查看更多>>摘要：The oxidation behavior of two Ferritic/Martensitic (F/M) steels including novel SIMP steel and commercial P91 steel were investigated by exposure to flowing deaerated supercritical water (SCW) at 700 C for up to 1000 h.The kinetic weight gain curves follow parabolic and near-cubic rate equations for SIMP and P91 steels,respectively.X-Ray Diffraction analysis showed the presence of magnetite and a spinel phase in flowing SCW for both steels.The morphology and structure of the oxide scales formed on these two steels were analyzed.The relationship between the microstructure and oxidation behavior and the reason that SIMP steel showed better oxidation resistance than P91 steel were discussed.
查看更多>>摘要：The corrosion damage of 20SiMn steel by sulphate-reducing bacteria (SRB) and the mitigation effect of organic silicon quaternary ammonium salt (OSA) were studied in sterilized mild alkaline simulated concrete pore solution (STR) with different additions of SRB and OSA at pH 9.35 for 28 days.Uniform corrosion occurs in STR medium while slight localized corrosion is observed in STR+OSA medium,and localized pitting corrosion occurs in STR+ SRB and STR+ SRB + OSA media.The largest pit depth reduces from 36.70 μm in STR + SRB medium to 3.31 μm in STR + SRB + OSA medium due to the mitigation effect of OSA.The corrosion rate reflected by weight loss and electrochemical impedance spectroscopy (EIS) results presents the order ofSTR ＜ STR + OSA ＜ STR + SRB + OSA ＜ STR + SRB,which also proves that the presence of SRB can accelerate corrosion in a carbonated medium.However,OSA as an efficient bacteriostatic agent can reduce the excessive growth of SRB and thus reduce corrosion.
查看更多>>摘要：In this work,the stress corrosion cracking (SCC) behavior of E690 steel base metal (BM) and different heat-affected zone (HAZ) microstructures,i.e.,coarse grain HAZ (CGHAZ),fine grain HAZ (FGHAZ),and intercritical HAZ (ICHAZ),was investigated at different cathodic potentials in artificial seawater by slow strain rate tensile tests,scanning electron microscopy and electron back-scattered diffraction measurements.The results show that the HAZ microstructures and BM exhibit different SCC susceptibilities:FGHAZ ＜ ICHAZ ＜ BM ＜ CGHAZ,which are controlled by anodic dissolution (AD) at the open circuit potential.With the cathodic potential equaling to-750 mY,the SCC susceptibility of the four microstructures increases because of the synergistic effect of AD and weak hydrogen embrittlement (HE).At-850 mV,AD is inhibited,and the SCC susceptibility of BM decreases,while the SCC susceptibility of the HAZ microstructures increases.At a potential below-850 mV,the SCC susceptibility of the four microstructures gradually increases because of the augment of HE,and the SCC susceptibility of the HAZ microstructures is higher than that of BM.The distinction reveals that the HAZ microstructures have the greater HE susceptibility than BM.
查看更多>>摘要：The well completion process in oil and gas industry,aiming to build effective exploitation,is divided into acidizing and formation water production process.Oxide scale (OS) formed on the inner wall of the HP-13Cr stainless steel tubes during the hot extrusion process changes the surface roughness.The effects of OS on the corrosion of HP-13Cr stainless steel during well completion process were studied by corrosion measurement,spectra analysis,microscopic observation and numerical simulation.The results indicate that the OS make no change of phase distribution and element composition of corrosion scale,while the increasing OS roughness is the dominant factor for accelerating corrosion rate during the well completion process.In acidizing process,the greater surface roughness OS of HP-13Cr stainless steel increases the corrosion rate obviously due to a larger interfacial area in contact with the aggressive environment.During subsequent formation water production process,the turbulence eddy,formed at locations characterized with greater surface roughness OS,can deteriorate the corrosion scale and accelerate the mass transfer of the corrosive species,resulting in more serious corrosion.
查看更多>>摘要：To realize a rapid evaluation of coating degradation under alternating hydrostatic pressure (AHP),appropriate physical models of electrochemical impedance spectroscopy (EIS) data fitting were respectively developed for epoxy coatings with and without pigments,based on their different water absorption behaviours.Power-law model was selected to evaluate the anti-permeability of epoxy varnish (EV) coating,which tends to form through pores in the coating structure.On the other hand,two-layer model based on Young theory was developed to evaluate the anti-permeability of pigmented epoxy coating.Consequently,the resistivity profile with coating thickness was calculated as a critical parameter to describe the anti-permeability of coating at different immersion time.The interpretation of water diffusion dynamics based on different coating structures was also given,which is responsible for the choice of distribution models.
