Offshore components often suffer from corrosion due to exposure to environments such as seawater, produced water, solvents, oxygen, CO2, H2S and other acids and abrasive particles. To protect equipment from degradation, coatings are applied to internal and external surfaces to provide electrical insulation, physical protection and corrosion and/or chemical resistance. Coatings can also provide thermal insulation, anti-slip, color coding, flame-retardant and anti-bio-fouling qualities to a given surface. This GATEKEEPER provides a general overview of the epoxy coatings used in offshore oil and gas service and discusses common causes of premature coating failure as well as factors affect coating quality.
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Epoxy coatings are commonly used in oilfield applications and are favored for their impact and abrasion resistance. Epoxy coatings are organic polymers which are created through chemical reactions between epoxy resins and co-reactants/hardeners/curatives. Epoxies are also thermosets, which means that once hardened or cured they cannot be melted down and reformed. During the process known as &#;curing&#;, terminal epoxy groups and mid-chain alcoholic hydroxyl groups allow for crosslinking to occur. Increasing the number of cross-links or cross-link density in a polymer decreases the mobility of individual polymer strands which causes the liquid polymer to solidify or &#;gel&#;.
Excessive heat will deteriorate chemical bonds within a thermoset and cause it to degrade, discolor, lose ductility, and/or undergo brittle failure. Epoxies are also vulnerable to photo-degradation and may chalk or discolor when exposed to UV rays.
Typically, for a coating to be fit-for-service, the following factors must be considered:
Compatibility with substrate
Ability to accommodate stresses and impacts caused by transportation and installation
Ability to function under expected operating conditions such as temperature, pressure, and chemical environment
Electrical conductivity
Cathodic protection (CP) compatibility
UV resistance
Gas/liquid permeability
In addition to inappropriate coating selection, unexpected environmental changes or events, error during the application process and failure to provide proper maintenance can all cause the failure of an epoxy coating. It is estimated that 60% to 80% of all premature coating failures are caused by inadequate preparation of the substrate surface for application (1).
Improper surface preparation leaves behind contaminants and can cause adhesion failure as well as under-coating corrosion. For example, gas or liquid trapped underneath a coating will expand and cause blisters and delamination during rapid gas decompression. Similar failures also occur when gas or liquid penetrates a coating due to adhesion or permeation issues. Hand and power tool cleaning, blast cleaning and/or solvents are used to clean substrates. Blast cleaning is also used to develop the surface roughness needed to avoid adhesion failure. Depending on the substrate, an anti-oxidation chemical treatment may need to be applied soon after blasting. In addition to performing general blast cleaning, surface irregularities such as weld splatter, weld seams, metal slivers and sharp edges should be removed or smoothed as they are common causes of coating failures. Most end users require inspection of surface profile through visual examination and replica tape prior to proceeding with the application process.
If an epoxy coating requires the substrate to be heated during the application process, the substrate should be uniformly preheated before application of coating. During the spray and cure process, ambient temperature and humidity should also be monitored and kept within acceptable range.
Most epoxies are applied via plural component sprays. There are some unique challenges and potential failure modes associated with this application method. Common issues that occur with spray gun use are clogged spray nozzles, spraying at too high a rate, moving the spray gun too rapidly, utilizing a coating material that is close to reaching its pot life, and off-ratio mixing in plural component sprays. Over application is also a common mistake made with epoxy coating. Though UV tolerance improves with dry film thickness, flexibility decreases and failure inducing residual stresses increase.
Many industries rely on steel pipes, valves, and connections to transport fluids and deliver other critical services. However, corrosion is often a major problem that they will face, which can cause significant damage to pipes and lead to costly repairs and replacements.
Fortunately, there are several methods of protecting pipes from corrosion, including coatings and linings.
Throughout this guide, we&#;ll focus specifically on Fusion Bonded Epoxy (FBE) coating, a highly effective and popular method of protecting pipes from corrosion&#;including what it is, how it works, and when it is needed.
Contact us to discuss your requirements of fusion bonded epoxy coating procedure. Our experienced sales team can help you identify the options that best suit your needs.
What is FBE CoatingFusion Bonded Epoxy (FBE) coating, sometimes referred to as powder coating, is a thermosetting resin coating that&#;s applied to steel pipes and is considered to be the industry standard for industries like oil and gas, water, sewage, and more.
FBE coating gets applied to both the exterior and interior of the pipe and is a highly effective method of protecting the pipe from corrosion.
When is FBE Coating Utilized?FBE coating is needed for pipes that are exposed to harsh environments, like those that come into contact with salt water, chemicals, and other corrosive materials.
It is also used to protect pipes that are buried underground where they are subject to corrosion from soil and moisture.
This type of coating is highly effective in protecting pipes from corrosion, abrasion, and chemical attack, which can cause costly damage and reduce the lifespan of the pipe. FBE coating can also help to improve the flow of fluid through the pipe by reducing friction and turbulence.
In addition to its protective properties, FBE coating is also environmentally friendly and can be applied without emitting any harmful substances. This makes it a popular choice for many industries that prioritize sustainability and environmental stewardship.
How is FBE Coating Applied?The FBE coating process involves applying an electrically charged epoxy powder to the heated pipe, which then melts and fuses to the surface. But before this is done, the pipe surface is cleaned and heated to ensure proper adhesion. In many cases, the pipe will be heated from 350-500° F during this process.
The result is a strong, durable, and uniform coating that provides superior corrosion resistance and prevents the pipe from deteriorating over time.
The fusion bonding that takes place throughout this process means the coating is irreversible and cannot return to its original form of powder, even upon further heating of the pipe. This means the coating will not melt even under extreme conditions.
FBE Coating AlternativesThere are some alternatives to steel pipe coating aside from FBE coating, including:
Each method has its own advantages and disadvantages, and the choice between these options will come down to the specific application and level of corrosion protection needed. So, you may want to consult with a corrosion expert to find the best coating for you based on the fluids being transported, the conditions the pipe will be exposed to, and other factors.
Overall, FBE coating is a highly effective method of protecting pipes from corrosion and damage. In turn, this can extend the life of the pipe and reduce the need for costly repairs and replacements. Because of this, it&#;s a popular choice in several industries that require reliable and durable piping systems, including oil and gas, water, and sewage.
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