scispace - formally typeset
Search or ask a question

Showing papers in "Materials and Corrosion-werkstoffe Und Korrosion in 2009"


Journal ArticleDOI
TL;DR: In this article, the variability of the chloride threshold values published in the literature is analyzed and data from mortar and concrete and from laboratory and field exposure are compiled and included in the analysis.
Abstract: Efforts are being devoted in standards and construction codes in order to give rules and guidelines for designing durable structures. Also efforts are focused in developing the models in a more accurate approach to the calculation of the service life of concrete structures. Service life models consider that reinforced concrete exposed to chloride polluted environments initiate corrosion when a certain amount of chlorides arrives to the rebar surface. The so-called chloride threshold level is considered as an essential parameter for assessing the probability of reinforcement corrosion, and becomes one of the key parameters needed for service life prediction, being of interest to have testing methods and expressions to introduce in the models. Numerous studies have been carried out to establish a critical chloride level for the onset of corrosion, but a wide range of chloride threshold values has been suggested which makes not feasible to define a single value. Present paper includes the analysis of the variability of the chloride threshold values published in the literature. Data from mortar and concrete and from laboratory and field exposure are compiled and included in the analysis. The influence of the testing method used for determination and several variables are considered.

98 citations


Journal ArticleDOI
TL;DR: In this article, a review of the steel-concrete interfacial zone (SCIZ) and its influence on the susceptibility of the metal to pitting corrosion when concrete is exposed to environments that cause ingress of chloride ions accompanied by leaching of hydroxyl ions is provided.
Abstract: This paper provides a brief review of research aimed at characterising the steel-concrete interfacial zone (SCIZ) and its influence on the susceptibility of the metal to pitting corrosion when concrete is exposed to environments that cause ingress of chloride ions accompanied by leaching of hydroxyl ions. For reinforced concrete made from Portland cements, exposed to aqueous solutions of sodium chloride, the buffering effect of solid calcium hydroxide (portlandite) at pH ~12.6 has been shown to restrain the gradual decline in the hydroxyl ion concentration of the concrete pore solution phase at depths corresponding to the embedded steel. When the concrete is produced under laboratory conditions that are carefully controlled to exclude macroscopic defects from the SCIZ and the steel is cleaned before being embedded, this can lead to observed chloride threshold levels being consistently greater than 1% chloride by mass of cement. The buffering action of cement hydration products formed in the SCIZ is believed to be partly responsible for this high tolerance to chloride-induced corrosion because it counters the generation of 'anodic acidity' that is a necessary condition for stable growth of pits to occur. Translating this behaviour of laboratory specimens to the performance of full-scale reinforced concrete structures has often proved difficult in the past and there is a need for further research in this area, particularly in relation to the role of non-traditional cements.

85 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of Zr addition and potentiodynamic polarization on the microstructure and corrosion resistance of Ti-22Nb and 6Zr alloy samples were investigated.
Abstract: The aims of this study were to investigate the effects of Zr addition and potentiodynamic polarization on the microstructure and corrosion resistance of Ti–22Nb and Ti–22Nb–6Zr alloy samples.The corrosion tests were carried out in 0.9% NaCl at 378C and neutral pH value, utilizing the OCP, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques.The results of XRD and optical microscopy indicated that the addition of Zr stabilized the b phase, which plays a crucial role in the corrosion resistance improvement of the Ti–22Nb–6Zr alloy. From the polarization curves, it can be seen that the alloys exhibited a wide passive region without the breakdown of the passive films and also low corrosion current densities. In addition, the values of the corrosion current densities and passive current densities decreased with the addition of 6 at% Zr into the Ti–22Nb alloy. The EIS results of these two alloy samples after 1-h immersion in 0.9% NaCl solution, and being fitted by RS(QPRP) model, suggested that the corrosion resistance of the passive films improved with the addition of Zr and only a single passive film formed on the surfaces. However, two time constants were observed for the Ti–22Nb and Ti–22Nb–6Zr alloy samples after potentiodynamic polarization, the spectra of which can be fitted using the Rs(Qo(Ro(QbRb))) model. In addition, the corrosion resistance of the two alloy samples was reinforced significantly because of polarization when compared to the immersed samples. All these observations suggested a nobler electrochemical behavior of the titanium alloys with the addition of Zr element and after polarization.

