重要性，以避免在工程关键评估 (ECA) 中使用非保守或过度保守的结果。此外，低浓度 H _2的影响研究了 S 和缓蚀剂对碳钢 FCGRs 的存在。提出了特定测试条件下的主要腐蚀过程。