Cathodic Protection and Bituminous Pipe Coatings

Pipelines combine coatings with cathodic protection (CP). The coating must work well with CP.

Cathodic disbondment

CP can cause coating to lose adhesion around defects. Good adhesion and low water absorption limit disbondment.

Gilsonite effect

Gilsonite’s adhesion and water resistance support coating performance in CP systems.

Testing

Cathodic disbondment tests per relevant standards.

How cathodic protection works

CP makes the pipe the cathode of an electrochemical cell, so any steel exposed at coating defects is protected from corrosion. Coating and CP work together: the coating protects most of the surface, CP protects the holidays.

Why disbondment happens

At coating defects, CP produces alkaline conditions that can attack the coating–steel bond, causing the coating to lift around the defect.

How to minimise it

• Thorough surface preparation and priming
• Coatings with good adhesion and low water permeability
• Correct CP potentials (not over-protected)

Bituminous systems

Gilsonite-modified enamels and mastics combine good adhesion with very low water absorption, supporting long-term performance under CP.

See pipe coating grade gilsonite.