| Our country spends lot of money on metal anticorrosion every year,so it is the first to seek an economic and effective anti-corrosion method.To protect the metal from the external environment,it is necessary to lay a protective layer on the metal surface as a physical barrier to organize the intrusion of corrosive media.Through the efforts of many researchers,it has been found that adding inorganic fillers,organic fillers,anti-corrosion additives to the coating,but the results are not very satisfactory.In recent years,it has been found that polyaniline has a greater advantage in anticorrosive properties than other fillers,and has attracted the attention of many researchers.However,its structure has become a headache problem for many researchers,an anti-corrosive coating with best properties can be obtained by modifing its structure.In our research,the chemical grafting method is used to improve the compatibility between WAR and PANI,and promote the uniform dispersion of PANI in WAR.Long-term corrosion resistance is also improved by chemically incorporating PANI into the WAR.N-alkylated PANI was prepared from eigenstate PANI,brominated alkane and sodium hydride?NaH?.Our team prepared a composite anticorrosive coating by blending waterborne alkyd resin with the modified PANI.The specific results are as follows:?1?Oxidative copolymerization method was used to prepare modified PANI dimer from An and PDA.WAR-PANI was synthesized by grafted PANI onto waterborne alkyd resin to improve compatibility between PANI and alkyd resin.It can be seen from FT-IR and TEM that the long chain of PANI was successfully grafted to the alkyd resin.Polarization and EIS results indicate that the corrosion resistance of WAR-PANI was much higher than WAR/PANI and WAR.When the GMA content was 2.67%,WAR-PANI shows the best performance.The corrosion density was reduced to 9.66×10-1111 A·cm2,and the impedance modulus and coating resistance were increased to 1.29×107 and 1.57×10 7 A·cm 2,respectively.WAR-PANI has a higher corrosion resistance than WAR and WAR/PANI because the interaction between PANI and the epoxy to forms a dense protective film on WAR.By analyzing the SEM images of different corrosion times,it was more intuitive to see the change of the surface corrosion of the composite coating before and after corrosion.After soaking 3.5wt%NaCl solution,when the GMA content was 2.67%,the surface morphology of WAR-PANI was less corrosive than WAR and WAR/PANI,which further proves that WAR-PANI had better corrosion resistance.?2?N-alkylated PANI was prepared from eigenstate PANI,brominated alkane and sodium hydride?NaH?.The influences of mass ratio of PANI to BrCnH2nBr,reaction time,reaction temperature and alkyl chain length on the modified PANI were disscussed.Finally,the optimum conditions for the modification were as follows:when the carbon atom was 12,the mass ratio of PANI to BrC12H24Br was 1:2,the reaction temperature was 40?,and the reaction time was 16 h.The presence of alkyl side chains in the PANI molecular chain was confirmed by FT-IR,UV-Vis,XRD and EA spectra.Studies on the solubility of PANI-BrC12H255 and PANI-BrC12H24Br in different solvents show that PANI-12Br?I?and PANI-12Br?II?have good solubility in organic solvents compared to PANI,and PANI-12Br?II?was better than PANI-12Br?I?in organic solvents.PANI-12Br?I?and PANI-12Br?II?were less thermally stable than PANI,and PANI-12Br?II?was less thermally stable than PANI-12Br?I?,indicating that the degree of alkylation of PANI-12Br?II?was higher than PANI-12Br?I?.The structure of PANI before and after modification was characterized by SEM.Experiments showed that the PANI structure after alkylation becomes dense,and PANI-12Br?II?was more dense than PANI-12Br?I?.?3?WAR/PANI-12Br?I?and WAR/PANI-12Br?II?composite emulsions were prepared by blending PANI-12Br?I?and PANI-12Br?II?with alkyd resin.The properties of WAR,WAR/PANI-12Br?I?,WAR/PANI-12Br?II?composite coatings were compared,and the effect of different PANI-12Br?II?dosages on coating properties were disscussed.Through the stability analysis of WAR,WAR/PANI-12Br?I?,WAR/PANI-12Br?II?composite emulsion,it was found that the TSI value of the alkyd resin decreased after the addition of polyaniline,indicating that the stabilityof the emulsionwas improved,and WAR/PANI-12Br?II?was more stable than WAR/PANI-12Br?I?.Through the test of water absorption of WAR,WAR/PANI-12Br?I?and WAR/PANI-12Br?II?composite emulsion films,the results showed that the presence of PANI leads to a significant decrease in water absorption of waterborne alkyd resin,WAR/PANI-12Br?II?has better water resistance than WAR/PANI-12Br?I?.Polarization and EIS results show that the addition of PANI can improve the corrosion resistance of the coating,and WAR/PANI-12Br?II?has higher impedance?5.12×109?·cm2?and corrosion voltage?-0.290 V?and the lowest corrosion current density?9.55E-9A·cm2?than WAR/PANI-12Br?I?,indicating thatWAR/PANI-12Br?II?hasbettercorrosionresistancethan WAR/PANI-12Br?I?.The dispersion stability index?TSI?curve of WAR/PANI-12Br?II?composite emulsion with different PANI-12Br?II?content was found when the PANI-12Br?II?content was 0.3%,the stability of the polymer is the best.Analysis of water absorption of WAR/PANI-12Br?II?film with different PANI-12Br?II?content found that when PANI-12Br?II?content was 0.3%,the water absorption of polymer is the lowest;Analysis of mechanical properties and electrochemical properties of WAR/PANI-12Br?II?coating with different PANI-12Br?II?content found that when PANI-12Br?II?content was 0.3%,the adhesion of the coating was the best and the anti-corrosion effect of the composite emulsion The best,the impedance value reached 1.37×1011?.cm2.Throughtheelectrochemicalanalysisofdifferentcorrosiontime WAR/PANI-12Br?II?-0.3%,it was more intuitive to see the change of corrosion of the composite coating before and after corrosion,even after immersing 3.5wt%NaCl solution for 480h,the impedance of WAR/PANI-12Br?II?-0.3%is still very high(1.37×1010?·cm2),which further proves that WAR/PANI-12Br?II?has better corrosion resistance. |
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