Investigation of Zinc-Filled Compositions for Protection Against Atmospheric Corrosion of Carbon Steel

The anticorrosive properties of zinc-filled coatings (ZFC) were studied. It is known that the zinc content in ZFC should be high, and it can be reduced without losing the protective efficiency (Z) of ZFC by introducing modifying additives. The studies were carried out using electrochemical methods in 0.5 M NaCl solution and gravimetric methods (in 0.5 M NaCl, in a G-4 heat and humidity chamber and in a salt spray chamber). The protective efficiency of zinc-filled compositions based on used motor oil (WMO) additionally containing 40 wt. % Zn powder and 5 wt. % inhibiting additive: paraffin, stearic or myristic acids was studied. Electrochemical polarization studies revealed that coatings containing 40 wt. % zinc powder do not provide protective protection due to a more positive potential than that of steel. ZFC with additives of stearic and myristic acids provide the highest protective efficiency. The obtained results confirmed the data of gravimetric tests. ZFC with additives of stearic acid provide Z = 87% in accelerated corrosion tests in 0.5 M NaCl, in a heat and moisture chamber Z = 97%. The best results were obtained for ZFC with additives of myristic acid: in accelerated corrosion tests in 0.5 M NaCl Z = 99%, in a heat and moisture chamber G-4 - Z = 98%. It should be noted that the thickness of the ZFC with myristic acid (274 Ојm) is higher than for the ZFC with stearic acid (166 Ојm). The first corrosion spots during tests in a salt spray chamber on samples without a coating were observed after two hours of exposure, the best results were obtained for the ZFC with myristic acid, when the first corrosion spots appeared only after 154 hours.