82 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the inhibition efficiency of the extract of Strychnos nux-vomica for the corrosion of mild steel in 1 M sulfuric acid using weight loss test (carried out at 303-323 K), electrochemical measurement, and scanning electron microscope (SEM).
Abstract: The inhibition efficiency of the extract of Strychnos nux-vomica for the corrosion of mild steel in 1 M sulfuric acid was investigated using weight loss test (carried out at 303–323 K), electrochemical measurement, and scanning electron microscope (SEM). The results of weight loss studies indicated that the inhibition efficiency increased with inhibitor concentration and the temperature of the system (following Temkin adsorption isotherm). Electrochemical studies proved that the inhibitor acts through mixed mode of inhibition and the inhibitor molecules adsorb on the metal–solution interface. SEM studies supported the adsorption of the inhibitor over the metal surface. The possible active ingredient responsible for the anticorrosion effect is identified as brucine which is isolated and screened for the anticorrosion effect using electrochemical studies and quantum chemical studies. The possible mode of corrosion inhibition of brucine is also derived using FT-IR studies.

75 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of four different and conventional heat treatments (i.e., hot rolling, normalizing, annealing, and intercritical annaling) on the resulting microstructural patterns and on the electrochemical corrosion behavior were investigated.
Abstract: Dual-phase (DP) steels are produced from a specific heat treatment procedure and have recently emerged as a potential class of engineering materials for a number of structural and automobile applications. Such steels have high strength-to-weight ratio and reasonable formability. The present study aims to investigate the effects of four different and conventional heat treatments (i.e., hot rolling, normalizing, annealing, and intercritical annealing) on the resulting microstructural patterns and on the electrochemical corrosion behavior. Electrochemical impedance spectroscopy (EIS) and Tafel plots were carried out on heat treated steel samples in a 0.5 M NaCl solution at 25 °C with neutral pH. An equivalent circuit analysis was also used to provide quantitative support for the discussions. The normalizing and the annealing heat treatments have provided the highest and the lowest corrosion resistances, respectively. The intercritical annealing and as-received (hot rolled) low carbon steel samples have shown similar corrosion behavior. Although a deleterious effect on the corrosion resistance has been verified for DP steel due to the residual stress from the martensite formation, it combines good mechanical properties with intermediate electrochemical corrosion resistance.

71 citations


Journal ArticleDOI
TL;DR: In this article, the effect of 2-(2-heptadec-8-enyl-4,5-dihydro-imidazol-1-yl)-ethylamine on the corrosion behavior of mild steel in aqueous hydrochloric acid was investigated using weight loss measurements, polarization scans, electrochemical impedance, and X-ray photoelectron spectroscopy (XPS).
Abstract: The effect of 2-(2-heptadec-8-enyl-4,5-dihydro-imidazol-1-yl)-ethylamine on the corrosion behavior of mild steel in aqueous hydrochloric acid was investigated using weight loss measurements, polarization scans, electrochemical impedance, and X-ray photoelectron spectroscopy (XPS). The inhibition efficiencies and coverage degrees increased with the concentration of inhibitor but decreased proportionally with temperature. It appears that the steric hindrance of the aliphatic chain on the imidazoline ring adsorption may affect inhibitor efficiency. Polarization curves showed that the oleic imidazoline (OI) acted essentially as a mixed type inhibitor, in which the blocking of active sites occurred. As a result of film formation, impedance spectra revealed a considerable increase in the charge transfer resistance as indicated by the second capacitive loop. XPS depth profile analysis observed the presence of nitrogen and carbon species on the inhibitor film, which were associated to the OI.

68 citations


Journal ArticleDOI
TL;DR: The superior high temperature oxidation resistance of FeCrAl alloys relies on the formation of a dense and continuous protective aluminium oxide layer on the alloy surface when exposed to high temp as discussed by the authors.
Abstract: The superior high temperature oxidation resistance of FeCrAl alloys relies on the formation of a dense and continuous protective aluminium oxide layer on the alloy surface when exposed to high temp ...

