Chamber exposures of children to mixed ozone, sulfur dioxide, and sulfuric acid

To help assess acute health effects of summer air pollution in the eastern United States, we simulated ambient "acid summer haze" as closely as was practical in a laboratory chamber. We exposed young volunteers who were thought to be sensitive to this pollutant mixture on the basis of previous epidemiologic evidence. Specifically, we exposed 41 subjects aged 9-12 y to mixed ozone (0.10 ppm), sulfur dioxide (0.10 ppm), and 0.6-microm sulfuric acid aerosol (100 +/- 40 microg/m3, mean +/- standard deviation) for 4 h, during which there was intermittent exercise. Fifteen subjects were healthy, and 26 had allergy or mild asthma. The entire group responded nonsignificantly (p > .05) to pollution exposure (relative to clean air), as determined by spirometry, symptoms, and overall discomfort level during exercise. Subjects with allergy/asthma showed a positive association (p = .01) between symptoms and acid dose; in healthy subjects, that association was negative (p = .08). In these chamber-exposure studies, we noted less of an effect than was reported in previous epidemiologic studies of children exposed to ambient "acid summer haze."     

Kinetics of mild steel corrosion in aqueous formic acid solutions

Abstract

The kinetics of the corrosion of mild steel in formic acid solutions of different concentrations has been studied at 25, 35 and 45°C. The corrosion rate was evaluated by weight loss and electrochemical polarisation techniques. There is good agreement between the data obtained by the two techniques. The maximum corrosion rate was observed in close vicinity of 20% formic acid solution. The anodic polarisation curves show active corrosion behaviour of mild steel over the whole range of potential at each concentration and temperature. The shape of anodic and cathodic polarisation curves was found to be almost independent of the temperature and the concentration of formic acid. However, the curves bodily shift towards the lower or higher current density side with the change in the concentration of the electrolyte. With the increase in temperature, the shift of polarisation curve regularly occurs towards the higher current density side. The surface morphology of the specimens has been studied by scanning electron microscopy. The micrographs indicate uniform corrosion of mild steel in formic acid solution.

On a étudié la cinétique de corrosion de l’acier au carbone en solutions d’acide formique à différentes concentrations, à 25, 35 et 45°C. On a évalué la vitesse de corrosion par des techniques de perte de poids et de polarisation électrochimique. Il y a un bon accord entre les données obtenues par les deux techniques. On a observé la vitesse maximale de corrosion dans une solution de près de 20% d’acide formique. Les courbes de polarisation anodique montrent un comportement de corrosion active de l’acier au carbone pour la gamme complète de potentiel à chaque concentration et température. On a trouvé que la forme des courbes de polarisation anodique et cathodique était presque indépendante de la température et de la concentration de l’acide formique. Cependant, le c?ur des courbes se déplace du côté d’une densité de courant plus faible ou plus élevée avec un changement de concentration de l’électrolyte. Avec une élévation de la température, le déplacement de la courbe de polarisation se produit régulièrement du côté d’une densité de courant plus élevée. On a étudié la morphologie de la surface des échantillons au moyen du microscope électronique à balayage. Les micrographes indiquent une corrosion uniforme de l’acier au carbone dans une solution d’acide formique.     

Kinetics of the dissolution of cobalt, nickel, and iron oxides in sulfuric acid

The modeling of dissolution of cobalt, nickel, and iron oxides in sulfuric acid shows that the rate-determining step of the dissolution is the passage of oxide complexes formed on the surface of oxide particles to a solution. A system analysis of the dissolution curves (??-??) of the oxides is developed to calculate the kinetic parameters ( $n_{H^ + } $ ,E _a). Cobalt oxide Co₃O₄ dissolves in H₂SO₄ more rapidly than nickel and iron oxides (Ni₂O₃ and Fe₂O₃).     

