Effective corrosion protection by eco-friendly self-healing PMMA-cerium oxide coatings

Abstract

Metallic alloys are extensively used in many technological applications, however their susceptibility to corrosion causes huge economical losses and can result in failure of critical components. Aiming to obtain environmentally friendly, self-healing and high efficient anticorrosive coatings, organic-inorganic hybrids consisting of poly(methyl methacrylate) (PMMA) covalently bonded to CeO2/Ce2O3 nanoparticles have been synthetized by the sol–gel process. Cerium oxide nanoparticles were covalently conjugated with the coupling agent 2-hydroxyethyl methacrylate (HEMA) and different proportions of methyl methacrylate (MMA), and subsequently the hybrid solutions were used to deposit films on A1020 carbon steel by dip-coating. The coatings are transparent, homogeneous, free of pores, have low surface roughness (<1.6 nm), and present good thermal stability (>220 °C). Excellent anticorrosive efficiency and durability was obtained by the nanoscale dispersion of cerium oxide nanoparticles into PMMA matrix, achieving for the sample with molar ratio of 1Ce:2HEMA:25MMA an impedance modulus up to 290 GΩ cm2, 8 orders of magnitude higher than the bare carbon steel, remaining essentially unchanged during 6 months exposure to saline solution. A detailed analysis of scratched coatings evidenced that Ce ions act as self-healing agents inhibiting the progression of the corrosion process. This work demonstrates that the active corrosion inhibition and environmental compliance make these PMMA-cerium oxide coatings a very promising alternative for the conventional protection systems.