66 citations


Journal ArticleDOI
TL;DR: In this paper, two types of AZ91 magnesium alloys containing rare earth element Ce or La were fabricated and various corrosion rate tests indicated that addition of RE obviously enhanced corrosion resistance.
Abstract: Two types of AZ91 magnesium alloys containing rare earth element Ce or La were fabricated. Hydrogen evolution and electrochemical tests were carried out to evaluate the corrosion behavior of new AZRE (RE = Ce or La) and AZ91. alloys in 3.5% NaCl solutions (pH 6.50). Various corrosion rate tests indicated that addition of RE obviously enhanced corrosion resistance of AZ91 magnesium alloy. The optimal content of RE was 0.92% for Ce and 0.66% for La. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and low-angle X-ray diffraction (XRD) were used to characterize the effect of RE addition on microstructure and corrosion product film of AZ91 magnesium alloy. The refined beta phase and formation of gamma phase in AZRE alloy were observed by SEM, which resulted in the improvement of corrosion resistance due to the depression of microgalvanic couples. Moreover, the enhanced protective effectiveness of corrosion products was another reason for the improved corrosion resistance.

59 citations


Journal ArticleDOI
TL;DR: The critical chloride content for initiation of reinforcement corrosion is an essential element in service life design and modelling of concrete structures as discussed by the authors, and the critical content is laden with questions regarding its definition, experimental assessment and practical aspects.
Abstract: The critical chloride content for initiation of reinforcement corrosion is an essential element in service life design and modelling of concrete structures.The critical content is laden with questions regarding its definition, experimental assessment and practical aspects. It should be addressed by a statistical approach. The paper discusses such issues, presents experimental evidence and considers its relationship to the electrical resistivity of concrete. A low concrete resistivity can be theoretically argued to relate to a low critical chloride content. Only part of the experimental data support this, however. The resolution of available data does not allow distinction with regard to the critical content between cement types. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

58 citations


Journal ArticleDOI
TL;DR: In this paper, a thorough mechanical, corrosion-mechanical, hydrogen permeation studies of X52 steel in as-received condition and after 30 years of service in gas pipeline have shown the degradation of the bulk metal properties due to the exploitation.
Abstract: The thorough mechanical, corrosion-mechanical, hydrogen permeation studies of X52 steel in as-received condition and after 30 years of service in gas pipeline have shown the degradation of the bulk metal properties due to the exploitation. The structure degradation of exploited steels decreased the resistance to crack propagation, to stress corrosion cracking (SCC), HE and HIBC. The exploited steel exhibited specific anomalies of mechanical behaviour: (1) decrease in resistance to brittle fracture with simultaneous decrease in hardness; and (2) the opposite change of the plasticity parameters: decrease in the RA accompanied by the increase in elongation. Deformation ageing and formation of micro defects, assisted by entering and accumulated hydrogen evolved in corrosion processes which takes place in brine deposited inside the pipes, have been proposed to be responsible for the metal degradation and specific modification of the properties during the long-term service of pipes. The extent of the steel degradation not being able to be detected by the standardized mechanical properties and routine microstructure observation can be efficiently determined by the specially modified methods and conditions. The information may be used in assessment of the conditions and of the life-time of operated and newly constructed gas pipelines.

56 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of the surfactant on the alumina dispersion, weight fraction in coatings, and corrosion resistance of the composite coatings under salt spray test were investigated.
Abstract: Electroless Ni-P-Al 2 O 3 composite coatings have been synthesized on mild steel shafts using surfactant cetyltrimethyle ammonium bromide (CTAB) as dispersant. The effects of the surfactant on the alumina dispersion, weight fraction in coatings, and corrosion resistance of the composite coatings under salt spray test were investigated. Results showed that alumina dispersion was improved, whereas weight fraction was decreased, with the increasing concentration of the dispersant CTAB. The corrosion resistance ofthe composite coatings was found to increase with the increase in CTAB concentration up to a certain optimum of 20 mg/L, beyond which a decreasing trend of corrosion resistance was observed under salt spray test. Compared with Ni-P coating, all the Ni-P-Al 2 O 3 composite coatings showed improved corrosion-resistant properties.

Journal ArticleDOI
TL;DR: In this paper, the relationship between burial soil and archaeological artefacts is studied by performing on site soil measurements using a combination of microbeam techniques, and the specific interest of this project lies in the study of ferrous thick corrosion layers formed in anoxic environments.
Abstract: In the context of the prediction of materials behaviour used in the nuclear waste storage, the understanding of iron corrosion mechanisms in anoxic environment is of great importance. Information can be obtained using complementary analytical tools. Interactions between burial soil and archaeological artefacts are studied by performing on site soil measurements. Moreover, archaeological artefacts are studied on transverse sections using a combination of microbeam techniques. The specific interest of this project lies in the study of ferrous thick corrosion layers formed in anoxic environments.

