The need for predicting pipeline service life and improving risk assessment relating to corrosion hazards requires establishing a correlation between the corrosion rate (CR) of pipeline steel and its coating condition, cathodic protection (CP) levels and surrounding soil conditions. This paper presents a systematic study of the CR of bare and coated—with and without a dent or holiday defect—X60 pipeline steel in simulated field environments. Three CP scenarios, i.e., no, optimized, and over-protection, were studied to cover a wide range of possible CP conditions that pipeline steel may encounter in the field. Two types of salt solutions (sodium chloride or sodium sulfate) with a variation of temperatures (10 °C, 40 °C, 65 °C) and pH values (2, 7, 12) were investigated to simulate different levels of soil corrosivity. A mathematical model was developed to reveal the impact of various parameters and their interactions on the CR of X60 steel. The coating condition was the most important factor. The individual effects of other factors including temperature, pH, salt composition and CP were not shown to be significant. Instead, the interactions between temperature and salt composition, and particularly the interaction between pH and CP appeared more important in determining the overall CR.

中文翻译：

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预测X60管线钢的外部腐蚀速率：一个数学模型

需要预测管道使用寿命并改善与腐蚀隐患有关的风险评估，需要在管道钢的腐蚀速率（CR）与涂层条件，阴极保护（CP）水平和周围土壤条件之间建立关联。本文对模拟现场环境中的X60管线钢裸露和涂层CR的系统研究进行了研究，无论有无凹痕或节假日缺陷。研究了三种CP方案，即“否”，“优化”和“过度保护”，以涵盖管道钢在现场可能遇到的各种CP可能情况。研究了两种类型的盐溶液（氯化钠或硫酸钠），它们分别具有温度（10°C，40°C，65°C）和pH值（2、7、12）的变化，以模拟不同水平的土壤腐蚀性。建立了一个数学模型，以揭示各种参数及其相互作用对X60钢的CR的影响。涂布条件是最重要的因素。其他因素对个体的影响，包括温度，pH，盐成分和CP均未显示出显着性。取而代之的是，温度和盐成分之间的相互作用，尤其是pH和CP之间的相互作用似乎在确定总体CR方面更为重要。