The purpose of this work is to prepare new core-shell pigments based on silca fume waste as core and ferrite pigments in the shell. Silica fume is a byproduct of the smelting process in the ferrosilicon industry. The reduction of high-purity quartz to silicon at temperatures up to 2,000°C produces SiO2 vapours which then oxidize and condense at low-temperature zones to tonnage amounts of tiny particles consisting of non-crystalline silica that is collected and sold rather than being land-filled because nowadays there is increasing environmental concern with regard to excessive volumes of solid waste hazards accumulation. Silica has no direct effect in protecting metals from corrosion, but on precipitating an effective anticorrosive pigment like ferrite on its surface with low concentrations, this can bring out new core-shell pigment with good anticorrosive performance and low cost. The new pigments will be constructed on a waste silica fume core comprising 80-85 per cent of its chemical structure and the ferrite shell that will be only about 20-15 per cent. These pigments are represented as efficient, economically feasible and eco-friendly.
The different ferrites and ferrites/SiO2 pigments were characterized using different analytical and spectro-photometric techniques, such as X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray and transmission electron microscopy (TEM). Evaluation of these pigments was done using international standard testing methods american standard testing methods (ASTM). After evaluation, the pigments were incorporated in solvent-based paint formulations based on medium oil-modified soya-bean-dehydrated castor oil alkyd resin. The physico-mechanical properties of dry films and their corrosion properties using accelerated laboratory test in 3.5 per cent sodium chloride for 28 days were determined.
The results of this work revealed that ferrite/SiO2 core-shell pigments were close in their performance to that of the ferrite pigments in protection of steel, and at the same time, they verified good physico-mechanical properties.
As silica fume has a large array of uses, these pigments can be applied in various industries such as painting, wooding coating, anti-corruption coating, powder coating, architectural paint and waterproof paints.
Ferrite, ferrite/SiO2 are environmentally friendly pigments which can impart high anticorrosive behaviour to paint films with concomitant cost savings.
The present work was supported by the National Research Centre Fund (NRC) under project number 1070002.
M. Ahmed, N., M. Abd El-Gawad, W., A. Youssef, E. and M. Souaya, E. (2014), "Employment of new modified ferrite pigments in anticorrosive alkyd-based paints", Pigment & Resin Technology, Vol. 43 No. 4, pp. 201-211. https://doi.org/10.1108/PRT-10-2013-0106
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