Internal Pipe Coating


What is Internal Pipe Coating?

The internal pipe coating increases their resistance to corrosion, enhances their flow, and reduces the creation of deposits. There are a variety of interior coatings for pipes, including Fusion Bonded Epoxy (FBE) Coating and Glass flake Coatings.

Around the world, corrosion is the single most important issue impacting the lifetime and dependability of underground pipes, both offshore and onshore. External coatings and internal coatings are two distinct kinds of oil and gas protective coatings, each with its own set of unique and rigorous requirements: external pipe coatings and internal pipe coatings. While most people think of anti-corrosion in terms of exterior protection, inside pipeline coating is just as vital as external protection when it comes to protecting a pipeline from corrosion.

Partially polymerized oils, including waxes and silicas, as well as dirt, can be found in oil and gas fluids. Solid particles include sodium chloride, potassium chloride, other salts, carbonates, sulfates, and other dissolved substances.

In the fluid, some of these particles disintegrate, while others stay in suspension. As they travel through pipes at speeds nearing 200 mph, these particles transform into fiercely corrosive missiles that cause severe damage. These fast-moving particles cause a significant amount of influence on coatings developed for internal pipeline applications.

Table of Contents

Fusion Bonded Epoxy (FBE) Internal Pipe Coating

FBE internal pipe coating is a type of high-performance coating created from anti-corrosion powder for typical working temperatures. This type of internal coated pipe is suited for temperatures up to 80 degrees Celsius.

- Application Methods of Internal FBE Coating

Before blast cleaning, a visual inspection is required to check for the presence of oil or grease. The surface of the pipe must be thoroughly cleaned using blast cleaning in order to eliminate rust, scale, and any other undesirable particles. This has a rough exterior finish. This sort of coating requires a roughness value between 50 and 100 microns. The inside surfaces of pipes are painted using a spray gun following blast cleaning. This helps to evenly distribute the coating on the heated pipe. The pipe revolves continuously about its longitudinal axis. After coming into contact with the heated surface, the powder melts and transforms into a liquid. This liquid FBE coating travels onto the surface of the pipe and immediately solidifies. This is the Fusion Bonding procedure.

- Advantages of Internal FBE Coating

  • This coating can withstand high temperatures.
  • This coating is resistant to corrosion.
  • It may be applied to pipes with diameters ranging from 2 to 48 inches.
  • It is ideal for a variety of thicknesses.
  • It has chemical resistance in soil conditions and good resilience to impact.

- Limitations of Internal FBE Coating

  • The maximum service life of FBE-coated pipes is 12 years, whereas the maximum design life of a plant is 25 years. Pipes must be replaced just once.
  • It has a complex design.
  • Applicators are difficult to get.

Glass Flake Internal Pipe Coating

It is also known as Chemflake or Belzona coating and conforms to SP-1246 PCS-8. This sort of coating is typically good for temperatures up to 93 degrees Celsius. Internal coatings of glass flakes are ideal for larger pipe diameters. Joining non-flanged pipe spools is often performed in the flanged pipe spool.

- Steps of Applying Internal Glass Flake Coating:

  • Cleaning: The blast cleaning procedure is utilized, which maintains a roughness value between 75 and 130 microns.
  • Spray: Spraying is accomplished using ordinary airless spray equipment.
  • Brush: It is also advisable to stripe coat and coat tiny regions. To obtain the specified dry film thickness, sufficient attention must be taken.
  • Curing: One coat requires approximately twenty-four hours to dry completely.

- Advantages of Internal Glass Flake Coating

  • It has good chemical and solvent resistance
  • Excellent adhesion and weather resistance
  • It possesses poor permeability
  • This coating possesses exceptional finish retention.

- Limitations of Internal Glass Flake Coating

  • This coating is sensitive to temperature and pressure and is only appropriate for a maximum of 10 bar pressure.
  • It cannot be utilized with caustic liquids or slurries.
  • It can cause skin irritation.
  • This coating requires periodic reapplication, and chalking is a time-consuming procedure.
  • It is highly expensive and only applied to a small number of spools.
  • The design life can only last between 3 and 4 years.

Internal Pipe Coating Technology

The use of the internal pipe coating in pipelines is becoming increasingly popular as a technique of efficiently controlling pipeline corrosion loss. Petroleum pipeline anticorrosion procedures primarily consist of selecting corrosive-resistant metal or non-metal substrates, adding corrosion inhibitors, and applying coating or linings to prevent corrosion from taking place.

- Corrosion Resistant Substrate Development and Application Technology

In essence, the selection of corrosion-resistant base material is intended to increase the internal pipe coating performance of the pipeline, making the choice of base material extremely significant. Corrosion-resistant substrates are classified into two categories: corrosion-resistant metal substrates and corrosion-resistant non-metallic substrates. Metal substrates are the most common type of corrosion-resistant substrate. In addition to excellent corrosion resistance, such as resistance to stress corrosion, pitting corrosion, and crevice corrosion, as well as resistance to various kinds of corrosion damage, the Fe-ni base corrosion resistant alloy, has outstanding mechanical characteristics and machining performance. Non-metallic base materials that are commonly used for corrosion resistance include glass fiber reinforced plastics, plastics, rubber, and ceramics, among other things. Pipes that are routinely used nowadays are split into two categories: lined steel pipe, which is the first kind, and robust polyethylene pipe, which is the second type.

