Corrosion Assessment of Zinc-Rich Primers Containing Polyaniline and the Effect of Acid as a Dopant

We investigated how adding the dopant acid for polyaniline (PAni)-containing zinc-rich primers (ZRPs) can influence the resulting ZRP’s corrosion performance. Two organic acids (camphorsulfonic [CS] and phenylphosphonic acid [H₂PP]), and two inorganic acids (phosphoric [H₂PO₄] and hydrochloricacid [HCl]) were tested and the different PAni-modified ZRPs exhibited differences in their cathodic protection and barrier mechanisms during exposure to a 3.5 wt% NaCl solution. The hydrochloricacid-doped PAni-containing ZRP had the best anticorrosion properties in terms of the zinc particle interfacial activation (sacrificial) and coating’s barrier properties. Corrosion resistance of the coating systems can be ranked as PAni-Cl > PAni-H₂PO₄ > PAni-HPP ≥ PAni-CS. The corrosion assessment of these coatings can be explained in terms of three stages: the activation stage of the zinc particles, the competition stage, and the steady state stage.