Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

Two-Dimensional Co_(2)(OH)1,4-Benzenedicarboxylate-Halloysite Nanotube Nanocomposite-Epoxy Coating with High Corrosion Resistance

Introducing inorganic nanomaterials into a polymer matrix greatly improves the anticorrosion performance of epoxy coatings(EP);however,poor compatibility between the materials can limit the improvement in properties.In this work,based on the high interface compatibility of two-dimensional(2D)Co_(2)(OH)_(2)BDC(BDC=1,4-benzenedicarboxylate)in the epoxy coating that we reported in previous work,we fabricated a 2D Co_(2)(OH)_(2)BDC-halloysite nanotube(HNT)nanocomposite have a structure consisting of alternating of nanosheets and nanotube by in situ synthesis.The nanocomposite was characterized by Fourier transform infrared spectroscopy,X-ray diffraction,and scanning electron microscopy.The mechanical and anticorrosion performance of the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was evaluated by mechanical tests and electrochemical impedance spectroscopy spectra.Compared with a conventional unreinforced epoxy coating,the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating had higher mechanical strength and toughness,and the low-frequency impedance modulus of 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was increased by three orders of magnitude,demonstrating the high corrosion resistance of our reinforced coating.

A High-Performance Composite Epoxy Coating Based on the Cooperative Enhancement of 2D Co_(2)(OH)2BDC and Electrospun PAN Nanofiber Membrane

Based on a two-dimensional(2D)Co-MOF(Co_(2)(OH)_(2)BDC)with a self-contained organic interface and low conductivity,a composite epoxy coating(2D Co_(2)(OH)_(2)BDC-PAN/EP)was constructed by a two-step preparation.First,a polyacrylonitrile(PAN)nanofiber membrane was electrospuned on the surface of Q235 steel,followed by coating using the epoxy coating(EP)containing 2D Co_(2)(OH)_(2)BDC.The 2D Co_(2)(OH)_(2)BDC-PAN/EP composite epoxy coatings showed robust mechanical performance and excellent corrosion resistance capacity.

Effect of Nano Al Pigment on the Anticorrosive Performance of Waterborne Epoxy Coatings

This paper presents the results regarding the effect of nano aluminum powder pigment concentration on the protective properties of waterborne epoxy films in 3.5 wt pct NaCl solution. The anticorrosive performance of the coatings with 0.5, 1, and 3 wt pct pigments and none pigment were investigated using electrochemical impedance spectroscopy （EIS）, scanning electron microscopy （SEM） and Raman spectroscopy techniques. The results show that adding appropriate amount of nano-aluminium powder pigment can enhance the barrier properties of the epoxy coating, which is attributed to the surface effect of nanoparticles and the compatibility of the pigment with the waterborne epoxy coatings.

The Role of Renewable Protocatechol Acid in Epoxy Coating Modification: Significantly Improved Antibacterial and Adhesive Properties

It is of great significance to design epoxy coatings with superior antibacterial properties and high adhesive properties, as well as excellent processing, superior durability, and high transparency. However, it is still a challenge because of the common complex design and synthesis. Herein, the bio-based monomer protocatechuic acid(PCA) was used as raw material, the catechol structure with high bonding and antibacterial properties was introduced into the flexible alkane segment of ethylene glycol diglycidyl ether(EGDE) through an efficient, and green method, and it was cured with isophorone diamine(IPDA) to prepare corresponding thermosets. The cured resins exhibited excellent allaround qualities, particularly in bonding and antibacterial. When 30% PCA was added to pure epoxy resin, the adhesion between substrate and coating increased from 4.40 MPa to 13.60 MPa and the antibacterial rate of coating against E. coli and S. aureus could approach 100%. All of this is due to the fact that the catechol structure present in PCA has the ability to interact with various substrates and alter the permeability of bacterial cell membranes. The architecture of this method offers a fresh approach to dealing with the issues of challenging raw material selection and complex synthesis techniques.

Enhanced corrosion resistance of epoxy resin coating via addition of CeO_(2) and benzotriazole

The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied.In this work,cerium dioxide(CeO_(2))and benzotriazole(BTA)were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel.Scanning electron microscopy results indicated that the CeO_(2) grains were rod-like and ellipsoidal in shape,and the distribution pattern of BTA was analyzed by energy dispersive spectroscope.The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO_(2) and BTA co-addition,and electrochemical impedance spectroscopy test analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating.And the optimal protective performance was provided by the coating containing 0.3%(mass)CeO_(2) and 20%(mass)BTA,which was attributed to the barrier performance of CeO_(2) particles and the chemical barrier effect of BTA.The formation of corrosion products was analyzed using X-ray diffraction.In addition,the corrosion resistance mechanism of the coating was also discussed in detail.

