| In the world, economic losses caused by metal corrosion becomes more serious, with industrial development, which makes to development superior methods of metal corrosion more important. The most effective and most widely used method of corrosion is the coating protection. Anti-rust paint, such as the traditional red lead, chromate, zinc chrome yellow rust, etc., are limited because of environmental pollution and doing harm to human health, although they have good performance. They has gradually been replaced by eco-rust paint.Zinc phosphate, as a new type of non-toxic, ecological anticorrosive pigment with excellent properties, has been employed in the coating industry. For example, it can be used in alkyd, epoxy, phenolic, chlorinated rubber, amino and other resin-based material. However, owing to its low activity resulting from weaker covering power, solubility, hydrolysis and low ability to overcome the early 'flash embroidery' problems, especially in water-based paint, it cannot completely replace traditional toxic anticorrosive pigment. Therefore, the development of efficient non-toxic anticorrosive pigments becomes the development trend.Many attempts have been made to modify zinc phosphate to improve anticorrosive ability in the world. Four ways of improving the activation of zinc phosphate pigments can be introduced:reducing particle size and adjusting particle shape, preparing the zinc phosphate hydroxid, chemical modification and combining zinc phosphate with other anticorrosive pigments.Nanometer powder of -BaB2O4 was synthesized by ultrasonic method, using Ba(OH)2·8H2O and H3BO3 as raw materials. In this method, H2O2 and a surface modification agent PEG-400 had been used. It avoided soft and hard agglomerates of paticles.First, a certain amount of Ba(OH)2·8H2O solution and H3BO3 solution (molar ratio is Ba:B=1:2) were prepared. Then, H3BO3 solution were dropped into Ba(OH)2·8H2O solution, under the conditions of ultrasound and stirring, to synthesize nanometer powder ofβ-BaB2O4.IR analysis showed that the initial product is BaB2O4·H2O2. TG-DTA-DTG analysis showed that BaB2O4·H2O2 was decomposed at about 553℃, losing crystallization of hydrogen peroxide. XRD analysis showed thatβ-BaB2O4 belongs to the space group of R3c(161) and C2/c(15). TEMphotograph showed that the particles are uniformly in shape and dispered well with average size less than 70nm in diameters. The function of H2O2, drops of acceleration,tempeture of ultrasonic wave and surface modifcation were discussed, and the best crafts parameters were obtained.In order to find a more simple preparation method, nano-BaB2O4 powder was synthesized by solid-state reaction at room temperature for the first time. The method is highly productive and can be easily operated. A certain amount of Ba(OH)2·8H2O and H3BO3 (molar ratio is Ba:B=1:2) were weighed and added in a mortar. Subsequently, the mixture was ground in wet form for 1 h at room temperature. Then, the above sample was dried at room temperature or 100℃to obtain the final products.XRD pattern demonstrates that the component of the as-obtained sample is BaB2O4·H2O and BaB2O4 when dried at room temperature or 100℃, respectively. TEM photograph of the powder shows that the particles are uniform and spherical with average size of 70 nm in diameter. Furthermore, the influence of grinding time and crystal transformation phenomenon were discussed, and the best crafts parameters were obtained.Then, CaZn2(PO4)2 and -BaB2O4 nanopowders were firstly synthesized by an ultrasonic-aid chemical precipitation method. Then BaB2O4 was mixed with CaZn2(PO4)2 to prepare CaZn2(PO4)2-BaB2O4 nanopowder ecological anticorrosive pigment. The TG-DTA, XRD and TEM measurements were used to characterize the structure and morphology of products. CaZn2(PO4)2-CaB2O4 nanopowders were firstly synthesized by an ultrasonic-aid chemical precipitation method. The XRD and TEM measurements were used to characterize the structure and morphology of products.The activation of pigment has been improved by two ways:one is the synthesis of well-dispersed nanometer-sized powder with narrow distribution; the other way is to mix the two kinds of pigment together to generate a hybrid ecological pigment. Finally, in order to test anticorrosive performance, we commissioned Chen Yang Hebei Corporation(China) to text technical indicators and do the paint experiments. The application experiments were carried out in aqueous alkyd, and the results were compared with the commercial ZPA (made in Germany) and zinc phosphate (made in China). It can be seen that nano-CaZn2(PO4)2-BaB2O4 and nano-CaZn2(PO4)2-CaB2O4 as an anticorrosive pigment has meet with various national standards, especially in resistance to salt solution, which is 120 h more than zinc phosphate and 24 h more than ZPA.It can be concluded that nano-CaZn2(PO4)2-BaB2O4 and nano-CaZn2(PO4)2-CaB2O4 can be employed in the coating industry as an excellent ecological anticorrosive pigment. |
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