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1.
Both on‐site investigations and laboratory studies have shown that different corrosion rates are obtained when different commercially available corrosion rate instruments are used. The different electrochemical techniques and the measurement parameters used, i.e. polarisation current and time, are in some studies considered the main reasons for the variations. This paper presents an experimental study on the quantitative effect of polarisation time and current on the measured polarisation resistance – and thus the corrosion current density – of passively and actively corroding steel. Two electrochemical techniques often used in instruments for on‐site corrosion rate measurements are investigated. On passively corroding reinforcement the measured polarisation resistance was for both techniques found to be highly affected by the polarisation time and current and no plateaus at either short or long polarisation times, or low or high polarisation currents were identified. On actively corroding reinforcement a large effect of the polarisation time was also found, but only a minor effect of the polarisation current. The effect of the polarisation time was, however, practically independent of the corrosion rate for actively corroding steel. For both techniques guidelines for polarisation times and currents are given for (on‐site) non‐destructive corrosion rate measurements on reinforcement steel in concrete. 相似文献
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The use of a sensor controlled guard ring has been developed in recent years to enhance the accuracy of linear polarisation corrosion rate measurements on reinforced concrete structures. The established method of measurement uses a galvanostatically controlled guard ring device. In the method reported in this article the reinforcing steel is polarised potentiostatically by an inner auxiliary electrode and the real time plot of the current response is displayed on a laptop computer which controls the guard ring device. The area of steel polarised is confined by a current applied from an outer guard ring electrode which is controlled by two sensor electrodes positioned between the inner auxiliary and outer guard ring electrode. The potential between the two sensor electrodes is continually monitored, and the current output from the guard ring electrode varied to maintain a constant potential difference between the two sensor electrodes. The method has been validated on an electrical test circuit simulating active and passive reinforcement corrosion. Further testing has been conducted on a reinforced concrete specimen and the results compared with those of commercially available galvanostatically controlled equipment and those of standard unconfined linear polarisation resistance measurements. 相似文献
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Cathodic protection (CP) has become a successful method for the rehabilitation of concrete structures affected by chloride-induced corrosion of reinforcing steel. CP involves applying an electrical current from an external anode through the concrete to the reinforcement. The current causes steel polarisation, electrochemical reactions and ion transport. Normally the anode is placed over relatively large surface areas, including those where the steel is passive. Conventional views assume that protection current will not significantly flow outside the anode area. In many cases this results in a conservative design. This paper presents principles and first results of numerical calculations for design of an example CP system by finite element modelling. The final objective is to develop a tool for more economical CP system design. In particular, a CP system for the protection of local damage in bridges (e.g. at leaking joints) has been simulated. The corroding area with respect to the size of the anode is varied. Current and potential distributions and depolarisation values are predicted, both close to and more distant from the anode. It appears that current densities required to achieve sufficient polarisation are much higher than those usually found in the field. Neglecting time-dependent repassivation processes is likely to be the main cause and further work is needed to include them. The present model can be used with reasonable confidence for preventive application to passive steel. 相似文献
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Reinforcement corrosion is influenced by different parameters like resistivity of concrete, setting conditions and also by concrete technology. Moreover the presence of cathodic areas and the possibility of unhampered cathodic reaction influences the reinforcement corrosion. In this paper the development of corrosion without large cathodic areas, called self‐corrosion, considering different concrete parameters, is studied. 相似文献
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Denise S. de Freitas Javier Alejandro C. Verdasco Lisiane G. Lima Israel L. M. Gonçalves Rodrigo B. Rabelo Olívia C. C. Poltronieri Conrado G. Ewbank Fabíola C. de Rezende Lílian Kinouti 《工业材料与腐蚀》2020,71(3):485-497
