Tymus M. Duraluminum alloys corrosion inhibition with chromate-free pigments and their synergistic compositions.

The thesis objective is to develop compositions of ecologically safe inhibiting pigments with synergistic action for effective substitution of toxic chromates in paint coatings on duralumin alloys. Object of investigation - duralumin alloy corrosion in synthetic acid rain and protective action of chromate-free compositions of inhibiting pigments. Subject of investigation - dependencies of duralumin alloy corrosion inhibition by chromate-free composition, its synergistic influence on protection of the alloy from local corrosion and effectiveness of use in paint coatings. Experimental methods - electrochemical impedance spectroscopy, direct current polarization, scanning electron microscopy with energy dispersive X-ray analysis, optical microscopy, X-ray photoelectron spectroscopy, capacitance and ohmic resistance method. It was investigated the effectiveness of alloy D16T and AA2024 corrosion inhibition by using mixtures of inorganic, mainly phosphate-based pigments and estimated their protection mechanism in comparison with strontium chromate. Thus, a comparative study of corrosion inhibition in acid rain solution and pigment extracts was carried out in order to find prospective candidates for chromate replacement. It was established that the composition of zinc phosphate and calcium ion exchange silica has significant anticorrosion effect for duraluminium alloys in an artificial acid rain solution, which is typical for industrial regions. In order to determine peculiarities of the mechanism of this synergy a model cell for galvanic corrosion at second phase particles was constructed from the matrix alloy and a large intermetallic component manufactured by vacuum-arc melting. It is clear from electrochemical data that the galvanic model is shown to imitate corrosion of commercial aluminium alloys. The polarisation behaviours of each part of this cell could be independently measured during exposure in the inhibitor solutions, while surface analysis could be performed on the cell components. In galvanic tests, both the chromate and chromate-free mixture performed well giving approximately 92% inhibitive efficiency. Inhibited organic primer on epoxy basis for aluminum alloys protection was developed. Physico-mechanical properties of the new material satisfy the requirements of paint standards. Experimental-industrial testing of new epoxy primer at SEIC "Techno-Resurs" and SIC "Lvivanticor" has shown promise of its use for anticorrosion protection system of metal constructions in industrial atmosphere.