| Among the metal materials, magnesium lithium alloys possess high specific strength,good deformation and electrical conductivity properties, and they have been widely used in aerospace, weapons, ships, computer application fields. However, low stability and poor corrosion resistance of magnesium lithium alloys, strongly restrict their application. Therefore,research on corrosion protection of magnesium lithium alloys to expand the scope of their application is one of the key research directions.In this paper,we mainly discussed the modification of montmorillonite (MMT) by organic compound, synthesis of polyaniline (PANI) and poly (o-methoxyaniline) (POA)particles, preparation of PANI/organic montmorillonite and POA/organic montmorillonite particles. Then the particles as fillers were added into epoxy resin (E-44) with different proportions, and the coatings were prepared on the surface of magnesium lithium alloys by pulling method. The influence of the fillers and their amount on corrosion resistance property of the coatings was investigated. The mainly contents of this paper were shown as the following:(1) Hexadecyltrimethyl ammonium bromide (CTAB) and montmorillonite (MMT) as the starting materials,a series of organic montmorillonites were prepared by changing the reaction temperature, reaction time and the molar ratio of CTAB and MMT. It showed that the modified organic montmorillonite with the largest layer spacing can be acquired when the conditions are 80?,1 h and the mole ratio of CTAB and MMT is 1:1;(2) Ammonium persulfate (APS) as the oxidant, hydrochloric acid as the doping agent,polyaniline and poly (o-methoxyaniline) as the conducting fillers were synthesized by oxidation polymerization, respectively;(3) Organic montmorillonite was dispersed in distilled water, subsequently aniline or o-methoxyaniline monomer was mixed in the suspension, the complex conducting polymer filler was prepared by in situ intercalation polymerization when APS as the oxidant and hydrochloric acid as the doping agent. Evaluated by thermogrametry analysis (TGA), the results showed that polymer nanocomposite filler possesses better thermal resistance performance when organic montmorillonite content is 0.1%. It indicated that the degree of polymerization is higher and it is benefit for improving conductive ability;(4) Polyaniline and poly (o-methoxyaniline) were added into epoxy resin respectively, and the coatings were prepared on the surface of magnesium lithium alloys. The performances of these coatings were characterized by electrochemical impedance spectroscopy (EIS) and differential scanning calorimetry (DSC). EIS showed that resistance of the coatings was improved with the increase of filler content. The anticorrosive performance of poly(o-methoxyaniline) coating was better than that of polyaniline coating. DSC results indicated that glass transition temperature of the coatings was improved by adding fillers, accordingly,diffusion capacity of inhibiting corrosion medium was increased;(5) Polyaniline/organic montmorillonite (PANI/OMMT) coatings and poly(o-methoxyaniline)/organic montmorillonite (POA/OMMT) coatings were prepared on the surface of magnesium lithium alloys. EIS showed that corrosion resistance of the coatings was further improved by the addition of organic montmorillonite; And with the increase of composite filler adding proportion, anticorrosive penetration performance was promoted,POA/OMMT coating with 2% content exhibited best corrosion protection. Water absorption test presented that the absorption rate of epoxy varnish coating was higher than other coatings,and accordingly, diffusion capacity of inhibiting corrosion medium was worse. DSC results showed that the glass transition temperature was increased by adding complex polymer filler. |
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