Microscale investigations of the metal-dusting corrosion mechanism on mild steel

The internal and external products from metal-dusting corrosion of a mild steel specimen have been investigated, with the intention of further exploring the corrosion reaction mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been employed. A section of a steel tube, which had been subjected to heavily corrosive attack under controlled conditions, was studied. Electron-transparent TEM samples from this specimen were observed in the cross-sectional and plan-view orientations of the corrosion interface. Deposit on the corroded surface contained amorphous carbon, graphitic crystalline carbon, and decomposition products. Supersaturated cementite is an intermediate reaction product and was present at the surface of the exposed alloy. Surface cementite was seen to decompose locally into the graphite, where graphite basal planes were oriented perpendicular to the cementite surface. Iron was transported through the graphite, and the mild steel disintegrated by continuous formation and disintegration of the surface cementite. The observations are discussed with reference to the prevailing model mechanism for metal-dusting corrosion.     

Effect of methane on sulfur dioxide and sodium sulfate-lnduced corrosion of nickel-base alloys

The corrosion of nickel-base binary alloys, with up to 20 wt pct Cr or Al, by sulfur dioxide contained in a nitrogen gas stream, has been found to be considerably enhanced between 800 and 1000°C in the presence of low concentrations of gaseous methane. The magnitude of the effect, which is related to the ability of the alloy surface to catalyze the decomposition of the hydrocarbon to solid carbon, decreases with increasing Cr and Al content of the alloy. Ni-Al alloys containing less than 10 wt pct Al are more readily attacked by SO₂ alone than are the corresponding Ni-Cr alloys, although the deleterious effects of added methane are more marked in the Ni-Cr series. The extent of high temperature corrosion of these alloys by deposited sodium sulfate at 900 to 1000°C is also generally increased when small amounts of methane are introduced, although in this case the addition of Cr to the alloy confers greater corrosion resistance than does the addition of an equivalent concentration of Al. In the presence of either sodium sulfate or SO₂, the addition of methane to the ambient nitrogen atmosphere results in localized reducing conditions and increased sulfur potentials near the alloy surface.     

Comparative study on the corrosion behavior of low alloy steels in sulfuric acid solution

The corrosion behavior of a weathering steel SPA-C and two acid resistance steels( S-TEN1 and ND) in sulfuric acid solution was investigated by using potentiodynamic polarization and weight loss measurement techniques.Both potentiodynamic polarization and weight loss measurement tests indicated that corrosion resistance of these three alloy steels was as follows: ND ≈ S-TEN1 SPA-C.Surface analysis of the corroded samples conducted after the immersion test indicated that two layers were formed on the substrates,with the outer layer comprising Fe SO_4·H_2O and the inner layer mainly comprising iron oxides.The addition of Cu,Cr,and Sb refined the corrosion products and improved the adhesion ability between the rust layer and the substrate.     

Galvanic interaction between chalcopyrite and manganese dioxide in sulfuric acid medium

Dissolution of chalcopyrite and managanese dioxide minerals in the presence of each other in sulfuric acid medium was studied using compact disc electrodes of the minerals under various H₂SO₄ concentrations (0.05 to 0.5 M). [H⁺] had a positive effect on the reaction rate. Strong galvanic interaction was observed to take place between chalcopyrite and manganese dioxide, the galvanic interaction predominating over the individual dissolution (self-corrosion) rates. Evans diagrams constructed from polarization curves of the two minerals were helpful in interpreting the leaching data. The electrochemical nature of the dissolution reaction was analyzed through application of the Butler-Volmer equation and was confirmed from polarization measurements conducted with the respective mineral electrodes.     

