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Effect of Hydrogen-Ion Concentration on the Submerged Corrosion of Steel
... Regarding the occurrence of steel rebar corrosion related to the neutralization and salt damage, some researchers have reported the effect of pH and chloride ions on the occurrence of corrosion of steel rebar in concrete. Whitman et al. 2) investigated the corrosion rate of iron from the amount of dissolved oxygen loss in electrolyte solution at arbitrary pH. They 2) reported that the corrosion rate of iron decreased owing to the film formation on the surface when the pH of the electrolyte solution was above 10. ...
... The , and correspond to "passive state," "de-passivation," and "corrosion" of steel rebar, respectively. Whitman et al. 2) reported that the corrosion rate of steel rebar is decreased at pH above 10. When the pH is below 10, the condition of steel rebar is corrosion ( ) in Fig. 6 Fig. 6, the plots do not obey the relation [Cl ¹ ]/[OH ¹ ] = 0.6 when the chloride ion concentration is larger than 3.4 mmol/dm 3 . ...
The relationship between chloride ion concentration and pH on de-passivation of steel rebar embedded in concrete was investigated by a two frequencies impedance measurement using probe electrodes. A saturated calcium hydroxide solution was used for the electrolyte solution as a simulated concrete pore solution. The pair of probe electrodes, which simulates the steel rebar, was immersed in the electrolyte solution prepared by an arbitrary concentration of chloride ions, and the two frequencies impedance measurement was performed. Air was supplied to the electrolyte solution to simulate the neutralization of concrete during the measurement. The charge transfer resistance related to the electrode/solution interface, Rct, was estimated from the two frequencies impedance measurement of probe electrodes in each electrolyte solution. This demonstrated that the Rct was drastically reduced by decreasing the pH of the electrolyte solution, namely, the de-passivation of steel rebar. The corrosion conditions of steel rebar were categorized as “passive state,” “de-passivation,” and “corrosion” based on the changes in the monitoring of Rct and pH in each electrolyte solution. These results were plotted on the two-dimensional diagram composed of chloride ion concentration and pH of the electrolyte solution. The conditions for the de-passivation of the passive film on steel rebar were discussed.
This Paper was Originally Published in Japanese in Zairyo-to-Kankyo 68 (2019) 303–308.
Fig. 2 Schematic of probe electrodes in the electrolyte solution and equivalent circuit between two electrodes. The Rct is the charge transfer resistance at the electrode/solution interface, the Rsol is the solution resistance, and the Cdl is electric double-layer capacitance at the electrode/solution interface. Fullsize Image
... is also considered as a representative reactive mineral (Dong et al. 2018), while RCl is considered as proxy for a relevant contaminant (Matheson and Tratnyek, 1994 Clearly, it has been a mistake to neglect water and its redox reactivity while discussing the mechanism of contaminant removal in the presence of Fe(0). Yet this knowledge was available in the scientific literature and in the English language for nine decades (Whitney, 1903;Whitman et al., 1924). ...
... CaCO3) are also influenced by pH value with indirect consequences on the dissolution of the metal and the permeability loss in filtration systems (Moraci et al. 2016). However, it is not correct to state that the universal oxide scale is favored by pH increase when the initial pH value is already in the range of "oxygen adsorption" (Whitman et al., 1924). ...
The global effort to mitigate the impact of environmental pollution has led to the use of various types of metallic iron (Fe(0)) in the remediation of soil and groundwater as well as in the treatment of industrial and municipal effluents. During the past three decades, hundreds of scientific publications have controversially discussed the mechanism of contaminant removal in Fe(0)/H2O systems, with the large majority considering Fe(0) to be oxidized by contaminants of concern. This view assumes that contaminant reduction is the cathodic reaction occurring simultaneously with Fe 0 oxidative dissolution (anodic reaction). This view contradicts the century old theory of the electrochemical nature of aqueous iron corrosion and hinders progress in designing efficient and sustainable remediation Fe(0)/H2O systems. The aim of the present communication is to demonstrate the fallacy of the current prevailing view based on articles published before 1910. It is shown that properly reviewing the literature would have avoided the mistake. Going back to the roots is recommended as the way forward and should be considered first while designing laboratory experiments.
... Aqueous iron corrosion occurs by two different mechanisms: chemical and electrochemical oxidation. Even though aqueous chemical iron oxidation (DRAZIC & POPIC 2005;EVANS 1945;GERASIMOV et al. 1985;KLAS & STEINRATH 1975) can not be excluded, immersed iron corrosion (e.g. in reactive walls) is generally agreed to occur through an electrochemical mechanism (DE LA RIVE 1830; MATHESON & TRATNYEK 1994;POWELL et al. 1995;SNOEYINK & JENKINS 1980;VERNON 1945;WEBER 1996;WHITMAN et al. 1924;WILSON 1923). A consideration of the simple voltaic cell helps materially to clarify one's ideas in this connexion. ...
... Although the role of oxide-film in influencing species transport to the iron surface has been well-established in the corrosion literature for decades (LAVINE et al. 2001;STRATMANN & MÜLLER 1994;VERNON 1945;WILSON 1923;WHITMAN et al. 1924) it is only poorly reflected in investigations regarding the processes of contaminant removal in "ZVI-H 2 O"-systems. While neglecting this key issue elusive arguments has been postulated unsupported by experimental evidence or supported by reproduced data from wrong experimental conditions (shaking or stirring). ...
... The same Fe silicate could also be formed according to the same reaction mechanism regardless of the pH investigated, but a change in the rate-limiting step governing its formation kinetics could occur at high pH. This could for example happen if the iron corrosion rate decreases sufficiently as the pH increases [47]. ...
Kinetics of Fe silicates formation during iron corrosion in deaerated Si-containing solutions (Si concentrations varying from ≈0 to ≈110 mg L⁻¹) were investigated for pH ranging from 7.5 to 10.1 at 50°C. All Si consumption curves showed an induction period characteristic of nucleation and growth processes involved in Fe silicate formation. The experimental data obtained at pH≈7.5 and pH≈8.1 were correctly reproduced with a simplified model considering only the growth mechanism from dissolved species. This model however failed to reproduce the results obtained at pH≈10.1. Improving the description of nucleation processes seems necessary to achieve a more predictive modelling.
... So, the acceleration of nanoparticle degradation can be also explained by the decrease of pH at the sites of PLA-particle surface contact, which assists the dissolution of iron and iron oxide. The increase in the corrosion of iron in steel with decreasing the solution рН value was investigated as far back as 1924 [33]. Table 1 compares the mass loss of Fe-Fe 3 O 4 @PLA with respective data available for other PLA composites. ...
