钢筋在混凝土模拟孔隙液中腐蚀电化学行为

采用动电位极化曲线法研究了钢筋在混凝土模拟孔隙液中腐蚀电化学行为.结果表明:随着Cl-离子浓度升高,PH值下降,腐蚀电流(Icorr)增大,破裂电位(En)降低:致使钢筋表面钝化膜破裂的临界Cl-离子浓度与孔隙液的pH值之间存在对数关系.提出了Cl-和OH-在钝化膜局部区域上的竞争吸附模型,并解释了实验结果.     

高强钢筋在混凝土环境中的腐蚀行为

通过电化学试验研究了HPB300、HRB400E、HRB500E三种钢筋在混凝土模拟空隙液中的腐蚀行为,并研究了Cl~-浓度(0.04 mol/L～0.08 mol/L)对这三种钢筋耐蚀性的影响。结果表明:在模拟孔隙液中,三种钢筋均能达到稳定的钝化状态;随着Cl~-的加入,钢筋的腐蚀速率均有所增大;由于HRB500E钢筋含有更多的Cr、Ni、V等合金元素,其晶粒度最小,耐蚀性最好。     

不锈钢钢筋的临界氯离子浓度

采用动电位扫描测量技术和扫描电镜测试了304L和316L不锈钢钢筋与Q235钢筋在模拟混凝土孔溶液中的临界氯离子浓度,并采用XPS分析了304L和316L不锈钢钢筋的钝化膜成分。结果表明,普通碳钢(Q235)、304L、316L不锈钢在pH=12.6的模拟混凝土孔隙液中的临界氯离子浓度分别约为0.06 mol/L、1.2 mol/L、4.0mol/L;相比304L不锈钢钢筋,316L不锈钢钢筋试样表面钝化膜中含有耐腐蚀性的Cr3+的氧化物量更高。     

球墨铸铁在不同pH值模拟水泥砂浆孔隙液中的钝化行为

利用Tafel极化法、电化学阻抗谱法和X射线光电子能谱法,研究了球墨铸铁在不同pH值模拟水泥砂浆孔隙液中的钝化行为,分析了模拟孔隙液pH值对球墨铸铁表面钝化膜稳定性和化学成分的影响。结果表眀,模拟孔隙液的pH值对球墨铸铁表面钝化膜的形成有重要影响;在pH值为12.5的孔隙液中,球墨铸铁表面能形成稳定的钝化膜,其成膜时间随孔隙液pH值的升高而减少,且成膜后各电化学参数均较稳定;在pH值为11.5的孔隙液中,球墨铸铁表面难以形成钝化膜;球墨铸铁表面钝化膜的主要成分为FeO,Fe_2O_3和FeOOH等铁化合物,且其表面的Fe~(2+)/Fe~(3+)比随着孔隙液pH值的升高而增加,较高的Fe~(2+)/Fe~(3+)比可体现钝化膜的稳定性和球墨铸铁的耐腐蚀性。     

Cl~-浓度对HPB300钢筋在模拟混凝土孔隙液中腐蚀行为的影响

采用自然腐蚀、线性极化、动电位极化、SEM扫描电镜和X射线衍射等方法研究了模拟混凝土孔隙液中Cl-含量对HPB300钢筋腐蚀行为的影响。结果表明,Cl-是引发钢筋锈蚀的重要因素,随着Cl-浓度增加,自然腐蚀电位逐渐负移,当Cl-摩尔浓度达到0.25mol/L时,自腐蚀电位基本不受Cl-浓度影响;线性极化电阻Rp逐渐减小;动电位极化阳极区钝化区电位范围逐渐变窄,过钝化电位由0.6V(SCE,下同)左右逐渐负移至-0.3V左右;腐蚀产物主要为FeO(OH)和FeCl2,产物膜孔隙率减小,微观形貌由片状变为块状。     

氯离子对模拟混凝土孔溶液中钢筋钝性影响的电化学研究

通过动电位极化曲线,电化学阻抗谱以及Mott-Schottky曲线的测试,研究了预钝化电位对模拟混凝土孔溶液中钢筋的钝化作用及氯离子对钢筋钝性的影响.结果表日月,在室温下相对于饱和甘汞电极电位为-0.200-0.200 V范围于不同电位分别预钝化4800 s后,钢筋表面均处于钝态;钝化膜内浅层施主浓度随预钝化电位的升高而减少,深层施主浓度则增加;预钝化电位为0.200 V时,钢筋钝化膜的电荷转移电阻最大;预钝化后的钢筋在含氯离子0.01-0.08 mol/L,pH值为1250的模拟混凝土孔溶液中浸泡24 h后,其表面钝化膜表现为高掺杂的n型半导体,在015-0.47 V电位区间内表现为一种类型的施主浓度,施主浓度随氯离子浓度的升高而减小.     

