Exfoliated hexagonal boron nitride based anti-corrosion polymer nano-composite coatings for carbon steel in a saline environment

Abstract

Polymer coating is the most suitable route to protect the metallic surfaces, and it has many purposes including anti-static coating, electromagnetic shielding, anti-reflective and anti-corrosion properties. The long term performance of the metallic surface can be achieved by polymer coatings. The discovery of nanoparticles introduced a new class of materials having higher surface area, high-performance polymer nano-composites appear attainable. For polymer anti-corrosion coatings, in addition to the inherited barrier effect provided by pure polymer films, the film blocking properties can be improved using plate-like nano-fillers. Incorporating fillers, such as graphene nano-platelets, has proven effective as anti-corrosion coating. These coatings usually improve the barrier, mechanical, electrical, optical, rheological, adhesion properties, and resistance against the environmental degradation; However, polymer coatings loaded with graphene displayed long-term enhanced corrosion after erupting the barrier due to inherited electrical conductivity and higher position in the galvanic series. Herein, we exfoliated the hexagonal boron nitride (h-BN) from micro particles into nano-sheets and incorporated it as fillers at different concentration in polymer coatings to enhance the barrier properties. For comparison, graphene nano-platelets were also used. Transmission electron micrographs confirmed the exfoliation of hexagonal boron nitride (h-BN). For exfoliation, we selected two different particles size i.e., 0.07 µm and 5.0 µm. The barrier properties of the coatings were determined in 3.5 % NaCl during different times of immersion, via different electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy and potentiodynamic. The coatings containing exfoliated h-BN (5.0 µm) particles exhibited improved resistance for longer periods of immersion compared to graphene nano-platelets. The improved corrosion properties can be attributed to the high aspect ratio, plate-like shape and electrically insulated nature of the exfoliated (h-BN) nano-sheets. Specifically, the thesis will be composed of the following steps: 1) preparation of exfoliated hexagonal boron nitride (h-BN) from different particles and synthesis of anti-corrosion coating by dispersion of fillers in polymer matrix via solvent blending, 2) electrochemical techniques for the determination of anticorrosion properties and 3) characterization of exfoliated nano-sheets and nanocomposites.