Smart-release inhibition of corrosion driven organic coating failure on zinc by cationic benzotriazole based pigments

A novel cationic benzotriazole pigment (CBP) based on the benzotriazolium cation (BTAH(2)(+)) exchanged into a sulfonated organic resin has been synthesized and evaluated as a means of inhibiting the corrosion-driven cathodic disbondment of organic coatings from the surface of galvanized steel. The CBP is acidic in nature (BTAH(2)(+) pK(a) approximate to 1.1) and is intended to be compatible with acidic coating formulations such as etch-primers. Delamination rates, as measured using a scanning Kelvin probe (SKP), were found to decrease monotonically with increasing CBP volume fraction (Phi(CBP)) and to approach zero when Phi(CBP) = 0.1. The mechanism of CBP operation is described.