Journal ArticleDOI
TL;DR: In this paper, the corrosion and electrochemical behavior of aluminum in inhibited and uninhibited 4 M KOH-methanol-water mixed solutions with a methanol/water volume ratio of 3:2 were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and EIS.
Abstract: The corrosion and electrochemical behavior of aluminum in inhibited and uninhibited 4 M KOH-methanol-water mixed solutions with a methanol/water volume ratio of 3:2 were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS). The results of hydrogen collection and electrochemical experiments showed that the addition of ZnO can obviously inhibit the corrosion of aluminum in the 4 M KOH-methanol-water solutions, and its inhibition effect can be enhanced in the hydroxy-tryptamine (HT)-containing KOH solution. The results of scanning electron microscopy (SEM) and energy dispersive analysis of X-ray (EDAX) revealed that ZnO produces the inhibition effect by the formation of a zinc-containing deposit layer on the surface of aluminum, and the cooperative effect of ZnO and HT may improve the deposit of zinc. The results of galvanostatic discharge indicated that aluminum can present good electrochemical activity in the 4 M KOH-methanol-water solution with 0.2 M ZnO and 1.0 mL/L HT.

Journal ArticleDOI
TL;DR: In this article, the authors discuss the challenges of the chemical, refinery, and petrochemical industries in order to develop more environment friendly processes and to manufacture "green" products, including issues such as the selection and development of corrosion resistant materials, coatings, and environment friendly inhibitors.
Abstract: The chemical, refinery, and petrochemical industries are facing new challenges in order to develop more environment friendly processes and to manufacture "green" products. Corrosion management is an essential element for the development of a sustainable industrial society, including issues such as the selection and development of corrosion resistant materials, coatings, and environment friendly inhibitors. In this paper, some specific challenges will be discussed. In the chemical industry, the replacement of volatile and toxic solvents by green ones such as supercritical water processes, ionic liquid, or the use of carbon dioxide as an alternative solvent, requires specific corrosion management policies. Another issue for the refinery industry concerns new feedstocks such as opportunity crudes containing corrosive naphthenic acids or the transformation of biomass feed into bio-oils and biomaterials. Synthetic gas is also becoming a crucial intermediate in natural gas, coal or biomass to hydrocarbon liquids (XTL) processes. Other environmental aspects are the limitation of green house gas (GHG) release from the plants by implementation of CO 2 capture processes and the environment friendly management of water including more restrictive steps concerning its disposal. The implementation of advanced inspection and corrosion control management is also a major element of progress for a sustainable development of the chemical, refinery, and petrochemical industries.

Journal ArticleDOI
TL;DR: In this paper, the exfoliation corrosion susceptibility and electrochemical impedance spectroscopy (EIS) of 7150 Al alloys with T6, T73, and RRA (retrogression at 175 °C for 3 h) tempers in EXCO solution were investigated.
Abstract: The exfoliation corrosion susceptibility and electrochemical impedance spectroscopy (EIS) of 7150 Al alloys with T6, T73, and RRA (retrogression at 175 °C for 3 h) tempers in EXCO solution were investigated. The anodic equilibrium precipitate η(MgZn 2 ) is continuous or closely spaced at the grain boundaries in the 7150-T6 Al alloy, resulting in its greatest susceptibility to exfoliation corrosion. The grain boundary η precipitates in the RRA and T73 treated 7150 Al alloys are coarsened and show a clear discontinuous nature; they possess similar exfoliation corrosion sensitivity and their exfoliation corrosion resistance is greatly increased. At the beginning of immersion in EXCO solution, the EIS plot of the 7150 Al alloys is composed of a capacitive arc in the high to medium frequency range and an inductive component in the medium to low frequency range. As immersion time is increased, exfoliation corrosion with different corrosion ratings occurs on the surface of the 7150 Al alloy with various tempers, two capacitive arcs appear in the high to medium and medium to low frequency ranges, respectively. The fitted medium to low frequency capacitance C 2 of 7150-T6 Al alloy, corresponding to the new surface caused by the exfoliation corrosion, is much greater than that of the T73 and RRA treated 7150 Al alloy, which is consistent with the greatest exfoliation corrosion susceptibility of the 7150-T6 Al alloy.

