In the oil and gas industry, oil country tubular goods (OCTG) coating is a vital part of drilling and extraction operations. To maintain their integrity in harsh underground environments, these goods are coated with protective layers. Here's an overview of the key components in OCTG coatings.
The first layer of an oil country tubular goods coating is the primer, which acts as an essential bridge between the metal substrate and the top coating. It provides initial corrosion resistance and aids in the adhesion of the subsequent coating layers.
The primer forms a secure bond with the metal surface, ensuring the other layers adhere more effectively and offering additional protection against oxidation and corrosion.
After the primer, an intermediate coat is applied. This layer typically contains anti-corrosive pigments and resin, which collectively enhance the coating's overall protective ability. The type of resin used can vary, with popular choices being epoxy, polyurethane, and zinc. The intermediate coat serves to further prevent corrosive elements from reaching the metal surface of the oil country tubular goods.
The topcoat is the final layer of the oil country tubular goods coating. This layer is designed to offer superior protection against harsh environmental conditions, such as exposure to chemicals, high temperatures, and abrasive substances.
Often, topcoats also provide UV resistance, contributing to the longevity of the OCTG. Furthermore, the topcoat gives the pipe a neat, finished appearance and can make identification easier through the use of specific colors or markings.
Fusion Bonded Epoxy Coatings
Fusion bonded epoxy (FBE) coatings are frequently used in oil country tubular goods applications. These thermosetting powder coatings are applied to the heated pipe, where they melt and form a hard, protective layer.
FBE coatings offer excellent adhesion, corrosion resistance, and insulation properties. They provide a uniform, seamless layer of protection, even on complex shapes and configurations.
Three-Layer Polyethylene and Polypropylene Coatings
A couple of similar materials, three-layer polyethylene (3LPE) and three-layer polypropylene (3LPP) are multi-layer coating systems commonly used on oil country tubular goods.
These consist of a layer of FBE, an adhesive layer, and a top layer of polyethylene or polypropylene. These coatings offer excellent corrosion protection, mechanical protection, and resistance to cathodic disbondment. They are particularly suitable for high-temperature environments.
While the exterior of oil country tubular goods faces harsh environmental conditions, the interior surface is not exempt from the need for protection. Internal coatings are designed to prevent corrosion from the inside, caused by exposure to liquids and gases during the extraction process.
For more information on OCTG coatings, contact a professional near you.