Subsea oil and gas
pipelines are frequently constructed by joining concrete-coated segments
together. During construction, concrete-coated pipe may sit for six months to
several years before installation. Capital spares are often ordered at the same
time as the initial pipes but with a designed preservation life measured in
decades of idle time. To ensure that these capital spares do not deteriorate
prematurely, Cortec® shares several technologies and tips for preserving
concrete-coated pipes from corrosion.
Challenges
of Protecting Concrete-Coated Spares
Subsea pipe spares are
often stored near the coast due to material handling difficulties. An
incredibly long storage period and an aggressive environment combine to pose a
frequently overlooked risk for long-term integrity. Although the concrete
coating will initially protect the outside of each steel pipe segment, the
concrete will absorb moisture, chlorides, and carbon dioxide over time,
eventually leading to corrosion. Extreme temperature swings and sporadic
inspection intervals can exacerbate the problem. To complicate matters, the
concrete coating makes it difficult to access and treat the OD (outer diameter)
of the steel pipe.
Migrating
Corrosion Inhibitors to the Rescue
Migrating Corrosion
Inhibitor™ (MCI®) Technology is typically used to protect reinforcing metals
embedded in concrete because of its ability to travel through concrete pores to
reach the surface of the underlying metal. The same mechanism makes MCI®
suitable for protecting the metal pipe OD of concrete-coated pipe. Migrating
Corrosion Inhibitors applied to the outside of the concrete pipe can gradually
migrate as much as several inches into the concrete to form a protective
anticorrosive molecular layer on the steel OD.