SML,ERW管线钢在海泥中的腐蚀行为

应用线性极化电阻,极化曲线和电化学阻抗测量技术,研究了API Spec X60两种管线钢,即ERW(电阻焊管)和SML(无缝钢管)在中国东海长江口地区不同类型海泥中的电化学腐蚀行为.结果表明,SML管线钢的耐蚀性明显优于ERW管线钢,管线钢在海泥中的腐蚀行为主要受阴极去极化剂-氧的扩散控制.     

体外电化学测试对镁合金体内降解行为的预测

可生物降解镁合金因同时具有优良的生物相容性和力学性能,在生物医学界显示出其作为新型骨科内植入物的巨大潜在优势和市场前景。目前,作为制约镁合金医用产业化的关键因素,即过快的降解速率已经成为研究重点。本文回顾了体外电化学测试技术对镁合金抗腐蚀性能的研究,并分析了模拟腐蚀体系对镁合金腐蚀行为的影响;同时评估了电化学测试方法作为快速有效预测镁合金体内降解性能前期分析手段的可行性与局限性。最后,对如何发展更合理的体外电化学测试技术来预测镁合金体内降解提出了可能的解决方法及构思。     

负极腐蚀膜对AZ镁合金点蚀的影响

为分析镁合金表面膜的活性位置,建立起镁负极的点蚀破坏与电化学特性的关联性,本文采用循环伏安和电化学阻抗技术研究了AZ镁合金在MgSO_4溶液中的点蚀行为,从电解质浓度、电位扫描速度、阴极极化角度探讨腐蚀膜对镁合金点蚀的影响。电化学阻抗谱由两个连续容抗弧构成,其电荷转移电阻和膜电阻均随MgSO_4溶液浓度增大而减小,当MgSO_4溶液浓度为1.5 mol/L时,AZ31B合金表面膜阻抗最低,容易发生点蚀。扫描速率从3.3 m V/s下降至0.17 m V/s时,AZ63合金点蚀滞后环面积先增加后减小,击穿电位负移。控制阴极极化起始电位负移,则击穿电位降低,滞后环的面积增加,AZ镁合金的点蚀倾向变大;而在阴极过电位下停留可降低表面膜的腐蚀破坏程度,有利于抑制镁合金点腐蚀的发展。     

AZ31和AZ61镁合金在模拟海水中的腐蚀电化学行为

应用极化曲线、电化学阻抗谱方法研究了两种Mg-Al-Zn系合金——AZ31和AZ61在模拟海水中的腐蚀电化学行为.根据两种镁合金在浸泡过程中腐蚀介质pH值的变化以及扫描电子显微镜对合金微观金相组织和腐蚀形貌的观察,讨论了镁合金的腐蚀机理及合金元素Al的含量对镁合金耐蚀性能的影响.结果表明,AZ61镁合金具有比AZ31镁合金更好的耐蚀性能,其原因主要是AZ61镁合金中Al含量较高使合金的微观组织结构更有利于耐蚀性能的提高.     

阳极氧化AZ91D镁合金在氯化钠稀溶液中的腐蚀行为

利用盐雾实验、极化曲线扫描、电化学阻抗谱和电化学噪声技术等电化学研究方法结合扫描电镜表面观测技术对AZ91D镁合金氧化膜在1%(w)氯化钠溶液中的耐蚀性能进行了评价. 结果表明, 氧化前后的镁合金腐蚀行为发生明显改变, 如未封孔的阳极氧化膜耐中性5%氯化钠盐雾试验时间超过200 h; 氧化后的镁合金自腐蚀电位明显正移, 点蚀诱导期延长; 阳极氧化膜的高频阻抗约为裸露镁合金的数千倍, 这些变化证明阳极氧化处理使镁合金获取了十分优异的耐蚀性能. 首次利用分形维数Df的变化规律初步描述氧化后AZ91D镁合金的腐蚀过程. 可以发现随着浸泡时间的延长, Df呈现出初期快速增长, 随后出现波动, 最后稍有降低的变化过程. 这种现象对应于氧化后AZ91D 镁合金在1%氯化钠溶液中腐蚀的三个阶段.     

六偏磷酸钠对AZ31镁合金电化学行为的影响

为提高AZ31镁合金阳极的活化性能以及抑制它的腐蚀,用电化学等方法研究了在中性3.5%Na Cl体系中,六偏磷酸钠(Na6(PO3)6)对AZ31镁合金电化学行为的影响。结果表明:Na6(PO3)6能大幅度抑制AZ31镁合金的腐蚀,但极化程度有所增大。当Na6(PO3)6的质量分数为2.0%时,AZ31镁合金的缓蚀率高达74.9%,腐蚀后其表面均匀,且活化性能有所改善,在-1.10V处时合金的电流密度高达0.033 m A.cm-2,开路电位Eocp负移程度最大(-1.59 V),活化电位Eact负移程度最大(-1.38 V)。试验结果为AZ31镁合金作为电极材料提供了参考。     