There is an increasing demand from oil and gas industry to ensure the integrity of assets and the enviroment in the critical conditions found in presalt wells. This study evaluates new formulations of corrosion inhibitors with different types and alkoxylation degrees of nitrogen-based inhibitors to assess corrosion behavior of carbon steel (API X65). For these studies, corrosion rates were determined through measurements of weight loss and linear polarization resistance (LPR). In the case of electrochemical measurements, experiments were carried out in a laminar flow and in a turbulent flow regime. All data were collected in the presence of CO2 and CO2/H2S mixtures. The results revealed that corrosion protection of carbon steel critically depends on the nitrogen-based inhibitor's alkoxylation type and degree as well as the condition to which they are exposed. It was possible to notice that an ethoxylated amine whose inhibition efficiency in the presence of CO2 was about 10%, when exposed to H2S environment at the same temperature showed an efficiency of 86%. It was also observed that the inhibitor with a higher ethoxylation degree presented better efficiencies than the one with a lower degree. 相似文献
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目的 开发工艺简单且具备优异防腐性和耐久性的超疏水混凝土涂层。方法 利用单宁酸(TA)和纳米二氧化硅(SiO2)共同构建混凝土材料表面的微/纳米粗糙结构,同时引入非氟的正辛基三乙氧基硅烷(OTES)作为低表面能物质以赋予颗粒表面疏水基团,采用一步喷涂法制备得到TA/SiO2@OTES超疏水混凝土涂层。通过研究不同浓度TA/SiO2对混凝土涂层的微观形貌以及润湿性的影响,确定了最佳掺入浓度。利用X射线衍射仪(XRD)和傅里叶红外光谱仪(FT-IR)等检测手段对混凝土材料表面的物质成分和化学键合进行了表征,并开展了吸水量、氯离子侵蚀、表面摩擦和水滴冲击等试验研究,综合评估了超疏水混凝土涂层的耐腐蚀性和机械耐久性。结果 当TA/SiO2质量浓度为4 mg/mL时,涂层所形成的微观形貌最佳,其接触角高达(156.8±1.6)°,滑动角低至(5.8±1.1)°;相较于普通混凝土,其抗氯离子侵蚀能力提高了60%以上。此外,经过50次砂纸线性摩擦以及50 min水滴冲击测试后,混凝土涂层仍具有超疏水性(接触角>150.0°,滑动角<10.0°)。结论 所制备的超疏水混凝土涂层展现出卓越的防腐蚀性以及机械耐久性,为超疏水材料在混凝土结构防护领域的应用提供了重要的参考依据。 相似文献
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The linear polarisation resistance (LPR) method can be used to measure the active rate of corrosion of steel reinforcement in concrete structures. However a single measurement may be sensitive to the ambient environmental conditions and thus may not be representative of the mean annual rate of corrosion. The LPR measurement may be dependent upon the temperature at the time of sampling and on any wetting/drying effects resulting from rainfall and wind or sunshine.Recent studies have examined the behaviour of a series of reinforced concrete specimens subject to chloride contamination or carbonation induced corrosion in a controlled laboratory environment. LPR measurements taken at frequent intervals have been related to a wet/dry cycle imposed upon the specimens to promote corrosion activity. In addition, similar studies have been carried out, of an in situ reinforced concrete specimen exposed to the ambient weather conditions. The study is only partly completed, but interim results show the variability of LPR measurements and the influences the environment may exert on single spot measurements. 相似文献
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A strong interest for the durability of reinforced concrete structures currently exists in industry and research [1]. Against the background of immense costs for maintaining reinforced concrete structures and repairing damage caused by corroding reinforcement steel, this interest lead to a German joint research project. The aim of this network‐based (www.bam.de/dfg537.htm) research group is, to deliver the basic knowledge of the corrosion propagation and to make a probabilistic tool available for engineers so that a complete design for durability, concerning reinforcement corrosion, will be possible. 相似文献
10.
In recent years, the use of corrosion inhibitors in producing high‐performance steel reinforced concrete structures has increased significantly to minimize the chloride and sulfate attacks. However, most inhibitors available in the market are toxic to the environment. Hence, one objective of the present investigation was to test a novel, eco‐friendly, so‐called green inhibitor extracted from a fruit waste (orange peel), and its effects were studied on the compression strength of the XD3 type concrete samples. The inhibitor was added to the concrete mix in concentrations of 1% and 3% by weight of cement in addition to two different superplasticizers (Mapei Dynamon SR 31, Budapest, Hungary and Oxydtron, Hungary). The test results on steel reinforced samples immersed in 3.5 wt% NaCl aqueous solutions at room temperature showed promising corrosion mitigating effects just after 6 months testing period. The lower corrosion currents (i.e., better corrosion resistance) after 6 months immersion were observed when the samples contained both green inhibitor and Oxydtron superplasticizer, especially with sample C2 (in this case 3% green inhibitor was added to the mixture of cement + Oxydtron superplasticizer). 相似文献
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Ewa Ura-Bińczyk Anna Dobkowska Mariusz Andrzejczuk Agata Roguska Bogusław Mazurkiewicz Wojciech Solarski Marek Balcer Małgorzata Lewandowska Jacek Banaś 《工业材料与腐蚀》2021,72(9):1518-1528
Corrosion monitoring station was installed at ‘Geotermia Mazowiecka’ geothermal plant in Poland. Linear polarisation resistance and electrochemical impedance spectroscopy techniques were applied to estimate the corrosion rate and the surface changes of K55 carbon steel, L80-13CR and 316 stainless steels directly in the geothermal water flux. The enhanced corrosion of K55 carbon steel and corrosion rate of L80-13CR and 316 stainless steels was observed. The formation of biofilm increased the resistivity of the surface. 相似文献
13.
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. 相似文献
14.