Effect of Nano Clay on Corrosion Protection of Zinc-rich Epoxy Coatings on Steel 37

Epoxy zinc rich coatings containing clay nanoparticles were prepared and the effect of clay content on the cathodic protection performance of the coatings was evaluated by electrochemical impedance spectroscopy（EIS） and immersion test. Open circuit potential（OCP） measurements and immersion tests were also carried out to better understand the behavior of zinc rich coating. EIS and OCP measurements showed that addition of 1 wt% clay improved the cathodic protection duration and sacrificial properties of the epoxy zinc rich coating. Transmission electron microscopy（TEM） photographs confirmed that clay nanoparticles were successfully dispersed in the coating matrix loaded with 1 wt% clay. Immersion test results indicated that addition of 1 wt% clay nanoparticles in zinc rich epoxy coatings increased the cathodic protection ability of coatings.

Amino-functionalized Ti_(3)C_(2)T_(x) with anti-corrosive/wear function for waterborne epoxy coating

Two-dimensional Ti_(3)C_(2)T_(x) flakes have great application potential in various areas due to their optical,electronic,electrochemical and mechanical properties,but their anti-corrosion and wear-resistance performance were not well understood.The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti_(3)C_(2)T_(x) into the epoxy coating.Here,few-layered Ti_(3)C_(2)T_(x) sheets with amino-functionalization were prepared,and as reinforced-additives were added into the waterborne epoxy coating.Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail.The results reveal that the composite coating with 0.5 wt.%amino-functionalized Ti_(3)C_(2)T_(x) sheets shows excellent corrosion protection(the lowest frequency impedance was 3.12×10^(9) cm^(2))and wear resistance(wear rate was reduced by 72.74%).The greatly improving performance of composite coatings mainly depends on:(a)good dispersity and compatibility of amino-functionalized Ti_(3)C_(2)T_(x) in organic matrix,(b)high adhesion strength between coating and metal substrate and(c)the intrinsic properties of Ti3C2Tx sheets.The work provides a good path for applications of MXene as multifunctional additives.

Corrosion Resistance of Graphene-Reinforced Waterborne Epoxy Coatings

Graphene （G） was dispersed uniformly in water and used as an inhibitor in waterborne epoxy coatings. The effect of dispersed G on anticorrosion performance of epoxy coatings was evaluated. The composite coatings displayed outstanding barrier properties against H20 molecule compared to the neat epoxy coating. Open circuit potential （OCP）, Tafel and electrochemical impedance spectroscopy （EIS） analysis confirmed that the corrosion rate exhibited by composite coatings with 0.5 wt% G was an order of magnitude lower than that of neat epoxy coating. Salt spray test results revealed superior corrosion resistance offered by the composite coating.

Corrosion resistance of tannic acid,d-limonene and nano-ZrO_(2)modified epoxy coatings in acid corrosion environments

The protection of rusted carbon steel in acid corrosion environments is of great significance for equipment to keep safe operation.In this work,we presented a method to protect the rusted steel by ru st conversion treatment and epoxy coating.Tannic acid was selected as rust conversion agent.Tannic acid,D-limonene and nano-ZrO_(2)were used to improve the corrosion resistance of epoxy coatings.The Raman spectra,Xray diffraction and 3 D confocal images were used to characterize the rust conversion reaction.Ad hesion test showed that the loss of wet adhesion of the optimal coating was relatively low due to the addition of tannic acid,limonene and nano-ZrO(2).The corrosion resistance of five different coatings was investigated by scanning electron microscopy(SEM)and electrochemical analysis.Results show that after 264 h acid immersion,the low frequency resistance of the optimal coating consisting of rust conversion treatment and additives is 10^(7)Ωcm^(2),three orders magnitude higher than that of the pristine coating.Moreover,SEM indicates that the optimal coating possesses a smooth surface and an unbroken interface between substrate and coating.Accordingly,the corrosion-resistant mechanism of the hybrid coating is proposed.

A facile approach to fabricating graphene/waterborne epoxy coatings with dual functionalities of barrier and corrosion inhibitor

A facile and environmentally-friendly method is developed to prepare graphene/waterborne epoxy(WEP)composite coatings.The graphene nanosheets are produced with electrochemical-exfoliation in the solution containing surfactants,cetyl trimethyl ammonium bromide(CTAB)and sodium dodecyl sulfate(SDS).The nanosheets containing solution thus formed are subjected to a quick dialysis and then directly used as a diluent for WEP without any further treatment.This preparation method overcomes the commonly identified problems of aggregations and‘corrosion promotion’effect associated with graphene,and increases the impedance of the composite coatings by more than two orders of magnitude.The analysis of anticorrosion performance suggested that the presence of surfactants not only improves the dispersibility of graphene nanosheets but also endows the composite coatings with both barrier and corrosion inhibition capabilities.The strategy reported herein may pave the path to the large-scale production of graphene anticorrosion coatings.

