FBE coatings have been in use for more than 40 years and are often thought of as an established and unchanging technology. Is this true? No, it couldn’t be further from the truth. FBE coatings today are substantially different from previous iterations.
Environmental conditions into which FBE coatings are placed and performance expectations have changed over time, often the severity has increased and the design life has been extended, sometimes as much as 100 years.
FBE Over The Years
FBE – fusion bonded epoxy – is a one-part, heat curable, thermosetting epoxy resin powder coating system that uses the heat in the product (often a pipe/pup/spool) to melt and adhere to the prepared metal surface. The resultant finish is smooth, tough, abrasion resistant and protects against many types of chemicals. This combination of properties make FBE a go-to choice for many environments and has been used extensively as a pipe coating solution for water, gas and oil transmission pipelines since the 1960’s.
Corrosion costs associated with steel structures are significant, especially in developed countries and so, selection of the most economically effective solution for mitigating the effects of corrosion is often a critical design decision.
The on-going protection of pipelines, valves and fittings ensuring long-term operation with minimal to no maintenance is extremely important. FBE as a coating solution represents a small fraction of the overall cost of a pipeline system. Consequently FBE coatings form the cornerstone of corrosion protection in many gas, oil and water treatment companies across the globe.
External Pipe Coating
When selecting the optimal external pipe coating solution there are a number of factors to consider:
- Physical and Chemical stability
- The effects of soil stress and how this can be combated
- Resistance to impact damage and overall adhesion
- Resistance to cathodic disbondment
FBE’s perform well in all situations where these are factors of influence. 3M first introduced FBE coatings for pipelines in 1960. Typically thickness was 300 – 450 µm (12 – 18 mils). In an effort to increase performance and design life, pipeline owners occasionally specified thicknesses of up to 1000 µm (40 mils). This level of thickness improves both high temperature cathodic protection and damage resistance.
Generally speaking FBE coatings often prove to be an excellent choice when excellent corrosion protection is required when aggregate backfill is used and the operating temperature is below 65oc (150of). When the environmental conditions are more demanding then, a dual or even a 3-layer solution is often the answer. These types of systems will extend the already excellent impact resistance and can improve on temperature resistance too.
FBE coating systems today are employed extensively because of the outstanding levels of adhesion and chemical resistance. Indeed sub-sea pipelines in some cases are protected with FBE coatings, pipelines over rocky mountains, through deserts and even in the artic are known to be FBE coated for protection. FBE coatings are the ideal solution when total damage control and cost of repair are accounted for.
The application process is a fairly straightforward process, requiring technical expertise and equipment, involving blast cleaning, heating and either dip or spray application of the powder coating materials. As an Eco-Friendly solution FBE coatings are often powder based and so have zero VOC’s.
FBE as a Multi-Layer Solution
2-layer FBE systems use a top-coat over the FBE, typically deposited during the melt-flow stage. The result is a 2-layer system with a strong bond. A 2-layer system offers:
- Improved impact resistance – the two layers act as an impact energy absorber
- Gouge resistance – rugged terrain and sharp backfill can sometimes cut through the initial FBE layer, the second layer adding thickness and so protection
- High-friction surface coating – a rough, high friction surface will help in reducing the potential for slippage
- High temperature performance – dual layer systems enable the FBE to be operated at a higher temperature, as high as 110oc (230of) which improves dramatically the cathodic disbondment performance
- UV resistance – FBE coatings develop a natural ‘chalk’ layer when exposed to UV and humidity. This isn’t necessarily a problem until the environmental conditions remove the ‘chalk’ layer and the process starts over again
3-layer FBE is a well-established solution for pipeline protection. High internal strength and excellent bond strength where cathodic protection is used make it a very user-friendly solution with FBE as the primary layer.
3-layer systems came from the European logic that high electrical resistance coatings combined with good mechanical properties were necessary to withstand the inevitable handling and constriction damage. The track record in Europe at least has been very good and extend the operating temperature range to 120oc (250of) where highly-crosslinked novolac-epoxy primers are used.
FBE as a Pipe Lining
For the majority of applications the optimal performance of the FBE is achieved at 400 µm (16 mils) and above. The single biggest advantage of FBE is that this kind of thickness can be achieved in a single operation.
There are a wide variety of applications where FBE has been applied as the corrosion protection coating system. Some notable examples;
- Desalination plants and gas transmission pipelines in Australia and the Middle East
- High-sand content seawater cooling pipework
- Seawater handling valves and pipework for the US Trident Submarine program
- Protection of downhole pipework exposed to H2S and CO2
There are other advantages too in addition to the corrosion protection provided;
- The flow characteristics of the pipework are improved thereby reducing energy requirements
- Protection of the pipework at installation
- Corrosion protection during storage
- Ease of pipeline cleaning and hydrostatic testing
- Cavitaion protection
- Drinking Water Inspectorate (DWI) and National Sanitation Foundation (NSF) approvals for use in potable water solutions
Clients and those specifying the FBE coatings are best advised to ‘police’ the applicator to prevent questionable practices and ensure high quality. When contracting an applicator the client is advised to ask for a Project Quality Plan (PQP) and Inspection Test Plan (ITP), in addition to arranging a site visit where possible during the application process to conduct an external audit.
At Northpoint this service is offered with every quotation as an optional extra and is often included in the scope of the service purchased. This allows our team to work closely with each client to ensure that you understand what is being offered and what has been purchased, whilst Northpoint gains a comprehensive understanding of the extent of the customer requirements.
Contact our team to discuss your requirements.
[Source Data – FBE a Foundation for Pipeline Corrosion Coatings, 3M, Austin TX]
Blog Author – Philip Dawson, Technical Advisor