The Study On Corrosion Resistance Coating Of Polyaniline

Emeraldine base(EB) form of polyaniline was synthesized by chemical method in the present work.Phosphoric acid and fluohydric acid were used to dope EB form of polyaniline.FT-IR analysis was used to confirm their chemical structure. Potentiodynamic polarization curves,electrochemical noise(EN) and scanning electrochemical microscope(SECM) were used to investigate the effect of EB-PANI on the corrosion behaviour of carbon steel.Stochastic analysis theory was used to study the mechanism of EB-PANI on carbon steel.In addition,electrochemical impedance spectroscopy(EIS) and electrochemical noise(EN) were used to investigate the protection performance of three kinds of polyaniline/epoxy coating on magnesiumlithium alloy.Also the stochastic analysis theory was used to study the mechanism of the three kinds of coating.Scanning electron microscope(SEM) was used to observe the surface of the samples after immersion.XPS was used to analysis the elements on the surface of different samples.The following results were obtained:EB-PANI increased the anodic Tafel slope of carbon steel and restrained the anodic process of carbon steel obviously.With immersion,the open circuit potential(OCP) of carbon steel decreased quickly,and carbon steel was passivated.The results of SECM and EN revealed that the protective film was formed on the surface of EB-PANI coating with immersion gradually.The results of stochastic analysis of EN showed that the corrosion generation rate and probability of corrosion on the surface of EB-PANI coating were lower than that of carbon steel in 3.5%NacCl solution,the corrosion of carbon steel was restrained.Three kinds of polyaniline/epoxy coating all showed very good performance on protecting magnesium-lithium alloy.Among those,the fluohydric acid doped polyaniline/epoxy coating behaved the best protection performance.The performance between the phosphoric acid doped polyaniline/epoxy coating and the EB form of polyaniline/epoxy coating was similar,but the former was better.The results of XPS analysis of the surface of the samples after immersion showed that it was the interaction between polyaniline,magnesium- lithium alloy and oxygen in the solution that made the polyaniline/epoxy coating performed great protection behaviors.The results of stochastic analysis of EN showed that both the corrosion generation rate and probability of corrosion of magnesium-lithium alloy were decreased,the corrosion of carbon steel was restrained.