钢筋在混凝土孔隙液中的腐蚀行为研究

以建筑工程用8235钢筋为对象,研究了其在混凝土孔隙液中的腐蚀行为,分析了氯离子浓度、溶液pH值以及缓蚀剂对钢筋表面钝化膜的影响。结果表明:随着混凝土孔隙液中氯离子含量的增加和pH值的降低,溶液的极化电阻降低、腐蚀电流密度增大,削弱了钝化膜效果。另外,NaNO2缓蚀剂的加入有效的保护了钝化膜,起到了较好的抗腐蚀效果。     

钢筋在混凝土孔隙液中的腐蚀行为研究

以建筑工程用8235钢筋为对象,研究了其在混凝土孔隙液中的腐蚀行为,分析了氯离子浓度、溶液pH值以及缓蚀剂对钢筋表面钝化膜的影响。结果表明:随着混凝土孔隙液中氯离子含量的增加和pH值的降低,溶液的极化电阻降低、腐蚀电流密度增大,削弱了钝化膜效果。另外,NaNO2缓蚀剂的加入有效的保护了钝化膜,起到了较好的抗腐蚀效果。     

NO_2~-和Cl~-对模拟混凝土孔隙液中钢筋腐蚀行为的影响

应用极化曲线法和电化学阻抗技术研究了NO_2~-和Cl~-对钢筋在不同pH值的模拟混凝土孔隙液中的腐蚀行为,结果表明,钢筋耐蚀性与溶液的pH值,以及NO_2~-和Cl~-的浓度相关,pH值的降低和Cl~-浓度的增高都会使钢筋的耐蚀性降低。在含Cl~-的模拟液中,随着NO_2~-浓度升高,钢筋腐蚀速率降低,在pH值为12.50和10.50的溶液中,当[NO_2~-]/[Cl~-]≥0.4时,NO_2~-对钢筋具有良好的阻锈作用。     

不锈钢在模拟混凝土孔隙液中的腐蚀行为研究

利用动电位扫描和交流阻抗法研究了普通碳钢与不锈钢在模拟混凝土孔隙溶液中的腐蚀行为及其差别,以及Cl-浓度、溶液pH值对腐蚀行为的影响,从而探讨了不锈钢取代碳钢作为混凝土钢筋骨架的可能性.结果表明：即便混凝土碳化导致孔隙液pH值下降后,氯离子对不锈钢的影响仍然较小,钝化膜致密完好,而普通碳钢的耐蚀性明显变差,钝化膜极易被氯离子侵蚀而破坏.     

丙烯酸系乳胶用于钢筋混凝土的防腐蚀研究

用电化学阻抗谱研究了丙烯酸系乳胶作为混凝土添加剂或钢筋表面涂层时对钢筋腐蚀行为的影响,加速腐蚀试验结果表明混凝土中添加乳胶后能够延缓钢筋表面钝化层的破坏,而对混凝土的渗透性能影响不大,乳胶涂层能够显著减小钢筋腐蚀速率,涂层的存在改变了钢筋表面的腐蚀状态,在此基础上提出了改善钢筋混凝土抗蚀能力的措施。     

Untersuchungen zum kritischen korrosionsauslösenden Chloridgehalt von Stahlfasern in künstlicher Betonporenlösung

Investigations into the critical corrosion‐inducing chloride content of steel fibres in artificial concrete pore solution It is well known, that reinforcement steel in concrete is normally protected against corrosion due to the high pH‐value of the pore solution of the concrete. This alkalinity leads to a passive layer on the steel surface, which prevents further corrosion. The passive layer can be destroyed by chloride ions diffusing into the concrete. The concentration of chloride in the concrete which leads to a destruction of the passive layer and therefore to corrosion of the steel is defined as the critical chloride content. Investigations in artificial concrete pore solutions show that the critical chloride content of black steel is strongly dependent on the pH‐value of the solution: the higher the concentration of the OH⁻‐ions the higher the critical chloride content. For steel fibres earlier investigations have shown, that steel fibres do not corrode in concrete even at high chloride contents. Therefore it could be assumed, that the critical corrosion‐inducing chloride content of steel fibres in concrete is distinctly higher than of conventional reinforcing steel. To verify this assumption the corrosion‐inducing chloride content of steel fibres is investigated in artificial chloride‐containing concrete pore solutions at different pH‐values. 5 different types of steel fibres, 1 lashing wire and as reference 1 reinforcing steel are investigated at 3 different pH‐value ranges. The concentration of chloride within the pore solution is gradually increased in time steps of 12 h. The beginning of corrosion is determined by current as well as potential measurements. Furthermore additional investigations are carried out with intermediate products of the fibre production (steel wires with different diameters) to investigate if the critical chloride content of the wires is increasing gradually with decreasing diameter. The investigations show, that steel fibres in artificial chloride‐containing pore solutions indicate an distinctly increased resistance against chloride‐inducing corrosion compared with conventional reinforcing steel for high pH‐values. With decreasing diameter of wires the critical chloride content increases gradually.     