... The validity of the suggested redox mechanism is based on strong supporting evidence that oxygen and protons are electron acceptor species that may be either together or individually the dominant factor influencing the iron oxidation in aqueous solutions [19,53,54], depending on acidity. Its reliability is also supported by a consumption of protons that corresponds to the stoichiometric production of ferrous ion determined by the overall redox reaction Fe 0 + (1/2)O 2 + 2H + → Fe 2+ + H 2 O (reaction 55 in Table S1). ...
To describe correctly the kinetics of Fenton-like process with zero valent iron, it is imperative to determine the rate of Fe²⁺ formation by ZVI oxidation at fairly acidic pH. With this purpose, experiments of ZVI oxidation were carried out in a well-stirred reactor in which air or N2 was bubbled through an aqueous solution at pH 2.5, 3 and 4 and 25 °C for 10,800 s. To mimic the Fenton-like process, the experiments were repeated at pH 3 and two different initial concentrations of H2O2. The results without H2O2 revealed that the rate-limiting step of Fe²⁺ formation is the electromigration of protons through an iron oxide barrier layer of negligible thickness. The solution of the Nernst-Planck equation was able to describe the flux of protons involved in the reduction half-reaction of ZVI oxidation. From the rate of protons consumption and the stoichiometry of the overall redox reaction, a rate expression for Fe²⁺ formation was obtained. A novel detailed kinetic model for the Fenton-like process with ZVI involving 20 species and 55 reactions was suggested. The only tuned parameters were the effective diffusivity of protons times the electric potential gradient, and the rate constant of precipitation of iron ion species. The results of species concentrations in the experiments with H2O2, and a large set of independent data of concentration of major species in reactors where powder iron and steel plates were immersed in aqueous acidic solution with and without H2O2, support both the rate equation for the Fe²⁺ formation and the Fenton-like kinetic model.
... The values of pH corr of the solutions are greater than the values of pH int . Whitman et al. 28) investigated the effect of pH in the neutral range on the corrosion of steel and showed that the corrosion rate of steel between pH 4 to 10 was approximately the same, and it can be considered that the corrosion rate of steel would not depend on the pH in a near-neutral solution. Because Table 3 shows the pH levels of the test solutions are greater than 4, it can be considered that the pH was not substantially affect the corrosion of the mild steel. ...
The synergistic effects of metal cations in a solution on the ability of sodium gluconate to inhibit the corrosion of mild steel were investigated by immersion and electrochemical tests. The effects of metal cations on the inhibition ability of sodium gluconate was investigated quantitatively, with particular focus on the parameter Y, which represents the “corrosion inhibitory effect of cations.” The results of the immersion and electrochemical tests showed that the inhibition ability of sodium gluconate improved with increasing Y value of the metal cations in model freshwater. The electrochemical and surface analyses indicated that gluconate ligands and large-Y metal cations formed a protective layer with few defects on the mild steel.
Fig. 11 Corrosion rates of specimens in a solution as a function of the Y value of the metal cation in the solution. Fullsize Image
... For higher pH values, iron corrodes according to the "O 2 adsorption" mechanism ( Table 2). The expression "O 2 adsorption" corresponds to the old view that iron is corroded by molecular O 2 [34]. It is well-established that at pH > 4.5, a heterogeneous oxide scale develops on the Fe 0 surface as shown in Equations 2 to 4, and this scale is responsible for contaminant removal in Fe 0 /H 2 O systems [8,10,16,28,35,36]. ...
Metallic iron (Fe0) has been demonstrated as an excellent material for decentralized safe drinking water provision, wastewater treatment and environmental remediation. An open issue for all these applications is the rational material selection or quality assurance. Several methods for assessing Fe0 quality have been presented, but all of them are limited to characterizing its initial reactivity. The present study investigates H2 evolution in an acidic solution (pH 2.0) as an alternative method, while comparing achieved results to that of uranium removal in quiescent batch experiments at neutral pH values. The unique feature of the H2 evolution experiment is that, quantitative H2 production ceases when the pH reached a value of 3.1. A total of twelve Fe 0 specimens was tested. The volume of molecular H2 produced by 2.0 g of each Fe0 specimen in 560 mL H2SO4 (0.01 M) was monitored for 24 hours. Additionally, the extent of U(VI) (0.084 mM) removal from an aqueous solution (20.0 mL) by 0.1 g of Fe0 was characterized. All U removal experiments were performed at room temperature (22 ± 2°C) for 14 days. Results demonstrated the difficulty of comparing Fe0 specimens from different sources, and confirmed that the elemental composition of Fe0 is not a stand-alone determining factor for reactivity. The time-dependent changes of H2 evolution in H2SO4 confirmed that, tests in the neutral pH range just address the initial reactivity of Fe0 materials. In particular, materials initially reacting very fast would experience a decrease in reactivity in the long-term, and this aspect must be incorporated in designing novel materials and sustainable remediation systems. An idea is proposed which could enable the manufacturing of intrinsically long-term efficient Fe0 materials for targeted operations as a function of the geochemistry.
... It was reported that the corrosion rate of carbon steels can be significantly increased by decreasing the pH or increasing the temperature of the corrosion media. 40 Therefore, to simulate the corrosion behaviour at the process temperature used for PIM manufacturing, the immersion tests were conducted in a relatively concentrated H 2 SO 4 solution Immersion tests were conducted at room temperature in accordance with the NACE TM0169 standard. 41 The samples were cut to approximately 7 × 8 × 1.5 mm 3 . ...
Carbide-reinforced martensitic steels, known as high-speed steels (HSSs), have been used as tool materials in various industries because of their high hardness and wear resistance. Nonetheless, such steels show severe degradation when used in a corrosive environment because typical Cr2O3 films, which generally realise passivity in these alloys, do not often work effectively. Here, we demonstrate that the corrosion resistance of a high-carbon-containing Fe–Cr–W-based alloy in a sulfuric acid solution can be significantly improved by the addition of trace Cu. The enrichment of Cu at the surface of the alloy as corrosion proceeds is key to inhibiting further corrosion. A theoretical model for a micro corrosion cell, which should be applicable to any material employed under the same corrosion conditions in fields such as the chemical and energy industries, was developed to interpret the experimental observations.
... Corrosion of steel reinforcement is the major durability concern of reinforced concrete (R/C) structure because it reduces the cross sectional area of rebar, compromises the bond between rebar and concrete, and causes cracking, delamination and spalling of concrete cover. Due to the high alkaline environment in concrete (pH ~12-13), steel reinforcement in concrete is inherently protected by a thin passivation layer mainly composed of iron oxide constituent Fe2O3 in very condense form [1]. Carbonation of concrete and ingress of acidic chemicals such as SO2 from environment, however, can reduce the alkalinity of concrete and cause depassivation of steel [2][3][4]. Besides, infiltration of chloride ion from deicing salt, seawater and other sources through concrete cover can also severely destroy the passivation layer. All these lead to corrosion of steel reinforcement [1,5]. ...
