蒸发室复合层腐(锈)蚀的要因探讨及修复工艺

本文对真空制盐核心装置蒸发室复合层在生产运行中产生腐蚀或锈蚀的原因进行了研究与探讨,并结合多年在盐行业施工的实践经验,对蒸发室复合层腐蚀或锈蚀部位修复工艺技术进行了总结,可供同行或类似工程的安装、维修提供参考或借鉴。

KOH溶液对麻竹竹蔸浸蚀效力的测定与分析

麻竹老竹和笋株择伐后的竹蔸占据丛蔸生长空间,是形成笋用麻竹林低效的重要原因。文中对KOH溶液浸蚀竹蔸试验的分析表明:强碱溶液浸蚀使竹蔸内壁变软,薄壁细胞受损、维管束剥离坍塌,外壁结构及硬度改变有限,但使竹蔸个体生理灭活,有利于自然界微生物参与促腐。强碱浸蚀导致竹蔸木质素、纤维素、半纤维素和灰分发生显著变化,0.50 g·mL^(−1)KOH溶液为本试验较佳处理浓度。KOH溶液施放蔸腔,pH值可降至弱碱性,反应产物碳酸钾等均为环境友好型物质。

Al_(0.5)FeNiCr和Al_(0.5)FeNiCrCoTi_(0.25)合金高温铝液熔蚀行为

采用电弧熔炼法制备了Al_(0.5)FeNiCr和Al_(0.5)FeNiCoCrTi_(0.25)两种合金,并在700℃铝液中放置1 h,研究其熔蚀行为。Al_(0.5)FeNiCr合金在熔蚀过程中主要生成单一的熔蚀反应层(厚约17μm),且反应层邻近铝的表面疏松,合金元素与Al生成不同的化合物,不断剥落并游离到铝液中;而Al_(0.5)FeNiCoCrTi_(0.25)合金则主要表现为元素与Al反应、扩散,生成两层致密的反应层,反应层由靠近基体Al_(0.5)FeNiCoCrTi_(0.25)合金的较薄的反应层Ⅰ(厚约11μm)及靠近Al的较厚反应层Ⅱ(厚约33μm)组成,并且无明显的剥落生成物。

Enhanced mechanical stability and corrosion resistance ofsuperhydrophobic coating reinforced with inorganic binder

The development of superhydrophobic materials has demonstrated significant potential in the realm ofcorrosion protection for aluminum alloy(Al alloy)surfaces.However,the limited mechanical stability ofsuperhydrophobic surfaces has impeded the rapid advancement in this field.In this research,we synthesized analuminum phosphate(AP)inorganic binder and combined it with hydrophobic fumed SiO_(2)(HF-SiO_(2))nanoparticles andpolydimethylsiloxane(PDMS)to develop a HF-SiO_(2)@PDMS@AP superhydrophobic composite coating with improvedmechanical stability on Al alloy substrates using a simple spray-coating technique.The findings indicate that the additionof the AP inorganic binder significantly enhanced the coating’s resistance to abrasion,maintaining its superhydrophobicproperties and micro-nano hierarchical structure even after being subjected to a sandpaper abrasion distance of 2000 cm.Electrochemical impedance spectroscopy(EIS)testing showed that the low-frequency modulus(|Z|0.01Hz)of theHF-SiO_(2)@PDMS@AP superhydrophobic coating increased by four orders of magnitude compared to the initial Al alloysubstrate,resulting in a substantial improvement in corrosion protection capacity.The impressive corrosion resistanceand mechanical stability exhibited by this coating have the potential to greatly expand the practical applications of suchmaterials for surface functional protection in marine and industrial environments.

Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy

The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses,including electrical conductivity,mechanical properties,local corrosion properties,and slow strain rate tensile stress corrosion tests.Microstructure characterization techniques such as metallographic microscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)were also employed.The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging,and it even exceeds 700 MPa.Furthermore,the yield strength increases by 52.7 MPa,reaching 654.8 MPa after T6I6 aging treatment.The maximum depths of intergranular corrosion(IGC)and exfoliation corrosion(EXCO)decrease from 116.3 and 468.5μm to 89.5 and 324.3μm,respectively.The stress corrosion factor also decreases from 2.1%to 1.6%.These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance.Similarly,when the alloy is treated with T6I4,T6I6 and T6I7 aging,the sizes of grain boundary precipitates(GBPs)are found to be 5.2,18.4,and 32.8 nm,respectively.The sizes of matrix precipitates are 4.8,5.7 and 15.7 nm,respectively.The atomic fractions of Zn in GBPs are 9.92 at.%,8.23 at.%and 6.87 at.%,respectively,while the atomic fractions of Mg are 12.66 at.%,8.43 at.%and 7.00 at.%,respectively.Additionally,the atomic fractions of Cu are 1.83 at.%,2.47 at.%and 3.41 at.%,respectively.

Understanding of tribocorrosion and corrosion characteristics of304L stainless steel in hot concentrated nitric acid solution

Spent fuel reprocessing plays a pivotal role in achieving efficient recycling of nuclear fuel.Among thedifferent forms of failure encountered in spent fuel reprocessing,tribocorrosion stands out as a critical concern.Herein,the tribocorrosion behavior,as well as the corrosion behavior,of 304L stainless steel(SS)in high-temperatureconcentrated nitric acid was investigated.The results indicated that 304L SS formed a thin(1.54 nm)and stable passivefilm on the surface,imparting high resistance to nitric acid corrosion.Meanwhile,it was found that the synergistic effectbetween corrosion and wear accounted for a high total tribocorrosion weight loss of over 85%,implying the dominantrole of the synergistic effect in the tribocorrosion process.Furthermore,the wear of 304L SS in deionized water revealedboth abrasive and adhesive wear characterizations,whereas the tribocorrosion in nitric acid only exhibited abrasive wearfeature.Eventually,the tribocorrosion and corrosion models of 304L SS in hot concentrated nitric acid were proposedbased on the comprehensive experimental findings.

Effect of cathode protection on Desulfovibrio desulfuricans corrosion of X80 steel in a marine tidal environment

The study systematically investigated the impact of zinc sacrificial anode(Zn-SA)cathode protection on the corrosion of X80 steel caused by Desulfovibrio desulfuricans(D.desulfuricans)in a marine tidal environment.Utilizing weight-loss analysis,electrochemical measurements,Raman spectroscopy,and 3D morphology microscopy,the research unveiled significant findings.Unprotected steel suffered pronounced localized corrosion in the presence of D.desulfuricans in the marine tidal environment.However,the implementation of Zn-SA cathode protection notably reduced the activity of both planktonic and sessile D.desulfuricans cells.Over time,the accumulation of calcareous deposits within the corrosion products increased,as evidenced by a rise in the resistance of the corrosion produt film(Rf).Remarkably,Zn-SA cathode protection demonstrated substantial inhibition of the steel’s corrosion rate,albeit exhibiting reduced efficiency as the vertical height of the steel within the tidal environment increased.

Corrosion behavior of B10 copper-nickel alloy beneath a deposit caused by sulfate-reducing bacteria with carbon source starvation in marine environments

Copper-nickel alloys can suffer severe localized corrosion in marine environments containing sulfate-reducing bacteria(SRB),but the effect of SRB on the under-deposit corrosion of copper-nickel alloys is unknown.In this work,the corrosion behavior of B10 copper-nickel alloy beneath a deposit caused by SRB with carbon source starvation in artificial seawater was studied based on electrochemical measurements and surface analysis.Results demonstrate that SRB with an organic carbon starvation can survive in artificial water but most SRB cells have died.The survived SRB cells can attach to the bare and deposit-covered B10 copper-nickel alloy,leading to the corrosion acceleration.Due to the limitation of organic carbon source,the pitting corrosion of B10 copper-nickel alloy caused by SRB is not serious.However,serious pitting corrosion of the deposit-covered B10 copper-nickel alloy can be found both in abiotic and biotic conditions,and the pitting corrosion and uniform corrosion are further accelerated by SRB.There is a galvanic effect between the bare and deposit-covered specimens in the presence of SRB in the early stage but the galvanic effect after 5 d of testing can be neglected due to the low OCP difference values.

