The corrosion characteristic and mechanism of Mg-5Y-1.5Nd-xZn-0.5Zr(x=0,2,4,6 wt.%)alloys in marine atmospheric environment

The microstructure and precipitated phases of as-cast Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were investigated by optical microscopy,scanning electron microscopy,energy-dispersive spectrometry and X-ray Diffraction.The exposure corrosion experiment of these magnesium alloys was tested in South China Sea and KEXUE vessel atmospheric environment.The corrosion characteristic and mechanism of magnesium alloys of Mg-5Y-1.5Nd-x Zn-0.5Zr(x=0,2,4,6 wt.%)alloys were analyzed by weight loss rate,corrosion depth,corrosion products and corrosion morphologies.The electrochemical corrosion tests were also measured in the natural seawater.The comprehensive results showed that Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy existed the best corrosion resistance whether in the marine atmospheric environment and natural seawater environment.That depended on the microstructure,type and distribution of precipitated phases in Mg-5Y-1.5Nd-4Zn-0.5Zr magnesium alloy.Sufficient quantity anodic precipitated phases in the microstructure of Mg-5Y-1.5Nd-4Zn-0.5Zr alloy played the key role in the corrosion resistance.

The corrosion behavior of Mg-Nd binary alloys in the harsh marine environment

The corrosion behavior of Mg-Nd binary alloys in the harsh South China Sea environment was researched by scanning electron microscopy,energy-dispersive spectrometry and X-ray diffraction analysis.In order to explain the corrosion mechanism,corrosion resistance was analyzed by weight loss rate and electrochemical measurement in the laboratory.With a continuous enlargement of Nd-content,Mg 12 Nd phases increased and multiplied.The weight loss rate of Mg-0.5Nd alloy was 0.0436 mg·cm^(-2)·y^(-1)(0.0837 mm·y^(-1)),whereas that of Mg-1.5Nd alloy was 0.0294 mg·cm^(-2)·y^(-1)(0.0517 mm·y^(-1))during the exposure corrosion in the South China Sea site.The mechanical strength of Mg-1.5Nd alloy was 148 MPa before the exposure in the harsh marine environment,while the residual mechanical strength was merely about 94 MPa after the exposure test.Both Mg-1.5Nd alloy and Mg-1.0Nd alloy occurred the brittle fracture,which resulted that the elongation was nearly equal to zero.The self-corrosion current density demonstrated that degradation rate of Mg-Nd binary alloys was as follows:Mg-0.5Nd>Mg-1.0Nd>Mg-1.5Nd.For the South China Sea corrosion site,a large amount of sea salts exited in the atmospheric environment.Due to the heavy rainfall and high humidity,sodium chloride in the atmospheric environment dissolved,more serious electrochemical corrosion occurred on the surface of Mg-Nd binary alloys.

Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.

The corrosion behavior and mechanical property of the Mg-7Y-x Nd ternary alloys

The corrosion behavior and mechanical property of Mg-7Y-x Nd(x=0.5,1.0,1.5 wt%)alloys were investigated.The microstructure and precipitations of Mg-7Y-x Nd alloys were studied by scanning electron microscopy,energy-dispersive spectrometry and X-ray Diffraction.The quantities of the Mg_(12)(Y,Nd)phase increased,whereas that of the Mg_(24)(Y,Nd)_(5)phase decreased with increasing Nd-content.The weight loss rate decreased from 17.5020 mg cm^(-2)·d^(-1)(36.7542 mm y^(-1))to 9.3744 mg cm^(-2)·d^(-1)(19.6862 mm y^(-1)).The electrochemical measurement also demonstrated the similar tendency.The loss in mechanical properties after corrosion reaction followed the order Mg-7Y-0.5Nd>Mg-7Y-1.0Nd>Mg-7Y-1.5Nd.The precipitations played dual roles in the corrosion resistance that depended on type and distribution.