Journal ArticleDOI
TL;DR: In this article, four research methods, such as weight loss test, electrochemical techniques, adsorption isotherm, and quantum chemical calculation, were employed to study the inhibition efficiency and inhibition mechanism of three 2H-pyrazole-triazole derivatives, BHOT, FHOT and CHOT in 1 M HCl solution for mild steel.
Abstract: Four research methods, such as weight loss test, electrochemical techniques, adsorption isotherm, and quantum chemical calculation, were employed in this paper to study the inhibition efficiency (IE) and inhibition mechanism of three 2H-pyrazole-triazole derivatives, BHOT, FHOT, and CHOT in 1 M HCl solution for mild steel. Using the electrochemical technique, three inhibitors were proved to show a mixed-type character for mild steel by suppressing both anodic and cathodic reactions on the steel surface. The adsorption models of three compounds were established at different temperatures according to their adsorption isotherms. The results of the quantum chemical calculation method indicated that the adsorption sites of 2H-pyrazole-triazole derivatives were strongly centralized on benzene ring, triazole ring, or other substituents. All the results showed that the three derivatives were excellent inhibitors in I M HCl solution for mild steel.

Journal ArticleDOI
TL;DR: In this article, the effects of Hf content and immersion time on the electrochemical corrosion behavior of theTi-22Nb-xHf(x ¼0,2,4,and6at%)alloys samples in 0.9% NaCl solution at 378C and neutral pH range, utilizing the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques.
Abstract: The aim of this study was to investigate the effects of Hf content and immersion time on the electrochemical corrosion behavior of theTi-22Nb-xHf(x ¼0,2,4,and6at%)alloysamplesin0.9%NaCl solution at 378C and neutral pH range, utilizing the potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. From the polarization curves, all these alloys exhibited typical passive behavior, which was indicated by a wide passive region without the breakdown of the passive films and low corrosion current densities. In addition, the values of the corrosion current densities and passive current densities decreased with increase in the Hf content. The EIS results, fitted by RS(QPRP) model,exhibited capacitive behavior (high corrosion resistance) with phase angles closed to � 808 and high impedance values at low and medium frequencies, indicating the formation of a highly stable film on these alloys in the test solution. The resistance of the passive films improved with increase in the Hf content and immersion time. All these observations suggested a more noble electrochemical behavior of the Ti-22Nb-xHf alloys compared to the Ti-Nb binary alloy.

Journal ArticleDOI
TL;DR: In this article, the influence of the investigated triazole Schiff bases, (benzylidine amino) triazoles (a), 4-hydroxy 3-(benzymethylidine amino)-triazole (b), 2-hydrox 3-naphthylidine amino-triazoles, and 2- hydroxy 3-(naphthyidine amino), triazolines, on the inhibition of corrosion of the metal surfaces is studied by density functional theory at the B3LYP/6-31G level.
Abstract: An examination of quantum chemical and corrosion inhibition studies is carried out to investigate whether any clear links exist between the results of quantum chemical calculations and the experimental inhibition efficiencies. The influence of the investigated triazole Schiff bases, (benzylidine amino) triazole (a), 4-hydroxy 3-(benzylidine amino) triazole (b), 2-hydroxy 3-(benzylidine amino) triazole (c), and 2- hydroxy 3-(naphthylidine amino) triazole (d) on the inhibition of corrosion of the metal surfaces are studied by density functional theory at the B3LYP/6-31G level. The calculated quantum chemical parameters correlated to the inhibition efficiency are, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the separation energy (ΔE), the dipole moment (μ), the softness (σ), the total negative charge on the whole molecule (TNC), the total charge on the azo-methine moiety, the molecular volume (V i ), and the total energy (TE). A good correlation between the quantum chemical parameters and the experimental inhibition efficiency is found. High inhibition efficiency for corrosion inhibitors can be achieved by controlling their electronic and structural properties.

Journal ArticleDOI
Liu Jialiang1, Yi Lu1, Xiaoyan Jing1, Ye Yuan1, Mi Lin Zhang1 
TL;DR: In this paper, the influence of silica sol addition on the ceramic coatings of Mg-Li alloy by plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte was investigated.
Abstract: We investigate the influence of silica sol addition on the ceramic coatings of Mg-Li alloy by plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte. Scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive spectroscopy are employed to characterize the microstructure and composition ofthe ceramic coatings. The anti-corrosion behavior of the ceramic coatings is evaluated by potentiodynamic polarization measurements in conjunction with electrochemical impedance analysis. The ceramic coating formed in the electrolyte containing silica sol contains SiO 2 and Mg 2 SiO 4 phase and has more uniform morphology and higher corrosion resistance than that formed in the electrolyte without addition of silica sol.