钨酸盐对镁合金在3.5%NaCl介质中的缓蚀作用

研究钨酸钠对AZ61镁合金在3.5%NaC l腐蚀介质中的缓蚀作用.电化学阻抗谱(EIS)、Tafel极化曲线、扫描电子显微镜(SEM)等测试表明,钨酸钠缓蚀剂可有效抑制镁合金在NaC l介质中的腐蚀,当钨酸钠浓度为0.01 mol.L-1可达到较好的缓蚀效果,缓蚀效率达75.5%.钨酸钠可参与镁合金表面膜的形成,使表面膜更致密,从而抑制镁合金的腐蚀;其缓蚀作用属于阳极抑制型缓蚀机理.     

AZ31镁合金表面聚吡咯的化学氧化合成及其耐蚀性能

以对甲苯磺酸钠为掺杂剂, 三氯化铁为氧化剂, 用化学氧化聚合法在AZ31 镁合金表面制备聚吡咯(PPy)膜. 采用傅里叶变换红外(FTIR)光谱分析了镁合金表面聚吡咯膜结构, 通过电化学极化曲线、电化学阻抗谱(EIS)研究了其耐蚀性能, 通过扫描电子显微镜(SEM)、X射线能量散射谱(EDS)分析了表面形貌和成分. 和镁合金裸样相比, 聚吡咯膜对镁合金腐蚀有一定的抑制作用. 硅烷预处理改善了镁合金/聚吡咯体系的耐腐蚀性能, 使腐蚀电位较镁合金裸样正移了110 mV, 电流密度减小了约2个数量级.     

Q235碳钢缝隙腐蚀的电化学噪声研究

应用电化学噪声和电化学阻抗技术研究Q235碳钢在NaHCO3+NaCl溶液中的缝隙腐蚀行为.结果显示,缝隙腐蚀过程可以被清楚地划分为3个阶段:孕育期、快速转换期和稳定发展期.电化学噪声的特征和噪声电阻在各阶段有着显著的变化.缝隙外、内表面积比(r)对缝隙腐蚀的孕育和发展有着十分重要的影响:r越大,孕育期越长.但是,在缝隙腐蚀稳定发展期,r较小时,缝隙外电极表面处于活性溶解状态,缝隙内外电位差很小,缝隙内腐蚀速率较小;倘如r很大时,则缝隙外电极表面处于钝态,缝隙内外电位差大,最终将导致严重的缝隙腐蚀.     

SRB和CO2共存环境中X60管线钢腐蚀电化学特征

对X60管线钢在硫酸盐还原菌(SRB)和CO2共存环境中进行浸泡实验, 对浸泡不同时间后的腐蚀形态及膜层的组成进行观察和分析, 并对膜层覆盖的X60钢的腐蚀电化学参数特征进行分析. 结果表明, SRB吸附形成的微生物膜覆盖程度加大导致X60钢电位正移, 腐蚀产物FeS和FeCO3含量增加导致X60钢电位负移. X60钢表面膜层中腐蚀产物含量较低时, 仅有一个与电极电位有关的时间常数, 当膜层中腐蚀产物的含量高时, 增加了与腐蚀产物膜有关的时间常数. 在浸泡初期, 随微生物膜覆盖程度增加, X60钢的电荷传递电阻增大; 随腐蚀产物含量增加, 电荷传递电阻先下降后增大. 随浸泡时间的延长, X60钢双电层电容和膜层电容均增大.     

能源塔常用材料在不同载冷剂中的腐蚀行为

能源塔中由于载冷剂存在腐蚀性,会对回路系统中的金属材料产生侵蚀而大幅降低能源塔的使用寿命,为了保障能源塔中设备的长寿命运行,需要明确能源塔回路系统材质与载冷剂的腐蚀兼容性。 本文对能源塔回路中常用的H65铜合金、3003铝合金和20#低碳钢3种材料在6种典型载冷剂中的腐蚀行为进行了研究,结果表明,H65铜合金与YH6830、3003铝合金与BL3500载冷剂、20#低碳钢与HG3500、YH6830型载冷剂搭配使用时腐蚀控制最为理想,对延长能源塔设备运行寿命具有指导意义。     

乌洛托品对模拟汽车冷却液中镁合金的缓蚀作用

镁合金具有高比强度、比刚度以及良好的铸造性、切削性、抗冲击减震性、导热性、无毒性和可回收性等优点,被认为是汽车工业中极好的铝合金及有色金属替代品[1]。用镁合金制造汽车部件,特别是发动机等大重量部件,可以大大减轻车身重量,进而降低能源消耗和废气污染。但是由于镁合     

On the correlation between thermal analysis results and corrosion behaviour of some metallic religious artefacts

The aim of this study was to investigate the effects of immersion time on the electrochemical corrosion behaviour of three brass alloys (CuZn) coming from religious artefacts in simulated acid rain at 25 °C, utilising the electrochemical impedance spectroscopy (EIS). The main parameters of the corrosion process were established. On the other hand, the alloys were also analysed by means DSC and TG/DTA before and after immersion in the corrosive environment. Finally, the obtained results were compared in order to correlate them with each other and with the corrosion process.     

