共查询到20条相似文献,搜索用时 15 毫秒
1.
A. Ray D. Mukerjee S. K. Sen A. Bhattacharya S. K. Dhua M. S. Prasad N. Banerjee A. M. Popli A. K. Sahu 《Journal of Materials Engineering and Performance》1997,6(3):335-343
An extensive investigation has been carried out to study structure-property characteristics and corrosion behavior in three varieties of thermomechanically treated (TMT) reinforcement bars (rebars) produced in an integrated steel plant under the Steel Authority of India Limited. Three experimental steel heats–one of plain-carbon and two of low-alloy chemistry-were chosen for the study. Of the two lowalloy heats, one was copper-bearing and the other contained both copper and chromium for improved corrosion resistance. Hot-rolled bars for each specific chemistry were subjected to in-line thermomechanical treatment, where quenching parameters were altered to achieve different yield strength levels. All the TMT rebars, regardless of chemistry and strength level, exhibited a composite microstructure consisting of ferrite-pearlite at the core and tempered martensite at the rim. Although a tendency toward formation of Widmanstätten ferrite was evident in bars of 500 and 550 MPa yield strength levels, no adverse effect on their strength and ductility was observed. From the standpoint of mechanical properties, the rebars not only conformed to minimum yield strength requirements, but also exhibited high elongation values (21 to 28%) and excellent bendability. Corrosion studies of both TMT and cold-twisted and deformed (CTD) rebars subjected to different laboratory tests indicated that corrosion resistance increased in this order: CTD, plain-carbon TMT, copper-bearing TMT, and copper/chromium-bearing TMT. 相似文献
2.
The use of stainless steel bars in reinforced concrete structures may be an effective method to prevent corrosion in aggressive environments where high amounts of chlorides may penetrate in the concrete cover. For an estimation of the service life of structures where stainless steel bars are used, the chloride threshold for these rebars should be defined, and the influence of chemical composition and metallurgical factors that may affect the corrosion resistance (strengthening, welding, etc.) should be assessed. To reduce the cost of stainless steel reinforcement, duplex stainless steels with low nickel content have been recently proposed as an alternative to traditional austenitic steels, even though, few results are available regarding their corrosion performance in chloride contaminated concrete. This paper deals with the corrosion resistance of low‐nickel duplex stainless steel rebars (1.4362 and 1.4162) as a function of the chloride content. Comparison is made with traditional austenitic steels. An attempt to define a chloride threshold for the different stainless steels is made by comparing the results of several test procedures both in concrete and in solution. 相似文献
3.
将含钢筋的混凝土试样部分浸泡在3.5% NaCl溶液中,测量溶液以及溶液上方混凝土中钢筋试样的腐蚀电位、宏电池腐蚀电流,通过极化电阻Rp值计算钢筋的腐蚀电流密度。结果表明位于溶液中混凝土内钢筋试样的腐蚀电流密度随着其在溶液中深度的增加而降低。位于溶液上方混凝土中钢筋试样的腐蚀电流密度随着其所处的位置升高而降低,说明溶液中混凝土中钢筋的腐蚀与氧含量密切相关。溶液上方的混凝土中钢筋的腐蚀与混凝土湿度密切相关。 相似文献
4.
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. 相似文献
5.
Ramen Datta R. Veeraraghavan K. L. Rohira 《Journal of Materials Engineering and Performance》2002,11(4):369-375
Torr steel rebars, also known as cold twisted deformed (CTD) rebars, are used extensively for the construction of reinforced
cement concrete (RCC) structures. These steels, which are characterized by a high carbon content and are subjected to a cold
twisting operation to attain the desired strength level and bond strength, suffer from low ductility and poor bendability
properties. Furthermore, these rebars are not suitable for coastal, humid, and industrial conditions where corrosion rates
are very high. To combat these problems, recent efforts at the Steel Authority of India Limited (SAIL) have led to the successful
development of corrosion-resistant thermomechanically treated (TMT) rebars with a minimum yield strength of 500 MPa. These
rebars are characterized by a low carbon content, exhibit excellent strength-ductility-corrosion properties, and are rapidly
replacing traditional torr rebars in corrosion-prone areas for a wide range of applications, namely, concrete reinforcement
structures, bridges, flyovers on dams, etc. A comprehensive evaluation of the weldability properties of corrosion-resistant
Cu-TMT rebars was carried out, and they were compared with those made of torr steel in order to assess their suitability for
various structural applications. Implant and restraint cracking (RC) tests were carried out to assess the cold-cracking resistance
of the weld joint under different welding conditions. The static fatigue limit (SFL) values were found to be similar, namely,
640 MPa (torr steel) and 625 MPa (Cu-TMT steel) under condition of no preheating and no rebaking using a heat input of 7.5
KJ/cm, indicating adequate cold-cracking resistance for both the steels. Restraint cracking tests yielded critical restraint
intensities (Kcr) in excess of 16,800 MPa for both of the steels. Based on the weldability tests, the optimized conditions
for welding were formulated and extensive tests were carried out on the welded joints. Both of the steels exhibited adequate
strength levels (tensile strength (TS): torr rebars, 524 Mpa; Cu-TMT rebars, 630 MPa) and adequate low-temperature impact
toughness properties, ensuring a high integrity of the fabricated products. 相似文献
6.
