Optimization of the composition of aluminum phosphate and walnut shell-based composition to increase the corrosion resistance of paint coatings

The object of the study is аnti-corrosion properties of walnut shell powder and aluminum phosphate mixtures. The existing problem is that the most effective chromate-containing pigments, which were traditionally used for the manufacture of paint and varnish coatings, are toxic. Given this fact, the research of scientists aims at finding alternative low-toxic compounds, which are phosphate pigments. Since they are inferior in efficiency, modern research is aimed either at the synthesis of new modifications and complex forms of pigments, or at the development of effective mixtures of pigments that would provide the necessary level of anti-corrosion protection of steel. Along with this, an urgent direction is to increase the level of environmental friendliness of paint and varnish coatings using annually renewable plant waste, which, due to the content of tannins, have proven themselves well for surface preparation before painting. The work investigated the effect of a mixture of non-toxic aluminum phosphate and finely ground walnut shell powder on the corrosion behavior of steel. An adequate mathematical model “composition – mass corrosion index” was proposed. The mathematical model allowed to establish the relationship between the composition and corrosion rate and find the optimal composition of the studied mixture. The calculations showed that at a ratio of aluminum phosphate and walnut shell powder of about 8:1, the mass corrosion rate of steel in the obtained extract is 0.020 g / (m2 · h). By experimentally verifying the optimal composition of the study, a mass corrosion index of 0.018 g / (m2 · h) was achieved, which confirms the theoretical calculations and ensures the practical applicability of the results obtained. The results of the study will be useful for specialists working in the field of developing water-based anti-corrosion paints and coatings, with an emphasis on studying the influence of pigments and fillers on the corrosion behavior of steel.