Advances in Damage-Resistant Coating Technology

Fusion bonded epoxy (FBE) coatings have been used on pipelines as protection against corrosion for over 40 years.  They have been used as a stand-alone product in single layer systems and as a primer in dual layer FBE and three layer polyolefin systems. Pipeline coating systems require physical properties that minimize damage during transit, installation and operation. Damage to the coating leads to higher potential corrosion sites on the metallic surface and could ultimately lead to a decrease in service life.  There are several ways that have been used conventionally to attempt to make a FBE coating more resistant to mechanical damage. In one conventional approach, the thickness of the overall coating is increased to provide added absorption of impact and abrasion. However, as the thickness of the coating increases the flexibility of the coating decreases. Another conventional approach to enhance damage resistance is to add an abrasion resistant overcoat that has a high filler loading to increase abrasion resistance and decrease impact damage. As with the thicker coatings, higher filler loadings can dramatically decrease the flexibility of the FBE coating. Yet another conventional approach to enhance damage resistance is to use a three layer polyolefin coating system.  Unfortunately, when damage does occur in these systems, cathodic shielding may allow corrosion to develop unchecked.  This paper will present a novel coating system that incorporates both damage resistance and flexibility in a system that is not subject to cathodic shielding.