Axial Distance for Protection of Rod-Shaped Auxiliary Anode to Inner Wall of Pipe in Small Diameter

Impressed current cathodic protection was applied to the pipes with four kinds of diameters in which rod-shaped auxiliary anodes were installed. And a self-designed linear reference device was utilized to real-time measure the cathodic protection potentials of points in the interior of the pipes in real sea. And the experimental data were compared with the simulated data calculated by software named Beasy. The results show that in the small diameter pipes the axial protection distance (one way) of the rod-shaped auxiliary anode was shortened with the decrease of pipe diameter. When the pipe diameter was no more than 100 mm, the axial protection distance of the rod-shaped auxiliary anodes was too short to protect the pipe. The protection effects of rod-shaped auxiliary anode to DN200 and DN125 pipes obtained by simulation were similar to the results from real sea experiments. But these two results were quite different when the pipe diameter was no more than 100 mm, which means that in real sea environment small diameter pipe is affected critically by environmental factors.