This paper reports the synthesis of waterborne epoxy phosphate emulsion (WEP) through the reaction between epoxy resin E44 and phosphoric acid and ammonia neutralization. Synthesized WEP was characterized by FTIR for the confirmation of reaction between epoxy groups and phosphoric acid and SEM for morphology. WEP acted as a modifier in two-component epoxy anticorrosion coating on rusty steel substrate. The anticorrosion properties of the coating on rusty steel were investigated by electrochemical impedance spectroscopy (EIS) and Tafel polarization curve. Tafel polarization curve revealed that waterborne epoxy coating containing WEP had better protection ability which is clearly reflected by the protection efficiency (96.6%). EIS study also showed the higher impedance value for WEP containing coating as compared to pure waterborne epoxy coating.
Haihua Wang,Wenjing Zhang,Yongning Ma,Guiqiang Fei,Huan Wen,Liyu Sun,Yanming Shao,Yong-Mook Kang
The compatibility between polypyrrole (PPy) and waterborne epoxy coating (EP) remains the main challenge. Here, phosphorylated poly (vinyl alcohol) (PPVA) and p-toluene sulfonic acid sodium (p-TSA) were simultaneously utilized as dopants to modify PPy and prepare water dispersible PPVA/p-TSA/PPy (PPVAT/PPy) solution. Additionally, poly (vinyl alcohol) (PVA) and TSA were also adopted to prepare PVA/p-TSA/PPy (PVAT/PPy) for comparison. Denser film with granular morphology was observed for PPVAT/PPy nanocomposite film. Compared with PVAT/PPy-40 %, the tensile strength of PPVAT-8.0 %/PPy-40 % increased from 248.8–283.9 MPa. PPVAT/PPy displayed higher compatibility and interactions with EP compared to PPy-TSA and PVAT/PPy. Compared with EP, the impedance modulus of PVAT/PPy+EP and PPVAT/PPy+EP increased from 3.17×10 5 to 1.07×10 8 and 1.62×10 9 Ω·cm 2 ; corrosion current density I corr decreased from 1.49×10 −6 to 7.72×10 -8 and 4.01×10 -9 A·cm -2 ; corrosion potential E corr displayed a positive shift of 230 mV and 269 mV, respectively. The corrosion inhibition efficiency of PPVAT/PPy+EP reached 99.83 %, which is much higher than that of PVAT/PPy+EP (93.97 %). PPVAT/PPy+EP nanocomposite coating has been proved to have preferable long-term corrosion resistance based on electrochemical impedance spectra (EIS), polarization curves and salt water spray test. The simultaneous incorporation of phosphate anions, sulfate ions and PPy into EP was beneficial to fabricate high-performance anticorrosion coating.
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