Assessing the corrosion protection property of coatings loaded with corrosion inhibitors using the real-time atmospheric corrosion monitoring technique

The atmospheric corrosion monitoring(ACM)technique has been widely employed to track the real-time corrosion behavior of metal materials.However,limited studies have applied ACM to the corrosion protection properties of organic coatings.This study compared a bare epoxy coating with one containing zinc phosphate corrosion inhibitors,both applied on ACM sensors,to observe their corrosion protection properties over time.Coatings with artificial damage via scratches were exposed to immersion and alternating dry and wet environments,which allowed for monitoring galvanic corrosion currents in real-time.Throughout the corrosion tests,the ACM currents of the zinc phosphate/epoxy coating were considerably lower than those of the blank epoxy coating.The trend in ACM current variations closely matched the results obtained from regular electrochemical tests and surface analysis.This alignment highlights the potential of the ACM technique in evaluating the corrosion protection capabilities of organic coatings.Compared with the blank epoxy coating,the zinc phosphate/epoxy coating showed much-decreased ACM current values that confirmed the effective inhibition of zinc phosphate against steel corrosion beneath the damaged coating.

Advancements in enhancing corrosion protection of Mg alloys:A comprehensive review on the synergistic effects of combining inhibitors with PEO coating

Magnesium(Mg)alloys are lightweight materials with excellent mechanical properties,making them attractive for various applications,including aerospace,automotive,and biomedical industries.However,the practical application of Mg alloys is limited due to their high susceptibility to corrosion.Plasma electrolytic oxidation(PEO),or micro-arc oxidation(MAO),is a coating method that boosts Mg alloys'corrosion resistance.However,despite the benefits of PEO coatings,they can still exhibit certain limitations,such as failing to maintain long-term protection as a result of their inherent porosity.To address these challenges,researchers have suggested the use of inhibitors in combination with PEO coatings on Mg alloys.Inhibitors are chemical compounds that can be incorporated into the coating or applied as a post-treatment to further boost the corrosion resistance of the PEO-coated Mg alloys.Corrosion inhibitors,whether organic or inorganic,can act by forming a protective barrier,hindering the corrosion process,or modifying the surface properties to reduce susceptibility to corrosion.Containers can be made of various materials,including polyelectrolyte shells,layered double hydroxides,polymer shells,and mesoporous inorganic materials.Encapsulating corrosion inhibitors in containers fully compatible with the coating matrix and substrate is a promising approach for their incorporation.Laboratory studies of the combination of inhibitors with PEO coatings on Mg alloys have shown promising results,demonstrating significant corrosion mitigation,extending the service life of Mg alloy components in aggressive environments,and providing self-healing properties.In general,this review presents available information on the incorporation of inhibitors with PEO coatings,which can lead to improved performance of Mg alloy components in demanding environments.

Synthesis of organic-inorganic 3D-nanocontainers for smart corrosion protection of friction stir welded AZ31B magnesium alloy-titanium dissimilar joints

The joining of different light metals through friction stir welding(FSW)is gaining interest as a method to decrease weight and improve fuel efficiency.However,to ensure durability,these welded metals may require surface treatments to protect against corrosion or wear.This study presents a novel approach for the simultaneous delivery of two distinct corrosion inhibitors to Ti-Mg dissimilar PEO treated joints on demand.The research focuses on the synthesis,characterization,and application of cerium@polystyrene(Ce@PS)nanocontainers,which are loaded with 8-hydroxyquinoline(8-HQ)to enhance corrosion protection.The synthesis involves several key steps,including the formation of a cerium-based outer layer around polystyrene nanospheres,the selective removal of the polystyrene core to create a porous structure,and the subsequent loading of the 8-HQ inhibitor.Structural and compositional analyses,conducted using scanning transmission electron microscopy(STEM)and energy-dispersive X-ray spectroscopy(EDS),confirmed the successful incorporation of 8-HQ within the nanocontainers.Additionally,Fourier-transform infrared spectroscopy(FTIR)provided detailed information about the chemical composition of the organic materials throughout the synthesis process.Thermal decomposition analysis verified the successful fabrication and stability of the dual-shell nanocontainers.Corrosion tests on Ti-Mg joints treated with plasma electrolytic oxidation(PEO)coatings and loaded nanocontainers demonstrated sig-nificantly improved corrosion resistance compared to untreated joints.This research highlights the potential of dual-shell nanocontainers,containing both organic and inorganic inhibitors,to offer prolonged corrosion protection,particularly against galvanic corrosion in dissimilar joints.The findings suggest that these synthesized nanocontainers hold promise for various industrial applications,particularly in the context of friction stir welded(FSW)Ti-Mg dissimilar joints,providing valuable insights for the development of advanced materials designed to mitigate corrosion.