Journal ArticleDOI
TL;DR: In this paper, the time-dependent corrosion damage of reinforced steel is documented by X-ray tomography, which is suitable to make corrosion pits and their development visible which are embedded in a mortar with a cover thickness of about 35 mm.
Abstract: Corrosion of steel reinforcement in concrete exposed to chloride containing environments is a serious problem in civil engineering practice. Electrochemical methods, e.g., potential mapping, provide information whether the steel reinforcement is still passive or depassivation has been initiated. By applying such techniques no information on the type of corrosion, its extent and distribution of corrosion products is available. Particular the corrosion progress is a significant problem. Especially in the case of macrocell corrosion in reinforced concrete structures, the development at the anode cannot be separated into corrosion damage resulting from macrocell corrosion or self-corrosion. Until now also in laboratory tests it is impossible to collect such information without destroying specimens after electrochemical testing was performed. To overcome this problem it was tried to study the steel surface within the mortar specimens by X-ray tomography (CT). Within the scope of these investigations it could be shown, that X-ray tomography is suitable to make corrosion pits and their development visible which are embedded in a mortar with a cover thickness of about 35 mm. In this publication the time-dependent corrosion damage of reinforced steel is documented by X-ray tomography.

Journal ArticleDOI
TL;DR: In this paper, the synergistic effect of ascorbate has been established from the present studies and a plausible mechanism of corrosion inhibition has been proposed, which is stable even at 60 °C in the presence of the inhibitor in the corrosive environment.
Abstract: Synergistic inhibition of corrosion of carbon steel in low chloride environment using ascorbate as a synergist along with 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) and Zn 2+ is presented. The synergistic effect of ascorbate has been established from the present studies. In the presence of ascorbate, lower concentrations of PBTC and Zn 2+ are sufficient in order to obtain good inhibition, thus making this formulation more environmentally friendly. Potentiodynamic polarisation studies inferred that this mixture functions as a mixed inhibitor, predominantly cathodic. Impedance studies revealed that an immersion period of 24 h is necessary for the formation of the protective film, with a very high charge transfer resistance. The film is stable even at 60 °C in the presence of the inhibitor in the corrosive environment. The surface analysis by X-ray photoelectron spectroscopy (XPS) showed the presence of iron, oxygen, phosphorus, carbon and zinc in the protective film.The XPS spectra inferred the presence of oxides/hydroxides of iron(III), Zn(OH) 2 and [Zn(II)―PBTC―ascorbate] complex in the surface film. This inference was further supported by the reflection absorption Fourier transform infrared spectrum of the surface film. A plausible mechanism of corrosion inhibition has been proposed.

Journal ArticleDOI
TL;DR: In this article, the effect of the extract of galbanum (Ferula gummosa Boiss) on the corrosion of 304 stainless steel in 2 M HCl solution was studied by weight loss measurements, Tafel polarization, and electrochemical impedance spectroscopy (EIS) methods.
Abstract: The inhibition effect of the extract of galbanum (Ferula gummosa Boiss.) on the corrosion of 304 stainless steel in 2 M HCl solution was studied by weight loss measurements, Tafel polarization, and electrochemical impedance spectroscopy (EIS) methods. It was found that the inhibition efficiency (IE) increases as the extract concentration is increased. Tafel polarization method revealed the mixed mode inhibition of galbanum extract (GE) with predominant control of anodic reaction. The effect of temperature on the corrosion behavior of steel indicates that inhibition efficiency of the natural substance increases with the rise in temperature. At all temperatures, the adsorption of the extract components onto the steel surface was found to follow the Temkin adsorption isotherm.

