Study of Anti-Corosion Properties of Pigments Fe2O3-Al2O3-MgO Obtained by Coprecipitation

Abstract

Promising pigments of the passivating type, in addition to phosphate ones, are other materials - oxyhydroxides, ferrites, molybdates, stanates, borates, tungstates, which are obtained using traditional technologies. condition. Researchers are becoming increasingly interested in the co-precipitation method, which makes it possible to vary the cationic and anionic composition of pigments and obtain nanodispersed products. In addition, developers of paints and varnishes are faced with the task of replacing toxic anti-corrosion chromium-, cadmium- and plumbum-containing pigments that are part of most modern inhibitory primers with pigments that are safe for human health. An alternative to such paint and varnish materials are oxide type fillers, which are anti-corrosion pigments, including oxyhydroxides, magnesium ferrites, cobalt aluminates, zinc ferrites, copper ferrites, magnesium aluminates, zinc aluminates, etc. The color of pigments and their anticorrosion properties depend on the chromophore ions included in the structure of the resulting compounds.Co-precipitation technology has a number of advantages over traditional ones and can radically reduce the cost of producing oxide materials. This process, based on the use of the internal chemical energy of the system, allows synthesis to be carried out at reduced temperatures, synthesis duration and energy costs. The simplicity of the equipment, the possibility of synthesizing a significant amount of the product of the desired phase and granulometric composition, and the environmental friendliness of the process also indicate the feasibility of using this method. Recently, attempts have been made to obtain pigments by co-precipitation, but no systematic studies have been carried out on the final products. The resulting products were in most cases poorly reproducible. In this regard, it becomes interesting to synthesize in a mode that would make it possible to obtain pigments with good color characteristics in a finely dispersed state, and eliminate the labor-intensive grinding stage, study the conditions for the formation of pigments with the structure of oxyhydroxides, the influence of their composition on color and anti-corrosion properties, study the patterns of formation of anti-corrosion properties, development of compositions for producing pigments using the co-precipitation method and subsequent heat treatment. Through experimental and theoretical studies, the influence of the nature of chromophore cations on the color tone, color purity, and anti-corrosion properties of pigments in the Fe-Al-Mg-O system has been established, which allows for the targeted synthesis of beige, red and yellow pigments with high anti-corrosion properties. The main technological properties of pigments are determined by the composition of metal-containing anions. The anti-corrosion properties of oxyhydroxide pigments are largely determined by the presence of hydroxide ions formed due to dissociation. The greatest effect is observed in the case of using metal compounds whose dissociation constants differ significantly. The protective effect is mainly determined by the slowdown of the anodic process. At the same time, anions containing aluminum atoms accelerate corrosion processes.