by Aneece Yousif
Today, the oil and gas industry is pushing the limits of pipeline life expectancy. With greater government regulation and scrutiny, it is critical to choose the proper coatings to protect the steel pipe from transit, handling and operation in harsh environments.
Some of the critical performance properties that need improvement are mechanical properties like gouge, impact and flexibility. For example, when pipes are being lowered into the ditch after joint welding and coating, they will experience some flexing. Handling pipes with unloaders or horizontal directional drilling machines may result in significant gouging of the existing coatings. Such applications require the coatings to be very flexible, yet maintain high degree of toughness to resist these mechanical abrasion types of forces that could result in a damaged coating, which poses a risk the pipeline at large.
Market Need for Rugged Coatings
The oil and gas industry has many options for field applied corrosion protection coatings, ranging from field-applied fusion bonded epoxies (FBE), two part liquid epoxies, heat shrink sleeves, tapes and coal tar enamel. More and more the popular choice has become the two-part liquid epoxy coating. Two-part liquid epoxies provide excellent corrosion protection and are easy to apply, but in many cases are less rugged and less flexible than the parent coating.
Field-applied abrasion resistant overcoats (AROs) are also an important tool in the pipeline protection toolbox. Every pipeline job has obstacles to overcome, such as roads or rivers, which may require directional drilling and/or thrust boring. In these cases, an ARO provides extra protection to the parent coating. Factory-applied AROs based on FBE powders are good solutions, but field joints require a rugged and flexible field-applied solution. Moreover, if only a short section of pipe needs additional protection, it may be more cost-effective to use a field applied ARO on a small section. However, many field-applied ARO solutions are difficult to apply and may lack the post-cure flexibility to provide effective corrosion protection.
A Solution for Multiple Applications
Recognizing the need for both rugged corrosion protection coatings and easy-to-apply AROs in the field, 3M has developed a 100 percent solids, two-part liquid coating known as an “abrasion resistant epoxy coating” or AREC.
An AREC is applied with the same ease as traditional two-part epoxy coatings. This makes it an easy way to protect factory-applied FBE coatings for directional drilling, thrust boring, river crossings or similar applications. ARECs are also ideal for the protection of field joints on pipe coated with a factory applied ARO, such as the 3M Scotchkote Fusion Bonded Epoxy Dual Coating System 6352.
With strong adhesion to both metal and FBE, ARECs are also effective for use as a primary corrosion protection coating for directional drilling, rocky terrain or other situations that require a rugged coating. An AREC can also demonstrate improved flexibility (greater than 4 degrees/pipe diameter at temperatures of 70 F/20 C) versus traditional liquid epoxy coatings for applications which require high flexibility after cure. With cathodic disbondment values lower than many traditional epoxy coatings, ARECs can also be used where long-term adhesion is critical.
In summary, ARECs exhibit enhanced cathodic disbondment, adhesion, abrasion resistance, flexibility and impact resistance performance over traditional two-part liquid epoxies. They are also easier to apply than some AROs. With these tools in their toolbox, oil and gas companies can help enhance the life cycle of their pipelines.
Aneece Yousif is product development engineer and Jerry Spartz is product manager for 3M Co.