Journal ArticleDOI
TL;DR: In this article, the effect of liquid junction potentials on the application of ion selective electrodes in concrete has been investigated and the influence of internal membrane potentials has been estimated by a theoretical model.
Abstract: When studying critical chloride content in reinforced concrete, the amount of chloride dissolved in the pore solution is an important parameter. Ion selective electrodes offer the possibility of measuring the chloride ion concentration (activity) in the concrete pore solution non-destructively. However, the potentiometric measurement might be disturbed by, amongst others, diffusion potentials (liquid junction potentials and membrane potentials). Laboratory samples designed to find critical chloride contents often involve chloride ingress by capillary suction, diffusion or migration, and thus chloride and pH profiles are usually present. As a result of these concentration gradients, membrane potentials are established, which markedly affect the determination of the chloride concentration. In addition, liquid junction potentials at the interface of the concrete sample and the reference electrode contribute to the measured potential. Experimental observations in the present work illustrate the effect of liquid junction potentials on the application of ion selective electrodes in concrete. Moreover, the influence of internal membrane potentials has been estimated by a theoretical model.

Journal ArticleDOI
TL;DR: In this article, a theoretical discussion about how these two factors affect resistivities of concrete and mortar is provided and experimental results on sensorized mortar probes are presented and correlated to analytical models of temperature and humidity influences.
Abstract: Concrete resistivity is directly related to relative humidity (RH) and is also affected by temperature. In this paper, a theoretical discussion about how these two factors affect resistivities of concrete and mortar is provided. Moreover, experimental results on sensorized mortar probes are presented and correlated to analytical models of temperature and humidity influences. All measurements were performed under controlled conditions. Temperature, RH, and resistivity were measured simultaneously in a particular zone of the probes. Temperature scanning was performed over short periods of time (approximately 1 h) and the probes were covered with waterproof paraffin each time for constant humidity content. This was feasible as all sensors were embedded. Water contents were ensured during the experiment by weighting the probes. Conclusions on the applicability of these techniques, their advantages, and limitations, and correlation to Archie and Arrhenius laws of the results are made.

Journal ArticleDOI
TL;DR: In this paper, the corrosion and electrochemical behaviors of pure aluminum in KOH-ionic liquid-water solutions with variable volume ratios of water and the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF(4)) were investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and Electrochemical impedance spectroscopy (EIS).
Abstract: The corrosion and electrochemical behaviors of pure aluminum in KOH-ionic liquid-water solutions with variable volume ratios of water and the ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIMBF(4)) were for the first time investigated by means of hydrogen collection, polarization curve, galvanostatic discharge, and electrochemical impedance spectroscopy (EIS) The results of hydrogen collection experiments showed that aluminum has a low corrosion rate in KOH-BMIMBF(4)-H(2)O solutions, and the corrosion rate decreases with increase in BMIMBF(4) content in the electrolytes The results of electrochemical experiments revealed that aluminum is electrochemically active over a very wide potential window in the KOH-BMIMBF(4)-H(2)O solutions, and its electrochemically kinetic mechanism is similar to that in the corresponding aqueous solution; the increase in KOH and water contents in the electrolytes may improve the anodic dissolution performance of aluminum it was found that aluminum presents excellent galvanostatic discharge performance in the 20 M KOH BMIMBF(4)-H(2)O mixed solution with 60% water

Journal ArticleDOI
TL;DR: In this paper, a fine description of the corrosion scales formed on the metallic rebars can be schematized, and mechanisms hypotheses are proposed in the discussion, on the basis of these results.
Abstract: The aim of this paper is to understand what the chemical influence of the concrete on the corrosion form present is, on rebars embedded for tens or hundreds years. Therefore, metal/concrete interface of samples coming from two French Historical Monuments has been characterized: ‘Bourse du Travail’, Bordeaux, 80 years old and ‘Maison du Bresil de la Cite Internationale de Paris’, 50 years old. The collected samples have been observed on transverse section in order to observe the whole corrosion system (metal/corrosion products/concrete). Morphology, elementary composition and structure have been studied with complementary analytical approaches (optical microscope, scanning electron microscope coupled to energy dispersive spectroscopy and Raman microspectroscopy). Thus, a fine description of the corrosion scales formed on the metallic rebars can be schematized. On the basis of these results, mechanisms hypotheses are proposed in the discussion.