This paper investigates corrosion of steel bar in reinforced strain-hardening cementitious composites (R/SHCC) through electrochemical techniques. Linear polarization resistance is engaged to determine corrosion rate of steel bar while electrochemical impedance spectroscopy is employed to study corrosion kinetics by probing the electrode and interface reactions. An equivalent circuit model is used to quantitatively interpret the impedance data of steel corrosion. Results show that polarization resistance Rp of R/SHCC is much higher than that of R/M and thus corrosion rate of steel bar in R/SHCC is much reduced. The Rp of R/SHCC is about two orders of magnitude higher while the corrosion rate of R/SHCC can be two orders of magnitude lower than that of R/M after 137 h accelerated corrosion. Rp of specimen is dominated by the charge transfer resistance Rct before cover cracking and governed by both Rct and cover resistance Rc after cover cracking. R/SHCC specimen possesses a much higher Rct and Rc than R/M due to high tensile ductility and damage tolerance of SHCC material together with tight crack with in SHCC cover.
... Early in 1924, three scientists from MIT have concluded that the decrease of pH accelerated metal corrosion when they examined the effect of hydrogen-ion concentration on the submerged corrosion of steel. 49 coating and its degradation products. So, the corrosion rate of MPS was adjusted by tuning PLA parameters, as shown in Figure 5. ...
The new principle and technique to tune biodegradation rates of biomaterials is one of keys to development of regenerative medicine and next-generation biomaterials. Biodegradable stents are new-generation medical devices applied in percutaneous coronary intervention etc. Recently, both corrodible metals and degradable polymers have drawn much attention in biodegradable stents or scaffolds. It is, however, a dilemma to achieve good mechanical properties and appropriate degradation profiles. Herein, we put forward a metal-polymer composite strategy to achieve both. Iron stents exhibit excellent mechanical properties but slow corrosion rate in vivo. We hypothesized that coating of biodegradable aliphatic polyester could accelerate iron corrosion due to the acidic degradation products etc. To demonstrate the feasibility of this composite material technique, we first conducted in vitro experiments to affirm that iron sheet corroded faster when covered by polylactide (PLA) coating. Then, we fabricated three-dimensional metal-polymer stents (MPS) and implanted the novel stents in the abdominal aorta of New Zealand white rabbits, setting metal-based stents (MBS) as a control. A series of in vivo experiments were performed including measurements of residual mass and radial strength of the stents, histological analysis, micro-computed tomography, and optical coherence tomography imaging at the implantation site. The results showed that MPS could totally corrode in some cases, while iron struts of MBS in all cases remained several months after implantation. Corrosion rates of MPS could be easily adjusted by regulating the composition of PLA coatings.
... Hence, the corrosion of Fe 0 is a critical process governing the efficiency of a ZVI bed reactor. In spite of the spontaneous reactions of Fe 0 with DO, H 2 O (or H 3 O þ ), and with the contaminants, these corrosion reactions are yet slow and thus limit the removal of contaminants (Whitman et al., 1924;Noubactep, 2010). Accordingly, enhancing the corrosion of ZVI has been regarded as an effective approach to promote the decontamination performance of ZVI bed. ...
Enhanced removal of As(V) and Se(VI) by zero valent iron (ZVI) has been recently revealed by using H2O2 as the corrosion accelerator, however, the detailed performance of such enhanced removal in ZVI column as well as the underlying mechanism is still unclear. In this study, the temporospatial evolution of As(V) and Se(VI) along a self-designed ZVI/H2O2 column in down-flow mode was systematically investigated. The variations of concerned aqueous parameters (pH, ORP, H2O2, Fe²⁺, As, and Se) were monitored at different positions along the column throughout the experiments. Results showed the corrosion degree of ZVI decreased with the depth of the column, as confirmed by SEM and XRD analyses of the solid samples from different layers. The retention of As and Se also decreased along the column, suggesting the uptake of As(V) and Se(VI) was highly dependent upon the ZVI corrosion evolution. In the initial stage, the influent H2O2 was mostly consumed by ZVI in the top layer. With the continuous corrosion of ZVI, the breakthrough of H2O2 would activate the ZVI at lower positions, resulting in the reactive zone continuously shifting downward along the column. The reduction of As(V) and Se(VI) to aqueous As(III) and Se(IV) was significantly inhibited at the positions in the presence of H2O2, whereas favorably enhanced in the presence of abundant Fe²⁺. The retention of As(III) in the lower part of the column was observed while that of Se(IV) was negligible, as related to the different effects of pH on the adsorption of As(III) and Se(IV). In addition, the evolution of different oxidation states of As and Se retained in the column were identified by XPS, further demonstrating the comprehensive mechanisms of As(V)/Se(VI) removal involving reduction and adsorption in the ZVI/H2O2 column.
... Uniform corrosion [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67], A. also called general corrosion, occurs when the anodes (i.e., the locations where the anodic reactions take place) and the cathodes (i.e., the locations where the cathodic reactions take place) move about the pipe surface such that the thinning of the pipe wall appears more or less uniformly. This type of corrosion takes place where the pipe surface is exposed to a bulk aqueous phase and, hence, only pipelines with waterannulus annular flow or stratified flow patterns experience this form of corrosion. ...
Chapter for the ASTM's Manual 37: Fuels and Lubricants Handbook: 2nd edition
... Die direkte Reduktion nach Gleichung 1 (Tab. 1) wird immer noch als Grundreaktion der Schadstoffentfernung in Fe 0 /H 2 O-Systemen angegeben [9][10][11]19], wenngleich (i) eine dauerhafte Anwesenheit von Oxidschichten an der Fe 0 -Oberfläche insbesondere bei pH > 4 (bis 4.5) allgemein bekannt ist [20][21][22][23][24][25], und (ii) eine indirekte Reduktion mancher Schadstoffe durch sekundäre (Fe II , H/H 2 ) und tertiäre (Fe 3 O 4 , green rust) Korrosionsprodukte möglich ist [26][27][28][29]. In manchen Fällen ist eine indirekte Schadstoffreduktion thermodynamisch sogar günstiger als die direkte Reduktion. ...
