Hydrolysis and Condensation of Silane Agent for Metallic Surface Treatment

Novel surface treatment technique by silane film is developing for metallic anti corrosion and coat improvement. The key points, hydrolysis and condensation, for the stability of the Silane agent(SA) solution is investigated, and the effective factors of stability for silane agent solution and the relative rule are discussed. It is found that stability of SA solution is related to the temperature, pH, solvents, SA concentration and additive by studying the state of the solution and the conductivity-time curve of SA solution. Meanwhile, controlling factors and improving methods for SA stability are proposed to guide the practical application of metallic surface anti-corrosion treatment by SA.     

Meso-scale numerical investigation on the crack process of concrete cover induced by rebar non-uniform corrosion

Concrete cover cracking induced by corrosion of steel reinforcement is a major influencing factor for durability and serviceability of reinforced concrete structures. In order to investigate the cracking process of concrete cover induced by rebar corrosion, the heterogeneity of concrete meso-structure and non-uniformity of rebar corrosion are accounted for. The undamaged concrete is assumed to be a three-phase composite material composed of aggregate, mortar matrix and the interfacial transition zone (ITZ). And a concrete random aggregate structure is established for the study on the mechanical behavior of the non-uniform radial corrosion expansion. In the present simulations, non-uniform radial displacement is adopted to simulate the non-uniform corrosion of the rebar; the plasticity damaged model is used to describe the mechanical behavior of the mortar matrix and the ITZ, and the aggregate is assumed to be elastic. The cracking of concrete cover due to the non-uniform corrosion of the middle located rebar is numerically simulated. The comparison of the analysis and the test result on failure pattern of cover concrete shows fairly good agreement. And then the failure patterns under uniform corrosion and non-uniform corrosion obtained from the macro-scale homogeneous model and the meso-scale heterogeneous model are compared. Furthermore, the influences of concrete cover thickness and rebar diameter on the failure pattern of concrete cover, the expansive pressure and the corrosion rate of the rebar when cover concrete cracks are investigated.     

Theoretical Contour Line of Reinforcement Bar of Non uniform Corrosion

Most of the previous studies on corrosion of the steel bar in reinforced concrete structures is based on the assumption that the bar is uniformly corroded. The actual measurement in projects proved that most of the reinforcement bar is in non uniform corrosion state. Based on electrochemical principles of metal corrosion and combined with the real corrosion course of the bar in concrete structures, a theoretical model of the contour line of reinforcement bar due to non uniform corrosion is established, through deducing the speed of corrosion and theoretical corrosion penetration and volume changes due to corrosion of reinforcement in general air at different position and different time. At the same time, the model is verified with the results from relative references and measured data.     

Q235钢在不同湿度红壤中的腐蚀形貌研究

采用10%、20%和30%的土壤湿度,土壤中埋藏2个月的Q235钢腐蚀试验显示,在酸性红壤中,土壤的湿度差异是影响红壤中Q235钢腐蚀性的主要因子。在实验条件下,不同湿度对土壤中Q235钢的腐蚀速度影响较大。在湿度为30%左右的土壤中试样的腐蚀速度最大。同时土壤湿度对Q235钢的腐蚀形貌有较大影响,随湿度增加腐蚀从局部腐蚀向均匀腐蚀转化。     

选区激光熔化TC4生物腐蚀和生物相容性分析

选区激光熔化(SLM)为降低TC4钛合金医用植入体的弹性模量、减小应力屏蔽效应提供了一种有效的解决方案,但这种材料在投入实际应用前尚需有充分的生物安全性评价。采用SLM技术制备出致密度为99.5%的TC4合金,通过电化学实验、溶血实验和细胞毒性实验测试了SLM成形TC4的生物腐蚀性能和生物相容性,并与传统铸轧工艺制备的合金进行了对比。实验结果表明：前者相比于后者有着更好的耐蚀性能,并且SLM成形TC4还具有优良的生物相容性,在生物医用植入物方面展现出很好的应用前景。     

Effect of surface defects on anodic oxidation coating of7075 aluminum alloy

The interface interaction between geogrid and soil is one of the key issues on geosynthetic reinforced soil structures. Comparative analysis of properties of geogrid clay interface under the different normal stresses and water contents of clay were conducted by medium sized pullout tests. The results show that ultimate pullout force of geogrid, interfacial cohesion and frictional coefficient are significantly affected by water content of clay. Ultimate pullout force of geogrid tends to be remarkably different when subjecting to different normal stresses at a lower water content. And frictional coefficient of interface decreases with the increase of water content, and interfacial cohesion has a tendency to increase followed by decrease with the increase of water content. Moreover, aforementioned three parameters can keep constant when water content is close to value at plasticity limit. The curves of load and displacement possess three stages: linear increase, non linear increase and ultimate pullout. As water content increases, the interval nonlinear changing stage is not conspicuous. Furthermore, it is found that geogrid strains in transversal ribs tend to increase but to reduce in longitudinal ribs when last level load is kept for given hours and then followed by unloading pullout force.     

