Preparation Of Nano TiO₂-PPy Self-healing Microcapsules And An Improvement On Silane Film

Silane treatment technology is forming silicone film with silicon oxygen bond in the substrate surface with organosilanes as the main raw materials,and has the following advantages: environmental protection,energy saving,low emissions and so on.But the single silane film thin,low density,low corrosion resistance,especially do not have the self-healing function as six chromium passivation,which affect its corrosion resistance and application.In this paper,the core-shell structure of organic conductive polymer coated with titanium dioxide nano micelles is prepared,and forming a composite conversion film with silane,which could lead the self-heling mechanism into the silane coating,while the silane film damaged,the mechanism of self-healing triggered and achieve the purpose of improving the coating corrosion resistance.The mechanism of anticorrosion is explored.The optimum process parameters of γ-AEAPS film were optimized by orthogonal experiment by setting different silane solution ratio,hydrolysis time and curing temperature.The corrosion resistance of the coatings were studied by Tafel curves and electrochemical impedance spectroscopy（EIS）.The results showed that the water alcohol ratio,hydrolysis time and curing temperature had significant effect on the corrosion resistance of the γ-AEAPS film.In the water alcohol ratio 1/4,hydrolysis 4h,curing temperature of 60-100 orthogonal conditions,silane film impedance is formed on the surface of low carbon steel value up to 2000 ohm.cm2.The reason is that the physical barrier hinders the diffusion and migration of electrons between the electrolyte solution and the metal interface.The SiOFe interface layer formed between the silane film and the metal matrix changed the surface state of the steel matrix,the cathodic inhibition was enhanced,the corrosion potential was shifted,and the corrosion resistance of the silane film was improved.In the 3.5% sodium chloride solution,the electrochemical impedance of γ-AEAPS film was reduced 60% in 0.25 h.Under the assistance of ultrasonic wave,the polypyrrole coated nano titanium dioxide core-shell composite microcapsules were prepared by in-situ oxidation polymerization,the morphology of microcapsules was studied by scanning electron microscopy（SEM）,through infrared spectroscopy（FT-IR）analysis and X ray diffraction（XRD）to study the microcapsule structure,analyzes the influence of different emulsifier and the concentration on the microstructure,particle size and morphology of polypyrrole coated nano titanium dioxide,and the formation mechanism of microcapsule was put forward.The results show that the PPyTiO₂ microcapsule preparation has close relationship with the emulsifier,the anionic surfactant is more favorable for the surface coating of titanium dioxid.SDBS had a significant effect on the dispersion,Due to the oxidation and crosslinking of the long chain structure of the sodium oleate in the emulsification process,the micelles are connected with each other.The pyrrole monomer is the core of the nanometer titanium dioxide,which forms the polypyrrole film wall with the nano crystalline structure,and forms the PPy-TiO₂ composite nano capsule with spherical,uniform particle size and diameter of about 100 nm.The formation of polypyrrole coated microcapsule particles is due to the chemical adsorption of anionic surfactant on the surface of TiO₂ powder In order to effectively restrain the self aggregation and promote the polymerization of pyrrole monomer on its surface.The PPy powder and PPy-TiO₂ microcapsules were doped into the γ-AEAPS sol,and forming PPy/γ-AEAPS and PPy-TiO₂/γ-AEAPS composite coating on the surface of low carbon steel,the composite coatings were characterized and analyzed by EIS and circuit fitting.The results showed that PPy,PPy-TiO₂ and γ-AEAPS respectively form the silane composite film which improved the corrosion resistance of the film,the amount of PPy is 0.3696g/m L,the PPy/γ-AEAPS film impedance value reached 8200 ohm.cm2,about 4 times as much as the γ-AEAPS.PPy-TiO₂ microcapsule was added into 0.4767g/ mL,PPy-TiO₂ silane film impedance is 3600 ohm.cm2.PPy and PPy-TiO₂ microcapsules mainly increase the density of the silane film by filling,and PPy forms a passivation film on the surface of the matrix to improve the corrosion resistance of the composite film,in the initial immersion shielding plays a major role,in the later period,the passivation film plays an important role.The particle size and uniformity have significant effect on the corrosion resistance of the film,the initial corrosion resistance of microcapsules was lower than that of PPy/γ-AEAPS film.The core shell structure of microcapsules endows PPy-TiO₂ composite silane film with self repairing function,with the corrosion of the composite film,the microcapsules begin to break down,and the released TiO₂ particles fill the cracks to enhance the mechanical filling effect,The impedance of the composite film increases,and shows the repair effect.When the corrosion of the electrolyte is greater than that of the microcapsule self-healing,the impedance of the composite film decreases.