Utilizing Arghel extract as corrosion inhibitor for reinforced steel in concrete

Inhibition of the corrosion of reinforced steel in concrete in 0.5 M NaCl by Arghel extract has been studied employing different electrochemical techniques in conjunction with optical images photo. Potential‐time measurements showed that introducing of Arghel extract into concrete shifts the potential of reinforced steel to more positive values. Potentiodynamic polarization curves measurements manifested that Arghel extract acts as anodic type inhibitor. Nyquist plots were characterized by a distinct charge transfer and diffusion components. A proposed equivalent circuit was used to analyze the impedance spectra of reinforced steel in concrete in 0.5 M NaCl. Optical images for the cracked lollipops samples of the reinforced steel in concrete that is immersed in 0.5 M NaCl for 18 months showed no corrosion attack even in the presence of a low concentration of Arghel which is in good agreement with the results obtained from the electrochemical techniques.     

海工钢筋混凝土的腐蚀与防护

海水具有很强的腐蚀性。如果不采取防护措施，海工钢筋混凝土结构会受到严重腐蚀。本文结合当前现有研究成果，对海洋环境下钢筋混凝土结构的腐蚀特征和防护技术进行了论述。     

Measuring the corrosion rate of steel in concrete – effect of measurement technique,polarisation time and current

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.     

Investigations of an ethanolamine‐based corrosion inhibitor system for surface treatment of reinforced concrete

Laboratory investigations were performed to assess the efficacy of a proprietary ethanolamine‐based corrosion inhibitor system when applied to the surface of reinforced concrete specimens that were chloride‐contaminated to varying extents in the presence or absence of carbonation. The corrosion responses of embedded steel bars at various depths of cover were monitored electrochemically during a controlled programme of cyclic wetting and drying undertaken for several months prior to the inhibitor treatment and for approximately eighteen months thereafter. Gravimetric measurements of the quantities and distribution of corrosion on the steel were also made on completion of the exposure tests. Analysis of aqueous extracts from treated concrete revealed that the ethanolamine component of the inhibitor system penetrated to depths of more than 15 mm within the concrete. It was found that, for inhibitor‐treated specimens, there was some reduction in the corrosion rate of pre‐corroding steel at low cover depths in non‐carbonated concrete with modest levels of chloride contamination. At higher levels of chloride contamination and in carbonated specimens, however, the ethanolamine‐based inhibitor was apparently ineffective under the conditions investigated.     

Polyaspartic acid as a green corrosion inhibitor for carbon steel

The inhibitor effect of the environmentally friendly corrosion inhibitor polyaspartic acid (PASP) on the corrosion of carbon steel in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Polarization curve results clearly reveal the fact that PASP is a good anode‐type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing PASP concentration, and the maximum inhibition efficiency was 80.33% at 10 °C. SEM reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Freundlich adsorption isotherm. A mechanism is proposed to explain the inhibitory action of the corrosion inhibitor.     

Conventional and pulse cathodic protection of reinforced concrete: Electrochemical behavior of the steel reinforcement after corrosion and protection

The applicability and efficiency of an alternative for impressed current cathodic protection (CP) for reinforced concrete, based on pulse technology, was investigated. The technique, denoted as pulse CP (pCP), was evaluated on the basis of a comparative analysis to reference (non-corroding), corroding, and conventional CP conditions, in terms of long-term monitoring of electrochemical parameters for the embedded steel with time of corrosion and protection. The hereby reported results are for the total duration of the experiment, i.e., 460 days of conditioning, also presented in comparison with earlier stages. Protection was applied after corrosion was initiated (using corrosion medium of 5% NaCl), at different time intervals (here reported are starting points 60 and 150 days of age). Both CP regimes used current density of 5 or 20 mA/m² steel surface. The pulse CP was applied as a pulse-shaped block current (square wave) with the current itself being the feedback control signal, using 12.5–50% duty cycle at 500 Hz to 1 kHz frequency. Under equal environmental conditions and for a comparatively long period of application, the pulse CP was found to perform as effectively as the conventional CP with regard to electrochemical behavior of the steel reinforcement. Furthermore, the pulse CP technique was found to achieve more rapidly the so called “open circuit potential (OCP) passivity” as a result of an enhanced ion transport (chloride withdrawal) and more favorable cement chemistry (increased alkalinity around the steel reinforcement).     

Corrosion of steel reinforcement in structural concrete with carbon material addition

Different types of carbonaceous materials have been added to concrete mixes and their effect on the corrosion of embedded steel has been studied. Using a constant water/cement ratio of 0.42 and different amounts of carbonaceous materials and different curing periods the evolution of the corrosion process in the embedded reinforced bars has been determined. The addition of small quantities of carbonaceous materials to the mixture produces a reduction of the concrete permeability. Tests demonstrate that a decrease of the corrosion level occurs when the content ratio of carbon material addition is increased.     