Corrosion of Q235 steel affected by Pseudodesulfovibrio cashew differed with electron acceptors

Sulfate and nitrate reducing bacteria are important culprits for microbiologically influenced corrosion(MIC)using sulfate and nitrate as electron acceptors,respectively.Sulfate and nitrate hold different standard electrode potentials,which may lead to differences in corrosion,but their effects on corrosion by the same bacteria have not been reported.The corrosion of Q235 steel affected by Pseudodesulfovibrio cashew(P.cashew)in the sulfate and nitrate media under carbon starvation was studied.It was found that sulfate and nitrate did not lead to differences in corrosion under abiotic conditions.However,P.cashew promoted corrosion in both cases,and the consumption of H_(2)was the main mechanism for MIC.In addition,corrosion was more severe in the sulfate media.The higher corrosivity of P.cashew with sulfate as the electron acceptor is closely related to the higher number of sessile cells in the biofilm,higher bacterial motility,more hydrogen production pathways,and the increased gene expression of enzymes related to energy synthesis.

Microstructural, wettability, and corrosion behaviour of TiO_(2) thin film sputtered on aluminium

The study investigated the application of radiofrequency(RF)-sputtered TiO2 coatings at various temperatures to enhance the hydrophobicity and corrosion resistance of Al6061 alloy.The research aimed to establish a correlation between the coating process and the resulting surface properties.Surface roughness and wettability were quantified with a surface profilometer and goniometer.Additionally,chemical boiling and salt spray corrosion tests were conducted to evaluate any topographical changes during these procedures.The analysis further involved the use of field-emission scanning electron microscopy(FESEM),energy-dispersive spectroscopy(EDS),and X-ray diffraction(XRD)techniques to characterize the deposited coatings.The findings indicated that the TiO2 coating applied at 500℃exhibited the highest water contact angle and superior corrosion resistance compared to other temperatures.Surface characterization confirmed that this specific TiO_(2) coating at 500℃ effectively delays corrosion due to its hydrophobic behavior,making it durable for industrial applications.

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.

Impact of cooling rate on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy

The impact of cooling rate after solution heat treatment on exfoliation corrosion resistance of a Li-containing 7xxx aluminum alloy was investigated by accelerated immersion and electrochemical impedance spectroscopy test,optical microscope,electron backscatter diffraction and scanning transmission electron microscope.With the decrease of cooling rate from 1700℃/s to 4℃/s,exfoliation corrosion resistance of the aged specimens decreases with rating changing from EA to EC and the maximum corrosion depth increasing from about 169.4μm to 632.1μm.Exfoliation corrosion tends to develop along grain boundaries in the specimens with cooling rates higher than about 31℃/s and along both grain boundaries and sub-grain boundaries in the specimens with lower cooling rates.The reason has been discussed based on the changes of the microstructure and microchemistry at grain boundaries and sub-grain boundaries due to slow cooling.

Investigation of mortar corrosion by an acidophilic sulfur-oxidizing microorganism A.thiooxidans

The corrosion behavior of the acidophilic sulfur-oxidizing microorganism(ASOM)Acidithiobacillusthiooxidans(A.thiooxidans)on mortar was investigated for changes of medium and mortar,as well as for weight lossand surface morphology of mortar specimens.Weight loss analysis showed that mortar weight was reduced by(15.1±2.2)%after 56 d.Morphological surface analysis of mortar specimens showed weakly structured fibrous substances with2−100μm in size.The pH variations of the mortar surface and medium indicated that biogenic sulfuric acid had beenproduced by A.thiooxidans.The results prove that A.thiooxidans accelerated concrete corrosion and caused concretefailure.