B.G. Callaghan 《Corrosion Science》1993,35(5-8)
3CR12, essentially a 12% Cr steel, was used in two series of exposure programmes to assess its performance as reinforcing in concrete. In the first exposure programme, steel and 3CR12 in the pickled and passivated condition were exposed in a specially designed marine climate simulator. Comparative performance after
years exposure confirmed 3CR12 as a viable durable reinforcing material for concrete. In the second exposure programme, steel, 3CR12, 316 and 304 stainless steel were exposed in the hot rolled condition (scale intact). Galvanised steel and powder epoxy coated rebar were also exposed. Exposures were carried out at a severely corrosive marine site and in the simulator. Within 2 years, the results from this programme emphasized the need to remove all hot-roll scale from the 3CRI2, the 316 and 304 stainless steel rebars before being used as reinforcing in concrete. Galvanized steel rebars performed poorly. Powder epoxy coated rebars showed severe under-rusting and corrosion. By comparison steel rebars performed extremely badly. Despite the highly alkaline conditions (i.e. the absence of carbonation), chloride penetration caused severe corrosion; the chloride front penetrating through 25 mm of good concrete cover within 2 years. 相似文献
7.
Z.Q. Tan 《Corrosion Science》2008,50(9):2512-2522
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. 相似文献
8.
Among the multitude of concrete structure pathologies, corrosion of rebars is one of the most important problems of concrete durability. In the context of sustainable development, it appears of primary importance to develop new means to protect the rebars against corrosion. This study aims to develop a new eco‐friendly and corrosion‐inhibiting admixture based on EPS 180 exopolysaccharides, biopolymers used in coatings already studied for the corrosion inhibition on steel in seawater. C15 rebars embedded in CEMI and CEMV cement paste containing EPS 180 were immersed in natural seawater and their electrochemical behaviour was studied using open circuit potential measurements and electrochemical impedance spectroscopy. These tests highlight the decrease of the cathodic reaction kinetics due to the EPS 180 action at the rebars surface, and the absence of effect on the passive layer. Capillary imbibition tests carried out on cement paste and mortars showed that although limiting the imbibition kinetics for cement pastes, the EPS 180 did not influence the water imbibition of mortars. Tests comparing capillary imbibition of soaked cement pastes and mortars with EPS 180 solution and the same samples containing the EPS 180 admixture highlight that the corrosion inhibition induced by EPS 180 admixture is more due to the modification of the cement – rebars interface than to the clogging of the cement porous network. 相似文献
9.
混凝土保护涂层抗氯离子渗透性研究 总被引:1,自引:0,他引:1
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.
相似文献
10.
The feasibility of using 2304 duplex stainless steel rebar in seawater concrete was determined by studying the passivation and corrosion behavior of steel in solutions simulated curing and service stage of concrete, respectively. The results demonstrate that 2304 duplex stainless steel rebar could be used with seawater concrete because of a stable passive film formed on the steel surface during the curing stage of concrete even in the presence of 2 M chloride ions. However, due to the synergistic effect of concrete carbonation, the rebar suffered a corrosive attack by chloride due to the lack of OH? inhibition. 相似文献
11.