钢筋非均匀锈蚀引起混凝土保护层内裂分析

根据自然环境下保护层锈胀开裂前的钢筋锈蚀形态,将锈蚀层简化为半椭圆状的非均匀分布,从而建立了钢筋非均匀锈蚀理论模型。经过求解得到了混凝土中锈胀应力理论解,并与有限元计算结果对比,验证了理论解的精确性。根据理论解可知最大周向应力在水平轴上,因此锈蚀层的发展会首先引起保护层内部水平裂纹的产生。增加钢筋直径可有效减低锈胀应力,提高结构抗锈裂的能力。与均匀锈蚀理论模型对比结果表明：均匀锈蚀要远小于非均匀锈蚀条件下的临界锈蚀层厚度,均匀锈蚀的计算结果偏于保守。因此,对锈胀问题进行理论分析时,应采用更接近真实锈蚀形态的非均匀锈蚀模型。     

Stress Corrosion of Concrete Exposed to the Action of Freezing-thawing Cycles

Through the method of accelerated freezing-thawing and room-temperature corrosion, the stress corrosion of three kinds of concretes subjected to 5.0%MgSO4(in mass)solution was studied. The considered concretes include High Strength Concrete(HSC), High-Volume Mineral Admixture Concrete(HVMAC) and High Durable Concrete(HDC) added with high-volume mineral admixture, air-entraining agent, superplasticizer, fibers and expansion agent. The results showed that the relative dynamic elastic modulus of concrete went through strengthen and deterioration stages subjected to stress corrosion, whether the room temperature or freezing and thawing conditions. The length of time of these two stages are closely related with the experimental temperature. Freezing and thawing action significantly accelerated the process of sulphate stress corrosion damage. Under the action of freezing and thawing, stress corrosion strengthening the period length of HSC shorter 96%, deterioration section of the length of time shorter 88%, compared with the length of time at the corresponding room temperature. Deterioration section of the length of time of HVMAC is reduced by 98%, while the HDC reduced by 71%. The effect of freezing and thawing, HDC freezing-thawing cycles when the stress corrosion damage occurred were longer 1.5 times and 13 times than the HSC and HVMAC. Thus in the cold regions, HDC showed more resistance to sulfate stress corrosion.     

氯氧镁水泥混凝土中钢筋的腐蚀与防护试验研究

结合氯氧镁水泥混凝土耐水性,研究氯氧镁水泥混凝土中钢筋的腐蚀与防护,试验变量包括钢筋种类、混凝土保护层厚度和腐蚀龄期等。钢筋种类包括裸露钢筋和美加力涂层钢筋;混凝土保护层厚度包括25、50 mm;腐蚀龄期包括60、120、180、240、300、360 d。试验采用自来水长期浸泡至试块2/3处,并采用扫描电子显微镜（SEM）和能谱仪（EDS）对腐蚀后的钢筋微观结构和化学元素组成进行分析,研究钢筋的腐蚀机理。结果表明,通过软化系数分析,氯氧镁水泥混凝土的软化系数处于0.78～0.87,说明试验设计的氯氧镁水泥混凝土可用于干燥地区、受潮较轻地区或次要建筑结构。通过极化曲线及其电化学参数分析,裸露钢筋腐蚀速率为美加力涂层钢筋腐蚀速率的40～80倍,说明涂层防腐效果明显。     

Time-variation full process mode of steel bar corrosion in concrete

This paper discusses the corrosion rate variation of reinforcing steels in concrete in constant climate environment. The corrosion current density of steel bar in concrete under a constant climate environmental condition and chloride attack. The results indicate that the corrosion rate (corrosion current density) of the steel bars is time-dependent during a corrosion process, and the time-dependent process can be divided into six phases in the full lifetime. The results also show that the effects of the concrete strength and the electrical resistivity of the concrete on the variation of the corrosion rate. This study conducts the mechanism analyses about the test results based on the microstructure of the interfacial transition zone (ITZ) between the steel bars and the concrete at different corrosion levels. The growth of the corrosion layer and the corrosion cracking are the main factors influencing the corrosion process. The time-variation mode of the corrosion rate of steel bars in full process is developed.     

索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明：吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。     

Study on the Effects of Air Pollution on Corrosion of Carbon Steel

This paper summarizes the results obtained from the first year atmospheric corrosion test of carbon steel specimens exposed in 12 sites in Asia. As shown by the results, the corrosion rates of carbon steel vary with the atmospheric environment and the difference can reach a factor of 16. Among the environmental pollution factors, the most detrimental factor is atmospheric sulfur deposition for atmospheric corrosion of carbon steel. Especially, in Chongqing, the high SO_2 levels plus humid and warm climate lead to the most serious atmospheric corrosion of carbon steel.     