Smart ZnS@C filler for super-anticorrosive self-healing zinc-rich epoxy coating

The zinc-rich epoxy cathodic protection coating is the most widely used anticorrosion material for marine steel.However,traditional conductive fillers lack the intelligent self-healing effect,which limits the long-term anticorrosion performance.Herein,with uniform carbon-coated ZnS(ZnS@C)nanoballs as the smart active release filler,we propose an anticorrosive and self-healing zinc-rich maleic anhydride epoxy coating.Due to the high pore filling efficiency of the nanoballs,the water vapor transmission rate of the coating with an initial corrosion efficiency of 99.92%and a low-frequency impedance of|Z|f=10mHz=3.88×10^(10) Ω·cm^(2),was reduced by 52%.The carbon-shell of the nanoball increases electron transmission paths in the coating and improves conductivity by nearly two orders of magnitude,which effectively activates more Zn-sites and extends the cathodic protection time.Moreover,once the steel-substrate undergoes regional corrosion,the SO_(4)^(2-)hydrolyzes from the ZnS-core of the nanoball and reacts with iron ions on the corroded area accurately and intelligently to fill the gap and self-heals into a new dense barrier layer(Fe_(2)(SO_(4))_(3),etc.),which significantly improves the shielding protection ability during the long-term usage of the coating.The effective anticorrosion time of the proposed coating could be up to 3,400 h.

Micron-scale ultrathin two-dimension zirconia nanosheets towards enhancing anticorrosion performance of epoxy coatings

Polymer nanocomposite coatings have attracted great interest in the anticorrosion fields due to their excellent properties.Nanofillers are necessary to achieve high anticorrosion performance of the polymer coating.Herein,we report a wet-chemical template strategy to prepare large-size ZrO_(2)nanosheets,in which the Zr^(4+)ions are anchored on the surface of a graphene oxide template via electrostatic adsorption,followed by a thermal treatment process to remove graphene.Atomic force microscopy(AFM)and scanning electron microscopy(SEM)images show that the size and thickness of as-prepared ZrO_(2)nanosheets are more than 2μm and~4.5 nm,respectively.The micron-scale ultrathin two-dimension(2D)ZrO_(2)nanosheets,for the first time,are utilized as the anticorrosive fillers in the epoxy coating to reduce the porosity,consequently promoting the gas and water barrier properties of the composite coating.The polymer coating containing 1.0 wt%ZrO_(2)nanosheets shows a high initial impedance(89.1 GΩ·cm^(2))that can protect the metal substrate from being corroded during long-term immersion(60 days),which is better than that of the reduced graphene oxide(rGO)-incorporated coating and the ZrO_(2)nanoparticles-incorporated coating.This work offers valuable insights into the design and preparation of novel and efficient 2D electric-inert nanofillers for anticorrosion coatings.

Cerium Methacrylate Assisted Preparation of Highly Thermally Conductive and Anticorrosive Multifunctional Coatings for Heat Conduction Metals Protection

Preparing polymeric coatings with well corrosion resistance and high thermal conductivity(TC)to prolong operational life and ensure service reliability of heat conductive metallic materials has long been a substantive and urgent need while a difficult task.Here we report a multifunctional epoxy composite coating(F-CB/CEP)by synthesizing cerium methacrylate and ingeniously using it as a novel curing agent with corrosion inhibit for epoxy resin and modifier for boron nitride through"cation-π"interaction.The prepared F-CB/CEP coating presents a high TC of 4.29 W m^(−1)K^(−1),which is much higher than other reported anti-corrosion polymer coatings and thereby endowing metal materials coated by this coating with outstanding thermal management performance compared with those coated by pure epoxy coating.Meanwhile,the low-frequency impedance remains at 5.1×10^(11)Ωcm^(2)even after 181 days of immersion in 3.5 wt%NaCl solution.Besides,the coating also exhibits well hydrophobicity,self-cleaning properties,temperature resistance and adhesion.This work provides valuable insights for the preparation of high-performance composite coatings with potential to be used as advanced multifunctional thermal management materials,especially for heat conduction metals protection.

