双功能铝酸钙改性硅溶胶钢筋涂层

制备了一种用于混凝土结构中钢筋表面腐蚀防护的硅溶胶涂层,以水玻璃为前驱体,在涂层制备中引入铝酸钙填料,研究了铝酸钙(C₃A)不同添加量对涂层防护性能的影响。采用XRD、FT-IR、SEM、离子色谱仪以及电化学测量技术对C₃A及水化物的结构形貌、离子交换能力、涂层的结构形貌及腐蚀防护性能进行表征。结果表明,铝酸钙在涂料制备中可以水化形成LDH,且水化后的LDHs具有的阴离子交换功能,可吸附腐蚀介质中的侵蚀性Cl-。同时LDHs本身的片层状结构有助于缓解涂层固化过程中产生的内应力,消除涂层产生的开裂,且可有效提高涂层的阻隔性能,减缓Cl-等侵蚀性离子到达钢筋表面的速率,进而提升硅溶胶涂层对钢筋腐蚀的防护性能。     

建筑工程用钢筋的腐蚀行为和腐蚀机理研究

研究了普通裸钢筋、镀锌钢筋、环氧涂层钢筋和新型复合涂层钢筋的腐蚀行为及其作用机理。结果表明,裸钢筋在混凝土中的腐蚀速度较高,镀锌钢筋比裸钢筋有较高的耐蚀性。复合涂层钢筋和环氧涂层钢筋均可对钢筋基体提供良好的保护。     

热电厂海水冷却塔腐蚀检查与防护策略

通过目视检查、混凝土表面保护涂层厚度和附着力检测以及混凝土钢筋锈蚀电位和混凝土电阻率测试等方法对某热电厂海水冷却塔进行了详细的检查和分析,发现海水冷却塔不同高度的腐蚀情况具有明显的差异。分析了各腐蚀区域腐蚀产生的原因,总结了海水冷却塔发生腐蚀的规律,依据标准规范要求对腐蚀环境进行了评级。针对性地提出了对海水冷却塔采用分区腐蚀控制的策略,能够使冷却塔的整体防腐蚀效果达到最佳,并降低电厂冷却塔腐蚀控制方面的长期成本投入。     

混凝土保护涂层抗氯离子渗透性研究

在NaCl溶液中对混凝土保护涂层进行干/湿循环加速腐蚀实验,用电化学循环极化法和高压渗水法对混凝土保护涂层的防护效果进行了研究,并将两种方法研究结果进行对比.结果表明：氯盐环境中,混凝土保护涂层可以有效提高混凝土的抗渗性,降低氯盐对钢筋的腐蚀破坏;循环极化测试法可用于研究钢筋钝化膜的溶解特性和钢筋的锈蚀趋势.      

环氧涂层钢筋及其应用

钢筋的腐蚀，尤其当有氯离子存在时，是混凝土结构腐蚀破坏的主要原因。在防止钢筋腐蚀的各种措施中，采用涂层既简便又有效。熔融结合环氧粉末涂层的综合防护性能优良，已经大量应用于钢质管道和钢管桩，也很适合于钢筋的保护。钢筋表面涂装环氧涂层可用静电喷涂方法，工艺基本成熟。环氧涂层钢筋的研究开发在美国始于20世纪的70年代，主要应用于撒布化冰盐的路桥和各类海工结构。我国在1997年就制订了环氧树脂涂层钢筋的行业标准。目前，国内已能生产环氧涂层钢筋，并开始实际应用。随着我国国民经济的发展，越来越多的工程要求使用环氧涂层钢筋，市场前景肯定十分广阔。     

提高海洋环境钢筋混凝土构筑物耐久性措施综述

针对海洋环境钢筋混凝土构筑物过早腐蚀破坏,从混凝土防护、钢筋保护、包覆隔离保护、施工技术四个方面综述目前国内外对海洋环境下保护钢筋减少腐蚀、延长构筑物服役寿命所采取的技术措施,内容涉及:高性能混凝土、抗海水腐蚀水泥、阻锈剂、混凝土表面涂层、提高保护层厚度、钢筋涂层、耐腐筋、电化学保护、纤维玻璃钢或钢护筒包覆隔离、预防早期开裂、透水模板。重点讨论各措施的基本原理、特点、主要缺点和发展方向及工程应用。其中海工高性能混凝土是最经济、最基本和不可替代的,其他作为高性能混凝土基本措施的有效补充。     

不同状态的钢筋在氯离子入侵过程中的腐蚀行为

采用极化曲线技术和扫描电镜结合能谱分析,对供货状态和打磨光滑状态的钢筋在混凝土氯离子侵蚀过程中的腐蚀行为进行了研究。通过不同浸泡时间,试样获得了不同的自腐蚀电位及自腐蚀电流密度,分析了不状态试样的表面形貌。结果表明,由于钢筋表面状态不同,钢筋在混凝土中的不同阶段表现出不同的电化学行为。在初期无氯离子的条件下,不同表面状态的钢筋表面钝化膜的稳定性不同,而随着氯离子在混凝土中的入侵,两种钢筋的腐蚀速率也存在很大的差异。结合表面状态分析表明,供货状态钢筋在混凝土氯离子入侵过程中比打磨光滑状态钢筋更易发生腐蚀。     

环氧树脂涂层钢筋在混凝土结构中的应用

介绍了混凝土结构中钢筋的腐蚀机理,在此基础上介绍了环氧树脂涂层钢筋的主要特点及其在混凝土结构中的应用,希望能为延长钢筋使用寿命、增强混凝土结构耐久性提供帮助.     

