查看更多>>摘要：Protection of silver mirror stacks from environmental degradation before launching is crucial for space applications.Hereby,we report a comparative study of the advanced protection of silver mirror stacks for space telescopes provided by SiO2 and Al2O3 coatings in conditions of accelerated aging by sulfidation.The model silver stack samples were deposited by cathodic magnetron sputtering on a reference silica substrate for optical applications and a surface-pretreated SiC substrate.Accelerated aging was performed in dry and more severe wet conditions.Optical micrographic observations,surface and interface analysis by Time-of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and reflectivity measurements were combined to comparatively study the effects of degradation.The results show a lower kinetics of degradation by accelerated aging of the stacks protected by the alumina coating in comparable test conditions.
查看更多>>摘要：Highly oriented Mg-Al layered double hydroxide (LDHs) films were deposited on magnesium alloy AZ31 with different deformation processes by an easy in-situ growth method.The characteristics of the films were investigated by optical microscopy (OM),X-ray diffraction (XRD),scanning electron microscopy (SEM),and electrochemical,immersion and hydrogen evolution tests.The corrosion protection performance ranked the LDHs films as the increasing series: CS-LDHs (as-cast sample with LDHs) ＜ AE-LDHs (asymmetric extrusion sample with LDHs) ＜ SE-LDHs (symmetric extrusion sample with LDHs) ＜ RS-LDHs (rolled sample with LDHs).A thicker and more compact LDH conversion coating was formed on the RS sample,and had the best corrosion protection performance.
查看更多>>摘要：In this work,TiO2 nanotube arrays (NTAs) sensitized with MoS2 microspheres (MoS2/TiO2 nanocomposites) were prepared on a flatTi substrate via two-step anodization and hydrothermal method sequentially.TiO2 NTAs were composed of many orderly nanotubes,whose large specific surface area was favorable for light absorption and MoS2 microsphere adhesion.The MoS2 microsphere as a narrow band gap semiconductor extended the TiO2 NTAs' absorption band edge to the visible region.The 2D structure of MoS2 microspheres and the construction of heterojunction electronic field at the interface of MoS2 microspheres and TiO2 NTAs promoted the separation of photoinduced carriers.The MoS2/TiO2 nanocomposites could provide higher photoelectrochemical cathodic protection for 304 stainless steel (304 SS) under visible light than pristine TiO2 NTAs.
查看更多>>摘要：In this study,crevice corrosion performances of a newly developed LDSS 2002 and three commercial stainless steels (AISI304,AISI316L and DSS 2205) were investigated and discussed.Crevice repassivation potential (ER,cREV),which was measured by the potentiodynamic-galvanostatic-potentiodynamic (PD-GS-PD) test,was applicable to crevice corrosion evaluation of 304 and 316L stainless steels.However,much lower ER,CREV values were obtained for DSS 2205 and LDSS 2002.These abnormal ER,CREV values for duplex stainless steels may be related to the selective attack of the less corrosion-resistant phase,the lower corrosion potential in the crevice-like solution,and more crevice corrosion sites in the PD-GS-PD test.A critical chloride concentration of crevice corrosion (CCCcREV) measurement was introduced for crevice corrosion evaluation of various stainless steels.The derived CCCCREV was proved to be a valid criterion for crevice corrosion evaluation of both the austenitic and duplex stainless steels.An order of crevice corrosion resistance of AISI 304 ≈ LDSS 2002 ＜ AISI 316L ＜ DSS 2205 was suggested,which agreed well with the orders of pitting resistance equivalent number and critical crevice index of the less corrosion-resistant phase in each material.
查看更多>>摘要：A corrosion study of two types of tungsten-copper (W-Cu) alloys in 3.38 wt.％ NaCl solution with different pH at 25 C were investigated using potentiodynamic polarization and immersion test.It is crucial that the corrosion behavior and preferential attacked phases of the W-Cu alloys were found to alter with pH.The micro-galvanic effect of tungsten phase and copper binder played a significant role.It was also proved that the existence of aggressive chloride ions could accelerate the Cu binder dissolution in acidic and neutral solution,which induced tungsten phase detachment and increased the corrosion rate of the W-Cu alloys.While Cl would accelerate the Cu binder dissolution of W-Cu alloys at high potential during polarization test in strong alkaline solution.
