Exfoliation and functionalization of α-zirconium phosphate in one pot for waterborne epoxy coatings with enhanced anticorrosion performance

Abstract

Having high aspect ratio and excellent gas barrier property, two dimensional α-zirconium phosphate nanosheets (α-ZrP) are one of the promising anticorrosive nanofillers. In this work, under mild conditions, layered α-ZrP were effectively exfoliated by Tris buffer solution and functionalized by situ polymerization of polydopamine (PDA) in one pot. And then the functionalized α-ZrP (f-ZrP) were introduced into waterborne epoxy (WEP) coatings that were applied on the mild steel for electrochemical corrosion tests. Results of TEM, XRD and AFM reveal that α-ZrP are successfully exfoliated with an interlayer space of 1.72 nm and a thickness of 0.78 nm. Characterizations of FTIR spectra, TEM image and EDS mapping confirm that α-ZrP are decorated by PDA. With PDA decoration, f-ZrP gain a better compatibility with WEP than pristine α-ZrP do, leading to a homogeneous distribution in the polymer matrix. And the exfoliation by Tris buffer provides f-ZrP with high aspect ratio, which is beneficial for f-ZrP/WEP to fight against the permeation of corrosive mediums. Therefore, after 15-day immersion in 3.5 wt% NaCl solution, the f-ZrP/WEP composite coatings show high value of |Z0.01Hz| (1.90 × 107 Ω·cm2), which is about one order of magnitude over that of blank WEP coatings (2.33 × 106 Ω·cm2).