Inhibiting properties of manganese-containing complex oxides obtained by calcination method

Issue 24(3) 2019
Pages 39-45

M. R. Ziganshina, Kazan National Research Technological University, Kazan, Russian Federation

E. A. Nurislamova, Kazan National Research University, Kazan, Russian Federation

R. N. Dzamukov, Kazan National Research University, Kazan, Russian Federation


Keywords: anticorrosive pigments, toxicity, manganese-containing complex oxides, calcination

http://www.doi.org/10.31615/j.corros.prot.2019.93.3-5

 

Carbon steel that is the main structural material is highly vulnerable to corrosion. The most common method of anticorrosive protection of steel objects is painting, and the main protective effect in a generally multilayer coating is provided by the first primer layer containing inhibitory pigments. Until recently, the most efficient pigments of this type were chromates that are known to be carcinogens. Until recently, application of complex metal oxides for this purpose has been actively developed in search for alternatives to toxic anticorrosive chromium-containing pigments. Analysis of the elemental base for anticorrosive pigments capable of replacing chromates shows that manganese is similar by its properties to chromium, which is characterized by different oxidation degrees and complexing ability. An important advantage of manganese-containing compounds in comparison with chromium-containing compounds is their significantly lower toxicity. However, to date, manganese-containing compounds are used as decorative pigments in preparation of paints and varnishes. In this work, anticorrosive and other physicochemical properties of complex oxides, including manganese with the oxidation degrees of +4 and +5 obtained by the calcination method were studied. As a result, it was shown that the obtained products are promising for use as anticorrosion pigments. The higher inhibitory properties of pigments containing manganese in the oxidation state of +5 are apparently the result of the alkaline reaction of their aqueous extract. As found in the experiments, the competitiveness of the synthesized pigments can be markedly increased by using natural ore, pyrolusite, as the source of manganese.