Multiple Tin Compounds Modified Carbon Fibers to Construct Heterogeneous Interfaces for Corrosion Prevention and Electromagnetic Wave Absorption

Currently,the demand for electromagnetic wave(EMW)absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent.Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption.However,interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption.In this study,multi-component tin compound fiber composites based on carbon fiber(CF)substrate were prepared by electrospinning,hydrothermal synthesis,and high-temperature thermal reduction.By utilizing the different properties of different substances,rich heterogeneous interfaces are constructed.This effectively promotes charge transfer and enhances interfacial polarization and conduction loss.The prepared SnS/SnS_(2)/SnO_(2)/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt%in epoxy resin.The minimum reflection loss(RL)is−46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz.Moreover,SnS/SnS_(2)/SnO_(2)/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces.Therefore,this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.

Evaluation of self-healing properties of inhibitor loaded nanoclay-based anticorrosive coatings on magnesium alloy AZ91D

This study emphasizes on the evaluation and comparison of the anticorrosive properties of sol-gel coatings with and without inhibitor loaded nanocontainers.In this case,naturally available clay nanotubes(halloysite)were loaded with cationic corrosion inhibitors Ce 3+/Zr 4+.These nanocontainers were dispersed in hybrid organic-inorganic sol-gel matrix sol.Coating was applied on magnesium alloy AZ91D using the sols containing modified and unmodified nanocontainers employing the dip coating method and cured at 130℃for 1 h in air.Corrosion resistance of coated/uncoated substrates were analyzed using electrochemical impedance spectroscopy,potentiodynamic polarization and weight loss measurements after exposure to 3.5 wt%NaCl solution for varying time durations between 24 h to 120 h.Self-healing ability of coatings was evaluated by micro-Raman spectroscopy after 120 h exposure to 3.5 wt%NaCl solution.Coatings generated after dispersion of corrosion inhibitor loaded clay in hybrid sol-gel matrix have shown more promising corrosion resistance when compared to just the sol-gel matrix coatings,after prolonged exposure to corrosive environment.

Corrosion protection properties of vanadium films formed on zinc surfaces

Vanadium films were prepared on zinc surfaces by using a solution containing vanadate. Corrosion protection properties of vanadium-treated （V-treated）, chromium-treated （Cr-treated）, and untreated zinc surfaces in contact with a 3.5 wt.% NaC1 solution were studied using potentiodynamic polarization, electrochemical impedance spectroscopy （EIS）, and neutral salt spray （NSS） tests. According to these results, the V-treated layer significantly improved the corrosion resistance of zinc surfaces. In comparison with the Cr-treated layer, the V-treated layer exhibited a better corrosion resistance. The composition of the V-treated layer was studied using X-ray photoelectron spectroscopy （XPS）. XPS measurements indicated that the vanadium layer formed on zinc surfaces and the vanadium-rich coating was a hydrated oxide with a composition of V2O5, VO2, and its hydrates such as V2O5.nH2O and VO（OH）2.