The life of a concrete structure exposed to deicing compounds or seawater is often been limited by chloride induced corrosion of the steel reinforcement. A complete assessment of the potential benefits afforded by new candidate rebar alloys must address both the lateral and radial corrosion propagation behavior in comparison to conventional steel as well as other factors that might affect the risk of corrosion‐induced concrete cracking. The radial (depth) and lateral (length) corrosion propagation behavior of 18% Cr + 2.8% Mo (S31653) stainless steel, 21% Cr (S32101) duplex stainless steel, and 9% Cr steel compared to plain ASTM A615 carbon steel were characterized in saturated Ca(OH)2 solution. Radial pit growth was found to be Ohmically controlled for all materials but repassivation occurred more readily at high applied potentials for 18% Cr + 2.8% Mo and 21% Cr stainless steels. Conversely, pit growth on plain steel propagated at all applied anodic potentials and did not repassivate until deactivation by cathodic polarization. Stainless steel also showed the highest resistance to lateral corrosion propagation from an active site during microelectrode array testing. 21% Cr duplex stainless and 9% Cr steel showed similar radial propagation behavior and corrosion morphology, which was intermediate to that of plain steel and S31653 stainless steel. Based on an existing concrete cracking model, it is expected that 9–21% Cr and 18% Cr + 2.8% Mo corrosion resistant rebar materials would require a greater depth of corrosion attack than carbon steel before damaging concrete via corrosion product formation. 相似文献
12.
This paper deals with the possible corrosion risk for steel rebars in cracked reinforced concrete structures by using acrylate gels for grouting. In the course of this project, 19 customary acrylate gels were analysed. The results of the conducted test procedures revealed that none of the tested acrylate gels can provide an active corrosion protection for the steel rebars due to their low electrolytic resistivity and low pH values. Just when applied in very thin layers (e.g., fine cracks) it seems to be possible that alkaline components of the surrounding concrete can penetrate through the gel to form a passive layer on the embedded steel rebar. 相似文献
13.
14.
Reinforced concrete structures – shall concrete remain the dominating means of corrosion prevention?
The acknowledged serious deterioration of reinforced concrete structures due to chloride induced corrosion has been the main fuel for research and development of very dense and impermeable concrete, so‐called high performance concrete (HPC). This development has dominated concrete research up through the 80'ies and 90'ies. The results have technically been successful. However, the practical use of such concretes on site have often posed serious difficulties, resulting in at times very low performance concrete structures although HPC was specified. The discrepancy between concrete quality reached in the laboratory, what is being specified in the design and what can realistically be achieved on site is seldom in balance. Alternative means of more or less reliable means of corrosion prevention, often based on organic materials, have during recent years been developed to protect our inorganic concrete and reinforcement. However, a highly reliable means of corrosion prevention has been the introduction of stainless steel reinforcement, which is available with dimensions and strengths directly interchangeable with ordinary carbon steel reinforcement. It has been proven that stainless steel and carbon steel can be in metallic contact when cast into concrete, without causing galvanic corrosion. This seems, for the present, to be like an unexpectedly simple and highly reliable solution to the corrosion problems. As exemplified, this technology is rapidly gaining momentum in highly corrosive environments – and concretes being much more robust to execution can now take over from HPC. 相似文献
15.
M. Manna 《Corrosion Science》2009,51(3):451-1846
Phosphate coatings have been obtained on three steel substrates: (i) ferritic-pearlitic (F-P), (ii) tempered martensitic (T-M) and (iii) tempered martensitic containing oxide scale (T-M-O) to simulate TMT rebar surfaces which are extensively used for concrete structure. Thinnest coating, constituting of coarse structure and hopeite as the principle phosphate was obtained on F-P steel substrate where as thickest coating, constituting of acicular structure and spencerite as the principle phosphate was obtained on T-M-O steel substrate. Oxide scale on the T-M-O steel substrate acted as catalyst for phosphate reaction. The phosphate coated F-P steel substrate showed better performance against corrosion and bond strength with concrete structure. 相似文献
16.
H. Z. López‐Calvo P. Montes‐Garcia I. Kondratova T. W. Bremner M. D. A. Thomas 《工业材料与腐蚀》2013,64(7):599-608
One of the most common corrosion protection methods in reinforcing concrete bars is the application of fusion‐bonded epoxy coatings. Although considerable research has been carried out on the performance of epoxy‐coated bars (ECR), there are still many uncertainties about their performance in cracked concrete. In this experimental program, reinforcing steel bars with six types of epoxy coatings embedded in concrete slabs with a 0.4 mm wide preformed crack intersecting the reinforcing steel at right angles were tested. Results of corrosion potentials, corrosion current density, coating adhesion tests, chloride content, and visual examination after 68 months of exposure to a simulated marine environment are reported. Results revealed that under the studied conditions the ECR did not provide total protection of steel reinforcement in cracked concrete. Their use however, tended to reduce significantly the damage caused by the chloride‐induced corrosion when compared with the uncoated bars embedded in concrete with similar characteristics. 相似文献
17.