新型自修复钢筋涂层的试验研究

将人为损伤的自修复涂层钢筋置于海水中浸泡,通过测量钢筋的自腐蚀电位、涂层下的钢筋腐蚀面积、涂层和钢筋界面间的粘附性,并观察涂层破损处的锈蚀状况,研究自修复涂层中的亚硝酸离子对破损涂层处钢筋腐蚀的抑制效果,及碱性环境对亚硝酸离子抑制效应的影响.结果表明,自修复涂层中的水泥和其碱性环境对抑制腐蚀有促进作用;涂层中添加的亚硝酸盐对钢筋腐蚀有显著的抑制效果;亚硝酸盐和水泥的复合抑制效果优于它们独立的抑制效果,且亚硝酸盐含量越高,腐蚀抑制效果越明显.并对自修复涂层的阻锈机理进行了探讨.     

外加应力条件下混凝土环境中钢筋的腐蚀行为研究

研究了不同外加应力条件下,40Si2Mn中碳钢在混凝土环境中的腐蚀行为,分析了钢筋腐蚀断裂的影响因素及其作用机理。结果表明,钢筋-混凝土试样在3.5%NaCl溶液中浸泡250天后,在外加应力为0%、20%和40%时试样未断裂,且表面裂纹数量明显少于相同外加应力条件下未埋入钢筋的混凝土试样;在外加应力为60%和80%的试样表面可见明显的较宽裂纹;随着外加应力的增加,相同腐蚀时间条件下,试样的腐蚀电流密度有所增大,相同腐蚀时间下的试样的阻抗值逐渐降低;随着外加应力的增加,钢筋表面的腐蚀区域逐渐增加,且在外加应力为80%时,钢筋表面出现了明显的尺寸较大的显微裂纹,此时钢筋已经受到严重腐蚀,承载能力下降。     

矿物掺合料对钢筋氯盐腐蚀行为的影响及其作用机理

用水泥提取液模拟混凝土孔隙液,用自腐蚀电位、动电位极化和电化学阻抗技术,研究单掺粉煤灰或矿粉、复掺粉煤灰和矿粉对混凝土中钢筋氯盐腐蚀行为的影响.结果表明,粉煤灰和矿粉均能有效降低钢筋受氯离子腐蚀的风险,减小腐蚀速率,并能不同程度地提高钢筋腐蚀的临界氯离子浓度.抑制氯离子腐蚀能力由强到弱依次为:矿粉>矿粉+粉煤灰>粉煤灰>水泥.且随氯离子浓度的增大,矿粉和粉煤灰的阻锈效率会有不同程度的下降.用矿粉和粉煤灰按适当比例复掺的方法来对抗氯离子腐蚀不仅经济,而且有不错的阻锈效果.     

铁质文物复合封护剂防蚀性能研究

利用电化学交流阻抗谱(EIS)和扫描电子显微镜(SEM),对所研制的铁质文物复合封护剂和纯丙乳液的防腐蚀性能进行了分析和比较。结果发现,用缓蚀剂和纳米材料改性的复合封护剂防蚀性能明显好于纯丙乳液。纯丙乳液中添加的高效缓蚀剂和分散均匀的纳米材料是复合封护剂防蚀性能提高的主要因素。     

氯离子环境下混凝土钢筋的电化学阻抗谱特征

用电化学阻抗谱(EIS)方法研究了混凝土钢筋浸泡在氯离子溶液中的阻抗谱特征,研究结果表明:浸泡初期,钢筋电化学阻抗谱为一半径很大的容抗弧,钢筋处于钝化状态;随着腐蚀的发展,钢筋的阻抗谱表现为双容抗弧,钢筋表面的钝化膜已破裂,钢筋发生了孔蚀,其腐蚀过程受电荷传递过程控制;在浸泡后期,阻抗谱低频段出现了Warburg阻抗,...     