耐蚀钢筋研究现状及腐蚀评价方法分析

在海洋环境中,钢筋锈蚀是导致混凝土失效的主要原因,提高钢筋耐蚀性是提高海洋环境中混凝土耐久性的根本。总结了近年来国内外耐蚀钢筋的种类及耐蚀钢筋的研究现状,并对混凝土中钢筋常用的物理检测方法和电化学检测方法进行了总结。评价了目前国内外常见的用于评价钢筋耐蚀性的方法的特点。     

Influence of a biopolymer admixture on corrosion behaviour of steel rebars in concrete

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.     

Corrosion behaviour of AA2024 aluminium alloy in different tempers in NaCl solution and with the CeCl3 corrosion inhibitor

The paper analyses the corrosion behaviour of naturally and artificially aged AA2024 alloy in NaCl solution and in the presence of an environment-friendly corrosion inhibitor, CeCl₃. On the basis of the values of polarisation resistance and corrosion current density, the corrosion resistance of the protective inhibitor film is established as well as the general corrosion resistance of this aluminium alloy. Resistance to pit formation is determined based on the difference in pitting and corrosion potentials while resistance to pit growth is determined based on the amount of charge consumed during pit growth. A scanning electron microscope is used to examine the morphology of the pits formed during the pitting corrosion testing, as well as to determine the cerium content on intermetallic particles and the matrix AA2024 alloy. The corrosion behaviour of AA2024 alloy is investigated after different test periods in NaCl solution and in the same solution with the CeCl₃ inhibitor. The corrosion resistance of both tempers of AA2024 alloy is more than one order of magnitude higher in the presence of CeCl₃. An explanation of the observed differences in the corrosion behaviour of the naturally and artificially aged AA2024 alloy is proposed. Different corrosion behaviour of the alloy after different test periods is also explained.     

Corrosion resistance of carbon steel in simulated concrete pore solution in presence of 1-dihydroxyethylamino-3-dipropylamino-2-propanol as corrosion inhibitor

The inhibition behaviour of 1-dihydroxyethylamino-3-dipropylamino-2-propanol (HPP) as an environment friendly corrosion inhibitor for reinforcing steel was investigated in simulated concrete pore solution contaminated by 0·1 mol L^?1 Cl^? by means of linear polarisation resistance, electrochemical impedance spectroscopy and cyclic voltammetry (CV). The surface morphology and corrosion products were also examined by scanning electron microscopy and X-ray diffraction (XRD). The results show that HPP can effectively inhibit the corrosion of reinforcing steel. The CV interpreted the corrosion inhibitor by restraining the reaction of cathodic reduction and anodic oxide. The XRD shows that the corrosion inhibitor reduces Cl^? adsorption on oxide film and reduces the production of corrosion products. In the conditions of this investigation, HPP behaves as an anodic corrosion inhibitor, protecting steel against corrosion in chloride contaminated environments.     

Influence of two specific inhibitors on steel corrosion in a synthetic solution simulating a carbonated concrete with chlorides

The present research aims at studying two corrosion inhibitors, that is sodium 2‐amino‐benzoate (2AMB) and sodium glycero‐phosphate (GPH), in a synthetic solution simulating the composition of the pore solution in a carbonated concrete, containing chlorides. Tests have been performed to verify if the simultaneous use of the two substances is compatible and if their addition can efficiently hinder the corrosion attack in the presence of both chlorides and carbonation. The synthetic solution has been prepared by bubbling carbon dioxide through a saturated (and filtered) solution of Ca(OH)₂, containing 0.1 M NaCl, in order to reach pH 7. Polarization curve recording and EIS technique have shown that, after an induction period of about 24 h, the highest inhibiting efficiencies are obtained by mixtures of the two additives at the concentration of 0.05 M, which still produce high inhibiting efficiencies (87%) at the end of 120 h immersion. At the end of this exposure period, also more diluted symmetric mixtures (0.025 and 0.01 M) exhibit comparable efficiencies. The analysis of EIS spectra gives interesting information concerning the inhibiting mechanism of the studied mixture.     

