In recent years, pipeline leaks in the energy and infrastructure sectors have mandated asset owners to implement more regulated inspection regimes. NACE SP05021 – Pipeline External Corrosion Direct Assessment (ECDA) Methodology was created as a guide to apply the ECDA process and mitigate external corrosion on typical pipeline systems. The collection of reliable and practicable field data is crucial in the success of an ECDA process. Techniques and guidelines to obtain quality data in the field across the indirect inspection processes are presented. Some of the datasets discussed include Close Interval Potential Survey (CIPS) data, Direct Current Voltage Gradient (DCVG) data, soil resistivity data, AC induced corrosion data and pipeline interference data. Continued diligence of the surveying field personnel, as well as adherence to guidelines, will eventually save pipeline owners unnecessary excavation costs while also ensuring locations at the highest risk of external corrosion are rehabilitated and repaired as part of the direct examination.


The External Corrosion Direct Assessment (ECDA) is formally listed as an acceptable integrity assessment method within Subpart O, Part 192 of the code of federal regulations regarding gas transmission pipeline integrity management2. It is a 4 step continuous improvement process to identify and address locations where external corrosion activity has occurred, is occurring or may occur1. In the pre-assessment phase, a comprehensive right-of-way inspection is performed, and pipeline operability data is collected to verify the feasibility of conducting a full ECDA for the pipeline under evaluation. In the indirect inspection phase, the status of cathodic protection and pipeline coating is tested using methods such as Close Interval Potential Surveys (CIPS) and Direct Current Voltage Gradient (DCVG) surveys. In the direct examination phase, specific locations identified in the previous phase are excavated to examine any defects or corrosion and complete any necessary repairs. In the post-assessment phase, a root cause analysis is performed and any future mitigation recommendations are compiled.

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