Eiffel 101: Coating Options for Steel Pipe

Because steel pipe is subject to oxidation and corrosion, the steel must be protected. One of the most popular and cost-effective ways to protect steel pipe is to coat the pipe in a protective finish. Common coating options include fusion bond epoxy, SynergyTM coating, scotch coating/fletcher coating, and galvanizing. Each of these options varies in their use and application, and different coatings will work better in different environments.

Fusion Bond Epoxy

Fusion body epoxy coating (also known as fusion bonding) is a heat applied powder coating made from epoxy-based resin and hardening agents. Due to the thermosetting properties of the resins, fusion bond epoxy can be bonded electrostatically to steel pipe through a heating process, which makes the coating more effective and longer lasting than if the pipe was simply dipped in the coating. The most efficient application method involves submerging the preheated material in a fluidized bed for a calculated period of time to achieve the desired coating thickness. Both the internal and external surfaces of steel pipe can be treated with fusion bond epoxy.

While fusion bonding is one of the most effective and durable coatings available, it can fail under certain conditions. Fusion bond epoxy coatings work best in mild environments since the coating may break down in extreme temperatures (both if the temperature is too high or too low).

Fusion bonding is commonly used in oil pipelines, sewage treatment facilities, electric power plants, food processing plants and natural gas pipelines. It has NSF-61 certification for use in potable water and FDA certification for use in food handling applications.

Synergy TM Coating

SynergyTM is a multilayer coating system consisting of a thermally activated primer, a crosslinked, thermoplastic elastomer layer, and a polyolefin top layer. These three elements are fused together with heat to create a coating that strongly adheres to steel pipe while protecting against mechanical damage. SynergyTM is impermeable to oxygen and moisture, has a high shear resistance, a low protection cost, and is touted as being durable, reliable and flexible. SynergyTM can be applied to pipes ranging in size from two inches in diameter to 36 inches in diameter.

Scotch Coating/Fletcher Coating

Scotch coating or fletcher coating (known by the brand names Scotchkote and Fletcherkote) is an epoxy powder steel pipe coating created to resist corrosion due to harsh elements, including saltwater, wastewater, petrochemicals, solvents, corrosive gases, bacteria, fungus, soil stress and backfill compaction. The coating also protects steel pipe against extreme temperatures, mechanical damage, compression, wear and abrasion.

Scotch coating is applied through a heat-cured, fusion bonding process, and its thermosetting materials allow for strong adhesion. This coating can be applied to steel pipe in a number of ways, including by a fluidized bed, flocking (air spray) or electrostatic spray.

Scotch coating is widely used in gas transmission, wastewater, potable water, non-potable water and water reclamation applications. Since the 1970s, many major energy and water transmission companies in the US have adopted scotch coatings to protect their steel pipe systems against corrosion.

Galvanizing

Galvanizing is the process of applying a protective zinc coating to steel pipe in order to prevent rusting. The most common application method is hot-dip galvanizing, which deposits a thick layer of zinc iron alloy onto the surface of the pipe. In instances where a thinner layer is needed, galvanizing can also be applied by electrogalvanizing (a process involving electroplating, where a current of electricity is run through the zinc solution with a zinc anode and steel conductor).

Galvanizing protects steel pipe by preventing corrosive substances from reaching the underlying steel. Even if the underlying metal becomes exposed, the pipe will still be protected as long as there is zinc close enough to be electrically coupled. Only after all of the zinc in the immediate area is consumed will localized corrosion of the steel pipe occur.

Galvanized steel pipe is best used where rust is an issue, particularly in pipe systems exposed to water (such as plumbing, water transport and HVAC systems).

To learn more about steel pipe, head over to our blog titled "All About Steel Pipe".

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