Improved anticorrosive property of waterborne epoxy coating by ultrasonic blending with small amounts of polyaniline

Abstract

In order to improve the anticorrosive performance of waterborne epoxy (WEP) coating, small amounts of polyaniline (PANI) were blended under ultrasonic irradiation to obtain PANI/WEP composite coatings with high dispersibility of PANI particles. The PANI/WEP composite coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). Their adhesive force level and hardness grade were tested based on the Chinese National Standard GB/T9286-1998 and GB/T6739-1996, respectively. These results indicated that, compared to the pristine WEP coating, the addition of PANI with suitable content could completely fill the micropores or microcracks and remarkably improve the hardness grade of composite coatings. The electrochemical impedance spectra (EIS) and Tafel polarization curves revealed that the addition of PANI not only could increase the impedance arc, but also could increase the impedance modulus at low frequency. Then, the salt spray tests were employed to observe the anticorrosive performance of PANI/WEP composite coatings. Finally, the enhanced anticorrosive mechanism of WEP coating by the addition of small amounts of PANI was proposed and discussed. The addition of PANI with suitable content could play an important role of physical and chemical barriers to improve the anticorrosive performance of waterborne epoxy coating.

Preparation and anticorrosion performance of nano polyaniline/polyurethane interpenetrating network composite coating

“…15,19 In contrast, in situ polymerization can be prepared by scaling up, and the powder obtained is PANI, which provides better selectivity in terms of being used as a filler and can be mixed with the coating resin or polymer matrix by dispersion methods such as milling and ultrasonication, which enable the properties of the resin and the PANI to be achieved at the same time. 20 Therefore, the method of obtaining PANI by in situ polymerization is more versatile. The obtained PANI in powder form is added to epoxy, PU, alkyd, acrylic resins etc., or it is directly used as a filler in commercially available PU and epoxy coatings.…”

“…24−26 Generally, at lower PANI concentrations the coatings have higher open-circuit potential and coating resistance, while at higher PANI concentrations PANI causes internal morphological changes leading to an increase in coating porosity and poorer corrosion performance. 27 Xu et al 20 used ultrasonic irradiation to mix a small amount of PANI powder into an epoxy resin emulsion. When a tiny quantity of PANI was applied, the dispersion of PANI in the composite coating became more uniform, allowing it to effectively fill the microporous pores and increase the anticorrosive capabilities of the coating.…”

“…Electrochemical deposition is achieved directly on the metal, which is limited by the area of the electrode, and the obtained electrodeposited coatings are thin, do not have good mechanical properties and cannot meet the requirements for flexibility and adhesion 15,19 . In contrast, in situ polymerization can be prepared by scaling up, and the powder obtained is PANI, which provides better selectivity in terms of being used as a filler and can be mixed with the coating resin or polymer matrix by dispersion methods such as milling and ultrasonication, which enable the properties of the resin and the PANI to be achieved at the same time 20 . Therefore, the method of obtaining PANI by in situ polymerization is more versatile.…”

“…Xu et al 20 . used ultrasonic irradiation to mix a small amount of PANI powder into an epoxy resin emulsion.…”