Catalytic decomposition of hydrogen peroxide by ferric ion in dilute sulfuric acid solutions

Hydrogen peroxide decomposition in acidic solutions is catalyzed by the free ferric ion, Fe³⁺. The following rate law for this reaction is determined by the initial rate method in solutions similar to those used for acidicin situ uranium leaching: wherek = 4.3 × 10⁻³ s^°1 at 25 °C. From 25° to 50 °C, the activation energy is 85.6 kJ/mol. The decomposition of hydrogen peroxide proceeds by a particular redox reaction sequence that depends on the ratio of the concentrations of hydrogen peroxide to free ferric ion. The rate law determined here is consistent with the form derived from the redox sequence for the case where the ratio of hydrogen peroxide to free ferric ion concentration is greater than 1.0. The magnitude of the rate constant indicates that the decomposition of hydrogen peroxide may cause rapid loss of this oxidant in leaching solutions containing ferric ion. Formerly a Graduate Student with the Department of Geochemistry and Mineralogy, Pennsylvania State University,     

Combined exposures of human ciliated cells to different concentrations of sulfur dioxide and nitrogen dioxide

In the present study we investigated the influence of two common air pollutants, sulfur dioxide (SO2) and nitrogen dioxide (NO2) on ciliary beat frequency (CBF). Ciliated cells were obtained by nose brush from 12 healthy volunteers and placed on a polycarbonate membrane which was in contact with Ringer's electrolyte solution. This allowed the supply of the cells by capillarity in parallel to the reaction of the pollutants with the cell surfaces. In an exposure chamber the cells were exposed for 30 min. at 37 degrees C either to SO2 (2.5-12.5 ppm) or to NO2 (3.0-15.0 ppm), or to a mixture of NO2 (12.0 ppm) and SO2 (2.5 or 5.0 ppm). CBF was measured by video-interference-microscopy. With SO2 we observed a dose-dependent decrease in CBF with Ringer's solution. 2.5 ppm SO2 caused a 42.8% decrease and 12.5 ppm a decline of approximately 100% (8.10 +/- 0.24 Hz vs. 0.28 +/- 0.20 Hz). In parallel, we observed a decrease in the pH-value from 7.4 to 3.6. 30 min. NO2 exposure (3.0-15.0 ppm) induced a significant dose dependent increase in CBF from 8.4 +/- 0.34 Hz to 9.4 +/- 0.44 Hz. Exposure to a mixture of SO2 and NO2 with Ringer's solution revealed that SO2 exerts a stronger influence on CBF than NO2. Exposure to both pollutants resulted in the same as exposure to SO2 alone. Our findings demonstrate a strong correlation between SO2-modified pH values and CBF. Exposure to a combination of two pollutants revealed the dominant influence of SO2 on CBF while the augmented effect of exposure to NO2 alone might be due to the oxidative potential of this gas.     

模拟酸雨中钢筋腐蚀行为的研究

利用线性极化法和交流阻抗法对A3钢在模拟酸雨环境下的腐蚀行为进行初步研究,并针对不同酸度、不同离子浓度和不同浸泡时间下的腐蚀结果进行了对比。结果表明：酸度的增加提高了金属的腐蚀速率,SO4^2-和Cl^-在酸雨溶液中对金属阳极溶解起加速作用;随着浸泡时间的延长,金属表面的腐蚀层发生变化,金属的腐蚀速率相应经过了增→减→增的过程。     

Effects of organic and inorganic phosphate ions on the charge-transfer band of ferric myoglobin

(1) Splitting of the charge-transfer band positioned at 630 nm of metmyoglobin disappeared on lowering the pH from 7.5 to 4.5 in the presence of Pi and PPi at the temperature of liquid N2. (2) The observed apparent pK value of the disappearance of the splitting depended upon the species of phosphate ions. (3) In the case of Pi, the low-temperature absorption spectra suggested that at least two phosphate ions bound to one myoglobin molecule.     

Inhibition of the corrosion of steel by acid dihydrazides

The corrosion inhibitory properties of homologous series of acid dihydrazides were studied. Gasometry, potentiodynamic polarization and impedance measurements were recorded for mild steel specimens immersed in 1.0 M H₂SO₄ or a mixture of 1.0 M H₂SO₄ + 1.0 M Na₂SO₄ having the same ionic strength with a pH range from zero to 7. Effect of presence of different concentrations of oxalic, malonic, succinic or pimelic dihydrazide on the corrosion rate of steel in the above solutions were investigated. The results indicated that the protection efficiency of the acid dihydrazides increased with the increase of the number of the methylene groups in the acid dihydrazide molecule. The results are discussed on the basis of the change of each, of the electron density of the donating atoms, of the inhibitor molecules, and the orientation of the inhibitor at the metal surface with the molecular structure of the inhibitor.     

