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Pipelines

Thick-film application, edge coverage and heavy-duty corrosion protection

Pipelines include the internal and external surfaces of metal water, gas and chemical pipelines. Long-term service under pressure and corrosive conditions places stringent requirements on pressure resistance, corrosion protection and adhesion.

Veri Coating offers smooth pure epoxy and heavy-duty pure epoxy powder coatings with GT0 adhesion, more than 1,000 hours of salt-spray resistance and suitability for C2-C4 corrosion-protection levels. Multiple coating passes can be used to achieve film thicknesses of 60-500 um.

Application notes: Pipe fittings should be preheated for degassing, and film thickness, curing and uniform coverage of internal surfaces must be verified.

Typical Powder Coating Challenges for Pipelines

Cathodic Disbondment ResistanceUnder cathodic protection, the coating disbonds outward from a defect.

Cathodic Disbondment Resistance

At coating defects on buried or cathodically protected pipelines, strong alkalinity and electrochemical action can cause adhesion loss and progressive disbondment from the defect edge. Inadequate surface preparation, coating porosity, incomplete cure and poor interfacial water resistance accelerate failure.

Formulation Design

  1. Use a highly crosslinked, low-water-absorption, heavy-duty pure epoxy system to improve adhesion at the metal interface and barrier performance.
  2. Optimise pigments, extenders, the curing system and melt wetting to reduce porosity and stabilise defect edges.

Process Control

  1. Thoroughly degrease and abrasive-blast the steel to the specified cleanliness and surface profile.
  2. Control preheat, film thickness and the cure window to avoid pinholes, undercure and thermal degradation.
  3. Use a repair system compatible with the main coating on welds, cutbacks and field joints.
Validation Focus
  • Cathodic-disbondment radius
  • Holiday detection
  • Adhesion
  • Water absorption/salt-water resistance
Hygienic Safety for Potable-Water PipelinesExtractables or discolouration from the coating may compromise potable-water safety.

Hygienic Safety for Potable-Water Pipelines

Internal coatings for potable-water pipelines remain in long-term contact with drinking water and must control heavy metals, residual monomers and migratable substances. Inadequate raw-material selection, cure or contamination control can cause odour, discolouration, extractables or excessive migration, affecting water quality and compliance.

Formulation Design

  1. Use epoxy resins, curing agents, pigments, extenders and additives that meet the target market's potable-water contact requirements.
  2. Avoid pigments and additives without hygienic assessment, and control extractable and migratable components.

Process Control

  1. Use dedicated production and cleaning controls to prevent cross-contamination.
  2. Complete the specified cure based on part temperature to minimise residual reactants and migratable substances.
  3. Conduct the immersion and migration tests required by the target regulations using the final formulation, film thickness and pipe substrate.
Validation Focus
  • Heavy-metal migration
  • Total organic matter/odour
  • Colour of soak water
  • Hygienic approval testing