Corrosion behavior of austenitic 304L and 316LN stainless steel clad reinforcing bars in cracked concrete

A study has been conducted on the chloride-induced corrosion behavior of 304L and 316LN stainless steel clad reinforcing bars (rebar) in concrete and in synthetic concrete pore solution. Metallographic examination of the as-received clad bars confirmed a strong metallurgical bond at the core/clad interface and some grain growth interdiffusion of species at the interface. Both bars showed a wide variation in coating thickness around the rebar circumference, from a minimum of 0.32 and 0.60 mm to a maximum of 1.4 and 2.8 mm in the 304L clad and 316LN clad, respectively. The electrochemical results and visual examination after autopsy showed that active corrosion was yet initiated on either the solid and clad stainless steel or carbon steel rebar in the sound noncracked concrete specimens. In contrast, corrosion had initiated in the bars embedded in cracked concrete at the base of the crack and extended along or around the bars. In the concrete and synthetic pore solution tests, the current densities of both solid and clad stainless steel rebar exposed to ∼21% chloride brine solution for days between 400 and 1,500 were similar. This was also the case for current densities of the straight and bent stainless steel bars tested in the synthetic pore solution test.     

Corrosion and Nano-mechanical Behaviors of Magnetron Sputtered Al-Mo Gradient Coated Steel

A gradient three-layer Al-Mo coating was deposited on steel using magnetron sputtering method. The corrosion and nano-mechanical properties of the coating were examined by electrochemical impedance spectroscopy and nano-indentation tests and compared with the conventional electroplated cadmium and IVD aluminum coatings. Electrochemical impedance spectroscopy was performed by immersing the coated specimens in 3.5% NaCl solution, and the impedance behavior was recorded as a function of immersion time. The mechanical properties (hardness and elastic modulus) were obtained from each indentation as a function of the penetration depth across the coating cross section. The adhesion resistance of the coatings was evaluated by scratch tests on the coated surface using nano-indentation method. The results show that the gradient Al-Mo coating exhibits better corrosion resistance than the other coatings in view of the better microstructure. The impedance results were modeled using appropriate electrical equivalent circuits for all the coated systems. The uniform, smooth and dense Al-Mo coating obtained by magnetron sputtering exhibits good adhesion with the steel substrate as per scratch test method. The poor corrosion resistance of the later coatings was shown to be due to the defects/cracks as well as the lesser adhesion of the coatings with steel. The hardness and elastic modulus of the Al-Mo coating are found to be high when compared to the other coatings.     

Effect of surface condition on the initial corrosion of galvanized reinforcing steel embedded in concrete

The present work was aimed at determining the effect of coating surface condition on the initial corrosion of hot-dip galvanized reinforcing steel bar (HDG rebar) in ordinary Portland cement (OPC) concrete. During zinc corrosion in OPC concrete, calcium hydroxyzincate (CHZ) formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc. A layer of zinc oxide and zinc carbonate formed, through weathering, on HDG bars increased the initial corrosion rate and passivation time compared with the non-weathered rebar exposed to concrete. HDG steel with an alloyed coating, i.e. containing only of Fe-Zn intermetallic phases, required a longer time to passivate than those with a pure zinc surface layer. The lower zinc content of the surface limited the rate of CHZ formation; hence, delayed passivation. Regardless of the surface condition, the coating depth loss after two days of embedment in ordinary Portland cement concrete was insignificant.     

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Abstract

The validity of the ac impedance technique has been tested using polished steel samples cast in concrete cubes, followed by immersion in oxygen-saturated sea water and distilled water. In order to accelerate the corrosion processes the concrete used was very porous with a low cover thickness and comparisons were made with samples of pre-rusted steel specimens.

The impedance results show that, as well as estimating the corrosion rates, information related to the surface film on the steel may also be obtained. The data are in accord with corrosion potential measurements; The results highlight a problem inherent in dc polarisation techniques when applied to the study of corrosion of reinforcing steel in concrete, namely, that steady state data are only obtained many hours after the initial measuring perturbation.     

Long term assessment of a hybrid electrochemical treatment

Monitoring the performance of systems installed to protect against/halt the corrosion of reinforcing steel in concrete is essential in ensuring that the reinforcing bar (rebar) is adequately protected and remains in a non‐corroding state. A chloride contaminated concrete test block containing a hybrid anode system has been periodically monitored over the past 4.5 years to assess the anode current output and thus, the protection offered to the steel. De‐polarisation and impedance analysis data have been acquired to calculate steel corrosion rates. Both tests indicated that the steel was passive in the concrete environment and that the anode was able to protect all of the embedded steel despite the difficult geometry of the sample. It was also found that after 2 years it was still possible to drive a high current from the installed anode.     

等效电路拟合钢筋锈蚀行为的电化学阻抗谱研究

简述了混凝土中钢筋锈蚀的电化学阻抗谱测试常用的等效电路,对比分析了不同等效电路的优劣性.根据混凝土中钢筋的钝化、初锈与锈蚀发展期三个阶段选取相应的等效电路进行拟合分析.结果表明,随着钢筋锈蚀的发展,等效电路拟合时需要增加时间常数;应用常相角元件CPE和Warburg扩散元件能更好地进行阻抗谱拟合.