Active corrosion protection of phosphate loaded PEO/LDHs composite coatings:SIET study

This work produced a Mg Al-layered double hydroxide by hydrothermal treatment of a plasma electrolytic oxidation(PEO) coating on magnesium alloy AZ31 in an phosphate electrolyte, followed by an ion-exchange reaction in 0.1 M phosphate solution. The coated specimens were scratched. Characterization, including utilization of the localized technique SIET, measured the pH and p Mg distributions and optical morphologies around the artificial defects during immersion in 0.05 M NaCl solution. In contrast with phosphate loaded PEO/LDHs, a stronger alkalinization area(with pH 11.4~12.3) appeared in the passive PEO specimens. Due to formation of insoluble Mg(OH)_(2) products, the p Mg map showed depletion of Mg^(2+) in this high p H area. Combined with optical morphologies and SEM images, the better self-healing ability toward defects for phosphate loaded PEO/LDHs was confirmed.

A route for large-scale preparation of multifunctional superhydrophobic coating with electrochemically-modified kaolin for efficient corrosion protection of magnesium alloys

Superhydrophobic coating has been widely studied for its great applicational potential, such as for corrosion protection of magnesium alloys while it has been restrained by expensive materials, sophisticated preparation process and infirm rough structures. In this study, the electrochemical method was adopted by using a two-electrode system for rapid hydrophobic modification to obtain superhydrophobic kaolin.By mixing the modified superhydrophobic kaolin with commercial epoxy resin and polydimethylsiloxane glue, a paint can be formed and easily used on various substrates for preparation of superhydrophobic coating via spraying method. The influence factors on wettability of the modified kaolin and the mixing ratio of each component of the coating were explored. Also, the wettability, durability and anticorrosion of the prepared coating were evaluated comprehensively. The coating was able to maintain superhydrophobic after immersed in HCl solution at pH 1, the NaOH solution at pH 14, and 3.5 wt.% NaCl solution for 16, 21, 30 days, respectively. In addition, the coating exhibited 4A grade adhesion, high hydrophobicity after abraded for 200 cycles on a 600-mesh sandpaper with 100 g weight, and 99.86% anticorrosion efficiency after soaked in 3.5 wt.% NaCl solution for 20 days, demonstrating a good robustness and anti-corrosion property. Furthermore, the coating showed good transparency, flexibility and was easy to make in a large scale by the spraying method, which is of great significance to promote the practical application of superhydrophobic coatings and the anticorrosion Mg alloys.

Corrosion Protection of AM50 Magnesium Alloy by Nafion/DMSO Organic Coatings

The effectiveness of the corrosion protection of Nafion/Dimethysulfoxid （DMSO） organic coatings for AM50 magnesium alloy prepared by simple immersion and heat treatment was investigated. Its corrosion resistance and morphologies of the Nafion/DMSO organic coatings were studied by electrochemical corrosion testing and optical microscopy. The results show that Nafion/DMSO organic coatings can improve the corrosion resistance of AM50 magnesium alloy effectively. Also, the corrosion resistance increases with the surface density of the organic coatings.

Multi-layer structures including zigzag sculptured thin films for corrosion protection of AISI 304 stainless steel

To increase corrosion resistance of the sample,its electrical impedance must be increased.Due to the fact that electrical impedance depends on elements such as electrical resistance,capacitance,and inductance,by increasing the electrical resistance,reducing the capacitance and inductance,electrical impedance and corrosion resistance can be increased.Based on the fact that these elements depend on the type of material and the geometry of the material,multilayer structures with different geometries are proposed.For this purpose,conventional multilayer thin films,multilayer thin film including zigzag structure(zigzag 1)and multilayer thin film including double zigzag structure(zigzag 2)of manganese nitride are considered to protect AISI 304 stainless steel against corrosion in salt solution.These multilayer coatings including zigzag structures are prepared by alternately using the conventional deposition of thin film and glancing angle deposition method.After deposition,the samples are placed in a furnace under nitrogen flux for nitriding.The cross sections of the structures are observed by field emission scanning electron microscopy(FESEM).Atomic force microscope(AFM)is used to make surface analyses of the samples.The results show that the multilayer thin films including zigzag structures have smaller grains than conventional multilayer thin films,and the zigzag 2 structure has the smaller grain than the other two samples,which is attributed to the effect of shadowing and porosity on the oblique angle deposition method.Crystallography structures of the samples are studied by using x-ray diffraction(XRD)pattern and the results show that nitride phase formation in zigzag 2 structure is better than that in zigzag 1 structure and conventional multilayer thin film.To investigate the corrosion resistances of the structures,electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization tests are performed.The results reveal that the multilayer thin films with zigzag structures have better corrosion protection than the conventional multilayer thin films,and the zigzag structure 2 has the smallest corrosion current and the highest corrosion resistance.The electrical impedances of the samples are investigated by simulating equivalent circuits.The high corrosion resistance of zigzag 2 structure as compared with conventional multilayer structure and zigzag 1 structure,is attributed to the high electrical impedance of the structure due to its small capacitance and high electrical resistance.Finally,the surfaces of corroded samples are observed by scanning electron microscope(SEM).