Comparative study on induced macrocell corrosion phenomenon in repaired ordinary reinforced and self-compacting concrete structures

Abstract

This paper aimed at an experimental investigation of the comparative corrosion phenomenon in the reinforcing steel of repaired chloride contaminated self-compacting concrete (SCRC) and ordinary concrete (OC) patches. This research is a continuation of a previous study in which macrocell specimens were prepared with OC having different chloride contaminations simulating the actual patch repair in the construction field. Here, in this research, the same specimens were prepared with SCRC to investigate more deeply the macrocell phenomenon in SCRC, which received limited attention in the past. Four prismatic specimens with two sets of 5 and 3% chloride contaminated SCRC at the two ends were prepared respectively, and the middle portion of these specimens was cast after 24 h with uncontaminated SCRC simulating the actual patch repair in the field. After 1 year of experimental observations of corrosion potentials and corrosion rates, interesting and novel results were obtained in comparison with OC and SCRC specimens.     

On‐site investigations on concrete resistivity – a parameter of durability calculation of reinforced concrete structures

For determination the electrolytic resistivity of concrete, resistances of realistic designed probes are measured during a one and two year period, respectively. Measurements are made with a commercially available instrument normally used for measuring earth resistances. Comparison to other usually applied methods show not only that the used method GEOHM is qualified for measuring the electrolytic resistance of concrete but also that the magnitude of measured values is realistic. To obtain electrolytic resistivities from these measurements the individual cell constant for the investigated system was derived from experimental research. First results of the in‐situ stored specimens are presented, intended future activities are sketched.     

Corrosion study of the X52 steel immersed in seawater with a corrosion inhibitor using a rotating cylinder electrode

A corrosion study of API X52 steel was carried out in natural seawater with several concentrations of a corrosion inhibitor (10, 100 and 200 ppm) using a rotating cylinder electrode (RCE) to control the hydrodynamic conditions at environment temperature, atmospheric pressure and 24 h of the exposition time. The rotation speed used was 1000 rpm (turbulent flow). The electrochemical techniques used in the corrosion studies were: linear polarisation resistance (LPR), electrochemical impedance spectroscopy (EIS) and polarisation curves (PCs). The superficial analysis was made using a scanning electron microscope (SEM). The results show a good correlation between electrochemical techniques used. In addition, under turbulent flow, the test solution with 10 ppm had the smallest corrosion rate (CR). It is important to mention that the morphology of the corrosion in all experiments was localised corrosion.     

Effects of Tafel slope,exchange current density and electrode potential on the corrosion of steel in concrete

A parametric study is carried out to investigate the effect of variations in anodic and cathodic Tafel slopes, exchange current densities and electrode potentials on the rate of steel corrosion in concrete. The main goal of this investigation is to identify the parameters that have significant influence on steel corrosion rate. Since there is a degree of uncertainty associated with the selection of these parameters, particularly during modelling exercises, it is intended that the results of this study will provide valuable information to engineers and researchers who simulate steel corrosion in concrete. To achieve this goal, the effect of a parameter on the corrosion rate of steel is studied while all other parameters are kept constant at a predefined base case. For each parameter, two extreme cases of anode‐to‐cathode ratio are studied. The investigation revealed that the variations in the anodic electrode potential have the greatest impact on the corrosion rate, followed by the variations in the cathodic Tafel slope.     

Theoretical considerations on the supposed linear relationship between concrete resistivity and corrosion rate of steel reinforcement

Traditionally, the assessment of service life of steel reinforced concrete structures has been focused on the prediction of the time required to achieve a transition from passive to active corrosion rather than to accurately estimate the subsequent corrosion rates. However, the propagation period, i.e. the time during which the reinforcing steel is actively corroding, may add significantly to the service life. Consequently, ignoring the propagation period may prove to be a conservative approach. On the other hand the prediction of the corrosion rate may result in a very complex task in view of the electrochemical nature of corrosion and the numerous parameters involved. In order to account for the various influences an essentially empirical model has been introduced in which the electrolytic resistivity of the concrete environment serves as the major parameter. This model will be discussed for carbonation‐induced corrosion based on the commonly accepted theory of aqueous corrosion. An alternative model for microcell corrosion is proposed which is based on the commonly accepted view that anodic and cathodic sites are microscopic and their locations change randomly with time. In line with this view electrolytic resistivity can be incorporated and thus may play a significant role in the kinetics of the corrosion process. For a wide range of corrosion current densities the relationship between corrosion current density, log(i_corr), and concrete resistance, log(R_con), can then be approximated by an almost ideal linear relationship. Assuming a fixed geometrical arrangement of anodic and cathodic sites on the steel surface, this linear relationship is also valid for concrete resistivity, ρ_con. However, from the theoretical treatment of the electrochemical processes underlying reinforcement corrosion it becomes evident that a linear relationship between corrosion current density and concrete resistivity does not necessarily imply that concrete resistance is dominating the overall corrosion cell resistance. In most cases a significant portion of the driving voltage of the corrosion cell will be consumed by the transfer of electrical charge involved in cathodic reactions, i.e. cathodic activation control will dominate.