钢筋在混凝土模拟孔溶液及水泥净浆中的腐蚀电化学行为

采用动电位扫描法研究钢筋在混凝土模拟孔溶液中腐蚀电化学行为，获得了不同ｐＨ值和氯离子含量对影响钢筋局部锈蚀的临界关系。采用交流阻抗技术研究了钢筋／混凝土模拟孔溶液和钢筋／水泥净浆体系的界面电化学反应机理及其电化学反应模型。结果表明，在高碱性、低氯离子含量或除氧条件下，钢筋在混凝土中将不发生严重局部腐蚀，钢筋的腐蚀电化学反应主要受扩散传质过程控制。     

Q235在不同含水量滨海盐土中腐蚀的电化学阻抗谱分析

利用电化学阻抗谱(EIS)研究了Q235在不同含水量滨海盐土中的腐蚀行为.结果表明:在质量分数为10%含水的滨海盐土中,Q235的腐蚀主要受阳极控制,而在20%,34%含水滨海盐土中,其主要受阴极反应中扩散步骤控制.在10%含水滨海盐土中,由于腐蚀面积和深度不断增加,常相位角元件Qdl导纳的模值Qdl-Y0随埋样时间延长而逐渐增加.在20%和34%含水滨海盐土中,Q235表面的氧浓度逐渐下降,Warburg阻抗的导纳在反应初期较大,随时间延长而逐渐减小,当反应进行到一定程度时,试样表面氧扩散速度和还原反应速度逐渐趋于平衡,表面氧浓度的下降速度逐渐减小,Warburg阻抗导纳的下降逐渐趋于缓慢.     

磁场对电化学腐蚀行为的影响

磁场在未来可能成为一种主要的防腐蚀方法,从腐蚀速率、腐蚀形貌、传质速率、自腐蚀状态、阳极溶解和阴极去极化等几个方面综述了磁场对电化学腐蚀过程的影响。磁感应强度与腐蚀速率为非正相关关系,磁场在电极表面的不均匀分布与其腐蚀形貌有良好的对应关系。磁场对电化学过程的影响最主要体现在液相传质步骤,对由电子转移步骤控制的电化学过程的影响微乎其微,主要影响由液相传质控制的钝化、活化及其相互转变的过程,但洛仑兹力和磁场梯度力对电化学过程的作用不同。磁场对阴极极化的影响主要体现在对溶液中参与阴极去极化反应离子的作用。提出了磁场在与电化学有关方向潜在的应用前景和将来的发展方向。     

热镀锌板在3种典型泥浆中的电化学阻抗谱特征

为了解汽车镀锌板在不同泥浆中的电化学行为和腐蚀机理,通过在湿热箱中进行加速腐蚀实验,采用电化学阻抗谱进行分析,讨论3种典型土壤配制的泥浆在不同时间对镀锌板电化学阻抗谱的影响.结果表明,镀锌板在格尔木、鹰潭和库尔勒3种泥浆中的腐蚀速度依次减小;在浸泡周期内,镀锌板在鹰潭泥浆和库尔勒泥浆中的阻抗谱均具有活化控制特征,而在格尔木泥浆腐蚀过程中出现了氧扩散控制特征.镀锌板在3种典型泥浆中的腐蚀速度受含水量、土类土质、含盐量、pH值等综合作用的影响.     

A7N01S-T5铝合金在84消毒液中的电化学行为

为了研究消毒液对高铁车厢铝合金腐蚀的影响,采用动电位极化和电化学阻抗2种电化学测量技术,研究了高铁车体A7N01S-T5铝合金在不同浓度(100,200,400,800,1 000 mg/L) 84消毒液中的电化学行为,取自来水作为对照试验,使用VHX-2000C超景深三维体式显微镜观察试验后铝合金电极的微观形貌。结果表明:电化学阻抗谱中的Nyquist谱电极过程受活化和扩散控制,随着消毒液浓度升高电荷转移电阻和低频阻抗值减小并趋于一致;极化曲线的阴极过程和阳极过程分别以析氢反应和氧化还原反应为主,随着消毒液浓度升高,自腐蚀电位在不断负移后趋于一致,点蚀电位不断负移,腐蚀电流密度逐渐增大后趋于一致;随着消毒液浓度升高合金表面腐蚀由点蚀发展为全面腐蚀,腐蚀区域扩展缓慢,腐蚀速度减缓。     