LDH conversion films for active protection of AZ31 Mg alloy

Zinc aluminium(Zn-Al)and lithium aluminium(Li-Al)–layered double hydroxides(LDH)coatings with incorporated inhibitors(Li-,Mo-and W-based)were successfully synthesized on AZ31 Mg alloy.Zn-Al LDH W and Li-Al LDH Li showed the highest corrosion resistance and were selected for further evaluation.SEM cross-section examination revealed a bi-layer structure composed of an outer part with loose flakes and a denser inner layer.XRD,FTIR,and XPS analysis confirmed the incorporation of the inhibitors.Post-treatments with corrosion inhibitors containing solutions resulted in the selective dissolution of the most external layer of the LDH coating,reducing the surface roughness,hydrophilicity and paint adhesion of the layers.Active corrosion properties were confirmed by SVET evaluation for the Zn-Al LDH W coating.The proposed active corrosion mechanism involves the ion-exchange of aggressive Cl-ions,deposition of hydroxides and competitive adsorption of W-rich corrosion inhibitors.

High-performance triboelectric nanogenerator based on ZrB_(2)/polydimethylsiloxane for metal corrosion protection

Metal corrosion causes billions of dollars of economic losses yearly.As a smart and new energy-harvesting device,triboelectric nanogenerators(TENGs)can convert almost all mechanical energy into electricity,which leads to great prospects in metal corrosion prevention and cathodic protection.In this work,flexible TENGs were designed to use the energy harvested by flexible polydimethylsiloxane(PDMS)films with ZrB_(2)nanoparticles and effectively improve the dielectric constant by incorporating ZrB_(2).The open-circuit voltage and short-circuit current were 264 V and 22.9μA,respectively,and the power density of the TENGs reached 6 W·m^(-2).Furthermore,a selfpowered anti-corrosion system was designed by the rectifier circuit integrated with TENGs,and the open-circuit potential(OCP)and Tafel curves showed that the system had an excellent anti-corrosion effect on carbon steel.Thus,the system has broad application prospects in fields such as metal cultural relics,ocean engineering,and industry.

Functionalized carbon dots for corrosion protection:Recent advances and future perspectives

Metal corrosion causes significant economic losses,safety issues,and environmental pollution.Hence,its prevention is of immense research interest.Carbon dots(CDs)are a new class of zero-dimensional carbon nanomaterials,which have been considered for corrosion protection applications in recent years due to their corrosion inhibition effect,fluorescence,low toxicity,facile chemical modification,and cost-effectiveness.This study provides a comprehensive overview of the synthesis,physical and chemical properties,and anticorrosion mechanisms of functionalized CDs.First,the corrosion inhibition performance of different types of CDs is introduced,followed by discussion on their application in the development of smart protective coatings with self-healing and/or self-reporting properties.The effective barrier formed by CDs in the coatings can inhibit the spread of local damage and achieve self-healing behavior.In addition,diverse functional groups on CDs can interact with Fe^(3+)and H^(+)ions generated during the corrosion process;this interaction changes their fluorescence,thereby demonstrating self-reporting behavior.Moreover,challenges and prospects for the development of CD-based corrosion protection systems are also presented.

