Effective Preservation Strategies for Concrete-Coated Subsea Pipelines

Concrete-coated subsea oil and gas pipelines are constructed by joining concrete-coated segments. These segments can sit for months or even years before installation. Capital spares, often ordered alongside the initial pipes, are designed to endure decades of idle time. To prevent premature deterioration, Cortec® offers essential technologies and tips for preserving these concrete-coated pipes from corrosion.

Challenges in Protecting Concrete-Coated Spares

Subsea pipe spares are typically stored near the coast, facing long storage periods and aggressive environments. While concrete coatings initially protect the steel pipes, they absorb moisture, chlorides, and carbon dioxide over time, leading to corrosion. Extreme temperature fluctuations and infrequent inspections exacerbate the problem. Additionally, the concrete coating hinders access to the outer diameter (OD) of the steel pipe, complicating preservation efforts.

Migrating Corrosion Inhibitors (MCIs) for Effective Protection

Migrating Corrosion Inhibitor™ (MCI®) Technology, designed to protect reinforcing metals in concrete, is ideal for preserving the metal pipe OD of concrete-coated pipes. MCIs travel through concrete pores, forming a protective anticorrosive molecular layer on the steel OD. Applying MCIs to the concrete surface allows them to migrate several inches into the concrete, providing long-term protection.

Timely Preservation of Capital Spares

Preservation of spare concrete-coated pipes should start immediately to prevent moisture and chloride intrusion. Delayed preservation can result in extensive rust removal and cleaning. Neglecting preservation can lead to severe corrosion, compromising the pipe segments and lead to new unplanned purchases, defeating the purpose of maintaining capital spares.

Protecting the Outer Diameter

Once the pipe’s integrity is confirmed and surfaces are clean, treat the concrete surface with MCI®-2020, a high-concentration Migrating Corrosion Inhibitor. For added protection, apply a water repellent to block additional moisture and chlorides. Alternatively, use MCI®-2018, a 100% silane water repellent containing MCIs, either alone or with MCI®-2020 for maximum protection. Both products meet ANSI/NSF Standard 61 for use in drinking water systems, making them suitable for pipelines in environmentally protected waters.

Safeguarding Pipe Ends and Inner Diameter

For uncoated ends of subsea pipes, apply MCI® CorShield®, a water-based removable coating that protects exposed metal in outdoor environments. The coating cures to a soft, non-tacky film, which hardens over time. If needed, the coating can be removed with an alkaline cleaner before installation.

To protect the inner diameter (ID) of pipeline segments, fog them with CorroLogic® Fogging Fluid VpCI®-339. This fluid forms a protective molecular layer that remains as long as the voids stay closed. Seal the pipe ends with MilCorr® VpCI® Shrink Film, a corrosion-inhibiting heavy-duty plastic, to keep debris out and ensure the protection remains effective.

Keeping Capital Spares Ready

Despite the unpredictable need for installing concrete-coated pipe spares, maintaining their readiness is crucial for emergency or routine replacements. Proper preservation ensures these pipeline segments are ready for use on short notice, helping oil and gas companies maintain operational efficiency and safety.