Preparation And Corrosion Resistance Of Polyaniline / TiO 2 Epoxy Coatings

Currently, on the one hand, in the process of acid oil and gas field development, corrosive H2S gas and Cl-in the formation water medium had caused severe corrosion to X70pipeline steel. On the other hand, as anticorrosion coating for pipeline, epoxy coating had poor ability against the acid gas corrosion, and was needed to be modified. Thus, in order to solve the problem of S2-and Cl" corrosion in aqueous solution to X70pipeline steel, researching on modified epoxy-based organic coating and coating protective effect, had theoretical and practical significance.Polyaniline/TiO2nanocomposites with different TiO2weight ratios were synthesized using chemical oxidative polymerization through polymerizing polyaniline (PANI) to the surface of inorganic nano TiO2. The obtained PANI/TiO2composites were characterized by FTIR, XRD, SEM and TG. The results suggested:When mass ratio of the TiO2/aniline was0.05, the yield76.80wt%of the PANI/TiO2was obtained. The PANI/TiO2contains all the main characteristic absorption bands of PANI; PANI/TiO2was in nano scale (60nm-95nm), the ball shape, and good dispersion. The PANI revealed the broad diffraction peak and a certain degree of crystallinity. The existence of the TiO2affected the crystalline behavior of the PANI to a large extent; When temperature was410℃, the PANI/TiO2nanoparticles began to break down.The orthogonal test was dessigned. With the method of blending, PANI/TiO2-epoxy coating was synthesized. The coating formula was screened as follows:PANI0.288wt%, TiO20.288wt%, epoxy resin28.818wt%, titanium dioxide1.441wt%, aluminum tripolyphosphate8.646wt%, zinc8.646wt%, talc8.646wt%, barium sulfate14.409wt%and polyamide28.818wt%. Optimalizing PANI/Ti02-epoxy coating with excellent mechanical properties was obtained:coating adhesion for level1; impact strength up to50kg-cm; excellent flexibility; pencil hardness of6H. The chemical resistant experiments verified that the coating also had the best corrosion resistance. The low frequency impedance modulus value can be up to5.112.The corrosion resistance of the coating in S2-,Cl-solutions and formation water was studied respectively by immersion corrosion tests and high pressure and temperature corrosion tests. At last, coating corrosion mechanism was discussed combined with XRD instruments. The studies showed:when the concentration of S2-was3wt%, the temperature80℃, and the immersion time120h, the coating corrosion current density minimum icorr was4.235×10-8A/cm2and it means the coating had better resistance against S2-solutions; when the concentration of Cl" was3.5wt%, the temperature65℃, and the immersion time72h, the coating corrosion current density minimum icorr was2.352×10-8A/cm2, meaning the coating had better resistance against Cl-solutions; when the pressure was3MPa, the temperature120℃, and the immersion time96h, the coating corrosion current density minimum icorr was2.352×10-8A/cm2and the coating had better resistance against formation water corrosion; Corrosion mechanism of the coating was shielding effect and passivation effect.