Fusion bonded epoxy piling coating is designed for corrosion protection of underground steel pipe, fabrications and reinforcing steel. One of the reasons why it’s a premier coating option is its unique properties. It’s capable of operating in ranges from -100° up to 230°F depending on which grade is being used, the soil type, moisture content, thickness, temperature and other conditions.
Advancements in Technology Lead to Additional Applications
Fusion bonded epoxy piling coating has been one of the premier coatings of choice on pipelines for many years due to its durability, corrosion protection properties and ease of application. Starting in the mid 1970s, it was used on the girth weld area as a field joint coating, and since that time, millions of girth welds have been coated utilizing this product.
In the mid 1980s, fusion bonded epoxy piling coating was used to coat induction bends, flanges, valves and other fittings used in pipeline systems, allowing companies to have a high quality corrosion protection coating from start to finish on their pipelines. Technological advances in the application techniques allows for a low cost, high production process for battling corrosion on the weld areas of pipelines.
How Fusion Bonded Epoxy Piling Coating is Applied
The protective fusion bonded epoxy piling coating is applied by electrostatic spraying. Surface preparation techniques are usually performed by abrasive blast cleaning, grinding and chemical washing prior to coating application.
The fusion bonded powder coating is cured before visible oxidation occurs. Then, it usually undergoes thickness measurements and bend testing, in order to ensure it conforms to the requirements for film thickness, flexibility and continuity, impact resistance, chemical composition and corrosion resistance.
As a thermoset polymer coating, the fusion bonded epoxy piling coating falls under the category of ‘protective coatings’ in paints and coating nomenclature. The name ‘fusion-bond epoxy’ is due to resin cross-linking and the application method, which is different from a conventional paint.
The resin and hardener components in the dry powder fusion bonded epoxy piling coating stock remain unreactive at normal storage conditions. At typical coating application temperatures, the contents of the powder melt and transform to a liquid form.
The liquid fusion bonded epoxy piling coating film wets and flows onto the steel surface on which it is applied, and it soon becomes a solid coating by chemical cross-linking, assisted by heat. This process is known as “fusion bonded”. The chemical cross-linking reaction taking place in this case is irreversible. Once the curing takes place, the coating cannot be returned to its original form. Application of further heating will not “melt” the coating, and thus it is known as a “thermoset” coating.
Application in Three Stages
Regardless of the shape and type of steel surface to be coated, the fusion bonded epoxy piling coating application has three essential stages:
- Thoroughly cleaning the steel surface
- Cleaned metal is heated to the recommended application temperature
- The actual application and curing stage
The advantage of coating pipe and rebar is that their round shape allows continuous linear application of the fusion bonded epoxy piling coating over the exterior surface, while the parts are moved in a conveyor, ensuring high throughput. On fittings and other irregular shaped areas, the coating is applied by manual spray guns. Another method of application is known as the “fluid-dip” process, in which the heated components are dipped in a fluidized powder bed.
Wide Range of Uses
For nearly 50 years, fusion bond epoxy coating has been used for a wide variety of corrosion applications. While not recommended as a protective coating in a sewer application, fusion bonded epoxy affords excellent protection in various water and salt-water applications. It has certification for use in potable water and FDA certification for use in food handling applications.