用等通道转角挤压法制备的超细晶铜的腐蚀性能

超细晶铜具有较高的使用价值,过去对其腐蚀性能研究不多.将工业纯铜退火后,通过等通道转角挤压(ECAP)法挤压成超细晶材料,采用浸泡和电化学方法,结合扫描电镜表面分析技术研究了退火态纯铜和ECAP制备的块体超细晶铜在HCl水溶液中的腐蚀性能.结果表明:用ECAP法制备的超细晶铜结构致密,具有比退火态铜更高的自腐蚀电位和更低的腐蚀电流密度,耐腐蚀性能更强;在不同浓度HCl溶液体系中,超细晶纯铜的失重速率比退火态纯铜小;随着溶液浓度的降低和浸泡时间的延长,超细晶铜和退火态铜的失重速率均减小并趋于稳定;浸泡腐蚀2周后,与退火态铜易发生局部晶间腐蚀相比.超细晶纯铜的均匀腐蚀占主要优势.     

电刷镀n-SiC/Ni镀层在海水中的静态腐蚀试验

介绍了电刷镀Ni、n-SiC/Ni镀层在海水中静态腐蚀400h后的失重情况.用扫描电镜(SEM)和能谱仪(EDS)分别观测了腐蚀形貌,并进行了成分分析,且在加速腐蚀状态下测试了极化曲线.结果表明,Ni可以与未配对的电子的氧形成强的化学键,也可以与基体铁形成微观腐蚀电池;电刷镀n-SiC/Ni镀层在海水中的静态耐蚀性比Ni镀层的好.     

X80管线钢焊缝在鹰潭土壤模拟溶液中的腐蚀行为

X80管线钢应用前景广阔,对其焊缝处的耐蚀性研究结论还不一致.通过失重法测试X80管线钢母材和焊缝在鹰潭酸性土壤模拟溶液中的腐蚀速率,用开路电位、动电位极化和交流阻抗等电化学法比较两者的腐蚀行为,借助金相显微镜、扫描电镜(SEM)、能谱仪(EDS)观察分析二者的显微组织、夹杂物数量及组成.结果表明:与X80管线钢母材相比,焊缝在鹰潭土壤模拟溶液中有更大的腐蚀速率和自腐蚀电流密度,更负的开路电位和更小的电荷转移电阻,其抗腐蚀性低于母材,这主要与X80焊缝中存在更多夹杂物和更粗大的显微组织有关.     

微弧氧化处理对铝合金钻杆与钢接头电偶腐蚀行为的影响

铝合金钻杆特殊的结构设计使其自身的异金属腐蚀敏感性较强,为了提高其耐腐蚀性能,选用微弧氧化技术(Micro-arc oxidation,MAO)对铝合金钻杆材料进行了表面处理。在构建的钻井盐水泥浆环境下,通过电化学腐蚀试验,测得了铝合金表面处理前后的极化曲线和电化学阻抗。结果表明:MAO涂层的试样具有较正的腐蚀电位、较小的腐蚀电流密度以及较高的阻抗;同时,与30CrMnSiA合金钢耦合,通过失重试验、E-t试验和I-t试验发现,MAO涂层试样与未经处理试样相比失重较小,腐蚀电位、腐蚀电流平稳,未发生大面积点蚀。     

丙烯基硫脲对纳米晶纯铁腐蚀行为影响研究

在室温添加丙烯基硫脲(ATU)的稀盐酸溶液中,对块体纳米晶工业纯铁(BNⅡ)和普通工业纯铁(CPⅡ)的电化学腐蚀行为进行了对比研究.结果表明:在空白室温1mol.L-1HCl中,BNⅡ的抗腐蚀能力比CPⅡ的强.当添加ATU,浸泡5min后,两种样品的EIS(电化学阻抗谱)均没有出现感抗弧.随着时间的延长,对于BNⅡ,EIS谱图上出现一Warburg阻抗.在浓度为100mg.L-1,进行动电位极化测试时,两种样品均出现阳极脱附现象,脱附电位Edes有明显差异.与CPⅡ相比,ATU对BNⅡ的缓蚀作用非常有限,甚至有促进其腐蚀的趋势.     

