RESEARCH ANTI-CORROSION PROPERTIES OF COMPOUNDS IN THE Fe2O3-MgO-Al2O3 SYSTEM

The most well-known anti-corrosion paints usually contain inhibitors based on hexavalent chromium or lead compounds. The use of these compounds is limited because they pollute the environment and pose risks to human health and the environment. Spinel compounds are becoming increasingly widespread as alternative products for protecting steel from corrosion. For example, ferrites have the general formula MFe2O4 (М = Co, Ni, Mg, Zn or Ca) and the spinel structure. The influence of cations on the anti-corrosion properties in the Fe2O3 -MgO-Al2O3 system was established using experimental studies. The compounds were obtained by the method of coprecipitation with subsequent calcination. Aqueous salt solutions were used to synthesize coprecipitated hydroxides. The synthesis conditions were varied according to the following parameters: the nature of the initial metal salts, the ratio of metal cations. The anti-corrosion activity of the pigments was evaluated by the potentiodynamic method, by comparing the anodic and cathodic polarization curves, as well as the corrosion potential and current curves calculated on the basis of Tafel plots. The phase composition of the pigments was determined by X-ray phase analysis. To study the influence of the cationic composition on the properties of ferrites, a simplex lattice design was used, which requires a minimum number of experiments to study the influence of factors on the selected response functions. Electrochemical tests showed that all pigments in the Fe2O3 -MgO-Al2O3 system protect steel from corrosion. This conclusion can be made in accordance with the shift of the corrosion potential to more positive values relative to the steel sample in the background solution. Low corrosion potentials correspond to high pH values of the aqueous extract, and a high anti-corrosion effect is observed for compositions containing magnesium cations. Comparison of isolines for protective effect and pH of aqueous extract shows almost complete coincidence. Complex oxide compounds of magnesium slow down both cathodic and anodic processes.