Hexagonal boron nitride as a cutting-edge 2D material for additive application in anticorrosive coatings: Recent progress, challenges and opportunities

Hexagonal boron nitride (hBN) is an eminent thermally and chemically stable 2D (layered) inorganic material. The hBN is associated with many characteristics, such as excellent thermal stability, hydrophobicity and high surface coverage, increasing its usefulness and prominence as a nanofiller in polymer-based coatings. However, the anti-corrosive property of hBN has received far less attention than that of graphene. In contrast to graphene-based coatings, hBN-based coatings are naturally insulating and do not suffer from galvanic corrosion. More notably, with hBN-based coatings, boron can easily oxidize in the presence of oxygen and produce oxide (boron oxide), which can passivate the metal surfaces and protect them from corrosion. They work because of the "labyrinth effect," which increases the difficulty in the dispersion of corrosive species by supplying more complex and convoluted pathways. Further, hBN-based formulations behave as self-healing coatings in the presence of the appropriate constituents. According to research findings, adding 0.5–1 wt% of hBN-based fillers to polymer coatings significantly enhances their anticorrosive properties. In epoxy and WPU coatings, hBN-based fillers are widely employed. This article discusses the anticorrosion potential of hBN and its composites. The corrosion protection mechanism of hBN-based fillers and nanofillers is widely discussed with the help of the "labyrinth effect" and “self-healing” coatings.