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.

Effect of combination of ultraviolet radiation and biocide on fungal-induced corrosion of high-strength 7075 aluminum alloy

The effect of ultraviolet(UV)radiation and biocide benzalkonium chloride(BKC)on fungal-induced corrosion of AA7075 induced by Aspergillus terreus(A.terreus)was deeply studied using analysis of biological activity,surface analysis,and electrochemical measurements.Results demonstrated that the planktonic and sessile spore concentrations decline by more than two orders of magnitude when UV radiation and BKC are combinedly used compared with the control.UV radiation can inhibit the biological activity of A.terreus and influence the stability of passive film of AA7075.Except for direct disinfection,the physical adsorption of BKC on the specimen can effectively inhibit the attachment of A.terreus.The combination of UV radiation and BKC can much more effectively inhibit the corrosion of AA,especially pitting corrosion,due to their synergistic effect.The combined application of UV radiation and BKC can be a good method to effectively inhibit fungal-induced corrosion.

Stable and reversible zinc metal anode with fluorinated graphite nanosheets surface coating

A highly stable zinc metal anode modified with a fluorinated graphite nanosheets(FGNSs)coating was designed.The porous structure of the coating layer effectively hinders lateral mass transfer of Zn ions and suppresses dendrite growth.Moreover,the high electronegativity exhibited by fluorine atoms creates an almost superhydrophobic solid-liquid interface,thereby reducing the interaction between solvent water and the zinc substrate.Consequently,this leads to a significant inhibition of hydrogen evolution corrosion and other side reactions.The modified anode demonstrates exceptional cycling stability,as symmetric cells exhibit sustained cycling for over 1400 h at a current density of 5 mA/cm^(2).Moreover,the full cells with NH_(4)V_(4)O_(10)cathode exhibit an impressive capacity retention rate of 92.2%after undergoing 1000 cycles.

Novel multifunctional epoxy based graphitic carbon nitride/silanized TiO_(2)nanocomposite as protective coatings for steel surface against corrosion and flame in the shipping industry

The chemical compound 3-(N-ethylamino)isobutyl)trimethoxysilane(EAMS)modified titanium dioxide(TiO_(2)),producing EAMS-TiO_(2),which was encased in graphitic carbon nitride(GCN)and integrated into epoxy resin(EP).The protective properties of mild steel coated with this nanocomposite in a marine environment were assessedusing electrochemical techniques.Thermogravimetric analysis(TGA)and Cone calorimetry tests demonstrated thatGCN/EAMS-TiO_(2)significantly enhanced the flame retardancy of the epoxy coating,reducing peak heat release rate(PHRR)and total heat release(THR)values by 88%and 70%,respectively,compared to pure EP.Salt spray testsindicated reduced water absorption and improved corrosion resistance.The optimal concentration of 0.6 wt%GCNEAMS/TiO_(2)yielded the highest resistance,with the nanocomposite achieving a coating resistance of 7.50×10^(10)Ω·cm^(2)after 28 d in seawater.The surface resistance of EP-GCN/EAMS-TiO_(2)was over 99.9 times higher than pure EP after onehour in seawater.SECM analysis showed the lowest ferrous ion dissipation(1.0 nA)for EP-GCN/EAMS-TiO_(2)coatedsteel.FE-SEM and EDX analyses revealed improved breakdown products and a durable inert nanolayered covering.Thenanocomposite exhibited excellent water resistance(water contact angle of 167°)and strong mechanical properties,withadhesive strength increasing to 18.3 MPa after 28 d in seawater.EP-GCN/EAMS-TiO_(2)shows potential as a coatingmaterial for the shipping industry.

