Anti-Corrosion Treatment for Welded Flanges in Buried Pipelines

Anti-Corrosion Treatment for Welded Flanges in Buried Pipelines

1. Surface Preparation

• Thoroughly clean the flange and weld area to remove rust, scale, oil, and dirt.

• Use abrasive blasting (e.g., sandblasting) to achieve a clean, roughened surface for better coating adhesion.

• Inspect and repair any weld defects before coating.

2. Coating Application

• Primer Coating: Apply an anti-corrosion primer designed for underground environments, usually epoxy-based or zinc-rich primers to prevent metal oxidation.

• Intermediate Coating: Apply a protective layer, often an epoxy or polyurethane, to enhance corrosion resistance and provide barrier protection.

• Topcoat: For additional mechanical protection, apply a tough, abrasion-resistant outer coating such as polyethylene or polypropylene wrapping or heat-shrinkable sleeves.

3. Cathodic Protection

• Use cathodic protection systems (impressed current or sacrificial anodes) to reduce electrochemical corrosion of the flange and pipeline steel.

• Ensure proper electrical continuity and monitoring of protection effectiveness.

4. Sealing and Joint Protection

• Seal weld seams, bolt holes, and flange faces with compatible corrosion-resistant sealants or tapes.

• Use flange gaskets and bolt coatings that resist corrosion and moisture ingress.

5. Inspection and Testing

• Perform holiday testing (spark or voltage test) to detect coating defects or pinholes after application.

• Conduct adhesion testing to verify coating bonding strength.

• Inspect cathodic protection system function regularly.

6. Handling and Backfilling

• Protect coated flanges from mechanical damage during handling, transportation, and installation.

• Use proper backfill materials (clean sand or fine soil) free of sharp stones to avoid coating damage.

• Ensure proper trench conditions to minimize mechanical stress on the coating.

Summary

Anti-corrosion treatment for welded flanges in buried pipelines involves thorough surface cleaning, multi-layer protective coatings, cathodic protection, sealing of joints, and careful inspection. Proper handling and backfilling further ensure long-term corrosion resistance and pipeline integrity.