| Graphene,a single layer of carbon atom,is considered as promising nanomaterial in the anti-corrosion field because of its outstanding chemical stability,high specific surface area and superior barrier properties.So far,the corrosion resistance properties of metallic substrate can be sharply enhanced by the coverage of a single or a few layers of graphene.However,once defects are generated,the galvanic corrosion induced by graphene may exacerbate the corrosion of metal substrate,which poses a potential threat to the safety and reliability of engineering and equipment.As an alternative direct deposition,the addition of graphene in the polymer matrix can effectively avoid the occurrence of galvanic corrosion because such composite coatings combine the unique barrier properties of graphene and ease of organic coating formulation.Unfortunately,the strong interlayer force between adjacent graphene sheets easily leads to its agglomeration in the polymer matrix.Therefore,in order to solve the high-efficiency dispersion of graphene in polymer matrix,this paper proposes a method for modifying graphene with siloxane and aniline oligomers.The corrosion resistance of modified graphene-based composite coating in NaCl solution was discussed and its protection mechanism was studied in depth.The main contents are as follows:Polyhedral oligomeric silsesquioxane functionalized graphene oxide(POSS-GO)was synthesized by one-step condensation reaction,and the problem of efficient dispersion in many organic solvents was solved.The prepared POSS-GO was added to the epoxy resin and its corrosion protection behavior and tribological behavior were investigated.The results showed that the POSS-GO was an effective anti-corrosion and lubrication additive.Compared with pure epoxy resin,the impedance modulus was increased by two orders of magnitude,and the friction coefficient and wear rate g were greatly reduced after the addition of 0.5 wt%functionalized graphene oxide.This excellent anti-corrosion and lubrication effect were mainly attributed to the effective shielding effect and good lubrication performance of POSS-GO.On the basis of high-efficiency dispersion,a porous graphene carrier by the reaction between octaamino POSS and graphene oxide was prepared.After that,the corrosion inhibitor of BTA was loaded into the porous structure,and it was added into epoxy coating to form functional coating.The self-healing property of obtained coating at different pH values and its long-term corrosion resistance in 3.5 wt%NaCl solution were explored.The results showed that the protective ability of the defective coating could be restored by BTA release from the modified graphene carrier.In addition,the long-term corrosion resistance of modified graphene-based epoxy coating was greatly improved compared to pure epoxy coating.Through analysis,the effective healing process of coating contained two conditions:first,the BTA released from the graphene carrier could form an adsorption layer on the exposed metal surface;second,the impermeable graphene greatly hindered the permeation of corrosion medium and corrosion extension around the defect.This new graphene-based carrier endowed efficient self-healing and long-lasting corrosion resistance to polymer coatings.Using toluene diisocyanate as a carrier,the hydrophobic POSS modified oligoaniline was obtained by the reaction between POSS-NH2 and oligoaniline.And the efficient dispersion of graphene in absolute ethanol was achieved on the basis of ?-? interaction between them and ultrasonic exfoliation.The anti-corrosion performance was investigated via preparing graphene/epoxy composite coating.This work revealed that the oligoaniline-intercalated graphene presented a good dispersibility in epoxy resin and and taked the synergistic effect on protective property.The addition of rarely 0.5 wt%graphene could endow coatings with superior anti-corrosion performance.Novel oligoaniline functionalized graphene sheets was prepared by intercalation and silanization of trianiline precursor,and the corrosion resistance of functional graphene/epoxy composite coating was studied.The results showed that the silanzied oligoaniline was hydrolyzed to form a chain,and oligoaniline could absorb on the graphene surface via ?-? interaction between them,improving the dispersion stability of graphene and the compatibility between G and epoxy matrix.The addition of 0.5 wt%silanzied oligoaniline-intercalated graphene greatly improved the long-term corrosion resistance of epoxy coating and endowed a certain self-healing property.The excellent anti-corrosion performance was attributed to two parts:(1)the well-dispersion graphene could fully exhibit its barrier property;(2)the silanized aniline trimer with intact electroactivity could induce the formation of passive film.A novel oligoaniline-modified silica hybrid coating was deposited as a pre-process layer on the surface of Q235 steel by one step coelectrodeposition of a mixture of tetraethyl orthosilicate and silanized oligoaniline.And then the surface of pre-process layer was coated by a silanized oligoaniline-intercalated graphene based epoxy coating.The results showed that the electrodeposited oligoaniline-modified silica coating exhibited a superior superhydrophobic properties compared to the electrodeposited silica coating and the sol-gel oligoaniline-modified silica coating.At the same time,the oligoaniline modified silica coating maintained the original redox properties of oligoaniline.After adding the oligoaniline modified silica pre-process layer,the corrosion resistance of graphene epoxy composite coating system was greatly improved.The anti-corrosion mechanism was the synergistic effect of the barrier property of inorganic silica and the special electroactivity of organic oligoaniline,which effectively inhibited the penetration of corrosive medium and induced the formation of passivation film. |
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