Preparation of an epoxy/polyaniline composite coating and its passivation effect on cold rolled steel

Aniline (ANI) was polymerized with the presence of solid epoxy resin (EP) powder through common oxidation polymerization and polyaniline (PANI) coated EP particles, that is a core-shell structure of PANI and EP, were achieved. Dedoped with aqueous ammonia, emeraldine base form (EB) coated EP particles (EP/EB) were obtained also. The particles were ground with an appropriate solvent by ball milling and a uniform dispersion of epoxy and nano PANI was obtained. The dispersion was formulated with curing agent to coat cold rolled steel (CRS) and the passivation effect was proved by electrochemical tests. All the EP/EB beared much higher yields compared to the pure EB polymerized under the same condition. UV-vis spectra indicate EB in EP/EB possess a lowered oxidation states with the decrease of ANI/EP in the reactants. Both UV-vis and XPS analyses indicate the existence of H-bonding between EB and EP molecules. All EP/EBs exhibit similar thermal behaviors to EP due to the extremely low EB loading. Corrosion potential measurements show that EB coating, which was prepared firstly by ball milling of EP/EB particles and then mixed and cured with a curing agent, provides excellent anti-corrosive effect for cold rolled steel (CRS) in extremely low EB loading, which comes from the nano-dispersed EB particles in the EB coatings attested by TEM.