Aluminium-Thiourea Mixtures as Corrosion Inhibitors for Mild Steel in 1·0% NaCl

Abstract

The inhibitive properties of mixtures containing aluminium salts and thiourea (so called aluminium-thiourea inhibitors) have already been investigated in relation to their inhibitive properties towards mild steel corrosion in distilled water and in water of high specific salinity (1·0% Na₂SO₄. This paper reports laboratory test data obtained during further investigations of aluminium-thiourea inhibitors in another corrosive medium, 1·0% NaCl at 20°c and under stagnant conditions. It was found that the corrosion rate of mild steel in sodium chloride solutions can be decreased markedly (by ~ 80%) if aluminium ions are used in the form of a mixture of sulphates and oxychlorides and in conjunction with thiourea, cationic surfactants and reducing agents (SnCl₂). Any change in the composition of the aluminium salts in the mixture, keeping a constant Al³⁺ concentration (for instance a substitution of sulphates/oxychlorides by sulphates/chlorides or chlorides/oxychlorides) reduces the inhibitive efficiency of the formulations tested. The author fails to find a satisfactory explanation of the very specific inhibitive behaviour of aluminium-thiourea mixtures in 1·0% NaCl.     

Impurity distribution in distillate of terbium metal during vacuum distillation purification

The distribution rules of impurities in distilled terbium metal were investigated by vacuum distillation purification experiment and theoretical analysis. It is found that Ti impurity in distilled terbium is 220 mg/kg in the initial stage of the distillation purification, increases slowly in the middle stage, and increases rapidly in the last stage, reaching 2260 mg/kg, and the modified separation coefficient of Ti is 1/19.02. The diffusion of the impurity Ti in liquid metal can reach a quasi-equilibrium state in the initial stage of distillation purification and the calculated results agree well with experimental results; the distribution profile of impurity Cu is opposite to Ti, being 380 mg/kg in the initial stage, decreasing linearly to 290 mg/kg in the last stage, and the modified separation coefficient is 17.99, and the theoretical calculated results are inconsistent with the experimental result.     

Solubility of anthracene in the seven-component liquid system 1-propanol+2-propanol+1-butanol+2-butanol+cyclohexane+heptane+2,2,4-trimethylpentane at 298.15 K

The solubility of anthracene in the seven-component liquid system 1-propanol+2-propanol+1-butanol+2-butanol+cyclohexane+heptane+2,2,4-trimethylpentane at 298.15 K was calculated and compared to measured values. The agreement was excellent, better than 1% at all compositions studied. The eight component system requires seven binary interaction parameters anthracene+solvent, and 21 binary interaction parameters between the solvents. All the solvent+solvent interaction parameters are positive, thus increasing the solubility in the large system. The solubility is determined 80% by the seven anthracene+solvent interactions, and 20% by the 21 solvent+solvent interaction parameters.     

Vacuum distillation refining of metallurgical grade silicon （Ⅰ） ——-Thermodynamics on removal of phosphorus from metallurgical grade silicon

The removal of impurity phosphorus from metallurgical grade silicon is one of the major problems on purification of metallurgical grade silicon for solar grade silicon preparation. The thermodynamics on vacuum refining process of the metallurgical grade silicon was studied via separation coefficient of impurity phosphorus in the metallurgical grade silicon and vapor-liquid equilibrium composition diagram of Si-P binary alloy at different temperatures. The behaviors of impurity phosphorus in the vacuum distillation process were examined. The results show that the vacuum distillation should be taken to obtain silicon with less than 10^-7 P, and the impurity phosphorus is volatilized easily by vacuum distillation in thermodynamics. Phosphorus is distilled from the molten silicon and concentrated in vapor phase.     

Stress corrosion cracking of a low carbon ultra-high strength steel in humid environments

Discontinuous crack growth was observed in the stress corrosion cracking of SD 19 steel in aerated distilled water and several humid environments at 295K. Whereas additions of nitrogen or argon did not stop crack propagation in water vapour environments, crack growth in water vapour/oxygen mixtures depended on the water vapour and oxygen partial pressures, and the stress intensity to which the cracks were loaded. This behaviour is interpreted by a model which relates the cracking characteristics to the environmental conditions prevailing inside the crack. The role of hydrogen in the propagation of localized regions of crack front is also discussed.     

