Generally, organic coatings which contain zinc ferrites are able to protect metal substrate, most often low-carbon steel, by inhibition mechanism. Conductive polymers are using a system of conjugated double-bonds to transfer a charge over the chain thereby providing their own electrical conductivity in the organic coatings. The charge from the chain in combination with the iron substrate generates electrons to the formation of passivation products on the surface of paint film. This paper is focused on combination of zinc ferrite with conductive polymer and using of synergic effect of these two components. The organic coatings were formulated from hematite and specularite on pigments concentration line 5, 10, 20 and 25 wt.% for better recognizing of the effectiveness of zinc ferrite component. The content of the conductive polymer was consistently set at 3 wt.% in each organic coating. A solvent-based epoxy-ester resin was used as a binder. The physico-mechanical and corrosion tests were performed for all samples. The corrosion signs were evaluated on the surface of coating and also on the surface of metal substrate. In the end, the efficiency was compared alone zinc ferrite and alone polymers and also their combinations.
This paper is focused on the heteropoly acids as another new possibility of dopant for conducting polymers which can be used as anticorrosive pigments for steel protection. The newly prepared pigments, silicotungstic and phosphotungstic heteropoly acids, were characterized by determination of oil number and density. The value of critical pigment volume concentration was determinated by these values. The pigment volume concentration was 0.5; 1; 3 and 5 % in epoxyester-resin witch was used as a binder. Organic coatings were applicated on steel panels which were tested by mechanical and corrosion tests. The main exam was exposition of testing sample in sulphur dioxide atmosphere. Another important exam was measuring the specific electrical conductivity and determination of corrosion loss. After 1584 hours, the samples were evaluated. Values of anticorrosion efficiency are increased for silicotungstic heteropoly acid pigment. But with long-term exposition, phosphotungstic heteropoly acid pigment has better and higher anticorrosion efficiency than the other sample.
A. Kalendová, E. Halecká, K. Nechvílová and M. Kohl
Mixed oxide-based pigments Mg–Zn–Fe with different particle morphologies were prepared by high-temperature solid phase reactions. The core shell pigments containing ferric oxide and non-isometric particles of layered silicates were also prepared. The pigments were tested in paints, the pigment volume concentrations in the modified alkyd resin based binder being 5%, 10%, and 15%. The paint properties were examined by accelerated corrosion tests and by physico-mechanical tests. The effect of the pigment particle morphology on the surface hardness of the paint films was also studied. The influence of pigment volume concentration on the coating properties, and the optimum concentrations providing the most efficient anticorrosive protection were processed. A higher anticorrosion efficiency was observed for the paints with pigments possessing the lamellar particle shape.