Abstract
From corrosion survey of burned pipelines, several interesting results were obtained as follows.
1) Cathodic protection utilizing A. C. stray current:
The underground water pipelines in a certain industrial area were cathodically protected by making use of alternating stray current with simple arrangement which merely comprised driving earth pipes (size: 34mmφ×10m) into ground near the pipelines and connecting them electrically to the pipelines through silicon diodes.
2) Relation between gas-pipe-to-soil potential and current in a certain city:
On the gas pipelines which have the drainage system to electric railway, relation between the pipe-to-soil potential and the line current was examined. The relation curve showed hysteresis for a certain range of line current. This phenomenon was considered to be related to the polarization of pipeline surface.
3) Case of cathodic protection for pipelines in some cities:
These pipelines having tendency of suffering from stray-current corrosion, could not drain the current to electric railway for several reasons, and were too small to apply the expensive impressed-current method. Therefore, the method by earth pipe with low resistance was adopted to get the drainage effect. The result of experiments showed that the better effect of drainage was obtained for the lower resistance of earth pipe and the higher resistance of pipe-surface coating.