- Corrosion Inhibitor Technology

With the addition of only a tiny quantity of corrosion inhibitor to the medium, protective films such as passivation films, adsorption films, precipitation films, and other protective films are created on the inner wall of the pipeline, preventing or slowing the progression of corrosion. The amount of corrosion inhibitor used is extremely minimal, and it has no effect on the surrounding environment. Adding corrosion inhibitors does not need the expansion of equipment, and its operation is easy and convenient. It also has the benefit of being able to utilize the same formula in a variety of settings. As a result, it is frequently employed in the oil and gas business.

- Internal Pipe Coating Technology

In order to handle the corrosion problem in pipelines of the collection and the conveying system as well as the water injection system, the inner coating of pipelines is a highly efficient solution. It is possible to minimize surface roughness and hydraulic friction coefficient in a pipeline when transporting gas by coating it. This can result in the reduction of the pipe diameter, which in turn can lower material and construction costs for the pipeline. Epoxy powder coating technology, liquid epoxy coating technology, and other coating technologies are some of the most often utilized coating techniques.

- Epoxy Powder Coating Technology

High adhesion, high film hardness, good corrosion and chemical resistance, no by-products during curing, high usage rate, and low viscosity are some of the properties of epoxy powder coating. It also has good film leveling and a smooth appearance. There are several different epoxy powder coating processes available, including electrostatic spraying, thermal spraying, vacuum suction coating, and fluidized bed, among others. Electrostatic spraying is commonly used to coat big diameter pipes within the pipe, and it is very effective. When coating small-diameter steel pipe, the fluidized bed hollow cone atomizing spraying technique (also known as the vacuum suction coating method) is typically utilized, whereas the fluidized bed method is typically used for special-shaped components. Material and labor costs, on the other hand, are prohibitively expensive. When running, the pipe and coating must be heated to a temperature of 250°F.

The friction resistance between the fluid and the pipe is successfully reduced by using an epoxy resin liner in the pipe. This internal pipe coating is applied to steel pipes that are used to transport oil, gas, water, and industrial and corrosive fluids, among other things. It can be applied in liquid or powder form. When corrosion and paraffin deposits are expected to occur in oilfield drilling tools (drilling pipes, sucker rods (packers), pumps (tubing), casing (and other components), it is very useful. It is also used in specific connections for safeguarding welded joints in oilfield drilling tools.

- Liquid Coating Technology

In its most basic form, liquid epoxy coating is made up of epoxy resin and an amine curing agent. Although liquid epoxy coating has outstanding adhesion, corrosion resistance, wear resistance, and physical qualities, the construction thickness of the coating is restricted, and the coating does not achieve the desired results. Aerosol spraying, electrostatic spraying, and high-pressure airless spraying are all methods of applying liquid epoxy coatings to the inside surface of pipes and tubes.

- Other Coating Technology

Having high adhesion, medium resistance, and weather resistance, chlorinated rubber coatings are extensively utilized in the petrochemical sector as primary supporting coatings to facilitate the building of simple and practical structures. Many big oil fields have used Ni-P alloy chemical coating tubing, which not only lowers the cost of the tubing but also has a certain anti-corrosion effect.

Corrosion Mechanism of Dissolved Oxygen

The presence of dissolved oxygen in oil and gas fields is one of the most critical elements contributing to corrosion. Oxygen functions as a polarizing agent, causing metals to corrode at a faster rate than normal. The following is the reaction mechanism for dissolved oxygen corrosion:

Anode: Fe-→Fe₂+ +2e;

Cathode: 2H+ +2e→H2; O2+ 2H₂O+4e→4OH⁻

The result is Fe(OH)₂, but the Fe(OH)₂ is very unstable and is converted to Fe(OH)₃. The Fe(OH)₃ is dehydrated to Fe₂O₃. Fe₂O₃ is the main component of the rust that causes damage to steel structures.

Corrosion Mechanism of CO₂

CO2, being one of the constituents of associated gas or natural gas in the oil and gas industry, will not cause corrosion of steel in the dry state, but will cause corrosion of steel when dissolved in water and steel electrochemical corrosion when dissolved in water.

The corrosion rate of CO2 dissolved in water is larger than the corrosion rate of hydrochloric acid when both are maintained at the same pH.

How to Repair Internal Pipe Coating?

Due to the fact that epoxy is a thick, viscous liquid, it coats, seals, and fixes as it travels through your plumbing system. Using filtered and compressed air, the epoxy is blasted through your potable water pipes once it has been well mixed. As the epoxy is blasted through your plumbing pipes, it fixes minor fractures and pinhole leaks while also strengthening the pipes. It’s also thick enough so that it won’t spatter within your pipes when you use it. Instead, it has a tendency to roll over on itself, resulting in a consistent coating along the inside diameter of your pipes’ interior diameter.

Once the epoxy has been blasted into position, it must be allowed to cure for a certain period of time, which can range anywhere from a few hours to a day or more. Once the epoxy resin has set, it hardens and creates a long-lasting surface.

Do Epoxy Internal Pipe Coatings Reduce the Internal Diameter of the Internal Coated Pipe?

In order to lower the internal diameter of plumbing pipes (internal coated pipe), epoxy coatings must be put on the interior of each pipe. Because epoxy coatings are often only a few millimeters thick, they do not significantly reduce the internal diameter of the pipe. Before the epoxy is blasted through the pipes, however, all plumbing pipes are thoroughly cleaned down to the pipe walls and then reassembled. When it comes to highly corroded plumbing pipes, this implies that they actually gain in diameter when compared to how they appeared before the application of the epoxy coating.

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