Corrosion behavior of Q235B carbon steel in simulated seawater pumped storage system under operational conditions

Seawater pumped storage systems have bright prospect for energy storage in the coming years.The operational conditions of seawater pumped storage system are complex and harsh,where metal materials suff er from severe general and local corrosion.The corrosion behavior of Q235B carbon steel in simulated seawater pumped storage system under operational conditions was studied by potentiodynamic polarization,cyclic potentiodynamic polarization,and scanning electron microscope(SEM).The results confi rm that the working pressure aff ected the corrosion resistance of Q235B carbon steel during the whole immersion period.The pressure promoted the electrochemical reaction of corrosion process and the corrosion rate increased with pressure at the initial immersion period.However,the stable rust layer formed after longtime immersion at diff erent pressures increased the corrosion resistance of carbon steel,and decreased the corrosion degree of carbon steel.Meanwhile,the working pressure aff ected the pitting corrosion behavior of Q235B carbon steel during the whole immersion period.The pitting corrosion potential was more negative and the tendency of pitting corrosion was higher at 4 MPa during the whole immersion period.However,pressure also accelerated the formation rate of protective rust layer on the steel surface.Q235B carbon steel has higher susceptibility to pitting corrosion at 4 MPa in the static seawater.

Smart anticorrosion coating based on stimuli-responsive micro/nanocontainer:a review

Smart coating for corrosion protection of metal materials(steel,magnesium,aluminum and their alloys)has drawn great attention because of their capacity to prevent crack propagation in the protective coating by releasing functional molecules(healing agents or corrosion inhibitors)on demand from delivery vehicle,that is,micro/nanocontainer made up of a shell and core material or a coating layer,in a controllable manner.Herein,we summarize the recent achievements during the last 10 years in the field of the micro/nanocontainer with different types of stimuli-responsive properties,i.e.,pH,electrochemical potential,redox,aggressive corrosive ions,heat,light,magnetic field,and mechanical impact,for smart anticorrosion coating.The state-of-the-art design and fabrication of micro/nanocontainer are emphasized with detailed examples.

Bifunctional nanozyme activities of layered double hydroxide derived Co-A1-Ce mixed metal oxides for antibacterial application

Marine biofouling is an expensive problem that needs evolved chemical or physical antifouling strategies.However,most of the current antifouling materials that would damage the environment through metal leaching and bacteria resistance are being halted.Nanozyme is one kind of environmental antifouling materials through generating reactive oxygen species(ROS).We prepared various contents of CeO2 that could uniform disperse compounding with Co3 O4 and CoAl2 O4 to form a stable Co-Al-Ce mixed metal oxide(MMO) by a layered double hydroxide derived method.We find that coupling with CeO2 can improve the peroxidase(POx) activity.When the molar ratio of Ce is 2.5% and the calcination temperature is 200℃,the POx activity of Co-Al-Ce MMO is the best caused by the good dispersion of catalytically active components and the high specific area(150.10±4.95 m2/g).This novel Co-Al-Ce MMO also exhibits an antibacterial mode of action Gram-negative bacteria in near-neutral pH solution through generating ROS(mainly ·O2-)in the presence of H2 O2.Ce containing MMO can be utilized as potential green marine antifouling material.

Double layered superhydrophobic PDMS-Candle soot coating with durable corrosion resistance and thermal-mechanical robustness

Nature-inspired superhydrophobic coatings with typical Cassie-Baxter contacts garner numerous interests for multifunctional applications.However,undesirable poor mechanical and thermal stability are still crucial bottlenecks for real-world employment.This work introduces a cost-effective,fluorine free and versatile strategy to achieve double-layered PDMS agglutinated candle soot coating with superior water-repellent superhydrophobicity.The surface morphologies,chemical compositions and wettability behaviors were investigated in detail.The mechanical stability,chemical stability and durable corrosion resistance of the fabricated PDMS-CS coating were evaluated through friction,calcination and electrochemical impedance spectroscopy.The results demonstrate a remarkably enhanced mechanical robustness and corrosion resistance,indicating PDMS units can act as an effective agglutinating agent between candle soot and underlying substrate.The synergistic effect of PDMS agglutination,porous network nanostructures and extremely low surface energy of incomplete combustion induced candle soot deposition contribute to the eventually robust corrosion resisting coating,which greatly increases the possibility for practical applications.

Hexagonal boron nitride/poly(vinyl butyral)composite coatings for corrosion protection of copper

Hexagonal boron nitride(h-BN)fillers are incorporated into poly(vinyl butyral)(PVB)coatings to improve the corrosion protection performance of copper.It has been revealed that the h-BN fillers exhibit an excellent dispersiblility in PVB coating due to the non-covalent interactions between h-BN fillers and the PVB molecules.Electrochemical characterization reveals that the corrosion resistance of the BN-reinforced PVB(BN-P)coating is 5-6 orders of magnitude higher than that of the pristine PVB coating.Photographs and metallography show that the copper substrate beneath the BN-P coating does not suffer from corrosion after immersion for 2 months,indicating that the BN-P coating can provide a long-term protective barrier for the underlying copper substrate.Loading 0-0.25 g h-BN fillers in 2.0 g PVB,the corrosion protection performance increases with increasing the loading of h-BN fillers.The scratch test results suggest that h-BN fillers do not accelerate copper corrosion when the BN-P coating is damaged.

