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用常规方法测量地下金属管线的对地电位时,不可避免地包含一个常被忽视或被误解的部分——IR压降,它并不反映腐蚀的电化学过程,所以,在阴极保护情况下,为了确切地衡量保护效果,求得阴极化电位,就必须从测量电位中除去IR压降。为此,文章叙述了IR压降(包括在阴极保护情况下)的测定方法;分析了IR压降的分布规律;介绍了IR压降在判别腐蚀类型和腐蚀程度时的应用;最后,文章重点阐述了辅助电极法,该法是基于设法减小参比电极至金属接地体之间的电阻,从而达到减少IR压降以致于使其小到可以忽略的方法。还给出了辅助电极的结构简图、测试接线图、提高辅助电极法测量准确性的有效措施等。现场的实践证实,在十余种消除IR压降的方法中,辅助电极法是一种工程上简便易行适用的方法。
The conventional method of measuring the earth potential of an underground metal pipeline inevitably involves an often neglected or misleading part of the IR drop, which does not reflect the electrochemical process of corrosion. Therefore, in the case of cathodic protection, In order to accurately measure the effect of protection and to obtain the cathodic potential, it is necessary to remove the IR drop from the measured potential. Therefore, the article describes the determination method of IR pressure drop (including in the case of cathodic protection); analyzes the distribution rule of IR pressure drop; introduces the application of IR pressure drop in distinguishing corrosion type and corrosion degree; finally, An auxiliary electrode method is described which is based on the idea of reducing the resistance between the reference electrode and the metal ground so as to achieve a method of reducing the IR drop so small as to be negligible. Also given the structure of the auxiliary electrode diagram, test wiring diagram, to improve the measurement accuracy of the auxiliary electrode method and other effective measures. Field practice has confirmed that in a dozen ways to eliminate IR drop, the auxiliary electrode method is a simple and easy to apply engineering method.