Die Reinigung belasteter Grundwässer durch den Einsatz von Eisenwerkstoffen (d.h. in Fe0/H2O-Systemen) hat sich in vielen Fällen als Alternative zur herkömmlichen Pump-and-treat-Technik zur Sanierung einiger im Wasser gelösten Schadstoffe etabliert. Alle in Fe0/H2O-Systemen ablaufende Prozesse beeinflussen die Schadstoffentfernung aus der wässrigen Phase. Für eine sachgerechte Untersuchung dieser Prozesse ist es wünschenswert, Parameter zu identifizieren, die Einfluss auf die Löslichkeit eines Schadstoffes bzw. die Reaktivität des Eisenwerkstoffs ausüben. Anhand einer Literaturstudie über die Eisenkorrosion bzw. die adsorptive Eigenschaften der Korrosionsprodukte wird in diesem Zusammenhang die Bedeutung des Säuregehalts (ausgedrückt über die Größe pH) herausgehoben. Der Wert des pH bestimmt die Korrosionsart, die Löslichkeit des Eisens (Entstehung der Korrosionsprodukte), das Wesen und die Reaktivität der Korrosionsprodukte (adsorptive Eigenschaften), und die Löslichkeit der Schadstoffe (Speziation). Ein weiterer wichtiger Parameter ist das Redoxpotential, welches gegenüber dem pH-Wert jedoch von geringerer Bedeutung ist. Des Weiterem werden Vorschläge unterbreitet, wie (i) eine effiziente Auswahl des Fe0/Lösungs-Verhältnisses getroffen und (ii) die Versuchsdauer eingestellt werden sollte.
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Afrika & Wissenschaft
Africa & Science / Afrique & Science
NS 2- August 2015
ISSN: 1862-6793
Nr. 00181- Aug 18th, 2015
Weekly Newspaper devoted to Science & Technology in Africa
Pour la promotion de l'esprit scientifique en Afrique
... Calcium phosphate dissolution rate was accelerated in acidic environment owing to the PLGA degradation 79,80 . Similarly, dissolution occurred also on the formed Fe(OH) 2 layer as hydroxide layers is more soluble in acidic environment 36,37,81 . The carboxylic acid group in the monomers (LA and GA) was further dissociated into H + through a heterolytic cleavage of OH bond. ...
Iron and its alloy have been proposed as biodegradable metals for temporary medical implants. However, the formation of iron oxide and iron phosphate on their surface slows down their degradation kinetics in both in vitro and in vivo scenarios. This work presents new approach to tailor degradation behavior of iron by incorporating biodegradable polymers into the metal. Porous pure iron (PPI) was vacuum infiltrated by poly(lactic-co-glycolic acid) (PLGA) to form fully dense PLGA infiltrated porous iron (PIPI) and dip coated into the PLGA to form partially dense PLGA-coated porous iron (PCPI). Results showed that compressive strength and toughness of the PIPI and PCPI were higher compared to PPI. A strong interfacial interaction was developed between the PLGA layer and the iron surface. Degradation rate of PIPI and PCPI was higher than that of PPI due to the effect of PLGA hydrolysis. The fast degradation of PIPI did not affect the viability of human fibroblast cells. Finally, this work discusses a degradation mechanism for PIPI and the effect of PLGA incorporation in accelerating the degradation of iron.
... It is well known that a CO 2 -containing solution is significantly more corrosive than normal weak acid solutions, and that, at a given pH, more corrosion of steel is caused by an aqueous CO 2 -containing solution than by hydrochloric acid. 4,5 Corrosion inhibition is currently the most widely used method for corrosion control in the oil and gas production industry. Significant progress has been achieved over the past two decades in understanding this phenomenon, 6-9 however a comprehensive understanding of the behaviours and mechanisms of important CO 2 corrosion inhibitors is often lacking. ...
A series of rare earth 4-hydroxycinnamate compounds including Ce(4OHCin)(3), La(4OHCin)(3), and Pr(4OHCin)(3) has been synthesized and evaluated as novel inhibitors for carbon dioxide corrosion of steel in CO2-saturated sodium chloride solutions. Electrochemical measurements and surface analysis have shown that these REM(4OHCin)(3) compounds effectively inhibited CO2 corrosion by forming protective inhibiting deposits that shut down the active electrochemical corrosion sites on the steel surface. Inhibition efficiency was found to increase in the order Ce(4OHCin)(3) < La(4OHCin)(3) < Pr(4OHCin)(3) and with increase in inhibitor concentration up to 0.63 mM. Detailed insights into corrosion inhibition mechanism of these compounds in carbon dioxide environment are also provided. (c) 2014 The Electrochemical Society. All rights reserved.
... The corrosion rate of iron slows significantly if the pH at the metal surface is high enough to precipitate Fe 2+ ions as Fe(OH) 2 (which has a minimum solubility at pH 11 [24]) and, once formed, is easily oxidized and hydrolysed to Fe(OH) 3 [57]. In general, the iron corrosion rate slows as the pH is increased above nine and drops to a negligible rate above 12 [58]. As long as archaeological iron is corroding during immersion, the Clions are prevented from diffusing out because they are attracted to the Fe 2+ ions being generated by the corrosion process. ...
Results are presented on the effectiveness of treating archaeological iron by immersion in an aqueous sodium hydroxide (NaOH) solution (2% w/v, pH 13.5, room temperature) followed by immersion in an aqueous 1,2-diaminoethane (ethylenediamine, EN) solution (5% v/v, pH 11.5, 50°C). This study was undertaken to determine the effectiveness of these solutions in removing dissolved chloride ions and to explain the occasional observation of rapid iron corrosion. Thirty-two archaeological wrought iron pieces were treated. Some were immersed in NaOH followed by EN, and, for comparison, others were treated first in EN, then NaOH. Each artifact was treated separately and solutions were changed on a regular basis. The chloride ion concentration was determined by potentiometric titration with a silver nitrate solution. For nine artifacts, solutions were analysed quantitatively for 26 different dissolved elements using inductively coupled plasma atomic emission spectrometry. The results demonstrate that chloride ions are more effectively removed from archaeological iron by immersion in NaOH than by immersion in EN. The results also demonstrate that heavily mineralized iron is more likely to remain unbroken if immersed in EN before immersing in NaOH. Unfortunately, the corrosion of iron can be stimulated by EN because it forms soluble complexes with iron(II) ions.
While chronic limb-threatening ischemia is a serious peripheral artery disease, the lack of an appropriate stent significantly limits the potential of interventional treatment. In spite of much progress in coronary stents, little is towards peripheral stents, which are expected to be long and biodegradable and thus require more breakthroughs in core techniques. Herein, we develop a long & biodegradable stent (LBS) with a length of up to 118 mm based on a metal-polymer composite material. Nitriding treated iron with elevated mechanical performance was applied as the skeleton of the stent, and a polylactide coating was used to accelerate iron degradation. To achieve a well-prepared homogeneous coating on a long stent during ultrasonic spraying, a magnetic levitation (Maglev) was employed. In vivo degradation of the LBS was investigated in rabbit abdominal aorta/iliac arteries, and preclinical safety and efficacy were evaluated in canine infrapopliteal arteries. First-in-man implantation of LBS was carried out in the below-the-knee artery, and the 6–13 months follow-ups demonstrated the feasibility of the first LBS.