With the implementation of the repair method “increasing the electrical resistivity by coating” (MR 8.3), no direct repassivation of the reinforcing steel is initially intended. The success of the repair is rather linked to the change of the corrosion-relevant parameters over time. These include an increase in the concrete resistivity due to dehydration and gradual decrease in corrosion currents and driving voltages on the reinforcing steel. Within the scope of a research project funded by the German Research Foundation (DFG), application limits for the repair principle W-Cl could be defined. The chloride content present in the concrete at the rebar is the significant limiting factor for the application. While the corrosion activity even with moderately dehydrated specimens under diffusion-retarding coatings at chloride contents of 1 wt% Cl−/c is in the range of the passive current density, this cannot be generally determined for chloride contents of 2 wt% Cl−/c. The type of coating has a decisive influence on the dehydration of the concrete. For example, less dense concretes under a permeable coating (acrylic dispersion/OS 4) can dry out to such an extent that the passive current density is reached. With semipermeable coatings and the presence of high chloride contents of 2 wt% Cl−/c, the repair principle W-Cl does not lead to success according to the available test results. 相似文献
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A cold zinc phosphating bath has been formulated and optimized with a view to study the role of sodium diethyl dithiocarbamate (DEDTC) as a complexing additive in such a bath. The resultant coatings were assessed for their physical properties and corrosion resistance. The study concludes that the addition of sodium diethyl dithiocarbamate (DEDTC) increases the coating weight, reduces the processing time and increases the corrosion resistance of the resultant coatings. 相似文献
16.
The repair method 8.3 “Corrosion protection by increasing the electrical resistance” according to EN 1504 (or the repair principle W-Cl according to the DAfStb directive “Protection and repair of concrete building materials”) represents a technically and economically interesting method for the repair of chloride-contaminated concrete components. The coating applied as part of the repair principle prevents further water absorption of the concrete and, due to its permeability to water vapor, allows the concrete to dehydrate. Over time, this leads to an increase in the electrolytic resistance and thus to a reduction in the rate of corrosion. The article deals with the basic principles underlying this repair principle, deals with the current regulatory situation, and shows the responsibility of the expert planner. Groundbreaking studies on the effectiveness of the repair principle were carried out by Prof. Raupach, to whom this article is dedicated, and are summarized in this paper. The objective of the new studies, which build on the aforementioned research, is to establish universally accepted application limits, for example, the level of the remaining chloride concentration, for the low-risk use of this repair method. 相似文献
17.
Zinc sacrificial anodes have been included in patch repairs to steel reinforced concrete structural elements suffering from corrosion since the mid‐1990s. A number of these anode‐containing repairs have been monitored with time. One of the first monitored sites was of a locally repaired cross beam of a bridge structure in Leicester, UK, which has now completed 10 years since its original repair and anode installation. This paper reviews the performance of the anodes installed at the Leicester site in terms of anode current output and steel reinforcement polarisation and corrosion rate over the period. It also presents results of analysis of recovered anodes exposed for 10 years which still show electrolyte continuity, uniform consumption of the zinc and coherent encasing mortar. The knowledge gained from the 10 year results has enabled the development of new, higher current output anodes, which are now trialled in this and other sites. 相似文献
18.
混凝土中钢筋锈蚀的电化学阻抗谱特征研究 总被引：3，自引：0，他引：3
关于混凝土钢筋锈蚀等效电路模型中各元件的物理意义理解不尽相同.为了对模型元件的物理意义给出合理解释,设计了由氯盐侵蚀和混凝土碳化导致钢筋锈蚀的两种加速试验.通过对钢筋锈蚀试块阻抗谱特征的分析研究,对模型元件的物理意义给出了合理解释.研究发现,氯盐锈蚀试块具有三段容抗弧,即三个时间常数;而碳化锈蚀试块阻抗谱与钝化钢筋试块... 相似文献
19.
An acidic sulphate bath solution has been developed by Hull Cell studies to electroplate industrial zinc coatings on mild steel. Histidine in combination with ninhydrin has been evaluated as a brighener for zinc. The brightness of the coating was enhanced in the presence of traces of additives: sodium taurocholate, polyvinyl alcohol, and ascorbic acid. Working conditions and plating bath composition were optimised to obtain a good quality zinc coating with current efficiency and throwing power of 100% and 35% respectively. The functional properties (adhesion, hardness, corrosion resistance and surface morphology) of the coating have been evaluated. 相似文献
20.
Fiber optic evanescent field spectroscopy for in situ monitoring of pH levels is presented. Cladding of plastic clad silica fiber is replaced with polymethyl methacrylate doped with pH sensitive chromoionophores. The chromoionophores include methyl red, thymol blue, and thymolphtalein for pH in acidic, neutral and basic environments, respectively. The evanescent wave is used to selectively excite the indicator molecules within the fiber cladding for sampling aqueous media surrounding the fiber. 相似文献