The Effect Of PANI On The Corrosion Resistance Of The Epoxy Coating On The Magnesium Alloy

Due to the unique doping mechanism and outstanding electrochemical properties, one of the applications of polyaniline (PANI) is the corrosion protection of metals. In the present study, the effect of polyaniline on the corrosion resistance of epoxy coating on AZ91D magnesium alloy has been studied.In this paper, the chemical oxidative method was applied to prepare the PANI. In the acidic aqueous solution, aniline was converted into the PANI by the ammonium persulfate as oxidant. The eigenstate PANI was achieved when PANI was de-doped by ammonia. Then, the eigenstate PANI was modified by doping hydrofluoric acid or dodecyl benzene sulfonic acid. Their structure was characterized by FT-IR. The results illustrated that the peak of benzenoid ring had little change but the peak of quinoid ring had some shifts to the lower wave number. Therefore, the location doped by hydrofluoric acid or dodecyl benzene sulfonic acid was on nitrogen atoms in the quinoid rings rather than in the benzenoid ring.Epoxy coating containing the eigenstate PANI and two kinds of the acid doped PANI were prepared on AZ91D magnesium alloy surface respectively, and the anti-corrosion properties of the coatings were studied by means of EIS and EN in 3.5%NaCl solution. The surface morphology of the coated AZ91D magnesium alloy after immersion was observed by SEM. XPS was used to analyze the elements on the surface of different samples. The following results were obtained:1,The addition of eigenstate PANI could significantly improved the corrosion resistance of epoxy coating. The XPS results indicated that the presence of PANI changed the chemical structure of the corrosion film on the surface of the AZ91D magnesium alloy, which improved the corrosion resistance of the coated AZ91D magnesium alloy.2,PANI doped with two kinds of acid had better corrosion resistance then eigenstate PANI. The XPS results indicated that PANI coating doped with hydrofluoric acid had the best protection ability of the corrosion, which due to form the MgF2 protective film and PANI protection film formed on the surface of metal.3,When the content of hydrofluoric acid doped PANI was 2%,5%,10% and 15% in epoxy resin, the best protection among four coating was the content of 10%.