Influence of natural inhibitor, pigment and extender on corrosion of polymer coated steel

Lupine (Lupinous albus L.) seeds extract was incorporated into a vinyl chloride–vinyl acetate copolymer based paint formulation to control steel corrosion in 0.5 M NaCl. Evaluation of this system included the use of electrochemical impedance spectroscopy (EIS) and a salt spray cabinet for accelerated aging tests. The EIS data demonstrated that highest protection was attained at a lupine threshold concentration of 0.025 g/L. Two white color pigments (ZnO and TiO2) and three extenders (CaCO3, mica and talc) were tested as paint additives. The accelerated aging tests showed that the coated steel panels containing TiO2 had a high degree of blistering while those containing ZnO exhibited reasonable hiding power and better protection efficiency. Field tests indicated that the presence of TiO2 enhanced the growth of fouling organisms over the coated steel surface.