模拟海洋工业大气环境中Q235钢及耐候钢的腐蚀行为

海洋工业大气环境是我国一种典型大气环境,目前缺乏Q235钢和耐候钢在其中腐蚀情况的对比研究。通过模拟加速腐蚀试验,利用腐蚀失重分析、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)和电化学测试,对比研究Q235钢和耐候钢在模拟海洋工业大气中的腐蚀失重、组织结构和电化学行为。结果表明:Q235钢表面的锈层没有明显的保护作用,耐候钢的耐蚀性优于Q235钢,适用于海洋工业大气环境。     

Mg-11Li-3Al-0.5RE合金在碱性NaCl溶液中的腐蚀特性

用静态失重法、动电位极化曲线和电化学交流阻抗谱等方法研究了Mg-11Li-3Al-0.55RE合金在碱性NaCl溶液中的腐蚀行为,结果表明:在碱性NaCl溶液中,随着Cl<'-浓度的升高,合金的平均腐蚀速率增大,腐蚀电流增大,体系中Rsol、Rt、Rf减小,腐蚀严重;当溶液的碱性增强时,合金的点蚀电位正移,表面膜钝化作用增强,Rf提高,同时Rt和Rsol增大,减缓了腐蚀的进行;在合金表面生成的腐蚀产物主要成分为Mg(OH)2、Al2O3和Li2O2;Mg-11Li-3Al-0.5RE合金的腐蚀以点蚀为主,逐渐向基体内部和四周扩大,形成较深的蚀坑.     

耐候高强度螺栓钢耐典型工业大气环境腐蚀性能研究

为了研究耐候高强度螺栓钢在典型工业大气环境下的腐蚀行为，从自制的10.9级耐候螺栓中取样，与35VB螺栓对比，进行周期为24,48,96,168,216 h的模拟典型工业大气环境周期浸润加速腐蚀试验，采用腐蚀失重、XRD、SEM、电化学测试等分析试验方法，研究耐候高强度螺栓钢在模拟工业大气环境下的腐蚀行为。结果表明：10.9级耐候螺栓钢和35VB螺栓钢的腐蚀失重量均随腐蚀周期的延长而增加，10.9级耐候螺栓钢的失重量明显低于35VB螺栓钢；随腐蚀周期的延长，10.9级耐候螺栓钢和35VB螺栓钢的腐蚀产物的衍射峰强度均增大，并且在相同腐蚀周期下，10.9级耐候螺栓钢中α-FeOOH相的衍射峰较强；在相同周期下，10.9级耐候螺栓钢与35VB螺栓钢相比，自腐蚀电位较正、自腐蚀电流密度较小，且容抗弧较大，说明加入了Cu、Cr、Ni合金元素的10.9级耐候螺栓钢在典型工业大气环境中具有较为优异的耐蚀性。     

不同浓度氨溶液中铜管的腐蚀机理

为了解铜管的氨腐蚀机理,采用电化学阻抗谱、扫描电镜(SEM)和失重试验对铜管在有氧条件下于不同浓度氨溶液中的腐蚀行为进行了研究.结果表明,氨含量小于100 mg/L时,铜管腐蚀非常轻微,大于500 mg/L时腐蚀加剧,浓度越高腐蚀越严重.氨浓度较低和较高时铜管腐蚀机理和产物不同:氨浓度小于2 000 mg/L时,铜管表面生成黑色产物膜[CuO和Cu(OH)2],开路电位正移,阻抗增加,且该过程发生在前期6 d,之后不再有明显变化,这说明产物膜的生成对铜管具有保护作用,铜管氨腐蚀发展迅速,一周之内趋于稳定;氨浓度大于2 000 mg/L时铜管腐蚀为活化溶解,生成可溶的铜氨配离子,表面没有产物膜机理生成,开路电位和阻抗都没有明显变化.     

AZ31镁合金在Hank’s模拟体液中的腐蚀行为研究

研究了AZ31镁合金在Hank's模拟体液中的腐蚀行为,包括腐蚀形貌、腐蚀速度和腐蚀电化学特征参数.通过扫描电子显微镜(SEM)比较了不同腐蚀环境中镁合金样品的腐蚀形貌特征.利用失重法测量了镁合金的腐蚀速度,并依此分析了Hank's模拟体液中各成分对镁合金腐蚀速度的影响.测量并分析了不同pH值下的动电位动态极化曲线.结果表明,镁合金在Hank's模拟体液中的腐蚀主要为氯离子引起的点蚀;H_2PO_4~-和HPO_4~(2-)具有缓蚀作用;pH值的升高可以提高镁合金腐蚀反应的自腐蚀电位,降低腐蚀反应的热力学倾向,稳定腐蚀过程中形成的钝化膜,从而降低了腐蚀速度.     

