Abstract An enormous attention has been paid to cobalt aluminate (CoAl2O4) blue pigments owing to their significant hue of blue colour. Nevertheless, several serious disadvantages, such as high cost due to the high cobalt consumption and poor solar reflectance, are associated with this pigment. Therefore, the development of cost effective and sustainable blue pigments with reduced Co content and improved solar reflectivity is a major focused area in pigment research. Herein, a new series of multifunctional blue coloured inorganic pigments with low cobalt content were prepared via the solid-state method. The structural and spectroscopic evaluations were indicated that the strong blue colour could be generated because of the distorted tetrahedrally organized cobalt chromophore. This structural distortion of the chromophore geometry was linked to the covalency and electron affinity factors. Colour (b* = −59.21) and solar reflectance (R* = 64%) measurements of the optimized composition (NaZn0.9Co0.1PO4) was observed to be superior than the commercially available CoAl2O4 blue pigment. Meanwhile, the optimized pigment loaded epoxy coated steel substrate in marine medium exhibited impressive corrosion resistance properties. The anticorrosive mechanism, further established through the XPS results, validated that the phosphatized inhibitive film served as the barrier for corrosion. The estimated Co content in NaZn0.9Co0.1PO4 was found to be around 10 times lower than the CoAl2O4 blue pigment indicating the cost-effective nature. The optimized pigment was able to retain its optical properties in the prepared acrylic coatings on Al sheet and concrete block. Further, the temperature shielding studies ensured a reduction of ~4 °C in comparison with CoAl2O4 coatings. Therefore, the developed multifunctional blue pigment could be employed for the economic production of blue exterior paint for anticorrosive cool roof coatings.

中文翻译：

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一种用于多功能冷屋顶和防腐涂料的经济高效的深蓝色无机颜料

摘要 铝酸钴 (CoAl2O4) 蓝色颜料因其显着的蓝色色调而备受关注。然而，一些严重的缺点，例如由于高钴消耗和较差的太阳反射导致的高成本，与这种颜料有关。因此，开发具有成本效益且可持续的蓝色颜料，降低 Co 含量并提高太阳光反射率，是颜料研究的主要重点领域。在此，通过固相法制备了一系列新的低钴含量多功能蓝色无机颜料。结构和光谱评估表明，由于扭曲的四面体组织的钴发色团，可以产生强烈的蓝色。发色团几何结构的这种结构扭曲与共价和电子亲和因子有关。观察到优化组合物 (NaZn0.9Co0.1PO4) 的颜色 (b* = -59.21) 和太阳反射率 (R* = 64%) 测量值优于市售的 CoAl2O4 蓝色颜料。同时，优化的颜料负载环氧树脂涂层钢基材在海洋介质中表现出令人印象深刻的耐腐蚀性能。通过 XPS 结果进一步建立的防腐机制证实了磷化抑制膜可作为腐蚀屏障。发现 NaZn0.9Co0.1PO4 中的估计 Co 含量比 CoAl2O4 蓝色颜料低约 10 倍，表明其具有成本效益。优化的颜料能够在铝板和混凝土块上制备的丙烯酸涂层中保持其光学性能。此外，与 CoAl2O4 涂层相比，温度屏蔽研究确保降低了约 4°C。因此，所开发的多功能蓝色颜料可用于经济生产用于防腐冷屋顶涂料的蓝色外墙涂料。