In this study, a corrosion inhibitor suitable for the corrosion inhibition of primary containment vessels at the Fukushima Daiichi Nuclear Power Station is investigated. Considering the internal environment of the primary containment vessels, the corrosion inhibitor should inhibit the freshwater corrosion of carbon steel under irradiation and should not come under effluent standards in Japan. Herein, a corrosion inhibitor was devised by combining Al lactate and Na molybdate that met the above conditions and its corrosion mechanism was investigated. It was found that 0.75 mM Al lactate and 0.25 mM Na molybdate were the most inhibitive to the corrosion of carbon steel. Since Al lactate has never been reported as a corrosion inhibitor for metallic materials, it could be developed as a novel corrosion inhibitor in this study. The corrosion inhibitor inhibited the freshwater corrosion of carbon steel even under gamma irradiation of 200 Gyh−1. Al and molybdate ions in the solution formed a metal cation layer on carbon steel with few defects and without iron. This metal cation layer inhibited both the cathodic oxygen reduction reaction and the anodic iron dissolving reaction, thereby enhancing the corrosion protection of carbon steel in freshwater.
The aim of this manuscript was to investigate the electrogeneration of iron-based solids and their use in the adsorption of an azo dye. Experiments of electrochemical generation of iron hydr(oxides) were carried out in a Hoffman cell and in a well-stirred batch reactor at 25°C. The oxidation of iron metal at the anode and the reduction of water at the cathode were the electrochemical reactions confirmed to occur. A 2² factorial design of experiments was applied to investigate the effect of initial pH and current on the current efficiency for the production of ferrous ion at an electrolyte concentration of 300 g L⁻¹. The current efficiency for Fe²⁺ was much lower than unity (0.204±0.009) and it was statistically independent of the examined factors (p>0.05). An approximately 3:1 molar mixture of amorphous ferric and ferrous hydroxides was electrogenerated before being possibly converted to dehydrated hydroxides such as magnetite. The iron hydroxides were formed by precipitation reactions of soluble iron species at a rate constant higher than 0.072±0.013 s⁻¹. Additional experiments of electrogeneration of these solid adsorbents at electrolyte concentrations between 250 and 1.5 g L⁻¹ revealed a significant (p≤0.05) decrease in the current efficiency for Fe²⁺ formation from 0.180±0.006 to 0.118±0.008. Experiments of tartrazine adsorption on the electrogenerated iron oxyhydroxides were carried out batchwise at different initial concentrations of the dye at 25°C. Electrogeneration of oxyhydroxides and adsorption were described correctly by detailed kinetic models. The crystallinity of the electrogenerated adsorbent was examined by X-ray diffraction analysis, while its specific surface area, pore volume and average pore size were from BET analysis. SEM and EDX analyses were conducted to examine its morphology and elemental composition.
We study unknown features obtained from Raman spectra of protective rusts consisting of Fe 3 O 4 discovered in the investigation of concrete buildings on Hashima Island in Nagasaki, Japan, a World Heritage site. The Raman shift shows not only the A 1g peak of Fe 3 O 4 but also a previously unknown peak at a higher wavenumber, i.e., at 700 to 800 cm − 1 or higher. Here, we investigate the characteristics of the unknown peak and indicate that the peak intensity becomes stronger than that of the original A 1g as the incident light intensity is increased. This phenomenon has never been noted in Raman spectroscopy. Therefore, we consider the physical meaning of the phenomenon. As a result, we are able to explain this phenomenon by adding a hypothesis to Albrecht's vibronic theory. We also see that the results obtained in this study can be considered applicable not only to protective rust but also to other materials.
FeCO3 cement can be produced by reacting CO2(aq) and particulate-Fe(0). Process conditions and solution compositions influence cement properties through kinetics of Fe-dissolution and FeCO3-precipitation. This study investigates Fe-dissolution in dilute systems (water(wt.)/Fe(wt.) = 1000) at 30/60 °C, and 1/10 barg CO2-pressures. Experimentally, time-evolution of solution composition shows increased [Fe] and solution-pH. As a proxy for high-pressure in-situ experiments, a modeling approach is developed to quantify with [Fe]-increase, the: decreased [H+], increased [HCO3-]/[OH–]/[CO32-], and undisturbed [CO2(aq)]/[H2CO3]. Fe-dissolution rates increase with: (a) pH-decrease with increased CO2-pressure, and (b) faster kinetics at higher temperatures, even with higher pH. Experimental and modeled pH are comparable at 1 bar, two causes are discussed for it being ∼ 1.2 times at 10 barg: CO2-depressurization, and Fe-precipitation. Lower CO2-mediated dissolution activation energies of ∼ 30 (1 barg) and ∼ 20 kJ/mol (10 barg) compared to strong acids (∼60 kJ/mol) are attributed to buffering action of CO2(aq).
The carbon capture and storage (CCS) process significantly contributes in reducing the atmospheric emissions of carbon dioxide (CO2). During the implementation of the CCS technique, the pipeline corrosion occurring due to the supercritical (SC) CO2 is a major concern. The corrosion of the steel pipelines is caused by contamination of water that reacts with the CO2 gas leading to the formation of corrosive species carbonic acid (H2CO3). To address to this issue, the strategies used are (i) use of corrosion resistant alloys (CRAs), (ii) corrosion inhibitors, and (iii) the protective layers of iron carbonate (FeCO3). One of the most important methods is the application of chemical additives to the corrosive medium that dissolves in the environment and adsorb on the target metallic substrate, thereby impacting corrosion mitigation. This article aims to overview the various organic corrosion inhibitors commonly applied in the SC CO2 corrosion. The requirement of greener inhibitor alternatives is emphasized, and some of the potential research aspects are conceived of. The mechanism of SC CO2 corrosion, factors affecting and chemistries of inhibitors and their shortcomings are discussed. This review also discusses the application of computational methods in predicting the inhibitive performance. This is a critical, timely, urgent and insightful review, identifying successes and shortcomings on the inhibitors available for SC CO2 medium, and pointing to potential avenues for further investigation.
A catastrophic earthquake of magnitude 9.0 occurred off the Pacific coast of Tohoku in Japan on March 11, 2011. The subsequent tsunami lost the cooling function of nuclear fuel at the Fukushima Daiichi Nuclear Power Station, resulting in a core meltdown. This is the outline of the Fukushima Daiichi accident. As an emergency action for fuel cooling, seawater was injected into the reactors and the spent fuel pools, resulting in various corrosion issues. This article first presents corrosion issues and mitigation activities immediately after the accident. Various corrosion mitigation methods that were examined for application to the reactors and the spent fuel pools, their selection process, the timing of application, and the result of application are described in detail. After the accident was resolved, the decommissioning work of the Fukushima Daiichi Nuclear Power Station is proceeding based on four technical issues: fuel removal from the spent fuel pools, fuel debris retrieval, contaminated water management, and waste management. This article also outlines the corrosion issues that have become apparent in solving these technical issues and the potential corrosion issues that may emerge in the future.
