The anticorrosive properties of different coatings on mild steel are insufficient and chromate corrosion protection is being eliminated owing to its toxicity. This paper shows an anti-corrosion bi-layer environmentally-friendly sol–gel coating doped with cerium (26 μm thick) on mild steel, combining a barrier effect with self-healing. Both layers have a siloxane-methacrylate composition based on the combination of a silicon alkoxide, a monomer and an organically modified silicon alkoxide as a cross-linker. Well-adhered coatings, with excellent barrier properties and current densities as low as 10−12 A cm−2 and impedances of 1010 ohm cm2, are demonstrated. Electrochemical measurements (EIS and polarization tests), SEM-EDX and micro-Raman analysis indicate depletion of Ce around defects and higher concentrations in the defect, supporting the activation of a self-healing process.
