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• Novel covalently bonded PMMA-TiO 2 and PMMA-ZrO 2 hybrid nanocomposites. • Homogeneous distribution of fiber-like TiO 2 structures and ZrO 2 nanodomains. • Transparent and defect free coatings with excellent anticorrosive performance. • Elevated thermal stability and high coating adhesion to steel substrate. • Efficient environmentally compliant protection of metallic surfaces. The covalent conjugation between the phases of organic-inorganic nanocomposites and the careful tuning of the proportion of the colloidal precursors are essential to yield homogeneous, cross-linked and dense coatings that are able to protect metallic alloys against corrosion. In this work, the sol-gel route was used to prepare organic-inorganic hybrid coatings based on poly(methyl methacrylate) (PMMA) covalently bonded to TiO 2 or ZrO 2 nanoparticles through the coupling agent 2-hydroxyethyl methacrylate (HEMA), applied for the first time as anticorrosive coatings for metallic alloy. Different formulations of the hybrids were prepared by varying the proportion of titanium isopropoxide or zirconium propoxide, methyl methacrylate and benzoyl peroxide, and applied on carbon steel by dip-coating. The optimized parameters yielded for the two hybrids transparent and homogeneous coatings, with a thickness less than 3 μm, low surface roughness (<1.8 nm) and elevated thermal stability (>200 °C). Electrochemical impedance spectroscopy assays showed that PMMA-ZrO 2 and PMMA-TiO 2 coatings exhibit corrosion resistance up to 10 GΩ cm2, 7 orders of magnitude higher than the bare carbon steel, remaining essentially unchanged for PMMA-TiO 2 during 14 days exposure to 3.5 % saline solution. The results suggest that PMMA-ZrO 2 and PMMA-TiO 2 nanocomposites are suitable for application as environmentally compliant highly efficient anticorrosive coatings. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid coatings deposited on different types of metallic alloys have shown outstanding anticorrosive performance. The incorporation of osteoconductive additives such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) into organic-inorganic hybrid coatings is promising to improve the osseointegration and corrosion resistance of Ti6Al4V alloys, which are the most widely used metallic orthopedic and dental implant materials today. Therefore, this study evaluated the capability of poly(methyl methacrylate) (PMMA)-TiO 2 and PMMA-ZrO 2 hybrid coatings modified with HA and β-TCP to act as bioactive and corrosion protection coatings for Ti6Al4V alloys. In terms of cell growth and mineralization, osteoblast viability, Ca+2 deposition and alkaline phosphatase assays revealed a significant improvement for the HA and β-TCP modified coatings, compared to the bare alloy. This can be explained by an increase in nanoscale roughness and associated higher surface free energy, which lead to enhanced protein adsorption to promote osteoblast attachment and functions on the coatings. The effect of HA and β-TCP additives on the anticorrosive efficiency was studied by electrochemical impedance spectroscopy (EIS) in a simulated body fluid (SBF) solution. The coatings presented a low-frequency impedance modulus of up to 430 GΩ cm2, 5 decades higher than the bare Ti6Al4V alloy. These findings provide clear evidence of the beneficial role of HA and β-TCP modified hybrid coatings, improving both the biocompatibility and corrosion resistance of the Ti6Al4V alloy. Unlabelled Image • Modification of PMMA-TiO 2 and PMMA-ZrO 2 coatings with hydroxyapatite and β-TCP • The coatings provided effective corrosion protection for a Ti6Al4V alloy • Osteoblastic growth and mineralization were enhanced with calcium phosphate addition • Higher surface free energy and roughness promoted osteoblast proliferation • Achievement of a bioactive and anticorrosive coating for metallic implants [ABSTRACT FROM AUTHOR]