Recent progress in self-repairing coatings for corrosion protection on magnesium alloys and perspective of porous solids as novel carrier and barrier

Featuring low density and high specific strength, magnesium(Mg) alloys have attracted wide interests in the fields of portable devices and automotive industry. However, the active chemical and electrochemical properties make them susceptible to corrosion in humid, seawater, soil,and chemical medium. Various strategies have revealed certain merits of protecting Mg alloys. Therein, engineering self-repairing coatings is considered as an effective strategy, because they can enable the timely repair for damaged areas, which brings about long-term protection for Mg alloys. In this review, self-repairing coatings on Mg alloys are summarized from two aspects, namely shape restoring coatings and function restoring coatings. Shape restoring coatings benefit for swelling, shrinking, or reassociating reversible chemical bonds to return to the original state and morphology when coatings broken;function self-repairing coatings depend on the release of inhibitors to generate new passive layers on the damaged areas. With the advancement of coating research and to fulfill the demanding requirements of applications, it is an inevitable trend to develop coatings that can integrate multiple functions(such as stimulus response, self-repairing, corrosion warning,and so on). As a novel carrier and barrier, porous solids, especially covalent organic frameworks(COFs), have been respected as the future development of self-repairing coatings on Mg alloys, due to their unique, diverse structures and adjustable functions.

Corrosion protection of composite coating combining ceramic layer,copper layer and benzotriazole layer on magnesium alloy

A novel composite coating was fabricated on AZ91 magnesium alloy by applying a composite surface treatment which combined the methods of plasma electrolytic oxidation(PEO)pre-treatment,electroless copper and benzotriazole(BTA)passivation. The cross-section microstructures and chemical compositions of coating were examined using scanning electron microscopy(SEM) equipped with energy dispersive analysis of X-rays(EDX).Potentiodynamic polarization curves and salt spray tests were employed to evaluate corrosion protection of the coating to substrate in 5%NaCl solution.It is indicated that electroless copper produces a rough interface between the electroless copper layer and the ceramic layer.The corrosion potential shifts to the positive direction significantly and the current density decreases by more than one order of magnitude.There is no visible galvanic corrosion pits on the surface of the composite coating combination of PEO and electroless copper after 168 h neutral salt spray testing.The color of copper after BTA immersion could be held more than 60 d.

Corrosion Protection of 5083 AA in SalineWater by Polyacrylonitrile Nanofibers

Polymeric nanofibers are a promising technology to protect the metal surfaces from corrosion.Through the literature search,the use of polyacrylonitrile nanofibres(PANNFs)as a corrosion inhibitor coating for aluminum alloys has not been evaluated.This work includes the development of a new,lightweight,high surface area and efficient coating of PANNFs that produced using electrospinning process to resist the corrosion of aluminum alloys(AA5083)which immersed in 0.6 M NaCl at alkaline medium(pH=12)and acidic medium(pH=1)at a range of temperatures(293–323)K.The PANNFs coating was successfully deposited on AA 5083 specimens,where these samples were considered as a collector electrode in the electrospinning process.The corrosion experiments of the aluminum alloys coated with PANNFs before and after immersion in both corrosive mediums were investigated using cyclic potential polarization(CPP).The results confirmed that the PANNFs coating was able to protect the surface of the aluminum specimens from corrosion,by reducing the corrosion current and increasing the surface polarization resistance,thus reducing the corrosion rate.The protection efficiency was found in the alkaline medium 98.8%while in the acidic medium 83.3%.So,it was in both mediums decreased with the increase in temperature.The shape,distribution and size of the polymeric nanofibers that formed the coating were also examined using field emission scanning electron microscopy(FE-SEM)and the percentages of the structural components of these fibers were detected using the X-ray dispersion spectroscopy(EDS).The surface of aluminum specimens was completely covered by PANNFs.These electrospun nanofibers have worn out and lined up spacing after immersion in the corrosive mediums.The diameters average of PANNFs was found to be about 200 and 150 nm before and after immersion,respectively.