Prediction and measurement of corrosion inhibition of mild steel by imidazolines in brine solutions

Imidazolines have been used for many years as corrosion inhibitors in the oil and gas industry. However, the mechanism of corrosion inhibition, the inter-relationship between surfactant adsorption and corrosion inhibition, and the main characteristic factors determining surfactant adsorption in aqueous medium have been rarely reported. This article uses recently developed methodology and equations to describe the interrelationship between the surfactant adsorption and corrosion inhibition. The main factors, such as the surfactant concentration, functional group, hydrophobic chain length, environment, etc., affecting corrosion inhibition, are discussed as well. A reasonable prediction model is developed to predict corrosion inhibition based on this method, which can be applied to relevant industrial uses of corrosion inhibition.     

15CrMoR钢的不同组织在硫酸介质中的腐蚀特性

15CrMoR钢属于低合金珠光体耐热钢,具有良好的抗氧化性和力学性能以及良好的抗硫酸和氢腐蚀能力.通过研究测定15CrMoR钢材在不同的显微组织状态下在硫酸介质中的腐蚀速率,得知15CrMoR钢在马氏体组织状态下比在贝氏体加铁素体和铁素体加珠光体组织状态下在硫酸介质中抗腐蚀性更好,因而可将15CrMoR这种低合金珠光体耐热钢更好地用于工业生产.     

Effects of alloying on polarization and corrosion of Type 430 stainless steel

Abstract

Anodic and cathodic polarization measurements were carried out on Type 430 ferritic stainless steels in nitrogenated sulphuric acid, with and without 0.5 normal sodium chloride, to determine the effects of Mo, V, W, Ta, Si, Re, Pd, Ge and U additions. These measurements were supplemented by weight-loss corrosion tests of the alloys in solutions of sulphuric, hydrochloric and nitric acids, and in ferric chloride solution.

Résumé

Pour pouvoir déterminer les effets d'additions de Mo, V, W, Ta, Si, Re, Pd, Ge et U, des mesures de polarizations anodiques et cathodiques ont été faites sur des aciers inoxydables ferritiques de type 430 dans de l'acide sulfurique azoté, avec ou sans chlorure de sodium 0.5 normal. D'autres mesures supplémentaires ont été effectuées sur des alliages par des essais de perte de poids en corrosion, dans des solutions d'acide nitrique, sulfurique et chloridique et dans une solution de chlorure ferrique.     

New leaching agents for oxides. The reaction of metal oxides with the mixed non-aqeous systems: dimethyl sulphoxide-sulphur dioxide,dimethyl formamide-sulphur dioxide and acetonitrile-sulphur dioxide

The metal oxides MgO, V₂O₅, CrO₃, MnO₂, CoO, CuO, Cu₂O, and ZnO react with the mixed non-aqueous system dimethyl sulphoxide (DMSO)-sulphur dioxide to form metal disulphates as final products. Other oxides (SnO₂, PbO₂, La₂O₃, and Ag₂O) react with the mixed solvent, but it has not been possible to characterise the final products. The oxides TiO₂, Cr₂O₃, Fe₂O₃, Co₃O₄, NiO, MoO₃, and Al₂O₃ do not react with the mixed solvent. The same differentiating behaviour is shown by dimethyl formamide (DMF)-sulphur dioxide, but products of indeterminate composition are obtained. DMF-SO₂ reduces the oxides of copper to copper metal. The system acetonitrile-sulphur dioxide reacts only with the oxides of copper. Likely mechanisms for the reactions are discussed.