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首页> 外文期刊>Corrosion Engineering, Science and Technology >Preferential weld corrosion of X65 pipeline steel in flowing brines containing carbon dioxide
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Preferential weld corrosion of X65 pipeline steel in flowing brines containing carbon dioxide

机译：X65管线钢在含二氧化碳的流动盐水中的优先焊接腐蚀

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The aim of this research was to investigate the cause of the severe localised corrosion that sometimes occurs at welds in carbon steel pipelines carrying hydrocarbons and inhibited brines saturated with carbon dioxide. A rotating cylinder electrode apparatus was designed so that electrodes machined from the weld metal, heat affected zone and parent material of welded X65 pipeline steel could be galvanically coupled and tested in high shear stress conditions. The galvanic currents flowing between the weld regions were recorded using zero resistance ammeters, and their self-corrosion rates were found by polarisation resistance measurements. The total corrosion rate of each weld region was obtained from the sum of the self-corrosion and galvanic contributions. In uninhibited conditions, the weld metal and heat affected zone were both cathodic to the parent material, and localised corrosion was prevented. However, when an oilfield corrosion inhibitor was present, a current reversal took place, which resulted in accelerated weld corrosion. Electrochemical impedance spectroscopy showed that the inhibitor film had lower electrical resistance and was less protective on the weld metal than on the parent material. At the highest shear stress, a second current reversal could occur when the inhibitor was removed from all regions of the weld, and there was a return to the original galvanic behaviour. It was concluded that preferential weld corrosion was caused by unstable conditions in which the inhibitor film was selectively disrupted on the weld metal but remained effective on the other weld regions.
机译：这项研究的目的是研究导致严重局部腐蚀的原因，这种腐蚀有时发生在载有碳氢化合物和抑制二氧化碳饱和的盐水的碳钢管道的焊接处。设计了旋转圆柱电极设备，以便可以将由焊接金属，热影响区和焊接的X65管线钢的母材加工而成的电极进行电流耦合，并在高剪切应力条件下进行测试。使用零电阻电流表记录在焊接区域之间流动的电流，并通过极化电阻测量发现其自腐蚀率。每个焊接区域的总腐蚀速率是根据自腐蚀和电流作用的总和得出的。在不受约束的条件下，焊缝金属和热影响区都是母材的阴极，可以防止局部腐蚀。但是，当存在油田缓蚀剂时，会发生电流逆转，从而导致加速的焊接腐蚀。电化学阻抗谱显示，与母材相比，抑制剂膜的电阻更低，对焊接金属的保护性更差。在最高剪切应力下，当从焊缝的所有区域去除抑制剂后，可能会发生第二次电流逆转，并且恢复到原始的电化性能。结论是，优先焊接腐蚀是由不稳定条件引起的，在不稳定条件下，抑制剂膜在焊接金属上被选择性破坏，但在其他焊接区域仍然有效。

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