MORPHOLOGY AND THERMAL PROPERTIES OF ZEOLITE MECHANOCHEMICALLY MODIFIED BY Ca, Zn AND Mn(II) CATIONS

Abstract

An important direction of new technologies of corrosion protection of metals is the use of inhibitory pigments in the composition of paints and varnishes, which are tolerant to the environment, have high efficiency and can replace chromates. Promising anti-corrosion pigments for paints and varnishes are ion-exchange substances, in particular modified zeolites, which will provide optimal selective resistance to aggressive environmental influences. In this work the dispersion and morphology of complex pigments based on synthetic zeolite and monophosphates of calcium, zinc and manganese are investigated. It was found that the modification of zeolites by metal monophosphates by mechanochemical method in a ball mill for 60 min at a speed of 200 rpm leads to decrease in fraction to 2.0 μm by ~44%… 64% and an increase from 2.0 to 10.0 μm by ~60%. The fraction up to 2.0 μm is represented by particles of irregular globular shape > 10.0 μm - agglomerates. Thermogravimetric studies have shown that all synthesized complex pigments are characterized by thermal stability. Thermolysis is characterized by 4 stages, which correspond to the removal of physically adsorbed water, chemically sorbed water, dehydroxylation of the surface by cleavage of OH groups, and phase transitions. Modification with metal monophosphates increases the thermal stability of pigments in the sequence Na-A: Ca(H2PO4)2 - Na-A: Zn(H2PO4)2 - Na-A: Mn(H2PO4)2. Thermolysis of samples in the temperature range from 15 to 700 °С is took place during four stages, most intensively at temperatures up to 400 °С. During mechanochemical dispersion of zeolites with calcium, zinc and manganese monophosphates, the amount of physically adsorbed water increases by ~18… ~41%, and chemically sorbed water decreases by ~19… ~41%. The specific surface area of zeolite Na-A: Ca(H2PO4)2 increases by ~8%, and Na-A: Zn(H2PO4)2 and Na-A: Mn(H2PO4)2 decreases by ~50% and ~22%, respectively. This may be due to the radii of the metal cations and the fraction content up to 2.0 μm when grinding zeolites. Based on the obtained results, the synthesized zeolites can be recommended for further studies of their inhibitory properties as pigments in the composition of paints and varnishes.