Metro Stray Current Interference Regularity of Buried Pipeline in Suzhou Area

Continuous potential monitoring in 24 h was carried out on three pipelines interfered by metro in Suzhou area and corrosion inspection coupons were embedded. Fourier transform was used to analyze the potential monitoring data in frequency domain, and the dynamic characteristics of potential interference frequency under metro interference were calculated. A quantitative evaluation method of pipeline corrosion rate was investigated based on the corrosion rates tested by inspection coupons and potential interference frequency of pipeline. The difference of the cathodic protection parameters of pipeline between the peak hours (7:00-9:00) of metro running and 24 h was compared and analyzed. The results showed that the difference of average value of off-potential between peak hours and 24 h was small, which was less than 60 mV and had nothing to do with the pipeline location area. The pipeline potentials had obvious frequency distribution characteristics. The main interference cycles were 0-250 s, in which fluctuation cycles of 0-150 s accounted for more than 80%. The differences of corrosion rate and effective corrosion rate calculated from between 24 h electric quantity data and peak hour electric quantity data were small. The effective corrosion rate of the pipeline in Suzhou area was 1%-30%.