Review on the corrosion-promotion activity of graphene and its inhibition

Graphene films(GFs) and graphene-reinforced nanocomposite coatings(GNCs) have received unprecedented attention for corrosion protection because graphene possesses a remarkable chemical inertness and is completely impermeable to aggressive chemicals. However, the high electric conductivity and positive potential of graphene make graphene-based metal protectors tend to exhibit an undesirable high corrosion-promotion activity(CPA), which is widely known as the phenomenon that graphene connecting with metal accelerates the corrosion of metal substrate by inducing micro-galvanic corrosion at the defect sites of GFs or GNCs in aggressive environments. Therefore, inhibiting the CPA of graphene is currently a key focus for the application of graphene in the field of corrosion protection. In this review, the mechanisms, influencing factors, and inhibition strategies of the CPA of GFs and GNCs are highlighted from the point of view of corrosion science to address the bottlenecks and challenges for future research and potential applications of graphene for corrosion protection.

Mitigation of hydrogen permeation into steel by bacteria:a new research proposal

A new research proposal was introduced aiming at solving the fundamental theory for reducing the risk of hydrogen embrittlement(HE)in high-strength steels by utilizing hydrogen-consuming microorganisms.The superior performance of high-strength steel can meet the material strength requirements for remote deep-sea marine engineering development.Due to the heavy corrosive marine environment,steel structures must be protected by cathodic protection.However,high-strength steel is sensitive to stress corrosion cracking and HE,and cathodic protection can promote hydrogen permeation into steel.Hydrogen-consuming microorganisms are widespread in the natural environment and they utilize the energy of hydrogen oxidation to survive.If we could make use of the hydrogen-consuming function of microorganisms to consume the hydrogen generated during the cathodic protection process,then the potential for cathodic protection can be reasonably lowered,ideally protecting the steel and simultaneously reducing the possibility of HE.

Fouling characteristics of cnidarians(Hydrozoa and Anthozoa)along the coast of China

Hydrozoans and anthozoans are an important component of a great variety of marine communities,particularly abundant and ubiquitous as part of the fouling assemblages around the globe.Several negative impacts have been associated to their occurrence on artificial substrata.In the coastal waters of China,a total of 76 species of fouling cnidarians were observed and classified.According to the occurrence frequency or biomass,the major species in the Bohai and Yellow Seas were Ectopleura marina,Bougainvillia sp.,and Eudendrium capillare;in the East China Sea Anthopleura nigrescens,Diadumene lineata,and Ectopleura crocea;and in the South China Sea Clytia sp.,Obelia sp.,and Actiniaria spp.The peak period of settlement of most species was mainly in summer and autumn.With the decrease of latitude,species number increased greatly and even cnidarian fouling was observed all year round in the East and South China Seas.Salinity was another factor aff ecting species distribution.Naturally,immersion time of substrata also directly aff ects the characteristics of cnidarians in fouling communities.

Biofilm inhibition mechanism of BiVO inserted zinc matrix in marine isolated bacteria

Biofilm plays an important role on microbial corrosion and biofouling in marine environments.Inhibiting biofilm formation on construction surfaces is of great importance.Photocatalytic material with visiblelight response,especially BiVO_(4),is regarded as a promising material for biofilm inhibition due to its green biocidal effect and high antibacterial efficiency.Approaches which can immobilize the photocatalytic particles onto metal surfaces with high mechanical strength are requisite.In this study,zinc matrixes were served as carriers for BiVO_(4)particles.The BiVO_(4)-inserted zinc matrixes were successfully obtained by ultrasound assisted electrodeposition.The insertion content of BiVO_(4)showed positive correlation with ultrasound power.Highly enhanced biofilm inhibition properties were obtained by BiVO_(4)inserted zinc·matrixes with an over 95%decreased bacterial coverage.It was proved that O2-(chief)andOH(subordinate)radicals were responsible for the high biocidal performance.Possible antibacterial mechanism was proposed,indicating that the photoinduced holes would both attack zinc crystals to generate active electrons to form O2-radicals,and react with H2 O to generate·OH,finally.Furthermore,corrosion resistance of the matrixes was proved to be stable due to the insertion of BiVO_(4).This study provides a potential application for photocatalyst in marine antifouling and anti-biocorrosion aspects.

