Improvement of alkyd film performance with mineral pigments

Abstract

The effect of three mineral pigments (white titanium dioxide, yellow iron oxide, and iron blue) on the alkyd film performance is studied in this paper. The protective films were realised on carbon steel substrate. The electrochemical measurements (electrochemical impedance spectroscopy- EIS and anodic polarisation) were carried out in 3%NaCl solution, at 25 degrees C temperature during a 1500 hours period. The interpretation of the impedance spectra established an electrical equivalent circuit with four time constants for the tested carbon steel/alkyd film systems in electrolyte solution, fitted to the experimental data. The water and ions permeability of the films was determined. It resulted that for a good performance of the pigment, its fineness degree must be < 0.5 mu m and the adsorption capacity in 40-50% range. The white titanium dioxide pigment presents the highest beneficial effect on the alkyd film performance.