Relationship between chloride ion concentration and pH on depassivation of steel rebar embedded in concrete was investigated by a two frequencies impedance measurement using probe electrodes. A saturated calcium hydroxide solution was used for the electrolyte solution as simulated concrete pore solution. The pair of probe electrodes, which simulates the steel rebar, was immersed in the electrolyte solution prepared by arbitrary concentration of chloride ions, and the two frequencies impedance measurement was performed. Air was supplied to the electrolyte solution in order to simulate the neutralization of concrete during the measurement. The charge transfer resistance related to electrode/solution interface, Rct, were estimated from the two frequencies impedance measurement of probe electrodes in each electrolyte solution, demonstrating that the Rct was drastically decreased with decreasing the pH of electrolyte solution, namely, the depassivation on steel rebar. The corrosion conditions of steel rebar were categorized as “passive state”, “depassivation”, and “corrosion” based on the changes of monitoring of Rct and pH in each electrolyte solution, and these results were plotted on the two dimensional diagram composed of chloride ion concentration and pH of electrolyte solution. The conditions for depassivation of passive film on steel rebar were discussed.
The main aim of this manuscript was to investigate the kinetics of zero valent iron (ZVI) oxidation to produce Fe²⁺ in hydrogen peroxide-water solutions. The experiments were performed in a batch reactor by submerging an iron plate in agitated aqueous H2O2 at 25 °C and pH ∼2-4. A shrinking core model described properly the kinetics of iron oxidation. The overall rate of this reaction was governed by the rate of transport of protons through an iron (hydr)oxide film formed over the iron plate. To validate the model, additional kinetic experiments were carried out at different surface area of ZVI, initial concentration of H2O2, and pH. The determined concentrations of total iron, Fe²⁺, Fe³⁺ and H2O2 were reproduced by a detailed kinetic model for the Fenton-like process with ZVI that comprised 14 species and 22 reactions. Tests of oxidation of chlorpyrifos confirmed the reliability of the model to describe the Fenton-like process with ZVI.
In this study, pH measurement was performed in a thin electrolyte droplet with a thickness <1000 µm by the measurement of the equilibrium electrode potential of an Sb/SbxOy electrode used as a pH sensor. The equilibrium potential of the Sb/SbxOy electrode was evaluated by using the Kelvin probe (KP) technique. To investigate the potential response of the Sb electrode in a thin electrolyte droplet, the dependency of the Volta potential difference between the Sb and a gold wire as a KP on electrolyte droplet thickness was measured. The Volta potential difference had a linear response with respect to the buffer solution pH, independent of the droplet thickness. This result indicates that the KP technique, combined with an Sb electrode, is sensitive to the pH of a thin electrolyte droplet of thickness ≥50 µm. This pH measurement technique was also applied to measure pH in a corrosion model of steel. The corrosion model consisted of two steel plates in the same plane as the anode and cathode, with a constant current between them. During the corrosion process, the pH value decreased from 6 to 5 near the anode and increased from 6 to 12 at the cathode. The changes in pH measured in the thin electrolyte droplet were in good agreement with the color changes of the solution containing pH indicators.
Fig. 7 Changes in (a) the applied current density between the steels, (b) the potentials of the anode and cathode sides of the steel, and (c) the pH near the steel. Fullsize Image
The oxidation of pyrite in soils causes their acidification under aerated conditions, which May promote the corrosion of buried steel structures. Hence, the purpose of this study was to elucidate the effect produced by the presence of pyrite minerals in soils on the corrosion behavior of steel. In order to assess the fundamental corrosiveness of pyrite toward steel, the chemical properties of its aqueous solution were investigated by conducting short-term laboratory tests. In addition, electrochemical measurements were performed to evaluate the effect produced by the soil particles on the diffusion rates of oxygen and hydrogen ions in the soil medium. The obtained results revealed that the corrosion rate of steel in the pyrite-containing solution was accelerated due to the continuous production of hydrogen ions during the pyrite oxidation under the aerated conditions. However, its magnitude in a water-saturated soil system was not influenced by the oxidation of pyrite, owing to the relatively low diffusion rates of dissolved oxygen and hydrogen ions.
Among the advanced high-strength steels, quenching and partitioning (Q&P) steels provide excellent ultimate tensile strength in combination with good ductility. The mass fraction of martensite and austenite can be tailored by the Q&P treatment. In this study, the impact of the microstructure on the corrosion behaviour is investigated. For this, the microstructures of two Q&P processing routes and a quenched and tempered state are analysed using scanning electron microscopy and X-ray diffraction. Electrochemical impedance spectroscopy is conducted using two different media in order to determine the time evolution of corrosion rates during short-time corrosion. The results of this study demonstrate that correlations between Q&P microstructures and the corrosion behaviour can be analysed in detail with these experimental methods.
This synopsis describes corrosion issues and mitigation activities shortly after the Fukushima Daiichi Nuclear Power Station accident. An earthquake of magnitude 9.0 occurred on March 11, 2011; the subsequent tsunami removed the cooling capacity of fuels in both the reactors and spent fuel pools (SFPs). Seawater was temporarily used for emergency fuel cooling, which induced various corrosion issues. Just after the accident, the temperatures within the reactors of Units 1 to 3 increased to several hundred degrees Celsius and the water quality of the cooling water seems to have become similar to that of concentrated seawater. To stabilize the fuel cooling, corrosion mitigation actions were required for mainly carbon steel components. The following corrosion mitigation measures were applied to the reactors: (a) temperature decreases, (b) dissolved oxygen removal from feedwater via deaeration, (c) dissolved oxygen removal from cooling water in the reactors via nitrogen gas injection, (d) salt removal from cooling water, and (e) sterilization of feedwater by hydrazine addition. The temperatures of SFP water in Units 1 to 4 were between 47°C and 93°C just after the accident. The maximum chloride ion concentration was approximately 2,000 ppm and the pH was in the range from 7.5 to 11.2. The mitigation of localized corrosion of the stainless steel pool liners and alkaline corrosion of the aluminum fuel racks was the top priority. In addition to (a), (b), and (d) listed above, (f) dissolved oxygen removal and sterilization by hydrazine addition and (g) pH control were applied to the SFPs. In the six years since the accident, no major corrosion problems have yet arisen. However, continued efforts to increase plant stability are underway for the long-term goal of decommissioning.
Thin water film is formed on metal surfaces that are exposed to the atmosphere. The conditions of this film change according to environmental factors, such as temperature, wind, and rainfall. Hence, it is difficult to investigate atmospheric corrosion on metal surfaces.