ECAP加工与热处理对工业纯铁点蚀行为的影响

通过多道次等通道转角挤压(ECAP)和退火热处理,制备不同组织结构状态的超细晶工业纯铁,采用透射电镜观察微观组织结构特征,并用电化学极化和阻抗谱技术表征超细晶纯铁在含氯离子的钝化介质中点蚀行为。结果表明:随着ECAP加工道次增加,低道次形成的高位错密度板条状结构转变为低位错密度等轴晶;ECAP样退火热处理后,位错减少、大角度晶界增加。ECAP加工道次对纯铁自钝化性能影响不大,开路电位和极化电阻变化均较小;耐点蚀性能与加工道次有关,点蚀电位随加工道次先下降后升高;退火处理后自钝化性能和耐蚀性提高,开路电位、极化电阻和点蚀电位均明显增大。     

高能喷丸处理工业纯钛焊接接头在10%HCl溶液中的腐蚀行为

采用高能喷丸处理技术(HESP)提高了工业纯钛焊接接头在10%HCl溶液中的耐蚀性,利用极化曲线和交流阻抗测试方法对其电化学腐蚀行为进行研究,结合Mott-Schottky曲线研究了工业纯钛焊接接头的腐蚀机理。结果表明,HESP处理工业纯钛焊接接头表层晶粒尺寸细化,从表层到基体晶粒尺寸由小到大呈梯度分布。HESP处理提高了工业纯钛焊接接头在10%HCl溶液中的耐蚀性,0.2 MPa-60min处理工艺是其最优处理参数。HESP处理焊接接头母材区在10%HCl溶液中的钝化膜具有n型半导体特性,材料表面缺陷较少,钝化膜排列致密,且处理后金属表面的钝化膜厚度大于未处理试样的钝化膜厚度,材料的耐腐蚀性能提高。     

The preparation and properties of iron base self-fluxing alloy spray-welding coatings with different rare earths and chromium content

This investigation studied the effects of rare earths (RE) and chromium on the high temperature oxidation resistance and aqueous corrosion resistance of iron base self-fluxing alloy coatings. Four coatings were prepared through smelting-atomizing and oxide-acetylene flame spraying. The properties of the coatings were evaluated by cyclic oxidation tests, weight loss experiments, electrochemical impedance spectroscopy (EIS), potentiodynamic scanning technique, scanning electron microscopy (SEM) and electron dispersive X-ray analysis (EDAX). The addition of RE greatly enhanced the oxidation resistance of the coatings. This effect was attributed to the fact that RE changed the ion diffusion patterns of the coatings in the process of scale forming, resulting in more protective scales with high adhesion. The increase of chromium content in the coatings enhanced the corrosion resistance of the coatings in nitric acid solution, but in hydrochloric acid and sulfuric acid solutions the result was reversed. Rare earth addition had a beneficial effect in sulfuric acid and nitric solutions, but in hydrochloric acid, the samples with RE had a corrosion rate slightly higher than that of the samples without RE addition. These results are explained by the effect that the addition of RE minimized the cathodic area of the coatings.     

Effects of grain size on the corrosion resistance of pure magnesium by cooling rate-controlled solidification

The aim of this study was to investigate the effect of grain size on the corrosion resistance of pure magnesium developed for biomedical applications. High-purity magnesium samples with different grain size were prepared by the cooling rate-controlled solidification. Electrochemical and immersion tests were employed to measure the corrosion resistance of pure magnesium with different grain size. The electrochemical polarization curves indicated that the corrosion susceptibility increased as the grain size decrease. However, the electrochemical impedance spectroscopy (EIS) and immersion tests indicated that the corrosion resistance of pure magnesium is improved as the grain size decreases. The improvement in the corrosion resistance is attributed to refine grain can produce more uniform and density film on the surface of sample.     

Corrosion behaviour of Al 1050 severely deformed by rotary swaging

In this study, corrosion behaviour of ultrafine-grained (UFG) commercial pure aluminium Al 1050 processed by rotary swaging (RS) was examined using potentiodynamic polarization and weight loss immersion test in 3.5% NaCl solution. Corrosion behaviour of UFG Al 1050 was compared with that of coarse grained (CG) as-received material. The results showed that ultrafine grain refinement by RS led to marked improvement of the corrosion resistance. The improvement in corrosion resistance is profited from the denser and stable passive film due to more grain boundaries, larger fraction of non-equilibrium grain boundaries and residual stress of the UFG pure aluminium. The weight loss tests revealed low corrosion rate values of RS material compared to CG as-received material. Scanning electron microscopy (SEM) analysis revealed a higher number of rectangular shallow pits (more close to patches of general dissolution); larger pits size was observed in the as-received compared to RS materials.     