查看更多>>摘要：Stainless steel (SS) has unsatisfied corrosion resistance in many aggressive environments,particularly under a low pH condition in the bioleaching industry.In this study,through surface analyses and electrochemical measurements,the corrosion resistance of a novel Cu-bearing 316L SS was evaluated in the presence of an acid-producing bacterium,Acidithiobacillus caldus SM-1 that was able to create an extremely acidic corrosive environment.The significantly enhanced anti-microbiologically-inducedcorrosion performance could be explained by the intracellular reactive oxygen species (ROS) and Fenton reaction on the Cu-bearing 316L SS.
查看更多>>摘要：Pitting corrosion of 2Cr13 stainless steel was investigated by deep-sea exposure test at various depths of 500 m,800 m and 1200 m in the South China Sea for 4 months.With the aid of electrochemical measurements in simulated deep-sea environments and grey relational analysis,the influence of deepsea environments on passive film and the mechanism of pitting corrosion were discussed.The results indicated that with the increase of sea depth,pitting depth of 2Cr13 stainless steel increased,which can be attributed to the change of chemical composition and the degradation of pitting resistance of passive film.Film growth was greatly retarded in the condition of low seawater temperature and low dissolved oxygen content of deep sea,resulting in an unstable and vulnerable film.Pitting depth was most influenced by hydrostatic pressure,which can increase the adsorption and penetration of Cl-ion,and promote the proliferation of point defects in passive film,leading to rapid deconstruction of protective oxides of the film.Pitting sensitivity of 2Cr1 3 stainless steel increased eventually with the combination of accelerated dissolution and suppressed self-healing of passive film in deep sea.
查看更多>>摘要：This work aimed to study the comprehensive effects of photo-oxidation and biodegradation on different failure stages of polyester coatings,which were exposed to the tropical rainforest atmosphere.The surface morphology,aging products,local aging characteristics and electrochemical behavior of the coatings were characterized with scanning electron microscope (SEM),fourier transform infrared spectroscopy (FTIR),electrochemical impedance spectroscopy (EIS) and high-resolution dispersive Raman microscope.The results showed that the surface of coatings became rougher and fungal hyphae distributed more densely on surface with the increasing of exposure time.From the aspect of polymer structure,the ultraviolet radiation destroyed the main chain of polyester through the photo-oxidation process,resulting in the breakage of aliphatic ester bonds and the formation of esters.Further,the metabolites of fungi can promote the hydrolysis of oligomers produced by the photo-oxidation.In a short,the photo-oxidation could facilitate the biodegradation of the coating.With the synergistic effect of UV photo-oxidation and fungal biodegradation,a rapid diffusion tunnel between the coating surface and the metal substrate was established at the pore defects of the coating,which finally accelerated the corrosion failure process of the coating.The main corrosion products include α-Fe2O3,ZnO and Zn5(OH)6(CO3)2.
查看更多>>摘要：In general,packaging materials which encapsulate light emitting diodes (LEDs) and microelectronic devices offer barrier protection against several environmental hazards such as water and ionic contaminants.However,these encapsulants may provide pathways for water and ionic contaminants to reach the metal/polymer interfaces and provoke local corrosion of electronics,which is a major reliability concern for polymer encapsulated LEDs and microelectronics.As the water and corrosive constituents play a crucial role in their reliability,water uptake kinetics,interracial ion transport and delamination behaviour of silicone coated copper model system,mimicking a typical microelectronics packaging system,is explored in the present work.Electrochemical impedance spectroscopy (EIS) integrated with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy studies revealed that water diffusion inside the silicone network is Fickian in nature and the evolution of the observed time constants are related to the diffusion and interfacial reactions.A decrease of impedance magnitude with time was observed in EIS measurements concurrently with water absorption bands shifting towards lower wavenumber in ATR-FTIR measurements,implying the growth of strong hydrogen bonding between water molecules and the silicone network.The estimated diffusion constant of water using the capacitance method was in the order of 7 × 10-12 m2 s 1 and the water absorption volume fraction was in the range of 0％ to 0.30％.Scanning Kelvin probe studies elucidated the ion transport process occurring at the silicone/copper interface in a humid atmosphere.The interfacial ion transport process is controlled by the interfacial electrochemical reactions at the cathodic delamination front and the estimated average delamination rate is 0.43 mm h-1/2.This work demonstrates that exploring ion and water transport in the silicone coating and along the silicone/copper interface is of pivotal importance as part of a detailed reliability assessment of the polymer encapsulated LEDs and microelectronics.
查看更多>>摘要：Atmospheric corrosion monitoring (ACM) sensors were employed to study the initial atmospheric corrosion,of carbon steels over a one-month period in six outdoor dynamic atmospheric environments in China.Based on the ～250,000 corrosion data sets collected,the environmental impacts of relative humidity,temperature and rainfall on the initial corrosion behavior of carbon steels were investigated.The results showed that rainfall was the strongest environmental factor influencing the initial atmospheric corrosion rate.Relative humidity significantly influenced the corrosion of carbon steels in low-precipitation environments and non-rainfall period.
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