According to overseas papers, the economic injury caused by corrosion is 3∼5% of GNP. As korean industrial structure have highly depended on heavy and chemical industry, the economic injury is supposed to 4∼5% of its GNP. So far, we didn't spend much time to be concentrated on corrosion, even if it is very important in many fields. So that, this paper analyze many factors which lead to corrosion with regard to corrosion circumstance of underground pipeline
This study is intended to examine the theoretical background on the corrosion and protection principle of underground steel pipeline, and is intended to enhance the economic feasibility and efficiency of cathodic protection through comparison, analysis, and verification of numerical analysis results and on-site experiment results by carrying out numerical analysis through exclusive cathodic protection system program in order to investigate proper separation distance between anode holes etc. in case of installing many anodes at the same time, in case of remote anode bed and close anode bed, and in case of installing anode horizontally to and vertically to the protected structure (buried steel pipeline), and by carrying out the real field experiment of underground piping in the similar condition.
The summary of study results is as follows.
(1) In case distance between holes is close, efficiency lowers due to mutual interference with many anode holes, therefore it is necessary to maintain comparatively uniform electric potential by keeping anode holes at intervals of 25 m or over.
(2) It was verified that the distribution of protection potentials was more uniform as separation distance from piping was increased in case of vertically burying anode. And protection with separation of at least 40 m was effective.
(3) According to the results of comparing the cases of vertically and horizontally burying 3 anode holes, the efficiency of protection system could be increased as anode was installed vertically to the piping or the separation distance from the piping was increased.
(4) In case of installing many anode holes, if intervals between holes are narrow, output ampere was decreased because of mutual interference. And as quantity of anode holes was increased, efficiency was decreased. Therefore, it was economical and efficient to keep anode holes at intervals of at least 30 m, and to install 3 holes or below, if possible.