Anticorrosion properties of ion-exchangable pigments in epoxide coatings

Abstract

Hexavalent chromium compounds (chromates) have been widely used as inhibitive pigments in the formulation of anticorrosive paints. However, their high toxicity and carcinogenic effects are forcing the development of effective chromate-free organic coatings. One such alternative, which is very attractive from a scientific point of view, is the use of ion-exchangeable pigments (IEPs). The few studies conducted with this type of pigment are not conclusive about their anticorrosive efficiency and controversy surrounds their functioning mechanisms, interchange capacity and anticorrosive performance. In the present research, which focuses on the anticorrosive protection of this type of pigment, calcium/silica (Ca/Si) IEPs were synthesized in first step, next epoxide paint coatings were formulated. IEPs have been applied on low carbon steel panels. The effect of these non-toxic pigments on the protective properties of coatings has been tested by means of natural and accelerated corrosion tests (humidity, salt spray and SO2). Experimental results have shown that IEPs are suitable to formulate anticorrosive paint films with improved anticorrosive effects.