Pipeline Protective Coating

The pipelines are sometimes exposed to extreme conditions: underground, aboveground and underwater.?The coating of steel pipelines on the outside, therefore, has a very important protective function to maintain longevity, while the internal coating protects and maintains both the medium to be transported and the inside of the pipelines.

Metal must be protected from water, chemicals, the environment, and other corrosive factors in order to prevent corrosion. An efficient coating solution possesses the necessary properties to provide long-term protection.

The following are some of the required properties of the acceptable Pipeline coating:

• Excellent adherence to the substrate:?It will result in long-term corrosion protection.
• Chemical and water resistance:?The coating can be applied on a variety of surfaces, both internally and externally.
• Abrasion and impact resistance:?The coating layer is protected from handling and stress damage by its abrasion and impact resistance.
• Cathodic Protection:?It is well established that pipe coating selection affects the criteria and design of cathodic protection (CP) systems. Coal tar-coated pipelines, for example, often require substantially greater cathodic protection voltages than FBE-coated pipes. As a result, if the CP process necessary for one coating system, such as coal tar, is applied to a different coating system, such as fusion-bonded epoxy, it may result in significant overprotection, as well as possible coating degradation.

Four (5) Types of External Coating of pipelines

Pipelines laid underwater and in the ground must last at least 50 years undamaged.?Different layers are used to coat the steel of the pipes.?The following options are among the most important for the external coating of pipelines.?

1. Fusion Bonded Epoxy (FBE)

Epoxies offer the best resistance to oxygen, moisture, and chlorides, all of which are key soil elements. They're also extremely insulating, having low conductivity and high dielectric resistance. That is why epoxies are the material of choice when corrosion resistance is a top priority. The epoxy coatings can be applied in a variety of ways, including brushing, spraying, utilising liquid epoxies, or electrostatically spraying fine epoxy powder on a heated pipe, which melts and fuses rapidly.

The coating is resistant to cathodic disbondment. FBE coatings are thermosetting materials that cannot be remelted once set. The coating's most significant needs are surface cleanliness, correct heating, and adequate cure. The pipe is first blast cleaned to Sa 21/2, then heated uniformly in an induction furnace. The FBE powder is then electrostatically sprayed, melting and fusing instantly. The hot-coated pipe is quickly quenched.

2. Three-Layer Polyethylene (3LPE) Coatings

These coatings will stick nicely to steel pipes if the surface has been properly prepared. Because 3LPE coatings are resistant to mechanical and chemical stresses, corrosive agents (e.g. moisture, acid rain, salt air and water), temperature variations, and UV exposure, they provide superior anticorrosive protection for above-ground oil and gas pipelines.

3. Polyurethane (PUR)

In addition to withstanding diverse environmental conditions such as strong UV radiation, high temperatures, acid rain, and saltwater, PUR coatings provide a unique mix of mechanical and corrosion-resistant properties. Because their properties can fit a variety of subsea installation and performance requirements, PUR coatings are typically chosen for usage in shallow and deep water.

4. Concrete Coated Pipe (CWC)

Concrete forms the outermost layer of concrete coated pipe, also known as concrete weight coating pipe (CWC pipe), and is normally several centimetres thick. In the case of underwater installations, the outermost layer of concrete around the pipeline ensures that it is not influenced by currents and remains safely on the seabed.

Cathodic corrosion protection for coating pipelines

Cathodic corrosion protection is the most dependable method of preventing corrosion on steel pipes that are buried or submerged. Active corrosion prevention is the term for this type of corrosion protection. Cathodic corrosion protection is a standard option that is utilised in the industry in addition to pipeline coatings. Cathodic corrosion protection plus coating is the most effective and long-lasting method for preventing corrosion.

External current anode: A direct current is generated here, which identifies any faults in the coating and prevents corrosion by using the soil or water as an electrolyte. More specifically, current leakage at faults (which causes oxidation by releasing electrons to the electrolyte) is prevented, preventing corrosion.

Sacrificial anode: An alternative is to attach a sacrificial anode made of base metal to the pipeline (cathode), which prevents pipeline corrosion by releasing and oxidising the electrodes (rather than the pipeline).

There are some coatings that aren't suited for cathodic corrosion protection or are only suitable to a limited extent. As a result, a pipeline protection system must be Fail -safe. Fail-safe refers to a coating technology that is compatible with cathodic corrosion protection.