氧化铝生产过程中NaOH浓度对16Mn钢腐蚀行为的影响

拜耳法处理高硫铝土矿生产氧化铝过程中,NaOH浓度、S2-浓度、腐蚀时间等因素对设备钢材的腐蚀产生一定的影响.为此,采用电化学和失重腐蚀方法研究NaOH浓度对16Mn钢腐蚀行为的影响,采用扫描电镜分析产物微观形貌,根据元素分布情况分析腐蚀产物的成分变化规律.结果 表明:16Mn钢的腐蚀速率随着NaOH浓度的升高而增加,达到最大值后有所减小,NaOH浓度为245 g/L时腐蚀速率最大.随NaOH浓度从235 g/L增加到245 g/L,16Mn钢的容抗弧半径减小,此时腐蚀主要受电荷转移控制,主要发生S2-的吸附;当NaOH浓度为255 g/L时阻抗谱出现典型的韦伯扩散现象,腐蚀过程主要受离子扩散和电荷转移共同控制,主要发生OH-的吸附.     

SAF2507在高温高浓度磷酸中的电化学性能

采用动电位极化、电化学阻抗谱技术对超级双相不锈钢SAF2507在高温高浓度磷酸中的腐蚀行为进行研究。结果表明,SAF2507在64%~72%的85℃磷酸中发生自钝化,且随着浓度增加到80%~88%时,腐蚀电流密度增大,其值仍较小。SAF2507在25~70℃的76%浓度磷酸中,有二次活化现象。随温度升高,SAF2507的反应过程由电化学步骤控制转变为电化学和扩散反应共同控制,且容抗弧半径逐渐减小,极化电阻逐渐减小,耐蚀性能下降。     

模拟油田环境中P110钢的CO2腐蚀行为

运用腐蚀失重和电化学测量技术,研究模拟油田环境中P110油井管用钢的CO2腐蚀行为.研究结果表明:随着试验时间的延长及腐蚀产物膜的形成,平均腐蚀速率逐渐降低,在试验时间达到72h后,腐蚀速率降低的趋势变缓,腐蚀产物膜下出现典型的局部腐蚀形貌;试样的自腐蚀电位Ecorr升高,腐蚀电流icorr减小,腐蚀速率降低.P110钢的阴极Tafel区出现明显的扩散特征;在反应初始阶段EIS具有两个时间常数,随着腐蚀的进行,腐蚀产物膜越来越厚,越来越致密,EIS的低频端出现Warburg阻抗与容抗的叠加,自腐蚀电位下的电极反应属于混合控制.     

不同添加剂对镀锌层钼酸盐钝化膜腐蚀电化学性能的影响

利用塔菲尔(Tafel)极化曲线和电化学交流阻抗谱,研究了不同添加剂单乙醇胺、硝酸铈、植酸和羟己叉基二膦酸对镀锌层钼酸盐钝化膜腐蚀电化学性能的影响,并与加速腐蚀试验结果进行了对比.结果表明,添加剂的加入明显改变了钝化膜层的自腐蚀电位,使钼酸盐钝化膜的耐腐蚀性明显增强,且钝化膜的阻抗谱呈明显单一的容抗弧,腐蚀过程受电化学控制.     

电化学沉积方法对聚苯胺涂层抗腐蚀性能及电化学性能的影响

聚苯胺涂层的电化学特性及耐蚀性与其合成方法及工艺有着密切的关系.在以硫酸为掺杂剂的合成溶液中采用循环伏安和恒电流方法在304不锈钢表面沉积出了聚苯胺涂层.用扫描电镜和电化学方法研究了聚苯胺涂层的表面形貌、抗腐蚀性能和电化学性能.结果表明:聚苯胺涂层表面为多孔结构;开路电位-时间曲线表明,在腐蚀介质中,2种聚苯胺涂层均提高了304不锈钢的腐蚀电位,电化学阻抗谱结果表明,2种聚苯胺涂层在腐蚀初期反应均受扩散步骤控制,对腐蚀介质有一定的阻挡作用,但恒电流方法制备的聚苯胺在浸泡24 h后,表现为基体金属的阻抗谱特征.因此,相对于恒电流方法,循环伏安方法制备的聚苯胺对304不锈钢的钝化能力更强,可为基体提供更好的保护.     