Journal ArticleDOI
Gro Markeset1
TL;DR: In this paper, the authors presented a statistical model for the critical chloride content derived from measurements based on corrosion sensors installed in a 37 years old jetty for each corrosion sensor location, the chloride content at different sensor rings is found from the chloride profile obtained from detailed profile grinding of the concrete core drilled out before installation of each sensor.
Abstract: In service life predictions of concrete structures in marine environment, the critical chloride content is a crucial parameter However, there is a lack of reliable data for this parameter This paper presents a statistical model for the critical chloride content derived from measurements based on corrosion sensors installed in a 37 years old jetty For each corrosion sensor location, the chloride content at different sensor rings is found from the chloride profile obtained from detailed profile grinding of the concrete core drilled out before installation of each sensor The critical chloride content for each sensor location is then obtained by comparing the chloride profile with the sensor reading at the depth of depassivation Further, the influence of the critical chloride content on the calculated service life is studied From the probabilistic service life calculations, it is found that the service life increases from 50 to 100 years if the characteristic value of the critical chloride content increases from 034 to 067% (by weight of cement)

Journal ArticleDOI
TL;DR: In this article, the authors considered the use of high-strength stainless steels as prestressing tendon with bond in concrete and found that 1.4401 is an optimal proposition regarding its satisfactory resistance against pitting corrosion and stress corrosion cracking in structure-related corrosive conditions.
Abstract: Experience with prestressed concrete over about half a century has indicated that the corrosion resistance of conventional prestressing steel does not always satisfy, especially the prestressing steels are susceptible to chloride attack (de-icing salts) and hydrogen (hydrogen-induced stress corrosion cracking). On the other hand corrosion agents, such as chloride, condensation water, can penetrate in the concrete and arrive at the surface of steels. Hence, corrosion damage of prestressing steels can happen and, in the extreme cases, the prestressed concrete structure collapsed resulting from the failure of the tendon. In this paper, consideration is made to use high-strength stainless steels as prestressing tendon with bond in concrete. The high-strength stainless steels of qualities 1.4301 (X5CrNi18-10), 1.4401 (X5CrNiMo17-12-2), 1.4436 (X3CrNiMo17-13-3) and 1.4439 (X3CrNiMoN17-13-5) with sequence of increasing austenite stability were investigated. For application in prestressing tendon with bond in concrete the cold-drawn high-strength stainless steel of quality 1.4401 is an optimal proposition regarding its satisfactory resistance against pitting corrosion and stress corrosion cracking (SCC) in structure-related corrosive conditions. The lower alloyed steel 1.4301 has an insufficient resistance against the chloride-induced corrosion because of the lack of molybdenum and the content of deformation martensite due to the strong cold-drawing of its unstable austenitic structure.

Journal ArticleDOI
TL;DR: In this article, the influence of the ammonia concentration on the two types of corrosion, dezincification or preferred removal of a phase, was investigated in brass pipes and fittings.
Abstract: Despite a generally good corrosion resistance to tap and industrial water, many brass taps and fittings have failed in the past by stress corrosion cracking (SCC) and selective corrosion (dezincification or preferred removal of a phase). The experimental investigations of the present study clarify the influence of the ammonia concentration on the two types of corrosion. Notched specimens made of the alloys CuZn39Pb3, CuZn40Pb2, CuZn37, CuZn36P-b2As and CuZn21Si3P are polarized anodically in pure tap water and tap water with realistic ammonia concentrations (15 and 30 ppm) under a simultaneous mechanical loading condition. The influence of stress and of the third alloying elements lead and arsenic are investigated and evaluated. The experiments show that the ammonia additions significantly increase the risk of dezincification of the a-b-brasses. The arsenic in the CuZn36Pb2As alloy avoids dezincification, but enhances the risk of SCC. The rate of selective corrosion and SCC consistently increases with increase in tensile stress.

Journal ArticleDOI
TL;DR: In this paper, the authors found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer.
Abstract: Grade 316L is a type of austenitic stainless steel with ultra-low carbon content and it exhibits superior corrosion resistance. However, pitting is always observed in 316L steel when it is exposed to media containing halide ions. In the present study, we found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer. In order to identify the causes of the failure, metallographic structures and chemical compositions of the matrix material were inspected by an optical microscope (OM) and a photoelectric direct reading spectrometer. Beside these, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as ion chromatography (IC) were used to analyze the micromorphologies of the corrosion pits and the chemical compositions of the corrosion deposits within them. Analysis of the results revealed the sources of halide ions and the factors accelerating the corrosion rate. Beside these, detailed mechanisms of pitting were discussed and six out of all the seven theoretical morphologies of pitting features were obtained in practice.