Studies On Process And Corrosion Resis Tance Of Electrodeposited Polyaniline

The new research displays that the polyaniline coating, as a kind of novel anti-corrosion material, is thought of an important material by more and more people and it will become one of the most important fields of conductive polyaniline. Because the conductive polymer (polyaniline, for example) is dissoluble in water or general organic reagent and has bad thermoplastic, so the production is difficult and the cost is high. And at the same time, the whole process includes a lot of volatile organic reagent, which can contaminate the environment and do harm to the workers' health. So adopting the electrochemical method to produce polyaniline is better than other methods.In this experiment ,we used aniline-sulphuric acid solution, under the constant potential and the constant current ,and successfully got the polyaniline in 1Crl8Ni9Ti .we also got some parameters(sulphuric acid 1.5mol/L, poly-temperature 10~30℃, current density 0.5~5mA/cm2.poly-time 2~10min.The Scanning electron microscope (SEM) analysis shows that the heated coating is almost the same as the common coating, except that the heated coating has certain crack in some part. X-rays diffraction indicates that the heated coating is the crystal structure.The corrosion-resistance studies showed that the pitting corrosion potential of the stainless steel coated with polyaniline has increased about 1.0V (vs. SCE) as compared with blank. The polyaniline coating can greatly improve the pitting corrosion resistance of a stainless steel and has better prospect in corrosion prevention of stainless steels.Studies showed that the poly-potential,coating color,and the anticorrosion capacity of 1Crl8Ni9Ti stainless steel all depends on the different acid(H2SO4, HC1, HNO3, H3PO4 and CH3COOH),but they all are electric conductive. With the decreasing of the pH of compound solution, the poly-potential and the poly-current of aniline decrease. The more smooth the stainless steel, the longer the depositing time, and the coating more smooth and tighter. The result is the coating in H3PO4- aniline solution has the best anticorrosion capacity.The polyaniline coating deposited on low carbon steel in oxalic acid - aniline solution by constant current anode polarization method showed that the progress included three successive stages: metal dissolving; passivation and polymerization. Thecoating with blue green color and well distributed, got under this condition, is found adhere well to the matrix of low carbon steel.Studies showed that the better conductive polyaniline coating on low carbon steel (08F) by means of electrochemical constant current method, in oxalic acid - aniline solution, depended on the following optimal parameters, oxalic acid 1.0mol/L .aniline 0.5 mol/L, poly-temperature 10~30C, current density 0.5~5mA/cm2,poly-time 2~ 10min.The corrosion-resistance studies showed that the coating improved the capacity of the corrosion-resistance and the anti pitting corrosion of low carbon steel.Studies showed that to get the coating on the low carbon steel we should adopt low concentration oxalic acid (or the dissolving time is shorter than the depositing time)other than strong acids such as H2SO4, HCl, HNO3, and so on .Studies showed that the coating is easily got on the easy passivate matrix (such as stainless steel), while some metal (such as Mg) must be treated especially before the coating deposited. And not all metal can get polyaniline coating (such as pure Cu).The polarization curve of the coating on the PbO2 showed the potential (1.66V) is lower than the potential of PbO2 (1.55V). The potential is lower, so the dissolving potential of Zn2SO4 is lower and the cost is lower too.