Electrochemical behaviour of Ti–Ni SMA and Co–Cr alloys in dynamic Tyrode’s simulated body fluid

The electrochemical behaviour of Ti–Ni shape memory alloy and Co–Cr alloys were investigated in dynamic Tyrode’s simulated body fluid on a Model CP6 Potentiostat/Galvanostat. The results indicated that, for all alloys, the anodic dissolution and the pitting sensitivity increased with the flow rate of the Tyrode’s solution increasing while the open-circuit potentials and pitting corrosion potentials decreased with the Tyrode’s solution increasing. Pitting corrosion of Ti–Ni alloy was easier than Co–Cr alloys. Since the solution’s flow enhanced oxygen transform and made it easy to reach the surface of electrodes, the plateau of oxygen diffusion control was diminished. All these indicated that the cathodic reduction and the corrosion reaction, which was controlled by the electrochemical mass transport process, were all accelerated in dynamic Tyrode’s simulated body fluid.     

Kinetics of the oxidative degradation of ceramic injection-moulding vehicle

The effective reaction depth during the pyrolysis of ceramic injection-moulded bodies in oxidizing atmospheres was deduced from isothermal thermogravimetry. The kinetic data were analysed (i) for the case of chemical reaction control, (ii) for mass transport control and (iii) for combined chemical and mass transport control. The shrinking core reaction modulus indicates that reaction rate was mainly controlled by the diffusion of oxygen into the surface region and degradation products out. The results are used to discuss the relative merits of oxidative and thermal degradation of organic vehicle for ceramic processing.     

Q235碳钢在滨海盐土中的腐蚀形貌、产物及机理分析

对Q235碳钢在10%,20%和34%(水饱和)含水滨海盐土中一个月的腐蚀形貌进行宏观和微观形貌观察,计算不同含水条件下的腐蚀失重,并对腐蚀产物进行Raman光谱分析。结果表明:由于受扩散控制的影响,Q235碳钢在10%含水滨海盐土中的腐蚀失重最大,其形貌以局部腐蚀为主;含水量增加,腐蚀失重迅速下降,腐蚀形貌由局部腐蚀转变为均匀腐蚀。Q235碳钢在20%和34%含水滨海盐土中的腐蚀产物主要是α-FeOOH;受腐蚀产物表面脱水的影响,在10%含水条件下的腐蚀产物出现分层结构,内层主要成分是α-FeOOH,腐蚀产物中的Fe2O3和Fe3O4等多分布在α-FeOOH外。     

碳钢在中性土壤中的腐蚀行为研究

总结了碳钢在不同湿度中性土壤介质中腐蚀初期的电化学阻抗谱特征 ;同时讨论了湿度对钢铁土壤腐蚀电化学行为和土壤腐蚀控制特征的影响。     

Corrosion reactions in molten sulphates

The redox potential in sulphate melts is controlled by the partial pressures of oxygen and SO₃ in equilibrium with the melt. The rate for the reduction of oxygen is limited by the solubility. Higher rates are observed for the reduction of SO₃ which is identified as the principal oxidizing species. Equilibrium potentials for reversible metal-metal ion couples for the principal components of superalloys are negative relative to the redox potential for the melt. The anodic oxidation of the metal therefore proceeds irreversibly in conjunction with the cathodic reduction of SO₃ An oxide layer is formed on the surface of the metal when the metal ion concentration at the surface, combined with the oxide ion concentration in the melt, which is related to the partial pressure of SO₃, exceeds the solubility limit for the oxide. The corrosion behaviour will depend on the mass transport processes through this oxide layer. Temperature gradients through the molten sulphate, and oxide ion concentration gradients established as a consequence of the corrosion reaction, may influence the morphology of the corrosion product. The gradient between the oxygen chemical potential at the outer surface of the molten sulphate, defined by the oxygen partial pressure in the gas and the oxygen chemical potential at the metal/metal oxide interface, defined by the dissociation equilibrium for the metal oxide, combined with the transport of SO₃ through the molten sulphate, increases the sulphur chemical potential at the metal surface and leads to the formation of the metal sulphide. Stress in the protective oxide layer caused by the growth of the sulphide phase at the interface between the metal and the oxide will eventually fracture the oxide and cause accelerated corrosion.     

