INTRODUCTION
ABSTRACT: In case it is inconvenient to interrupt power supply or there exists stray current, the cathodic protection test probe can be applied to evaluate the efficiency of the cathodic protection system. The measurement accuracy of the test probe largely depends on its structure, and is studied extensively in this work, including the porous tip’s porosity and aperture, the coupons’ geometry and distance, as well as the type of the built-in reference electrode and electrolyte. Both laboratory experiments and field tests are carried out, showing that the designed cathodic protection test probe performs well in measuring the polarized potential and the native potential.
Cathodic protection, as an economical and effective method in preventing buried steel pipes from corrosion, has been widely used in the world. Besides, this method requires all CP stations along the pipe, together with ground protection and sacrificial anodes connected to the pipe, to be switched off simultaneously, and this makes the whole measuring system very complex and hard to be realized in the projects.3~5 Nowadays, with the rapid development of infrastructures like electrified railways and high-voltage transmission lines, the phenomenon of stray current becomes very common, and under this situation how to obtain the accurate CP polarization potential becomes very important. In the recent years, an innovative CP polarization measuring technology – test probe, has drawn more and more attentions because of its unique advantages. Test probe is a further development of coupons, in which coupons and reference electrode are assembled inside an insulated shell. The effect of stray current can be eliminated through reasonable structure design, so that the accurate coupon polarization potential can be measured. Although some related studies have been available, most of them are still at initial stages and only a few products in the market can be used.