Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


External Corrosion Direct Assessment

Last updated: April 15, 2019

What Does External Corrosion Direct Assessment Mean?

External corrosion direct assessment (ECDA) refers to a structured process done in four phases. ECDA improves safety of pipelines through assessing and reducing the impact of external corrosion on pipeline integrity. This process prevents corrosion defects proactively from growing to a size that may ultimately hampers a pipeline’s structural integrity by:

  • Locating and addressing corrosion activity
  • Fixing corrosion defects
  • Removing the causes of corrosion

ECDA cannot be successfully assessed on all pipelines. Therefore, other assessment methods precautions should be taken when selecting ECDA techniques.


Corrosionpedia Explains External Corrosion Direct Assessment

ECDA is a continuous process to improve pipeline safety and monitor external corrosion. Through using ECDAs, pipeline operators or owners can identify and address locations where corrosion has occurred or has the potential to occur.

Since buried pipelines are out of sight, it is a key concern for monitoring the integrity of this pipeline to many manufacturers and process engineers. So a comprehensive system needs to develop to the continuous evaluation of the buried structure’s condition. This system is known as ECDA. ECDA involves the following four steps:

  • Pre-assessment: In this step, the following is done:
    • Collect historic and current data to determine whether ECDA is feasible
    • Define ECDA regions
    • Select indirect inspection tools
  • Indirect inspection: In this step, above-ground inspections are done to identify and define the severity of coating faults, other anomalies and areas where corrosion activity may have occurred or may be occurring.
  • Direct examination: includes analyses of indirect inspection data to select sites for excavations and pipe surface evaluations. The following is also done:
    • Evaluation of pipeline coating performance
    • Corrosion defect repairs
    • Mitigation of corrosion protection faults
  • Post-assessment: In this step, analyses of data are collected from the previous three steps to assess the effectiveness of the ECDA process and determine reassessment intervals.

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