This paper aimed to develop a measurement system for the pH distribution on a metal surface in simulated atmospheric environment. The surface pH distribution was measured with agar film including pH indicators and MgCl2. The pH indicators used were a universal indicator and an MR-BTB indicator. Agar film of 0.5 mm thickness was placed on an iron specimen. The specimen was set in a chamber with a relative humidity of 100% to prevent the agar film from drying out. The surface pH distribution was determined from the color of the agar film with an RGB color model. The surface pH distribution on the iron showed that anodic reactions produced acidic regions and cathodic reactions produced basic regions. The observed phenomena were the same as that found under a water droplet which contained the pH indicator and MgCl2.Therefore, we conclude that the agar film could simulate thin water film in an atmospheric environment and allow measurement of the surface pH distribution on iron under atmospheric corrosion.
Homogeneous Electrodes and Traditional Electrochemical Methods Mixed Electrodes and Uniform Corrosion Models Mixed Potential Theory and Electrochemical Corrosion Measurement Electrochemical Impedance Investigation of an Electrode–Solution Interface Electrochemical Noise Monitoring of Rapid Electrode Processes Issues and Difficulties in Traditional Electrochemical Methods References
Physicochemical mechanisms of metal corrosion at refineriesʼ units are described. Low- (T < 100 °C) and high- (T > 200 °C) temperature
corrosion problems are analyzed. Corrosion by hydrochloric acid and its prevention, electrochemical mechanism of corrosion
in acid, neutral and alkali aqueous solutions of electrolytes are explained. Main factors affecting corrosion rate and its intensity are temperature, pressure, flow regime, and media. The following chemical compounds and mixtures are analyzed from corrosiveness: water, air, hydrogen sulfide, substances containing nitrogen, phenols, polythionic acids, organochlorine and organic chloride compounds, aluminum chloride, sulfuric acid, and alkaline solutions
(sodium hydroxide, sodium carbonate, ammonium hydroxide, amines, sour water, and spent caustic).
Polyaniline films were formed on an Fe substrate using the oxidative electropolymerization technique at 288 K in aqueous solutions with pH values ranging from 2 to 10 and containing aniline, p-toluenesulfonic acid and oxalic acid as supporting electrolytes. The effects of the electrolysis conditions on the morphologies and corrosion resistances of the films were subsequently investigated. Although the polyaniline films were partially formed in solutions of pH 2–4, the films completely formed and their surfaces became smooth when deposited in solutions of pH 7–10. Polyaniline films with smooth surfaces and good corrosion resistance were obtained at 8–30 A·m−2, whereas the films obtained at current densities greater than 50 A·m−2 exhibited non-uniform surface morphologies and poor corrosion resistance. Films obtained at anode potentials of 0.4 V and 0.8 V vs. NHE were not formed completely, and the films formed at an anode potential of 2.0 V exhibited very rough surfaces. Films formed from a solution containing only p-toluenesulfonic acid as a supporting electrolyte exfoliated from the Fe substrate after being immersed in a 3 mass% NaCl solution for 3 h. Although the films prepared from a solution containing only oxalic acid as a supporting electrolyte exhibited good adhesion to the substrate, they contained numerous defects and pores; consequently, they improved the Fe's corrosion resistance less than films deposited from a solution containing p-toluenesulfonic acid. In the case of polyaniline films formed in an electrolyte solution containing both p-toluenesulfonic acid and oxalic acid, the Fe exhibited improved corrosion resistance, and the films exhibited good adhesion to the Fe substrate.
Continuing to verify the principles of electrolytic corrosion, we turn from liquid amalgams to solid metals and to solutions with pH up to ca. 7, which is the overall range of ‘acid’ corrosion by superposition of anodic metal dissolution and cathodic hydrogen deposition by reduction of hydrogen ions rather than water. To exclude superposed oxygen reduction, the solution is assumed to be deaerated. The temperature is at 25°C or at some similar ambient value. The solution volume is supposed to be large, so that initial concentrations remain virtually constant during the course of the corrosion reaction, which is: Me + zH+ → Mez+ (z/2)H2. The metal surface is thought to be bare, i.e. free of films such as air-formed oxide films, and free of layers of solid corrosion products such as oxides or hydroxides.
Sorption and reduction of trichloroethylene (TCE) on zerovalent iron (ZVI) were examined using batch experiments in the presence and absence of cysteine and potassium sulfate. Cysteine, an amino acid containing a -SH functional group, did not significantly affect TCE adsorption at concentrations lower than 1.0 mM. However, the rates of TCE reduction and iron corrosion dramatically decreased at comparable or even much lower concentrations. The results suggest that there are two types of surface sites on the iron: the reactive sites responsible for TCE reduction and the non-reactive sites responsible for the bulk of TCE adsorption. The reactive site density was estimated to be only 2% of the total surface sites. A two-site analytical model was proposed to explain the experimental results, in which adsorption took place on both reactive and non-reactive sites, but dechlorination reactions occurred only on reactive sites. Additionally, it was observed that the rate of TCE reduction was proportional to the rate of iron corrosion. This suggested that the same types of surfaces might be responsible for both dechlorination of TCE and iron corrosion, and/or the hydrogen producing corrosion process took place prior to the dechlorination reaction.
Numerous impurities always occur in various sources of water. Water is a unique solvent, which dissolves most of the inorganic and organic compounds. These comprise acidic and alkaline compounds, and dissolved oxygen. The content of impurities in the water used in textile wet processing was investigated, because of their possible destructive effect on wet processes, machineries, boilers and other related materials. The present study was carried out according to standard titrimetric and redox reaction methods. Remedial measures were also studied for water adequacy.
The effect of corrosion in the oil industry leads to the failure of parts. This failure results in shutting down the plant to clean the facility. The annual cost of corrosion to the oil and gas industry in the United States alone is estimated at $27 billion (According to NACE International)-leading some to estimate the global annual cost to the oil and gas industry as exceeding $60 billion. In addition, corrosion commonly causes serious environmental problems, such as spills and releases. An essential resource for all those who are involved in the corrosion management of oil and gas infrastructure, Corrosion Control in the Oil and Gas Industry provides engineers and designers with the tools and methods to design and implement comprehensive corrosion-management programs for oil and gas infrastructures. The book addresses all segments of the industry, including production, transmission, storage, refining and distribution.
Scale, or deposits, can build up in the wellbore tubulars and other downhole components, causing considerable damage to the life of the well. Infrastructure provides the support for the wells system and with oil and gas consumption on the rise and transportation required to feed that demand, all petroleum and pipeline engineers must have accurate corrosion and scaling information. The Fundamentals of Corrosion and Scaling for Petroleum and Environmental Engineers will provide the quick knowledge that engineers need to not only enhance the reliability of corrosion and scale control technologies but also manage scale deposits, prevent fatigue and ensure equipment integrity. © 2008 by Gulf Publishing Company, Houston, Texas. All rights reserved.
