Pipelines are recognized as the most efficient and safe methods for transporting liquids and gases over long distances. Due to increasing demands for longer onshore and deeper offshore pipelines, the importance of the protection from and prevention of leaks in pipelines has also increased. For higher durability in corrosive environments, selection of the proper coating materials is vital. Due to the high resistance of polymeric materials in various environmental conditions, polymeric coatings are often used for pipe protection;​ however, there are several challenges associated with these materials.

One of the major concerns with the polymeric coating of metallic surfaces is the different thermal properties of the polymer coating and the steel substrates. Due to the variation in the coefficients of thermal expansion (CTEs), temperature fluctuations may induce interfacial stresses between coating and substrate, which can result in disbondment of the coating. The presence of any debonding between the coating and the pipe may weaken the coating’s performance in protecting the pipes from corrosion. In addition to minimizing CTE mismatch, high-performance polymeric coatings should possess properties, such as high adhesion, low gas permeability, high corrosion resistance, and excellent mechanical strength. Recently, it has been shown that the use of advanced composites as protective layers is one way to overcome some of the problems associated with the existing coating materials.

There are some critical factors affecting properties of the composite materials such as dispersion and geometry of inclusions. Effective dispersion of nanoparticulates within the polymers without damaging the high aspect ratio geometry of fillers has a key role in the manufacture of polymer composites for coating purposes. Effects of the dispersion and the geometry of the fillers on properties of composites can be predicted through modeling and simulations in order to material selection and application design. In this study, as a preliminary evaluation of polymer composites for coating applications, these aspects are investigated through a variety of experimental tests and modeling approaches.

To overcome some of the challenges associated with existing pipeline coatings, the use of polymeric nanocomposites as coating materials are proposed in this research. By employing novel inclusions such as hexagonal boron nitride (hBN) nanoplatelets, carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and zinc particulates within a conventional polymer coating, high-performance polymeric nanocomposites can be created for the purposes of pipeline protection. The excellent performance of the proposed polymer-based composites are due to unique mechanical, electrical, thermal, and anti-corrosive properties of the additives. The addition of 2D nanoplatelets such as hBN and GNP to the pure polymers may result in the fabrication of nanocomposites with lower CTE, high gas barrier, high mechanical stability, and anti-corrosive performances. Application of CNTs and zinc particles as hybrid compositions can also improve corrosion protection of the composite coatings due to the synergistic effects of zinc particles as sacrificial material and CNTs as connectors of an electrically conductive network.

This research is aimed at investigating the feasibility of using these nanocomposites as coating materials. Initially, the effects of dispersion and geometry of CNTs on the final properties of nanocomposites were examined. Then, two random walk models were developed to study the effects of the addition of inclusions on the electrical and thermal conductivities of nanocomposites. Finally, the selected nanoparticulates were added to polymers, and the coating capabilities of composites were evaluated. From the tests and investigations conducted on the developed composite coatings, it was observed that thermal expansion, gas barrier, mechanical strength, adhesion, and corrosion protection performances were improved compared to the pure polymeric coatings. The corroded area on the cathodic disbondment test specimens reduced down up to 90% for the composite with zinc (20 wt.%), MWCNTs (2 wt.%), and GNPs (2 wt.%), compared to a specimen coated with a pure polymer. It is seen that the presence of nanoparticulates decreased gas penetration and thermal expansion of the matrix by 75% and 65%, respectively.

The outcomes of this research are advantageous for pipeline protection applications and may be appropriate for coating other metallic surfaces located in highly corrosive environments. Besides, considering the obtained results, the fabricated composites could be employed in several other industries such as packaging and electronics.