Preparation and Characterization of Carboxyl-terminated Poly(butadiene-co-acrylonitrile)-epoxy Resin Prepolymers for Fusion-bonded-epoxy Powder Coating

Liquid carboxyl-terminated poly（butadiene-co-acrylonitrile）（CTBN）-epoxy resin（EP） prepolymers were prepared with different contents of CTBN.The chemical reactions between EP and CTBN were characterized by Fourier ransform infrared（FTIR） spectroscopy and gel permeation chromatography（GPC）.The scanning electron micrograph（SEM） and dynamic mechanical analysis（DMA） of curing films showed phase separation,and the rubber particles were finely dispersed in the epoxy matrix.Mechanical properties analysis of curing films showed that impact strength and elongation at break increased significantly upon the addition of CTBN,indicating good toughness of the modified epoxy resins.Thermogravimetric analysis（TGA） showed that the incorporation of CTBN had little effect on the thermal stability of EP.Fusion-bonded-epoxy（FBE） powder coatings modified with CTBN-EP prepolymers were prepared.The experimental results demonstrate the ability of CTBN-EP prepolymers,toughening technology to dramatically enhance the flexibility and impact resistance of FBE coatings without compromising other key properties such as corrosion protection.

Developing polydopamine modified molybdenum disulfide/epoxy resin powder coatings with enhanced anticorrosion performance and wear resistance on magnesium lithium alloys

Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive application.There are limited approaches to exploit such anti-corrosion and mechanical properties of magnesium lithium alloys.Herein,the epoxy resin powder coating with polydopamine modified molybdenum disulfide(MoS_(2)@PDA-EP powder coating with 0,0.1,0.2,0.5,1.0 wt.%loading)was well prepared by melt extrusion to investigate its anticorrosion performance and wear resistance.The results revealed that the addition of MoS_(2)@PDA enhanced the adhesion strength between coatings and alloys,wear resistance and corrosion protection of the powder coatings.Among them,the optimum was obtained by 0.2 wt.%MoS_(2)@PDA-EP powder coating which could be attributed to well dispersion and efficient adhesion with coating matrix.To conclude,MoS_(2)@PDA-EP powder coating is meaningfully beneficial for the anticorrosive and wear performance improvement of magnesium lithium alloys.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Preparation of Poly(o-toluidine)/Nano ZrO2/Epoxy Composite Coating and Its Application for Corrosion Protection of Steel

The main objective was to study the anticorrosion performance of poly（o-toluidine）/nano ZrO2/epoxy composite coating.Poly（o-toluidine）/nano ZrO2 composite was prepared by in situ polymerization of o-toluidine monomer in the presence of nano ZrO2 particles.Fourier transformation infrared spectroscopy（FT-IR）,UV-visible spectroscopy（UV-vis）,X-ray diffraction（XRD）,Scanning electron microscopy（SEM）,and Thermogravimetric analysis（TGA） were used to characterize the composition and structure of the composite.Poly（o-toluidine）/nano ZrO2 composite was mixed with epoxy resin through a solution blending method and the three components poly（o-toluidine）/nano ZrO2/epoxy composite coating was coated onto the surface of steel sample by the brush coating method.The anticorrosion performance of poly（o-toluidine）/nano ZrO2/epoxy composite coating on steel sample was studied by polarization curve and electrochemical impendence spectroscopy in 3.5% Na Cl solution as corrosion environment and also compared with that of poly（o-toluidine）/epoxy composite coating and pure epoxy coating.It was observed that the composite coating containing poly（otoluidine）/nano ZrO2 composite has got higher corrosion protection ability than that of poly（o-toluidine）.The electrochemical measurement results demonstrated that poly（o-toluidine） fillers improve the electrochemical anticorrosion performance of epoxy coating and the addition of nano ZrO2 particles increases the tortuosity of the diffusion pathway of corrosive substances.

The Durability of Epoxy Resin Coating

The durability of epoxy resin coating was studied under environments with relative humidity （RH） of 98%-100%, at 55 ℃ for 900 h, at 65 ℃ for 700 h and at 75 ℃ for 400 h, respectively. Peel strength test, dynamical mechanical thermal analysis （DMTA）, infrared spectroscopy （IR） and energy dispersive X-ray spectroscopy （EDX） were employed for measurements. Peel strength indicated the development of adhesive property of the coating, DMTA indicated the development of physical property, IR revealed the development of chemical structure, and EDX showed surface element change of the coating. All these results show a good time- temperature equivalence characteristic between humidity aging time and temperature.

Effects of direct stray current on the performance of cathodic disbonding epoxy powder coatings

The influence of the direction and magnitude of direct(DC)stray current on the disbonding performance of epoxy powder coating was studied by using electrochemical impedance spectroscopy and scanning electron microscopy technology.The results show that the application of DC stray current could accelerate the anodic dissolution.The peeling degree of the coating increases as the magnitude of positive DC stray current interference increases in the range of 2–8V.With 16V positive stray current disturbance,the degree of coating disbonding decreases.With the application of negative stray current,the coating peeling becomes more serious,and the degree of peeling increases as the DC stray current increases.