Explains AC induction on pipelines near power lines, how AC concentrates at coating holidays, and how mitigation provides a controlled grounding path.
A complete impressed current CP circuit showing electron flow in metal, ionic current in soil, anode discharge, and cathodic protection current pickup on the structure.
A visual explanation of oxygen depletion near the steel surface and why potentials shift more negative.
Shows protection/current density decreasing with distance from a CP connection and how coating quality affects attenuation and criteria compliance.
Shows how ON potentials include IR drop and how instant-OFF approximates polarized potential by removing IR drop (soil voltage gradient).
A before/after visual showing native vs polarized pipe-to-soil potentials (vs CSE) and how cathodic polarization reduces anodic metal loss.
Shows how reference electrode placement affects ON readings due to soil voltage gradients and why instant-OFF reduces IR error regardless of placement.
Shows how stray DC current is picked up by an affected structure and corrosion occurs where current leaves the structure; mitigation uses a drain bond return path.
A steel surface with anodic (metal loss) and cathodic (reduction) reaction sites, showing electron flow in metal and ionic movement in the electrolyte.