Preparation And Study Of The Anticorrosion And Antifouling Composite Organic Coatings

Marine fouling refers to the negative adhesion of the marine organisms(bacteria,microalgae,invertebrates,etc.)on man-made surfaces which include bridges,ships,warships,marine pipelines,nuclear power plants,and petroleum,drilling platform,etc.The fouling adhesion can increase the consume fuel of ship and greenhouse gas emissions,and even destroy the local ecological balance.It will also have a serious negative impact on the equipment operation and the local aquaculture industry.More importantly,the marine fouling on metal surface will change the chemical environment of the surrounding microenvironment,stimulate or promote the corrosion reaction of the metal and then bring serious economic losses and even serious safety hazards.Studies have been shown that the coatings can effectively alleviate the negative adhesion of marine fouling on man-made metal surfaces.However,a single coating could not satisfy demand for the metal protection.Therefore,based on the synergistic effect of excellent biocides or anti-corrosion inhibitors,how to improve the anti-corrosion and anti-fouling performances of the coatings and extend the service life of the coatings are the keys to prepare the designed coatings.The main research results and progresses are as following:1.A functional organic/inorganic hybrid coating with integrated terpolymer and hybrid Ag@TA-SiO2 nanospheres was designed and fabricated for antifouling purpose for the first time.The silicon-containing terpolymer(GHM)was fabricated via a simplified free radical co-polymerization process with glycidyl methacrylate(GMA),2-hydroxyethyl methacrylate(HEMA)and 3-(methacryloxypropyl)trimethoxysilane(MPS).It was expected that the(3-aminopropyl)triethoxysilane(APTES)would become immobilized at the epoxide ring of the GMA and eventually crosslinked,acting as a backbone for the final polymeric coating(PGHMK).Meanwhile,Ag nano-particles were decorated with tannic acid(TA)to have a composite surface structure and loaded with silica(SiO2)to form raspberries.The PGHMK coating was expected to act as an effective antifouling barrier,and the embedded Ag@TA-SiO2 as a functional biocide carrier to collectively inhibit biofouling.The results indicated that the coating suppressed 98.6%of protein adsorption,and its anti-bacterial efficiency reached 99.1%and 82.7%for E.coli and S.aureus,respectively.The coating could also remarkably reduce the attachment of microalgae N.Closterium and Dicrateria zhanjiangensis by 93.5%and 97.6%,respectively.It is envisioned that the composite coating may provide a promising and protective antifouling and antibacterial surface for marine engineering structures.2.PGHMK composite coating showed the good antifouling performance,but it’s important to improve its anticorrosion behavior.Therefore,the composite MXene sheets and polybenzoxazine resin were prepared using some natural and renewable materials for a sustainable purpose.A novel polybenzoxazine(PCD)was firstly synthesized from green curcumin,1,2-bis(2-aminoethoxy)ethane and paraformaldehyde through thermal polymerization with the polymerized high crosslinking network as an inhibitor carrier.Bisphenol-derived and bisamine-derived materials promote the cross-linking of benzoxazine and serve as a carrier to support 2D composite MXene@HNTs for excellent anticorrosion coatings with high efficiency and durability.Secondly,the sustainable and naturally renewable halloysite nanotubes were loaded onto the external surfaces or intercalated into the interstratified interfaces of the MXene as a MXene@halloysite(MH)composite inhibitor.The MH could not only efficiently enhance the anticorrosion performance of the nanocomposite,but also effectively reduce the aggregation of the nanotubes.In addition,all the coatings(only 13 μm)were prepared to detect the performance of anticorrosion.When MH was introduced into the PCD framework,the PCD-MH composite coating exhibited great corrosion resistance behavior relative to the others,and PCD-MH coating exhibited the higher |Z|0.01Hz values after exposuring to the corrosive medium for 50 d,respectively 2.68×107Ω·cm2(immersed in 3.5 wt%NaCl solution)and 3.56×107 Ω·cm2(exposed to 5.0 wt%NaCl salt-spray environment).This work may lead to many promising applications of MXene-based nanosheets in the field of metal-protection.3.A single function of the coatings cannot satisfy the industrial application.It is of great significance to effectively improve the anti-fouling and anti-corrosion properties of the coatings in the field of marine industrial applications.Therefore,in this work,a sustainable high-performance polybenzoxazine coating(PCD)made of benzoxazine monomer synthesized via the Mannich reaction of curcumin,3-aminopropyltriethoxysilane and paraformaldehyde.This curcumin-based polybenzoxazine resin was experimentally demonstrated to be an effective barrier layer,which could evidently reduce the corrosion rate of the substrate metal,and significantly resist the fouling attachment.In addition,it was found that an increased content of PEG in the resin could further improve the antifouling performance of the coating.Molecular dynamics(MD)simulations suggested that a carefully selected density of PEG molecules in the polybenzoxazine framework could critically affect the hydration layer and the interaction energy.Therefore,PEG(Mw=800)was chosen in this study,and 10 wt%or 15 wt%PEG was added into the coating(PCBG-10 and PCBG-15)with higher binding energy and better antifouling performance.The results showed that the polybenzoxazine coatings(PCB or PCBG-X)performed excellently in anticorrosion even after long-term exposure in corrosive environments,and some of the polybenzoxazine coatings,like PCBG-10 and PCBG-15,possessed a superior antifouling capacity.To simultaneously enhance the anticorrosion and antifouling,a double layer coating system was designed using the PCB resin as the sub-layer and the PCBG-10 or PCBG-15 film as the up-layer.The great long-term corrosion resistance of the coatings(P10 or P15)was confirmed by electrochemical measurements in salt immersion for 180 d with the |Z|0.01Hz values of 6.01×l07 Ω·cm2 and 2.32×107 Ω·cm2 as well as in salt-spray environment for 150 d with that of 3.69×107 Ω·cm2 and 6.87×107 Ω·cm2,respectively.It is expected that this new design of the promising polybenzoxazine resin coating system will find wide applications in marine industry and relevant fields.4.A coating can prolong its service life when it effectively performs the excellent anti-corrosion and anti-fouling performances.Thus,via improving the crosslinking between the coating and the nano-filler,the coating can realizes the dual functions to meet the demands.Therefore,in this work,a designed halloysite nanotube(H)was prepared to in-situ controlly grow Ag NPs.The external sheet of the halloysite nanotube was grafted with 3-aminopropyltriethoxysilane(APTES)and 2-furoyl chloride,which effectively enabled the interaction between Ag+ ions and the nitrogen/oxygen atoms of the grafted chemical units via their active lone pair electrons and empty orbits,respectively.Ag nanoparticles were precisely controlled in-situ to grow on the H external sheet and inner lumen.The strong Ag+-N/O interaction allowed the Ag+cations dissolved from the Ag nanoparticles to be partially stored on the nanotubes for slow release.The interaction was experimentally verified by antibacterial measurements and computationally illustrated by density functional theory(DFT).The Ag+-runctionalized halloysite nanotubes were in-situ introduced into a composite coating system during polymerization,in which the inorganic nanotube fillers were bonded in the polymeric framework that was synthesized mainly using naturally renewable curcumin and furfurylamine.Such a sustainable composite coating with a high density structure exhibited outstanding corrosion resistance in 3.5 wt%NaCl immersion and in 5.0 wt%NaCl salt-spray for as long as 126 days and it showed the high EIS value(IZI0.01Hz=1.51×1010Ω·cm2),much longer than most of the coating systems reported so far.It also exhibited great antifouling performance,such as the bacterial killing and the anti-attachment of proteins and bacteria.The study may open a new way to the extended practical application of the eco-friendly and multifunctional composite coating in the marine industry.