Corrosion process of carbon steel in aqueous solution under the atmospheric environment and the oxygen depleted environment has been reviewed by focusing the corrosion film formed on carbon steel in neutral pH. In the neutral solution under the atmospheric condition which contains oxygen, the critical pH to form the corrosion film and the precipitation ratio of dissolved iron ions depending on pH and the parabolic growth rate law were discussed. Under oxygen depleted environment, H2O works as oxidizing agent to oxidize Fe to produce Fe3O4 film with production of H2 gas. At high temperatures, the dissolution process of the Fe3O4 film controls the corrosion rate, whereas, at lower temperatures, the film growth process controls the corrosion rate and a steady dissolution rate of Fe3O4 film determines the corrosion rate after long exposure time.
The atmosphere in many cities along the coastal lines such as Qingdao in China has been polluted with SO2 due to the development of industry, and has been changed to coastal-industrial atmosphere. The corrosion behavior and mechanism of steel in coastal-industrial atmosphere with the co-existence of SO2 and Cl- is different from that in the coastal atmosphere containing only Cl- or the industrial atmosphere containing only SO2. It is necessary to study the corrosion mechanism of steel in the coastal-industrial atmosphere. However, almost all the atmospheric corrosion data of steels was obtained by the field exposure test, which could not reflect the dependence of SO2 or Cl- on the atmospheric corrosion evolution of steels due to the difficulties in controlling the field conditions. So the effect of SO2 on the corrosion evolution of Q235B steel in the simulated coastal-industrial atmospheres was investigated by the dry/wet cyclic corrosion test (CCT), as well as XRD, electrochemical impedance spectroscopy (EIS) and polarization curve measurements. The results indicate that in the initial stage, the SO2 inhibits corrosion of Q235B steel. During the later stage, the corrosion rate of the steel increases with increasing the SO2 concentration to a certain level but further increasing the SO2 concentration contributes to a decreased corrosion rate. Besides, higher SO2 concentration can promote the formation of alpha-FeOOH while inhibit the formation of gamma-FeOOH and beta-FeOOH. Evolution of Q235B steel corrosion rate in the atmosphere with SO2 concentration is due to the change of corrosion products.
CO2 corrosion of pure iron was studied. The activation energy of CO2 corrosion of pure iron at CO2 pressure 3 MPa was very similar to that of the hydration reaction of CO2. Although the cathodic reaction is a superposition of the diffusion controlled reduction of H+ ion and direct reduction of H2CO3, the latter was the main reaction at high CO2 pressure 1.1-3 MPa and/or at high temperature 313-353 K. CO2 corrosion falls into three types, depending on the temperature, and is closely related to the properties of the corrosion film caused by formation of FeCO3. The effect of environmental conditions and metallurgical factors on CO2 corrosion behavior, specifically both structure and constituents of corrosion products, were studied. The applicability of de Waard-Milliams equation, which is used for engineering purposes to predict the corrosion rate of carbon steel, was studied experimentally and theoretically. Anti-CO2 corrosion tubular materials and their properties are discussed.
The computer program AQUASIM was used to model biological treatment of perchlorate-contaminated water using zero-valent iron corrosion as the hydrogen gas source. The laboratory-scale column was seeded with an autohydrogenotrophic microbial consortium previously shown to degrade perchlorate. Consortium biokinetic parameters and data from column experiments were used to verify the model. The model was then used to simulate full-scale performance of an in-situ zero-valent iron permeable reactive barrier perchlorate-treatment system. Simulation results indicate full-scale field treatment systems have the potential to degrade significant concentrations of perchlorate in the presence of oxygen under a variety of operating conditions.
This study was performed to observe the change of stainless steel pipe interacting with alkaline solution. We used STS316L and STS304 as samples which were soaked in alkaline solution. We measured the samples by use of FE-SEM, EDX, SIMS to observe the surface and depth profile of both samples. The result showed that the precipitate appeared on the surface of both samples from 5 days. but the precipitate was confirmed to be decreased as time passes. but the quantitative change of precipitates at both samples was different as time passed. The EDX showed that the precipitate is Potassium from solution of Electrolysis. The result also showed that the primary elements of stainless steel pipeline and of Alkaline Solution were changed. The change of primary elements was severe between 5 days to 16 days and was stable around 40 days at both samples. The reaction of STS316L with alkaline solution was lower than STS304. We hoped that this study would be the foundation of developing the electrode of the alkaline hydrogen generator.
Researches into underground corrosion of steel structures are very few because of its mildness. And corrosion rates in underground corrosion are given only qualitatively or as a certain value based on statistical analysis of mass exposure test result without evaluation of soil condition. So we started to try to evaluate quantitatively the effect of environmental factors on underground corrosion. In this research, the basic underground corrosion properties of steel could be clarified. High temperature acceleration tests were carried out with the parameters of soil grain size, pH of solution, chloride ion concentration and aeration condition. The conclusions are as follows ;(1) Under aerated condition : 1) Corrosion rate of steel in clay, containing no chloride ion, is much smaller than that in aerated water, and can be regarded almost constant between pH 2 to pH10. 2) Corrosion rate of steel in clay and in fine sand, containing chloride ion, is almost constant regardless of the chloride concentration. And uniform corrosion is observed in fine sand while ununiform corrosion is observed in clay, and the corrosion rate is much higher in clay. With electrochemical hydrogen permeation method, pH on the surface of steel goes down from almost 8 to almost 4 in Sumi clay. Furthermore, at the result of polarization resistance measurement, Rp in clay and that in fine sand are not so much difference. 3) In clay, the aeration has little effect on the corrosion rate because of the low oxygen diffusion.(2) Under deaerated condition : 1) Effect of pH without chloride ion : i) In spite of the soil type the effect of pH to corrosion rate is small from pH 2 to pH 12 under soil environment, ii) Under non-soil environment the effect of pH to corrosion rate is small in pH 6 and over, while corrosion rate become very large under pH 2. iii) Corrosion rate is almost the same regardless of soil existence in 6 and over. 2) Larger the grain size, the corrosion rate increases in pH 1, while corrosion rate is almost the same from pH 2 to pH 12 regardless of the grain size with the exception of clay.
831,805; 1,177,725 Collecting ammonia from char: 287,570; 297,948 Cooling bone black: 61,851; 68,915; 77,935; 93,208; 101,019; 186,327; Decarbonizing bone black: 530,632
- Chemically
- Bone
Chemically treating bone black: 831,805; 1,177,725 Collecting ammonia from char: 287,570; 297,948 Cooling bone black: 61,851; 68,915; 77,935; 93,208; 101,019; 186,327; Decarbonizing bone black: 530,632; 585,658; 586,278; 592,547; 1,184,397