# Environmentally Friendly Anticorrosive Polymeric Coatings
## 4 Developments in Environmentally Friendly Polymeric Coatings
### Polyurethane
[79] studied different surface treatments of ZnO particles using silane compounds, demonstrating an increase of the anticorrosive property of the coating. materials are graphene and graphene-like materials such as molybdenum disulphide (MoS\({}_{2}\)). [PERSON] et al. [80] introduced MoS\({}_{2}\) nanosheets into an acrylic emulsion, forming a three-dimensional network structure with chemical cross-linking points. The addition of MoS\({}_{2}\) sheets to the coating promotes an inhibition of the corrosive medium transmission and a reduction of the coating hydrophobicity. Carbon nanotubes (CNT) are another reinforcing agent for acrylic coatings because the presence of CNT reduces the through-porosity. The water diffusion and absorption in the CNT/acrylic coating are slower than those of the native acrylic coating, as [PERSON] et al. explained in their work [81]. Pure acrylic coatings have the tendency to result in surfaces with lots of micropore defects, which may be formed during the drying process. [PERSON] et al. [82] demonstrated that adding graphene-modified CeO\({}_{2}\) nanoflake in waterborne acrylic coating promotes a reduction of the amount of micropores and an increase of the anticorrosion performance of the final paint. This is due to the combination of the excellent barrier stability of graphene and the good corrosion inhibition of CeO\({}_{2}\), which can inhibit corrosion by releasing Ce\({}^{3+}\). The mechanism proposed by the authors is shown in Figure 6.  
Moreover, [PERSON] et al. [83] used silica nanoparticles obtained from rice husk following an eco-friendly process as efficient filler for acrylic anticorrosive coatings. Organic-inorganic hybrids coatings, consisting of poly (methyl methacrylate) (PMMA), provide highly efficient anticorrosion coatings, especially when PMMA is covalently  
Figure 6: Schematic representation of corrosion mechanism by Gr-P-CeO\({}_{2}\) coatings with different barriers on mild steel substrate: (**a**) no barrier, (**b**) Gr (graphene), (**c**) CeO\({}_{2}\) nanoflakes modified with PABA (p-aminobenzac acid), (**d**) CeO\({}_{2}\) nanoflakes unmodified, (**e**) Gr-CeO\({}_{2}\), the agglomeration between CeO\({}_{2}\) and Gr has reduced the corrosion resistance, (**f**) the best anticorrosion ability because it used PABA to link Gr and CeO\({}_{2}\) together by chemical bonding, which enhances the dispersion of the fillers in the coating [82]. bonded to cerium nanoparticles, as studied by [PERSON] et al. [84]. The electrochemical characterization of the resulting hybrid coatings showed a significant improvement in the anticorrosion properties, showing an impedance modulus 8 orders of magnitude higher than the bare carbon steel after 6 months of exposure to a saline solution [78; 79]. The use of green corrosion inhibitors is also a potential pathway for the introduction of more environmentally friendly acrylic coatings into the market. The aqueous extract of the henna leaves is under investigation as a corrosion inhibitor for carbon steel, nickel, and zinc in alkaline, neutral, and acidic solutions. [PERSON] et al. [85] evaluated the anticorrosion behavior of henna leaves extract incorporated in an acrylic resin in order to protect aluminum alloy 5083 from corrosion. The formation of conducting pathways that reduce the protection ability was observed. More research focused on green approaches for polymeric coatings is needed.