Analysis on the adsorption corrosion behavior of two kinds of azole drugs on 45 steel surface analysis

The adsorption behavior of different concentrations of sulfamethoxazole and tinidazole on 45 steel surface is analyzed by establishing a Temikin isotherm equation-based segmentation adsorption model, when they are used as corrosion inhibitors in 3% HCl solution. Adsorption parameters obtained by the model show their corrosion inhibiting performance increase first and then decrease as their concentrations increase. And the main reason is the intermolecular hydrophobic attractive force in high concentration range of inhibitor is stronger than the electrostatic repulsion, and then hydrophobic aggregation happens, resulting in the decrease of adsorption performance on the surface of 45 steel.     

Comprehensive Effects of Temperature and Relative Humidity on Rebar Corrosion in Concrete

The corrosion rate of steel in concrete is highly dependent on the heterogeneous structure of the concrete and the environmental exposure conditions. Temperature and relative humidity are two important environmental factors that simultaneously influence the corrosion process and cannot be separated or isolated from each other. The interaction of temperature and relative humidity for characterizing the corrosion rate has been sufficiently studied. The resules show that the higher the temperature is, the greater the relative humidity is when rebar corrosion rate reaches the max, and as to different relative humidity, the increasing extent of rebar corrosion rate with rise in temperature is different.     

混凝土在硫酸盐溶液中的腐蚀模型

混凝土在硫酸盐溶液中的腐蚀破坏是一种常见的混凝土破坏形式,研究混凝土抗硫酸盐腐蚀破坏对于混凝土工程具有重要意义。混凝土在硫酸盐溶液中受腐蚀的过程是一个循序渐进的过程,这个过程包括固液界面的表面吸附、硫酸盐溶液的扩散过程以及硫酸盐在混凝土试件内部的化学反应和物理结晶等物理化学过程。研究表明：可以采用Fick第二扩散定律来描述硫酸盐在混凝土中的扩散过程;硫酸盐溶液中,混凝土试件的固液相界面处发生物理吸附和化学吸附,并存在表面化学反应。     

A Method for State Diagnosis of Grounding Grid

This paper discuses the method with which the corrosion of the grounding grid can be diagnosed .A grounding grid can handled as a circuit network. With the application of circuit network graph theory and the fault diagnosis theory of analog circuit and optimization, the fault diagnosis equations can be set up. This equations is figured out by Matlab, and the corrosion status of the grounding grid can be deduced from the result.     

Experimental Analysis on Mechanical Properties of Corroded Stud Shear Connectors

Four series stud push-out specimens were conducted to study static mechanical behavior when stud shear connectors of composite beams were corroded. Firstly, the studs were manually rapidly corroded by electrochemical methods, and then a static load test was performed on them. Test results show that when corrosion occurs at stud rod especially close to combined surface, the ultimate bearing capacity reduces most by 18%, slip under the same load increases, and slip relative to the ultimate load reduces most by 12%. When corrosion occurs at the large end of stud, it has little effect on ultimate bearing capacity of push-out specimens, but deformation performance of stud shear connectors is affected seriously.     

Study on CO2 removal by monoethanolamine/polyamine aqueous

Aqueous monoethanolamine (MEA) is the mostly used absorbent for removing carbon dioxide (CO2) from fuel gas in the industry. Improving the performances of aqueous MEA is the key for the effective CO2 removal. The absorption, regeneration performances and corrosion properties of MEA and its four blends with polyamines (MEA/polyamines) at the same concentration are studied. The polyamines, including N-(2-hydroxyethyl) ethylenediamine (AEEA), piperazine (PZ), diethylenetriamine (DETA) and triethylenetetramine (TETA), are considered. The results show that the absorption and regeneration capacity of four kind blends of MEA/polyamine are much better than that of MEA when the content of polyamines are low. The corrosion rate of MEA/polyamine is low than that of MEA. However, with the increase of polyamines content in blends, the regeneration rates of the blends decrease. It is concluded that MEA/polyamine with suitable polyamine content is a high efficiency absorption solvent comparing with MEA. Among the four blends of MEA/polyamine, the performance of MEA/DETA and MEA/TETA are the best.     

Review of Research on Damage of Corrod Reinforced Concrete

The research result shows that the corrosion of reinforcement is one of the dominating factor for decreasing the durability of reinforced concrete structures. In this paper, the significance of the research of corroded reinforced concrete is presented, and an attempt is made to integrate the latest development with regard to the mechanical behaviors of reinforcement corrosion, the damage of concrete due to corroded bars, bond relationship between corroded bars and concrete, as well as the load capacity of corroded reinforced concrete flexural member and compressive member and the seismic behavior of corroded reinforced concrete element. And the trend of its development in future is discussed as well.     

塑料包装薄膜粘连性研究及其应用现状

针对塑料薄膜的粘连现象及其对生产和应用的影响,综述了粘连的起因及解决方法,介绍了测试薄膜粘连性和摩擦系数的方法,并简单介绍常用果蔬保鲜膜的粘连现象及其对应用的影响。