在稀硫酸中添加硫脲对块体纳米晶纯铁腐蚀行为的影响

研究了在稀硫酸溶液中添加硫脲(TU)对块体纳米晶工业纯铁(BNII)室温电化学腐蚀行为的影响,并与普通工业纯铁(CPII)的室温电化学腐蚀行为进行了比较.结果表明:将CPII在添加TU的稀硫酸溶液中浸泡5 min,其电化学阻抗(EIS)谱图中出现感抗弧.随着浸泡时间的延长,CPII的EIS谱图表现为一非圆心下偏的半圆;而在相同的条件下,BNII的EIS谱图表现为两个时间常数的容抗弧,表明硫脲对其腐蚀行为有促进作用.动电位极化(PDP)测试结果表明,两种材料的样品均出现阳极脱附现象.     

Influence of grain-boundary pre-precipitation and corrosion characteristics of inter-granular phases on corrosion behaviors of an Al–Zn–Mg–Cu alloy

In this paper the influence of high-temperature pre-precipitation treatment on corrosion behaviors of 7055 aluminum alloy is investigated. High-temperature pre-precipitation treatment enhances the discontinuing distribution of the coarse precipitates along the grain boundary, and increases the Cu content of grain-boundary precipitates, which obviously improves stress corrosion resistance, suppresses the serve fracture of sub-grain boundary under the stress corrosion and reduces inter-granular corrosion (IGC) susceptibility with the same strength and ductility. The electrochemical corrosion results of inter-granular phases indicate that the Cu-rich, discrete and coarse grain-boundary precipitates and the decreasing potential difference among inter-granular phases in the grain boundary are responsible for the enhancement of corrosion resistance of 7055 alloy.     

In vitro and in vivo studies on Ti-based bulk metallic glass as potential dental implant material

In this study, a high glass forming system, Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 (TZHCNSS) bulk metallic glass (BMG), is studied in terms of microstructure, surface analysis, mechanical properties, corrosion resistance, in vitro cytotoxicity and in vivo biocompatibility. It is found that the as-prepared TZHCNSS samples are fully amorphous by XRD and TEM observations, as well as DSC curve. Comparing with pure Ti, TZHCNSS BMG shows superior mechanical properties with higher hardness and better wear resistance. Due to the oxide film formed on its surface, TZHCNSS BMG shows great corrosion resistance close to pure Ti in electrochemical measurements. The pitting corrosion potential in artificial saliva solution is much higher than that in SBF solution. The indirect and direct cytotoxicity results show that TZHCNSS extracts had obvious low cell viability on both L929 and NIH3T3 cells. However, the in vivo testing results proved that TZHCNSS BMG could integrate with bone tissue, showing excellent osseointegration.     

A Generalizable Top‐Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen–Nitrogen Exchange Reaction

A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top‐down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen–nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two‐step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium‐ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom‐up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high‐performance nanostructured electrode materials that can meet the industrial demand of cost‐effectiveness for mass production.     

Effect of fluoride on the corrosion behavior of nanostructured Ti-24Nb-4Zr-8Sn alloy in acidulated artificial saliva

The surface of titanium dental implants is highly susceptible to aggressive fluoride ions in the oral environment. Nanotechnology has proven an effective approach to improve the stability and corrosion resistance of titanium by applying a passive film. In this study, we investigated the effects of fluoride on the corrosion behavior of nanostructured(NS) Ti-24 Nb-4 Zr-8 Sn(Ti2448) alloy in acidulated artificial saliva(AAS)at 37 ℃, and then conducted comparisons with its coarse grained(CG) counterpart. Electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), as well as surface analysis including X-ray photoelectron spectroscopy(XPS) with argon ion sputtering, and scanning electronic microscopy(SEM) were employed to evaluate the effects of fluoride on sensitivity to pitting and the tolerance of Ti2448 to fluoride in AAS solution. The results demonstrate that corrosion current density increased with F-concentration. In all respects, the NS Ti2448 alloy presented corrosion resistance superior to that of its coarse grained(CG) counterpart at low F-concentrations(0.1%).Furthermore, a high content of F-(1%) was shown to promote the active dissolution of both alloys by increasing the rate of corrosion. Following immersion in the fluoridated AAS solution for 60 days, a tissuefriendly compound, Ca_3(PO_4)_2, was detected on the surface of the NS when F-= 0.01% and Na_2 TiF_6 was identified as the main component in the corrosion products of the CG as well as NS Ti2448 alloys when F-= 1%. High concentrations of F-produced pitting corrosion on the CG alloy, whereas NS Ti2448 alloy presented general corrosion in the form of lamellar separation under the same conditions. These findings demonstrate the superior corrosion resistance of the NS Ti2448 alloy as well as lower pitting sensitivity and higher tolerance to fluoride due mainly to grain refinement.