Preparation and evaluation of nanosized mixed calcium iron oxide (CaFe 2 O 4 ) as high heat resistant pigment in paints H. Abd El-Wahab, A.M. Hassan and A.M. Naser Chemistry Department, Faculty of Science, Al Azhar University, Cairo, Egypt O.A. Fouad Central Metallurgical Research & Development Institute, Cairo, Egypt, and A.M. El-Din and O.A.G. Wahba Paint and Chemicals Industries (Pachin) Co., Cairo, Egypt Abstract Purpose – The purpose of this paper was to prepare and evaluate a nanosized mixed calcium iron oxide as a high heat-resistant pigment. Heat-resistant pigments can be defined as chemical substances that impart color to a substrate or binder and retain their color and finish at elevated temperatures. Mixed metal oxides have been widely used as pigments in coating formulations. Design/methodology/approach – This work presents synthesis of nanosized calcium iron oxide as an inorganic pigment by using simple synthesis technique, namely, solid-state calcination method, to study its heat and corrosion resistance. The prepared pigment was characterized by using X-ray diffraction, infrared spectroscopy, scanning electron microscopy and inductive coupling plasma. It was incorporated into paint formulations, and the heat, corrosion and mechanical resistance of dry paint film was evaluated. Findings – In this work, the prepared calcium iron oxide pigment showed excellent heat and corrosion resistance. Research limitations/implications – Heat-resistant coatings are required for industrial applications, mainly for reactors, exhaust pipes, space craft, stacks and similar equipments that are permanently and occasionally exposed to elevated temperatures. It was previously quite difficult to formulate heat-resistant organic coatings because of binder deficiencies; new vehicles for such applications are now available. Thus, the development of silicon resins has markedly advanced the utility of heat-resistant paints. High-temperature pigments are inorganic chemical compounds that impart and retain their color and finish to a substrate or binder at elevated temperatures. Practical implications – The nanosized mixed calcium iron oxide could be used as a pigment in paint formulations. It was found that it significantly enhances the heat, corrosion and mechanical resistance. It can also find numerous applications in other paint formulations for surface coating. Originality/value – The paper shows how the pigment consisting nanosized mixed calcium iron oxide could be used in heat-resistant paint formulations for coating metal surfaces. Keywords Nanotechnology, Pigments, Corrosion resistance, High temperature, Iron, Oxides, Paints Paper type Research paper Introduction Mixed metal oxide pigments help to reach opaque coating by pigment mixing to achieve the desired color. Chemically they are synthetic metal oxides with a structure similar to neutral minerals such as rutile TiO 2 and ferrite/corundum (Fe 2 O 3 / Al 2 O 3 ) and spinel mineral as MgAl 2 O 4 . Properties of complex inorganic color pigments or mixed metal oxides are color fastness, resistance to chemicals and temperature changes and stability in organic solvents. They don’t bleed and migrate in coatings. These pigments are heat-stable to temperatures exceeding 1,000°C and they are suitable for a majority of applications (Tracton, 2006). They have been widely used as a semiconductor in dye-sensitized solar cells (Nwanya, 2011), catalysts (Farzaneh et al., 2008), electrodes in electrochemical double-layer capacitors (Jayalakshmi, 2009), solid oxide fuel cells (Madsen et al., 2007), resistors (Williams, 1999), gas sensors (Zakrzewska, 2001), transparent optical device (Hosono, 2007) and pigments (Jitendra et al., 2008). Prediction of heat build-up of solar- reflecting coatings based on physico-chemical properties of complex inorganic color pigments was also studied (Malgorzata et al., 2011). Polytetrafluoroethylene and polycarbonate resins also possess high heat stability. For moderate heat exposure, polyvinyl formal, butyl rubber, neoprene and some polyurethanes and epoxies are usable. In pigmentation heat-resistant coatings, the formulator has to operate within certain restrictions. Pigments that are unable The current issue and full text archive of this journal is available on Emerald Insight at: www.emeraldinsight.com/0369-9420.htm Pigment & Resin Technology 44/3 (2015) 172–178 © Emerald Group Publishing Limited [ISSN 0369-9420] [DOI 10.1108/PRT-12-2013-0114] Received 19 December 2013 Revised 7 August 2014 Accepted 6 October 2014 172