用明度差法研究了电镀锌未钝化及涂覆型钝化试片在湿热实验中的初期腐蚀行为。通过考察明度差△L随时间及温度的变化关系,发现未钝化镀锌层的初期腐蚀规律符合对数方程,而钝化后的符合Wagner方程,即印化膜的存在改变了腐蚀的历程,使钝化膜内锌离子的外护散或膜外氧的内扩散成为腐蚀的控制步骤,有效地提高了镀锌层的耐蚀性,采用明度差法可以反映电镀锌钢板腐蚀的程度。 相似文献
18.
采用腐蚀失重法与显微镜技术,研究了电气化铁路接触网热浸镀锌部件材料在模拟典型大气环境(海洋环境、工业环境、城市环境)介质中的腐蚀及其形貌。结果表明,热浸镀锌材料在模拟城市大气环境介质中的腐蚀最为严重,工业环境次之,海洋环境腐蚀最轻。二次加工与成型会引起镀锌层局部破损致使基材局部暴露与镀锌层形成电偶对,会加重热浸镀锌部件的腐蚀,且破损面积越大腐蚀越严重。同样,热浸镀锌部件与不锈钢紧固件耦接会形成电偶腐蚀,也会加重热浸镀锌部件的腐蚀。建议针对电气化铁路各段不同的大气环境,选择不同的接触网零部件材料、或者采用相应的防腐措施。在接触网构件加工和装配过程中,建议改进加工工艺程序,避免热浸镀锌部件的二次加工或者成型;建议采用绝缘措施,以达到热浸镀锌部件与不锈钢紧固件之间的绝缘耦接,避免电偶腐蚀发生。 相似文献
19.
In harsh chloride bearing environments stainless steel reinforcing bars offer excellent corrosion resistance and very long service life for concrete structures, but the high costs limit a more widespread use. Manganese bearing nickel‐free stainless steels could be a cost‐effective alternative. Whereas the corrosion behavior of stainless steels in alkaline solutions, mortar and concrete is quite well established, only little information on the reasons for the high pitting resistance are available. This work reports the results of pitting potential measurements in solutions simulating alkaline and carbonated concrete on black steel, stainless steel DIN 1.4301, duplex steel DIN 1.4462, and nickel‐free stainless steel DIN 1.4456. Duplex and nickel‐free stainless steels are fully resistant even in 4 M NaCl solutions with pH 13 or higher, the lower grade DIN 1.4301 shows a wide scatter between fully resistant and pitting potentials as low as +0.2 V SCE. In carbonated solutions with pH 9 the nickel‐free DIN 1.4456 shows pitting corrosion at chloride concentrations ≥3 M. This ranking of the pitting resistance can be rationalized based on XPS surface analysis results: both the increase of the Cr(III)oxy‐hydroxide and Mo(VI) contents in the passive film and a marked nickel enrichment beneath the film improve the pitting resistance. The duplex DIN 1.4462 shows the highest pitting resistance, which can be attributed to the very high Cr(III)oxy‐hydroxide, to a medium Mo(VI) content in the film and to a nickel enrichment beneath the film. Upon time, the protective properties of the surface film improve. This beneficial effect of ageing (transformation of the passive film to a less Fe2+ containing, more hydrated film) will lead to higher pitting potentials. It can be concluded that short‐term solution experiments give conservative results in terms of resistance to chloride‐induced corrosion in reinforced concrete structures. 相似文献
20.
Corrosion induced deterioration of steel reinforcement (rebar) in concrete has increasingly become a greater world‐wide concern. This insidious dilemma focuses on the potentially dubious structural integrity of many concrete structures. The steady rise of rebar corrosion and the eventual deterioration can be directly related to several influential factors, some of which include; poor quality construction materials, the increased use of de‐icing salts, severe marine environments and increased atmospheric contaminants, such as carbon dioxide. Over the years various methods have been developed to protect either the rebar or the concrete. Today, the most recent emerging corrosion protection technology is that of Migrating Corrosion Inhibitors (MCIs). Recently, improved test methodologies have been developed which can better assess the effectiveness of corrosion inhibitors. Several of these recent electrochemical and non‐electrochemical test methods were utilized to measure the effects of migrating corrosion inhibitors. This paper includes an explanation of these test methods and presents an overview of the test results. 相似文献