1D Bi_(2)S_(3) nanorods modified 2D BiOI nanoplates for highly efficient photocatalytic activity:Pivotal roles of oxygen vacancies and Z-scheme heterojunction

In this study,a novel Bi_(2)S_(3)/BiOI Z-scheme photocatalyst with 3D porous hierarchical network-like heterostructure(BSBI NHs)and rich oxygen vacancies(OVs)was fabricated by a facile ion exchange method followed by the in-situ growth process.A possible formation mechanism of BSBI NHs was studied,showing the self-assembled process of in-situ interwoven growth of 1D Bi_(2)S_(3) nanorods(NRs)on the surface of 2D BiOI disk-like nanoplates(NPs),which followed the Ostwald ripening and epitaxial growth.The modification of BiOI NPs by Bi_(2)S_(3) NRs brought about the formation of Z-scheme heterojunction and massive OVs,which improved the visible-light response property and promoted the separation of photoexcited charge carriers of BSBI NHs.BSBI NHs exhibited a significantly enhanced photocatalytic activity compared with Bi_(2)S_(3) and BiOI,and BSBI-1 can remove almost all bacteria and Rhodamine B(RhB)after 60 min visible light illumination.In addition,the photocatalytic mechanism was studied and speculated based on the tests of active species capture,electron spin resonance(ESR),and density functional theory(DFT)simulation calculation,proving the primary roles of·OH,·O_(2)^(-)and h^(+)during the photocatalytic reaction.This work provides new insights into the design and exploitation of novel heterojunctions with highly efficient photocatalytic performances for environmental remediation applications.

In-situ topotactic construction of novel rod-like Bi_(2)S_(3)/Bi_(5)O_(7)I p-n heterojunctions with highly enhanced photocatalytic activities

In this work,a novel Bi_(2)S_(3)/Bi_(5)O_(7)I p-n heterojunction with three-dimensional rod-like nanostructure was successfully constructed through an in-situ topotactic ion exchange approach.A possible evolution mech-anism from Bi_(5)O_(7)I nanobelts(NBs)into Bi_(2)S_(3)/Bi_(5)O_(7)I rod-like heterostructures(BSI RHs)was proposed,depicting the self-assembly process of internal Bi_(5)O_(7)I NBs and outside networks interwoven by Bi_(2)S_(3)nanorods(NRs),which abided by the Ostwald ripening and epitaxial growth.Owing to the formation of p-n heterojunction and rich oxygen vacancies(OVs),the visible-light absorption ability and separation of photogenerated charge carriers of BSI RHs were highly promoted,leading to a greatly improved photocatalytic ability than that of Bi_(2)S_(3)and Bi_(5)O_(7)I.BSI-1 exhibited the strongest photocatalytic performance,and almost all rhodamine B(RhB)and Pseudomonas aeruginosa(P.aeruginosa)can be thoroughly removed within 90 min.Moreover,a possible photocatalytic mechanism of BSI RHs was proposed based on the tests of active species trapping,electron spin resonance(ESR),photoelectrochemistry(PEC),and photoluminescence(PL)combined with the density functional theory(DFT)simulated computation,vali-dating the dominating roles of·O_(2)^(−)and h+during the photocatalytic process.This work is expected to motivate further efforts for developing novel heterostructures with highly efficient photocatalytic performances,which presents a promising application prospect in the fields of energy and environment.

Enhanced photoelectrochemical cathodic protection performance of MoS_(2)/TiO_(2)nanocomposites for 304 stainless steel under visible light

In this work,TiO_(2)nanotube arrays(NTAs)sensitized with MoS_(2)microspheres(MoS_(2)/TiO_(2)nanocomposites)were prepared on a flat Ti substrate via two-step anodization and hydrothermal method sequentially.TiO_(2)NTAs were composed of many orderly nanotubes,whose large specific surface area was favorable for light absorption and MoS_(2)microsphere adhesion.The MoS_(2)microsphere as a narrow band gap semiconductor extended the TiO_(2)NTAs’absorption band edge to the visible region.The 2D structure of MoS_(2)microspheres and the construction of heterojunction electronic field at the interface of MoS_(2)microspheres and TiO_(2)NTAs promoted the separation of photoinduced carriers.The MoS_(2)/TiO_(2)nanocomposites could provide higher photoelectrochemical cathodic protection for 304 stainless steel(304 SS)under visible light than pristine TiO_(2)NTAs.