Recent progress in corrosion protection of friction stir welded high-strength aluminum alloy joints

Friction stir welding （FSW） has been widely used in many industries, with which high-strength aluminum alloys can be well joined. However, the corrosion resistance of FSW high-strength Al alloy joints is relatively poor, which limits their industrial applications. The joints shall be protected against corrosion. In this review, therefore, the current status and development of corrosion protection for FSW high-strength Al alloy joints are presented. Particular emphasis has been given to different protection methods ： lowering heat input, post-weld heat treatment, surface modification and spray coatings. Finally, opportunities are identified for further research and development in corrosion protection of FSW high-strength Al alloy joints.

Research advances of magnesium and magnesium alloys globally in 2023

Magnesium materials have attracted the attention of many researchers,and the related research is expanding.This article summarizes the advance in the research and development of magnesium materials globally in 2023 from bibliometric and scientific perspectives.More than 4680 articles on Mg and its alloys were published and indexed in the Web of Science(WoS)Core Collection database last year.The bibliometric analyses show that the traditional structural Mg alloys,functional Mg materials,and corrosion and protection of Mg alloys are still the main research focus.Therefore,this review paper mainly focuses on the research progress of Mg cast alloys,Mg wrought alloys,bio-magnesium alloys,Mg-based energy storage materials,corrosion and protection of Mg alloys in 2023.In addition,future research directions are proposed based on the challenges and obstacles identified throughout this review.

Preparation of alkaline-responsive nano-electrospinning and anticorrosion properties of self-healing coating

In this paper,1-butyl-3-methylimidazole tetrafluoroborate([BMIM]BF4)is used as corrosion inhibitor.Polyacrylonitrile(PAN)is used to load the corrosion inhibitor.PAN/[BMIM]BF4 hybrid nanofibers are successfullysynthesized by electrospinning technology.The alkyd varnish is coated on the fiber membrane to prepare a compositecoating,and then a series of tests are carried out on the self-healing and anticorrosive performance of the compositecoating.It is observed by scanning electron microscope that the fiber morphology is stable and there is no bead-likestructure.The composition of the composite fiber is analyzed by Fourier infrared spectroscopy,and it is confirmed thatthe hybrid nanofiber was successfully prepared.3D laser confocal scanning microscope was used to observe thecorrosion morphology and profile of the carbon steel.The composite coating shows good self-healing performance.[BMIM]BF4 can form a protective film on the surface of the bare carbon steel substrate through physical adsorption orchemical adsorption in an alkaline environment.Electrochemical impedance spectroscopy was tested and analyzed.It isfound that the maximum corrosion inhibition efficiency of the coating is 88.5%in 3.5 wt.%alkaline NaCl solution.Compared with the blank coating without nanofibers,the composite fiber varnish composite coating exhibits good selfhealingand anti-corrosion properties.

Photothermal self-healing polyurethane coating based on hollow nanofillers in seawater

Herein,a novel composite coating with excellent self-healing and corrosion resistance activated byphotothermal responsive hollow core-shell nanofillers was developed.A photothermal nanofiller(Co_(9)S_(8)@Bi_(2)S_(3))with ahollow core-shell structure was synthesized and then added to polyurethane(PU)to prepare PU-Co_(9)S_(8)@Bi_(2)S_(3)compositecoating.Applying 808 nm near-infrared irradiation induces a photothermal effect in Co_(9)S_(8)@Bi_(2)S_(3),which subsequentlyinitiates the reconstruction of reversible hydrogen bonds,facilitating the self-healing of coating scratches.The excellentphotothermal self-healing performance of PU-Co_(9)S_(8)@Bi_(2)S_(3)coating was demonstrated by scratch tests and moleculardynamics simulations.The electrochemical impedance spectroscopy test results showed that the PU-Co_(9)S_(8)@Bi_(2)S_(3)coating has good self-healing and anti-corrosion properties.The low-frequency impedance modulus of the coating afterthree self-healing sessions was still close to 109Ω·cm^(2)after 30 d of immersion in seawater.This study provides a newstrategy for developing multi-cycle self-healing coatings triggered by photothermal effects.