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 and field emission scanning electron microscopy. 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 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.
Highlights
IntroductionMany methods have been attempted to protect the metallic surface against corrosion, for example, polymeric coatings [3], inorganic coatings [4], hydrid coatings [5], self-healing smart coatings [6], photocathodic protection [7] and so on
The phenomenon of metallic corrosion worldwide exists in various fields such as mechanical equipment, bridge construction, chemical industry, shipping and ocean engineering, which has resulted in huge economic losses and been greatly concerned by governments and enterprises [1,2].Many methods have been attempted to protect the metallic surface against corrosion, for example, polymeric coatings [3], inorganic coatings [4], hydrid coatings [5], self-healing smart coatings [6], photocathodic protection [7] and so on
According to the Chinese National Standard GB/T9286-1998 and GB/T6739-1996, PANI10WEP and PANI15WEP coatings exhibit the highest hardness grade among these five coatings and all the coatings have the adhesive force level of “0” that is the highest level of the given standard. These results indicate that the addition of PANI can improve the hardness grade of composite coating compared to the pristine waterborne epoxy (WEP) coating
Summary
Many methods have been attempted to protect the metallic surface against corrosion, for example, polymeric coatings [3], inorganic coatings [4], hydrid coatings [5], self-healing smart coatings [6], photocathodic protection [7] and so on. The polymeric coatings are more popularly used for the protection of metallic surface, which can form a protective barrier to inhibit the penetration of corrosive media including H 2O, O2 and other ions. Well designed polymers usually exhibit good adhensive property and stability. The coating technologies for polymers are simple and diverse, such as brush coating, spray coating, bar coating, roller coating, flow coating, spin coating and dip coating [8]. The conventional solvent-based polymeric coatings are seriously suppressed and alternatively replaced by the emerging waterborne-based ones [9]
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