Synthesis and application of cost-effective Egyptian blue nano-pigments for versatile decorative and anticorrosive coatings

Abstract

Cobalt aluminate blue pigments are the most admired pigments and have received great attention owing to their significant blue hue and high corrosion resistance. However, this pigment has significant drawbacks, such as the high consumption of rare and expensive cobalt. As a result, the creation of cost-effective and long-lasting blue pigments devoid of Co is a key focus of pigment research. Herein, two multifunctional Egyptian blue pigments (CaCuSi4O10) were synthesized at the nanoscale via the solution combustion method. Two proportions of Cu content were chosen to prepare Egyptian pigment in sky blue (EB 1) and Egyptian pigment in strong blue (EB 2). The structural and spectroscopic evaluations were illustrated. After that, the prepared pigments were incorporated into epoxy resin in different ratios (e.g., 5, 15, 25%) to investigate their anticorrosive and decorative properties. Their anticorrosive performances in simulated concrete pore solutions were evaluated using potentiodynamic anodic polarization, electrochemical impedance spectroscopy, scanning electron microscopy/energy-dispersive X-ray analysis techniques. The results demonstrated that rebar coated with EB 1 at the ratio of 5% showed superior corrosion resistance than other ratios (e.g., 15% and 25%), with a corrosion rate of 5 × 10−6 µm/year and charge transfer resistance reaches 8.292 × 106 Ω.cm2 in NaCl and 1.01 × 107 Ω.cm2 in Na2SO4. As a consequence, it can be concluded that the Egyptian blue pigments (EB) may be suitable alternatives for the more expensive commercial anticorrosive blue pigments (e.g., cobalt aluminate pigments), and they could be employed effectively in the economical manufacturing of multi-functional blue coatings that have both anticorrosive and decorative properties.