Effect of Applied Voltage on the Reliability of Coating Flaw Detection of Pipe with Different Buried Depths

these limitations, the area potential and earth current (APEC) survey was recently proposed [25]. This method uses 3 reference electrodes. Gas pipelines were usually buried at a constant depth in the soil, but the pipelines in nuclear power plants were buried with different depth and multiple layers. Therefore, detection reliability for coating flaws in nuclear power plants was low and thus detail survey conditions are needed. As described above, three kinds of survey method have an advantage and a disadvantage. Many researchers External corrosion control of buried pipe can be achieved by the combination of barrier coating and cathodic protection. Coating damage and deterioration can be induced by many reasons; damage during handling and laying, enhanced failure at low temperatures, failure during commissioning and operation, disbanding due to inadequate surface cleaning, rock penetration during installation and service etc. This work focused on the effect of survey conditions on the reliability of coating flaw detection of buried pipes. The effects of applied voltage and anode location on the detection reliability of coating flaw of buried pipe in soil with the resistivity of ca . 25.8 k Ω ·cm were discussed. Higher applied voltage increased the detection reliability, regardless of buried depth, but deeper burial depth reduced the reliability. The location of the anode has influenced on the detection reliability. This behaviour may be induced by the variation of current distribution by the applied voltage and buried depth. From the relationship between the applied voltage and reliability, the needed detection potential to get a desire detection reliability can be calculated to get 100% detection reliability using the derived equation.