Application of Ion-exchange Compounds as Corrosion Inhibiting Pigments to Organic Anticorrosion Coatings Ⅰ Cation-exchange Pigments

It is well documented that chromate pigments and other heavy metal compounds must be eliminated from organic anticorrosion coatings due to their toxic nature and carcinogenic effects in the future. The novel ion-exchange pigments can play a double role of absorbing the harmful ions such as H+, Cl-, SO2-4 and releasing the inhibiting ions on contact with aggressive electrolyte invading the coating. The released inhibitors can provide active corrosion protection to the defects in the coating and substrate, on the other hand, the uptake of harmful ions decreases the aggressiveness of the corrosive medium, and thereby reduces the rate of ecorrosion processes. Therefore, such new inhibiting compounds have been developed as the potential alternate materials of the traditional toxic pigments, and have attracted a lot of attention. In this paper, the application of ion-exchange pigments, such as Ce3+, Zn2+ cation-exchanged bentonite, Ca2+ cation-exchanged silica and MoO2+2 cation-exchanged zeolite, to organic anticorrosion coatings is reviewed.