Scalable, fluorine free and hot water repelling superhydrophobic and superoleophobic coating based on functionalized Al_(2)O_(3) nanoparticles

Hot water droplet and oils induced air cushion failure, intensively used fluorine-containing chemicals,tedious preparation process, etc. are the main bottlenecks of the current artificially fabricated superhydrophobic materials, restricting their large-scale production and real-world applications. Herein, a facile,scalable, fluorine-free spray-coating strategy was employed to achieve superhydrophobic and superoleophobic polymerized organosilanes/Al2O3 nanoparticles(POS/Al_(2)O_(3) NPs) coatings. The POS/Al_(2)O_(3) NPs coating was achieved through hydrolytic condensation of tetraethyl orthoilicate(TEOS) and hexadecyltrimethoxysilane(HDTMS) in the presence of Al2O3 NPs. A variety of analytical techniques including scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), energy dispersive X-ray photoelectron spectroscopy(EDS) were used to investigate the fabricated coatings. The POS/Al_(2)O_(3) NPs coating features high contact angle(>158°) and low sliding angle(<5°) for water, glycerol, and ethylene glycol droplets with different surface tensions, verifying both superhydrophobic and superoleophobic properties. Moreover, the coatings present extremely low surface adhesion force, excellent liquid-driven self-cleaning ability, and hot water repellency. The superamphiphobic POS/Al_(2)O_(3) NPs coating exhibits promising applications in various fields including self-cleaning, corrosion resistance, and preventing scald as this strategy is applicable on various substrates.

Preparation of Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite films and its performance of photoelectrochemical cathodic protection

A Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite film with high performance of photogenerated cathodic protection was prepared by hydrothermal and photoreduction methods.The results showed that when the CuFe_(2)O_(4) hydrothermal reaction time was 6 h and the AgNO_(3) concentration was 0.1 M,the Ag@CuFe_(2)O_(4)@TiO_(2) nanocomposite material performed the best cathodic protection capability for 304 stainless steel(304SS).In this case,the protective potential achieved-930 mV(versus SCE)associated with the photocurrent density of 475μA/cm^(2),which was 14.8 times that of pure TiO_(2) nanowires.In the dark,the nanocomposite provided cathodic protection of up to 485 mV for 304SS.Due to the heterogeneous junctions at the two interfaces among the three kinds of nanocomposite materials,the build-in electric field was fabricated,which promoted the separation efficiency of photogenerated electrons and holes and effectively improved the photochemical cathodic protection of 304SS.

CuInS_(2)/TiO_(2) heterojunction with elevated photo-electrochemical performance for cathodic protection

Semiconductor quantum dots with high quantum yield and photovoltaic conversion efficiency have ushered in a brilliant moment for constructing internal electric field heterojunctions for photogenerated cathodic protection applications.In this paper,TiO_(2)nanotubes grown vertically on the surface of titanium substrates were modified via a combination of conventional electrochemical oxidation and a one-step solvothermal pathway to sensitize with CuInS_(2)quantum dots.Compared with pure TiO_(2)photoelectrodes,the modification improves sunlight absorption efficiency and provides photoelectron cathodic protection to the 304 stainless steel(304 SS).Through 9 h solvothermal reaction,the CuInS_(2)/TiO_(2)coupled with protected 304 SS exhibited an excellent property when the simulated sunlight irradiation.Its mixed open circuit potential is negatively shifted to-0.99 V,at the mean time with a stable photocurrent density(118μA cm^(-2)).The results indicate that CuInS_(2)and TiO_(2)established a p-n heterojunction with wellmatched energy level,which can effectively facilitate the carrier separation and retain the strong redox capbility of photo-induced electrons and holes.

Corrigendum to“CuInS_(2)/TiO_(2)heterojunction with elevated photo-electrochemical performance for cathodic protection”,[Journal of Materials Science&Technology 122(2022)211-218],

The authors regret the order of authors.Among the authors in the list,Ning Wang designed the experiments and Juan Liu conducted the experimental work under the supervision of Ning Wang.Therefore,after consultation,we decided to adjust the author order and all the authors agreed to make this adjustment.In the final version of the article,Ning Wang is the first in the order of authors and Juan Liu is the second.