Realizing efficient electrochemical oxidation of 5-hydroxymethylfurfural on a freestanding Ni(OH)_(2)/nickel foam catalyst

With the continuous improvement of solar energy production capacity,how to effectively use the electricity generated by renewable solar energy for electrochemical conversion of biomass is a hot topic.Electrochemical conversion of 5-hydroxymethylfurfural(HMF)to biofuels and value-added oxygenated commodity chemicals provides a promising and alternative pathway to convert re-newable electricity into chemicals.Although nickel-based eletrocatalysts are well-known for HMF oxidation,their relatively low intrinsic activity,poor conductivity and stability still limit the poten-tial applications.Here,we report the fabrication of a freestanding nickel-based electrode,in which Ni(OH)_(2) species were in-situ constructed on Ni foam(NF)support using a facile ac-id-corrosion-induced strategy.The Ni(OH)2/NF electrocatalyst exhibits stable and efficient electro-chemical HMF oxidation into 2,5-furandicarboxylic acid(FDCA)with HMF conversion close to 100% with high Faraday efficiency.In-situ formation strategy results in a compact interface between Ni(OH)_(2) and NF,which contributes to good conductivity and stability during electrochemical reac-tions.The superior performance benefits from dynamic cyclic evolution of Ni(OH)_(2) to NiOOH,which acts as the reactive species for HMF oxidation to FDCA.A scaled-up device based on a continu-ous-flow electrolytic cell was also established,giving stable operation with a high FDCA production rate of 27 mg h^(-1)cm^(−2).This job offers a straightforward,economical,and scalable design strategy to design efficient and durable catalysts for electrochemical conversion of valuable chemicals.

Corrosion behavior of 2A97 Al-Cu-Li alloys in different thermomechanical conditions by quasi-in-situ analysis

As a promising material in the aircraft industry,2A97 Al-Cu-Li alloy exhibits high corrosion susceptibility that may limit its application.In the present work,to illustrate the influences of precipitate and grain-stored energy on localized corrosion evolution in 2A97 Al-Cu-Li alloy,cold working and artificial aging were carried out to produce 2A97 Al-Cu-Li alloys under different thermomechanical conditions.Quasi-in-situ analysis,traditional immersion test and electrochemical measurement were then conducted to examine the corrosion behavior of 2A97 alloys.It is revealed that precipitate significantly affects Cu enrichment at corrosion fronts,which determines corrosion susceptibility of alloys,whereas grain-stored energy distribution is closely associated with localized corrosion propagation.It is also indicated that quasi-in-situ analysis exhibits a consistent corrosion evolution with traditional immersion tests,which is regarded as a proper method to explore localized corrosion mechanisms by providing local microstructural information with enhanced time and spatial resolutions.

Effect of organic carbon sources on the anodic corrosion of magnesium AZ31B by sulfate-reducing prokaryote

Corrosion caused by sulfate-reducing prokaryotes(SRP)is an important cause of magnesium alloy anode failure in oil pipeline.In this study,the effects of Desulfovibrio sp.HQM3 on the corrosion behavior of AZ31B magnesium alloy anode in organic carbon sources with different contents in simulated tidal flat environment were analyzed using weight loss test,surface analysis and electrochemical analysis technologies.The results showed that the weight loss rate of coupons in low carbon sources contents(0%,1%,10%)was higher than that in 100%carbon sources.Electrochemical analyses showed that the corrosion current density(J_(corr))under low carbon sources contents was larger,while the charge transfer resistance(R_(ct))was lower,leading to a higher corrosion rate compared to those under 100%carbon sources content.Observations from scanning electron microscopy(SEM)and confocal laser scanning microscopy(CLSM)revealed more severe pitting corrosion on the alloy surface in the absence of carbon sources.In addition,a large number of nanowires were observed between bacteria on the alloy surface using SEM.Combined with thermodynamic calculations,it was demonstrated that the corrosion of coupons by Desulfovibrio sp.HQM3 in the absence of carbon sources was achieved through extracellular electron transfer.