AC Voltage Gradient (ACVG) is a non-destructive survey technique used to detect and locate coating defects on buried pipelines.

AC Voltage Gradient (ACVG) is a non-destructive survey technique used to detect and locate coating defects on buried pipelines. By applying an alternating current signal to the pipeline and measuring voltage variations along its length, ACVG identifies areas where the protective coating has failed — exposing the pipe steel to corrosion risk.

Coating failures such as holidays, disbondments, and mechanical damage reduce the electrical resistance of the pipeline surface, causing measurable voltage gradient anomalies. ACVG surveys pinpoint these defects, enabling pipeline operators to prioritize excavation, repair, and recoating activities as part of their pipeline integrity management program.

ACVG is commonly used alongside DCVG (Direct Current Voltage Gradient) surveys and integrates into ECDA (External Corrosion Direct Assessment) frameworks. For unpiggable pipelines where inline inspection is not feasible, aboveground coating surveys like ACVG provide essential data for corrosion prevention and risk-based maintenance planning.