Role of a hybrid dye-clay nano-pigment (DCNP) on corrosion resistance of epoxy coatings

In this work, we combined the desirable color characteristics of cationic dyes and the good barrier properties of organoclays by synthesizing hybrid dye-clay nano-pigments (DCNPs) via cationic exchange of two cationic dyes (i.e. basic blue 9 and basic yellow 87) and different commercial organoclays (Cloisite 15A, 20A and 30B). Then, different amounts of synthesized DCNPs were incorporated in an epoxy coating and their corrosion resistance behaviors were investigated by using electrochemical impedance spectroscopy (EIS) and salt spray test. The dry and wet adhesions of samples were measured employing pull-off adhesion test. In addition, the morphology of dispersed DCNPs in epoxy matrix was evaluated by using different techniques including XRD and TEM. Results showed that the extent of intercalation/exfoliation of DCNPs was greater than that of organoclays. Moreover, it was found that DCNPs based on Cloisite 20A had the best dispersion properties among different nanoclays. It was revealed that the corrosion resistance of coatings containing DCNPs (based on Cloisite 20A) was superior in comparison to coatings containing only Cloisite 20A. Finally, results demonstrated the technical feasibility of preparation of colored epoxy coatings with superior corrosion resistance by the incorporation of DCNPs (in the range of 1-5 wt.%) into epoxy matrix.