Influence Factors of Coupon Instant-Off Testing Method under Dynamic DC Stray Current Interference

Through field test, the influence of factors such as test piece embedding time, instant-off delay time, coupon buried depth, external interference electric field and reference electrode position on the test results of coupon instant-off method was studied. By comparing the test results under different conditions, the influence laws of different factors were obtained. The results showed that the larger the exposed area of the coupon, the longer it took to reach a stable polarization state, and the longer the shallow buried coupon took to reach a stable polarization state. For the test of the instantaneous instant-off potential of the coupon, a reasonable instant-off delay time should be set . Under the current test conditions, the longest time required for the polarization stability of the coupon was 25 h, and the instant-off delay time of 150 ms was reasonable. The current flowing in the soil would generate a ground potential gradient between the coupon and the reference electrode, which would affect the correct reading of the instant-off potential of the coupon. The error caused by the external electric field could be reduced by reducing the distance between the coupon and the reference electrode.