Alternating current (AC) techniques are a family of non-destructive pipeline inspection methods used to detect corrosion, coating defects, and structural anomalies.

Alternating current (AC) techniques are a family of non-destructive pipeline inspection methods used to detect corrosion, coating defects, and structural anomalies in buried pipelines — without requiring shutdowns or depressurization. These in-service inspection techniques are essential for pipeline integrity management across oil & gas, water, and energy infrastructure.

Key AC techniques include:
• AC Interference Testing — detects metal loss and corrosion from external AC sources near power lines or rail systems.
• AC Voltage Gradient (ACVG) Surveys — locates coating failures by measuring voltage variations along the pipeline.
• AC Corrosion Mapping — creates detailed corrosion maps of the pipeline surface using resistance measurements.
• AC Magnetic Flux Leakage (MFL) Surveys — identifies wall thinning and corrosion through magnetic field anomalies.

AC techniques are frequently used within ECDA (External Corrosion Direct Assessment) programs and can be combined with advanced methods like Current Magnetometry Inspection (CMI) for comprehensive assessment of unpiggable pipelines. Their non-intrusive, aboveground approach makes them ideal for inspecting pipelines in challenging terrain, urban areas, or offshore environments.