查看更多>>摘要：This study investigated the deterioration of a lubricant-infused anodic aluminium oxide surface in a 1 M NaGl solution for ～200 days.Direct observation by cryo-SEM and quantitative analyses by UV spectroscopy and EIS revealed that the long-term deterioration of the lubricant-infused surface was divided into two stages: the surface-adhered lubricant layer gradually dissolved at a constant rate until the substrate was exposed;afterwards the lubricant infused in the nanochannels began to diffuse and was depleted after ～200 days.The EIS results also revealed that the defects reduced the corrosion resistance of the lubricant-infused surface considerably.
查看更多>>摘要：A doublely-doped layered double hydroxide (LDH) film was produced on an anodized magnesium alloy AZ31.The Ce-doped Mg-Al LDH film was prepared by in-situ hydrothermal treatment method,and the intercalation of vanadate was realized by ion-exchange reaction.The structure,morphology and composition of as-prepared LDH film were investigated by X-ray diffractometer,field-emission scanning electronic microscope and energy dispersive spectrometry.Results indicated that a uniform and compact LDH film was formed and the intercalation ofCe3+ and vanadate would change the crystal structure of LDHs.The results of the potentiodynamic polarization,electrochemical impedance spectra,hydrogen evolution and corrosion weight loss tests showed the Ce3+ and vanadate anions significantly improve the impedance of LDH film,and the active double-doped LDH film could effectively protect the magnesium substrate from corrosion.
查看更多>>摘要：A cerium film was prepared on the surface of rebar by chemical conversion method to enhance its corrosion resistance.The film in the simulated concrete pore solution was measured by electrochemical method,transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS).The effect of temperature on film formation was studied,and the optimum temperature was determined at 35 ℃.The film produced by too high formation temperature has more defects,resulting in the lower corrosion resistance.The Ce film resistance increased with time evolution until 800 h,then decreased and stabilized.The Ce film layer has a double-layer film structure,the upper layer is an oxide of cerium,and the underlayer is an oxide of iron.Results revealed that after being immersed in the simulated concrete pore solution,the corrosion resistance of the Ce film was enhanced by self-densification.
查看更多>>摘要：The microstructure and corrosion behavior of Al-Zn-Mg alloy (namely 7 × × ×) after natural aging treatment (NAT) and artificial aging treatment (AAT) in aqueous NaCl solutions containing different aggressive ions have been investigated in current work.Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates.The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT.The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy (EIS).The corrosion potential (Ecorr) of the aluminum alloy is more negative in 3.5 wt.％ NaCl containing 0.052 wt.％ NaHSO3 solution than that in 3.5 wt.％ NaCl solutions with or without 0.907 wt.％ NaHCO3.Charge transfer resistance (Rot) results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT.With the immersion time increasing,mostly pitting spreads over the surface of the alloy only in NaCl solution,whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO3 or NaHCO3.
查看更多>>摘要：The surface properties of weathering steel (WS) is very important for its service performance and safety,and the localized corrosion induced by inclusions is closely related to the surface properties of WS and its application.In the current work,a common spherical (Al,Mg,Ca,Mn)-oxy-sulfide inclusion was selected to investigate the corrosion evolution of complex inclusion and its effect on localized corrosion on WS surface.The results indicate the inclusion in WS consists of (Ca,Mn) sulfides part and (Ca,Al,Mg) oxides part with complex core-shell structure.Locally preferential dissolution occurs in (Ca,Mn) sulfides part as well as metal matrix around the inclusions.Furthermore,both parts of the inclusions with poor conductivity and high-density dislocation at metal matrix around the inclusions was found,which suggests that traditional micro-galvanic corrosion cell may not be the cause of inclusion-induced localized corrosion on WS surface at initial stage of corrosion.The variation in maximum and average depth around the inclusion or selected region with immersion time indicates that localized corrosion induced by inclusions is overwhelmed by uniform corrosion of WS in the latter stage of immersion,then the rust formed on WS surface consists of two layers.
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