单氟磷酸钠在混凝土模拟孔隙液中的缓蚀特性

采用动电位极化曲线和电化学阻抗谱研究了Na2PO3F在模拟混凝土孔隙液中对钢筋的保护作用。Na2PO3F的加入导致混凝土钢筋的腐蚀电位负移,对钢筋的阴极和阳极电化学过程均有抑制作用,是一种混合型缓蚀剂。Na2PO3F能够在钢筋表面形成沉淀型保护膜,阻挡侵蚀性离子对钢筋的侵蚀。     

硫脲-二乙烯三胺缩聚物对混凝土中钢筋的缓蚀作用

用动电位极化曲线及电化学阻抗谱研究了硫脲－二乙烯三胺缩聚物在浊凝土孔隙模拟液及混凝土中对钢筋腐蚀的抑制作用。结果表明它是一种混合型缓蚀风筋的点蚀有较好的抑制作用。在模拟液中添加１％的该缓蚀剂就可以使对氯离子的容忍度从０．０２ｍｏｌ／Ｌ提高到０．１ｍｏｌ／Ｌ。它与ＮａＮｏ３有交好的协同作用。它妈能吸附于钢筋表面,又能提高混凝土密实程度,减缓腐蚀介质向混凝土内的渗透。能谱分析的结果表明它能够富集于钢筋     

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 of Carbon Steel and Corrosion-Resistant Rebars in Concrete Structures Under Chloride Ion Attack

Corrosion of reinforced concrete is the most challenging durability problem that threatens reinforced concrete structures, especially structures that are subject to severe environmental conditions (i.e., highway bridges, marine structures, etc.). Corrosion of reinforcing steel leads to cracking and spalling of the concrete cover and billions of dollars are spent every year on repairing such damaged structures. New types of reinforcements have been developed to avoid these high-cost repairs. Thus, it is important to study the corrosion behavior of these new types of reinforcements and compare them to the traditional carbon steel reinforcements. This study aimed at characterizing the corrosion behavior of three competing reinforcing steels; conventional carbon steel, micro-composite steel (MMFX-2) and 316LN stainless steel, through experiments in carbonated and non-carbonated concrete exposed to chloride-laden environments. Synthetic pore water solutions have been used to simulate both cases of sound and carbonated concrete under chloride ions attack. A three-electrode corrosion cell is used for determining the corrosion characteristics and rates. Multiple electrochemical techniques were applied using a Gamry PC4? potentiostat manufactured by Gamry Instruments (Warminster, PA). DC corrosion measurements were applied on samples subjected to fixed chloride concentration in the solution.     

Corrosion of reinforcing steel in simulated concrete pore solutions: Effect of carbonation and chloride content

The corrosion susceptibility of as-received reinforcing steel bars (rebars) in solutions simulating the pore liquid of alkaline and carbonated concrete has been studied by means of potentiodynamic polarisation tests and polarisation resistance measurements. The effect of different degrees of carbonation and the presence of several chloride contents in the simulated pore solutions was investigated. Results show the beneficial effect of high alkalinity on the localised corrosion of steel caused by chloride ions. From the results of the potentiodynamic tests a critical chloride concentration above which pitting could take place was evaluated for each solution. The chloride threshold values here found are of the same order than those previously reported in the literature for film-free steel. The results obtained in solutions simulating carbonated concrete showed that under weak carbonation conditions carbon steel does not passivate while in the presence of high levels of carbonate and bicarbonate the resistance to localised corrosion is improved.     

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.     

Detection and identification of concrete cracking during corrosion of reinforced concrete by acoustic emission coupled to the electrochemical techniques

The tenacious oxide passive film, which is formed on the surface of embedded reinforcing steel under high alkaline condition of concrete, protects the steel against corrosion. However, the condition of passivity may be destroyed, due to processes such as leaking out of fluids from concrete, atmospheric carbonation or through the uptake of chloride ions. Passive steel reinforcing corrosion induced by chloride is a well-known problem, especially where chloride-containing admixtures or chloride contaminated aggregate are incorporated into the concrete. The objective of this work is on one hand to study the effect of chloride ions on passivity breakdown of steel, respectively, in simulated concrete pore solution (SCP) and in concrete reinforcement, and on the other hand to reproduce the carbonation phenomena by applying to the concrete samples a heating–cooling cycles. In this context, the acoustic emission coupled to the electrochemical techniques (potentiodynamic and electrochemical impedance spectroscopy (EIS)) are used.

The results show clearly that [Cl⁻]/[OH⁻] ratio of 0.6 is the critical threshold where the depassivation set-up can be initiated. In addition, the carbonation process is very aggressive with chloride ions and shows a perfect correlation with acoustic emission evolution.

A physical model of the reinforcement/electrolyte interface is proposed to describe the behavior of the reinforcement against corrosion in chloride solution.