含氯混凝土中钢筋宏电池腐蚀的研究

为了确定含氯混凝土中钢筋的宏电池腐蚀的特性 ,研究了钢筋腐蚀速度与混凝土电阻间的关系。在宏电池阴阳极之间串联可变电阻来模拟混凝土电阻的变化。实验结果显示钢筋腐蚀反应的自然腐蚀电位主要为阳极反应决定 ,而腐蚀反应速度为阴极反应控制。混凝土电阻对钢筋腐蚀反应速度影响很大。     

Influence of temporal resolution and processing of exposure data on modeling of chloride ingress and reinforcement corrosion in concrete

The impacts of temporal resolution and processing of exposure data on the long-term chloride ingress and reinforcement corrosion in concrete were studied. Exposure data from one simulated and two real climates was processed to create boundary conditions for a one-dimensional geometry studied using a numerical heat and mass transport model that includes full coupling of heat, moisture and ion transport. Heat, moisture, and chloride concentration distributions were passed to a simplified reinforcement corrosion initiation and propagation model. The numerical study indicates that processing and temporal resolution of the exposure data has a considerable impact on long-term hygrothermal distribution, chloride ingress, and reinforcement section loss results. Use of time-averaged exposure data in the heat and mass transport model reduces the rate of chloride ingress in concrete and affects prediction of reinforcement corrosion initiation and propagation. Randomly sampled exposure data at daily, weekly, or monthly resolution yields prediction of reinforcement corrosion initiation and propagation closer to original resolution results than time-averaged exposure data.     

热浸镀层的海水全浸腐蚀行为研究

在舟山站进行了锌铝合金镀层的海水全浸腐蚀试验,失重腐蚀测试结果表明,其腐蚀深度随全浸时间按抛物线规律变化。XRD和EPMA分析结果表明,镀层表面的钙质沉积层与镀层金属的腐蚀产物及其凝聚的粘土胶体一起构成的复杂的腐蚀产物层,抑制了镀层腐蚀的传质过程和受扩散控制的氧去极化作用,从而使锌铝合金镀层表现出优异的耐海水腐蚀性能。     

氢氟酸介质中铝的缓蚀剂的研制

研制了一种新型氢氟酸介质中铝的缓蚀剂,采用失重法和电化学方法对该缓蚀剂进行了评价。实验结果表明,该缓蚀剂用量为2．5％时,温度40~C以下,氢氟酸的质量分数在6Z以下时有非常好的缓蚀效果。该缓蚀剂为混合型缓蚀剂,对阳极和阴极过程都有抑制作用。     

Effects of the experimental conditions of chemical vapour deposition on a TiC/TiN double-layer coating

Deposits of titanium nitride (TiN) were formed on TiC-coated 94wt.%WC-6wt.%Co substrates by chemical vapour deposition using a TiCl₄, H₂ and N₂ gas mixture. The effects of the deposition temperature, the total flow rate of the reactant gases and the partial pressure of TiCl₄ on the deposition rate, the preferred orientation and the surface morphology of the TiN deposit were investigated. The controlling mechanism of the TiN deposition reaction and its relationship with the deposition temperature and the total flow rate of the reactant gases were also investigated.The deposition rate and the TiN crystal growth along the (220) preferred orientation are increased with an increase in the deposition temperature and an increase in the partial pressure of TiCl₄ at a total flow rate of less than 700 cm³ min^-1. The particle size of the TiN deposit is reduced with an increase in the partial pressure of TiCl₄ and is increased with an increase in the deposition temperature at a total flow rate of less than 700 cm³ min^-1. When the total flow rate is greater than 700 cm³ min^-1, the deposition rate, the TiN crystal growth along the (220) preferred orientation and the particle size of the TiN deposit no longer vary.When the deposition temperature is lower than 1000 °C, the TiN deposition reaction is controlled by the surface reaction; at a temperature above 1000 °C, the reaction is controlled by mass transport. When the total flow rate is less than 700 cm³ min^-1, the deposition reaction is controlled by mass transport; with a total flow rate greater than 700 cm³ min^-1, the reaction is controlled by the surface reaction.