Corrosion resistance and durability of superhydrophobic surface formed on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution

The corrosion resistant performance and durability of the superhydrophobic surface on magnesium alloy coated with nanostructured cerium oxide film and fluoroalkylsilane molecules in corrosive NaCl aqueous solution were investigated using electrochemical and contact angle measurements. The durability of the superhydrophobic surface in corrosive 5 wt% NaCl aqueous solution was elucidated. The corrosion resistant performance of the superhydrophobic surface formed on magnesium alloy was estimated by electrochemical impedance spectroscopy (EIS) measurements. The EIS measurements and appropriate equivalent circuit models revealed that the superhydrophobic surface considerably improved the corrosion resistant performance of magnesium alloy AZ31. American Society for Testing and Materials (ASTM) standard D 3359-02 cross cut tape test was performed to investigate the adhesion of the superhydrophobic film to the magnesium alloy surface. The corrosion formation mechanism of the superhydrophobic surface formed on the magnesium alloy was also proposed.     

Review of corrosive environments for copper and its corrosion inhibitors

This review paper deals with corrosion of copper and its alloys in corrosive environments and their corrosion inhibitors. The main corrosion inhibitor groups for copper are introduced and a review of adsorption models is provided. The main part of this work is to investigate different corrosive environments for copper and its alloys and their corrosion inhibitors used in such environments to protect copper. According to the literature, the corrosion inhibition behavior of organic corrosion inhibitors and their derivatives in comparison with inorganic ones are further evaluated. Knowing maximum corrosion inhibition efficiency of a specific corrosion inhibitor in a specific corrosive environment is helpful to choose the most appropriate corrosion inhibitor compound.     

Ellipsometric analysis of corrosion behavior of 3C magnesium alloy surface touched by simulated sweat

As an optimum shell material, AZ80 magnesium alloys are widely applied in the 3C (computers, communications and consumer electronics) industries. The case of 3C products corroded by a sweaty hand has been simulated and the corrosion characters have been investigated by ellipsometric technology. Thickness variation of corrosive medium film on a Mg alloy surface was monitored. Surface structure of a corrosion layer was described with a three‐layer optical model (substrate—EMA—Cauchy) and thickness of each layer for different soaking time was obtained by fitting experimental data with the model. The corrosion product films with a refractive index of 1.45–1.62, loose corrosion product layer, can only provide limited protection to the substrate when a Mg alloy surface is corroded by sweat again. Copyright © 2010 John Wiley & Sons, Ltd.     

Micro‐arc oxidation and electrophoretic deposition of nano‐grain merwinite (Ca3MgSi2O8) surface coating on magnesium alloy as biodegradable metallic implant

Magnesium alloys are promising biomaterials as biodegradable implant for orthopedic applications. However, their low corrosion resistance and poor bioactivity have prohibited their implant applications. In order to enhance these two properties, a nano‐grain merwinite coating was prepared on magnesium alloy. Its corrosion and the bioactivity behavior were characterized with electrochemical and immersion tests. The results showed that the nano‐grain merwinite coating can improve both the corrosion resistance and the bioactivity of the magnesium alloy making it an appropriate material for biodegradable bone implants. Copyright © 2014 John Wiley & Sons, Ltd.     

Advances in coatings on Mg alloys and their anti-microbial activity for implant applications

Magnesium matrix composites reinforced by calcium phosphate could not show the desired effect on the magnesium breakdown rate. Rapid disintegration rate limited the magnesium alloys used as biodegradable implant material. The rate of degradation can be minimized and biological activity can be improved in the magnesium alloy by Hydroxyapatite (HA) coating with the improvement of bone induction and conduction abilities. Various alkali post-treatment and conversion coating methods are applied to deposit HA coatings and biocompatible dicalcium phosphate dihydrate (DCPD) on magnesium alloy so that corrosion resistance and surface biocompatibility can be improved to be used in bone tissue engineering applications. Magnesium's corrosion resistance will weaken its antibacterial properties, which are linked to and proportional to the alkaline pH at the time of breakdown. The goal of this study is to bring together and compare contemporary research on different coatings on magnesium and related alloys in relation to antibacterial functionalized activities. A though review has been performed on in vivo and in vitro cytocompatibility, material property, corrosion resistance, and antibacterial properties of the coatings. Increased degradation behavior, biocompatibility, and bioactivity have been achieved following multiple procedures such as alkali treatment with HA electrochemical deposition on magnesium alloy. Multifunctional coatings can make safe and bioactive magnesium alloy surfaces for biodegradable implant applications.