FBE, 3LPE or 3LPP: Which Pipe Coating Should You Choose?

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Pipe coating systems that are external to pipes help prevent corrosion of steel pipes that occur due to soil, moisture, chemicals, and marine environments. Three main types of such coating systems are fusion bonded epoxy, three layer polyethylene, and three layer polypropylene. Each type offers varying degrees of corrosion protection, mechanical strength, and heat resistance. The fusion bonded epoxy coating is good for its adhesive properties, while the 3 layer polyethylene coating provides both the protection of epoxy and the toughness of polyethylene. Selection of the appropriate coating system is based on temperature of operations, installation, handling considerations, and standards for coatings.

Why Pipe Coating Selection Matters

There are various corrosive threats posed by water, chemicals, salts, and sea water for steel pipes. The external coating ensures that there is protection of the steel surface, while the cathodic protection offers another form of protection against corrosion. Choosing an inappropriate coating would result in the early disbondment, mechanical damage and corrosion under the coating, leading to increased costs of maintenance. The choice of the appropriate coating is determined by two elements. These include temperature of operation and installation. This implies that different pipes are exposed to different temperatures and mechanical stress depending on their application; be it buried pipe, off-shore pipe, and pipes installed using HDD.

What Is FBE Coating?

Fusion bonded epoxy (FBE) is a one-layer thermoset powder coated over heated steel pipes where it melts and fuses chemically to the prepared surface. It is corrosion resistant, adheres well and is compatible with cathodic protection, suitable for pipeline installations in the ground. FBE coatings are available to meet a variety of standards including: ISO 21809-2 and CSA Z245.20; and thicknesses can be chosen depending on the project requirements. But FBE is less impact and abrasion resistant than thicker coating systems. If the installation is particularly challenging, like horizontal directional drilling (HDD), it may be necessary to use an abrasion resistant overcoat or a harder coating system.

What Is 3LPE Coating?

Three-layer polyethylene (3LPE) is an external pipeline coating system that combines corrosion resistance with strong mechanical protection. It consists of a fusion bonded epoxy (FBE) primer, a copolymer adhesive layer, and a polyethylene outer layer. The epoxy protects the steel against corrosion, the adhesive bonds the layers, and the polyethylene resists impact, abrasion, and moisture penetration. This combination makes 3LPE suitable for buried onshore oil, gas, and water pipelines exposed to soil stress and handling damage. The coating system is covered by standards such as ISO 21809-1, DIN 30670, and CSA Z245.21, with thickness and performance requirements determined by project specifications.

Galvanised Pipe Coating: A Lower Cost Alternative

Galvanised coating applies a layer of zinc to steel pipe, most commonly by hot dip galvanising. It protects the steel in two ways. The zinc acts as a physical barrier, and it also protects sacrificially, corroding in preference to the steel at scratches or damaged spots.

Galvanising generally costs less than FBE or three layer systems. It is common on above ground structural piping, scaffolding tube, fencing, and water pipe in non aggressive soil. It is not normally specified for buried oil and gas transmission pipelines, where FBE, 3LPE or 3LPP give much better long term corrosion protection and are the standard specification under ISO 21809.

If your project needs plain carbon steel pipe to be coated or galvanised afterwards, see our range of carbon steel pipes.

Internal Pipe Coating: Why It Is a Separate Decision

Internal pipe coating is specified independently of the external coating. It is driven by the fluid being carried, not by soil or burial conditions.

• Internal FBE, typically 250 to 400 microns, smooths the bore to reduce friction and protects against corrosion from produced water and CO2. Reported flow efficiency and pumping energy savings depend on the line, so ask for project specific data rather than relying on a general figure.
• Cement lining is common for water service.
• PTFE or rubber linings are chosen for chemical compatibility with aggressive process fluids.

Specify the internal and external coating together on the same pipe order. The internal lining has no bearing on the external coating's temperature or mechanical rating, and the reverse is also true. If the line will also be inspected by pigs, check that the internal lining and any weld areas will allow pig passage. Our guide to piggable pipes explains what to look for.

FBE vs 3LPE vs 3LPP: Pipe Coating Selection Guide

The table puts the three main systems side by side. Figures are typical values from the governing standards and industry data. They vary slightly by source and by coating grade, so confirm them against the current standard and your project specification.

Property	FBE	3LPE	3LPP
Layer structure	Single epoxy layer	FBE primer + adhesive + PE	FBE primer + adhesive + PP
Thickness (external)	About 400 to 600 microns	About 1.8 to 3.0 mm	About 2.0 to 4.0 mm
Max continuous temperature	About 80 to 95 degrees C, grade dependent	About 80 degrees C	About 110 degrees C
Short term peak	Higher for modified grades	Grade dependent	Higher still for some grades
Governing standard	ISO 21809-2, CSA Z245.20	ISO 21809-1, DIN 30670, CSA Z245.21	ISO 21809-1, DIN 30678
Mechanical and abrasion resistance	Moderate, brittle under impact	High	Very high, suited to HDD
Typical use	Water pipe, above ground, internal lining	Onshore buried gas and oil, below 80 degrees C	Hot or waxy crude, HDD, deepwater

Which Coating for Which Job?

Project Scenario	Recommended Coating	Why
Onshore buried gas pipeline below 80 degrees C	3LPE	Mechanical protection and soil stress resistance
Onshore buried crude or waxy crude above 80 degrees C	3LPP	Standard 3LPE is limited to about 80 degrees C
HDD installation	3LPP	Better abrasion resistance during pull-through
Offshore or subsea pipeline	3LPE or 3LPP, usually with a concrete weight coat	Mechanical protection and temperature range
Above ground piping	FBE with a paint topcoat	Three layer systems degrade under prolonged UV unless protected
Well casing, external	FBE	Thinner profile and lower soil stress
Water injection or produced water lines	3LPE external with internal FBE lining	Corrosion protection inside and out
Above ground structural or non critical buried piping on a limited budget	Galvanised coating	Lower cost
Maintenance recoating of older coal tar epoxy sections	Coal tar epoxy repair system matched to the existing coating	Compatibility

This is a starting point. The final choice depends on the project specification, such as an operator standard, and on the coating applicator's qualified procedures.