Preparation and Anticorrosion Properties of Doped Polyaniline/Epoxy Coating
|School||Harbin Engineering University|
|Keywords||Polyaniline Epoxy resin Mg-Li alloy Anticorrosion coating Anticorrosion mechanism|
The polyaniline (PANI) was synthesized by chemical oxidation polymerisation and emulsion polymerisation with ammonium persulfate as the oxidant in this paper. The hydrochloric acid, phosphate acid, sulfosalicylic acid and o-tosylate acid were used as doped acid, respectively. The PANI was characterized by infrared spectrum, X-ray diffraction, scanning electron microscope and conductivity test.The results of infrared spectra showed that the polyaniline was synthesized successfully with different methods and different doped acids, which all had the "benzene quinone "structure. The result of conductivity test showed that the conductivity of polyaniline doped with hydrochloric acid and chemical oxidation polymerisation was highest; The result of SEM showed that different doped polyaniline had different shape; The result of X-ray diffraction indicated that the polyanilines doped with hydrochloric acid in chemical oxidation polymerization and doped with sulfosalicylic acid in emulsion polymerisation have the higher crystallization.The anticorrosion coating was prepared by the polyaniline doped hydrochloric acid in chemical oxidation polymerization, epoxy resin E-44, curing agent T-31, pigment titanium dioxide, talc powder, nano-SiO2 and the solvent. The mixed solvent was toluene and n-butanol (the ratio of mass was 1:1). The best mass ratio of the coating (relative to mass of the epoxy resin) was curing agent 35%, solvent 40%, titanium dioxide 2%, talc powder 5%, nano-SiO2 2%.The anticorrosion coating was prepared by adding 0%～5%PANI on the surface of tinplate and Mg-Li alloy. The anticorrosion properties were investigated by open circuit potential, electrochemical impedance spectroscopy and polarisation curves in 3.5% NaCl solution. It was finded PANI/epoxy resin coating on the surface of tinplate and Mg-Li alloy both had good anti-corrosion properties. The open circuit potential of the coating on the surface of Mg-Li alloy was less than the tinplate about 0.6～1.2V. The results of the polarization curves and electrochemical impedance spectra showed that the coating of adding 4% polyaniline on the surface of tinplate had the best anticorrosion properties, and the coating of adding 2% polyaniline on the surface of Mg-Li alloy had the best anticorrosion properties. The results of electrochemical tests showed that the corrosion potential of polyaniline-containing coating increased, the corrosion current decreased about 2～7 orders of magnitude, and the impedance increased 2-5 times, which proved polyaniline on the surface of Mg-Li alloy and tinplate had good anticorrosion properties.The anticorrosion mechanism of the polyaniline-containing coating on the surface of Mg-Li alloy and tinplate is due to its passivation, shielding and corrosion inhibition.