Mixing rules in cubic equations of state applied to refrigerant mixtures

Two equations of state and four mixing rules are applied to the calculation of the bubble point pressure of several refrigerant mixtures. An equation of state proposed by one of the authors, known as the PTV equation, and a modified Soave-Redlich-Kwong equation of state, known as Predictive Soave-Redlich-Kwong (PSRK), have been used. The mixing rules considered in the study include the classic van der Waals mixing rule with one and with two parameters for the PTV equation, and a model that includes the excess Gibbs free energy for the PSRK equation. Eighteen data sets from the literature for five binary refrigerant mixtures containing R134A (CH₂FCF₃) were considered for analysis. A special program was implemented for these calculations in which the fundamental equation for phase equilibria, the equality of fugacity of each component in all phases, was applied. Correlations for the interaction parameters as functions of the acentric factor are proposed. We present conclusions about usefulness of the different models and a recommendation for the best equation of state + mixing rule combination for correlating vapor-liquid equilibrium in the refrigerant mixtures studied.     

Mixing rules in cubic equations of state applied to refrigerant mixtures

Two equations of state and four mixing rules are applied to the calculation of the bubble point pressure of several refrigerant mixtures. An equation of state proposed by one of the authors, known as the PTV equation, and a modified Soave-Redlich-Kwong equation of state, known as Predictive Soave-Redlich-Kwong (PSRK), have been used. The mixing rules considered in the study include the classic van der Waals mixing rule with one and with two parameters for the PTV equation, and a model that includes the excess Gibbs free energy for the PSRK equation. Eighteen data sets from the literature for five binary refrigerant mixtures containing R134A (CH₂FCF₃) were considered for analysis. A special program was implemented for these calculations in which the fundamental equation for phase equilibria, the equality of fugacity of each component in all phases, was applied. Correlations for the interaction parameters as functions of the acentric factor are proposed. We present conclusions about usefulness of the different models and a recommendation for the best equation of state + mixing rule combination for correlating vapor-liquid equilibrium in the refrigerant mixtures studied.     

Purification of Alkaline Earth Metals

The study demonstrates that alkaline earth metals can be sublimed or distilled to give metal of very high purity. The metallic impurities are the most easily separated although the other alkaline earth metals require a fractional sublimation. The interstitial elements 0, N and C can be reduced to very low levels if entrainment is prevented by subliming or distilling under a small torr pressure of an inert gas. Hydrogen transfers to the product in either distillation or sublimation and must be removed by vacuum traction from a Ta capsule. Alkaline earth metal purification by sublimation and distillation started in 1960 to supply pure Ca, Ba and Sr for phase equilibria studies and was expanded to provide high purity Ca for metallothermic preparation of very pure rare earth metals as described by Spedding et al.1 The objectives were to produce metals of the lowest possible interstitial solute concentration with a high yield and in a convenient form for handling in inert atmosphere gloveboxes. Enhance d process reliability with regard to product purity also eliminates expensive and time-consuming chemical analyses on each batch of metal.     

Identification of the sugars content in the production of champagne by the electrochemical impedance spectroscopy method

The peculiarities of the stepwise preparation of cryoconcentrates from grape must (test) and liqueurs from sugar (control) used in sparkling wine production via electrochemical impedance spectroscopy is considered. The application of a measuring system with platinum electrodes and models considering the heterogeneity of the electrode’s surface in electrochemical reactions gives the possibility to determine certain peculiarities of the electrochemical systems under study. A unified calculation model taking into account the consideration of the electrode surface’s heterogeneity in the electrode redox reaction is proposed for liqueur samples, while a model with inductive resistance for cryoconcentrate samples. The use of the models proposed allows one to find the quantitative correlation between the electrode’s resistance and the sugar concentration in liqueur samples. A symbate correlation between the sugar concentration and titratable acids and the impedance of the constant phase and the inductance element is found in cryoconcentrate samples, which allows one to assume the presence of the reversible deprotonation of the grape must sugars.     

Modeling of diffusional phase transformation in multi-component systems with stoichiometric phases

In many multi-component systems, phases can be considered stoichiometric. If two phases not stably coexisting are brought into contact, multiple new phases may nucleate at the interface and develop into a sequence of layers with different phase compositions, which grow between the original phases. Inert markers at the original contact may show “splitting” of the marker (Kirkendall) plane, called polyfurcation. Nearly exclusively binary systems have been studied theoretically or experimentally. A thermodynamic model for the kinetics of diffusional phase transformation in multi-component systems and motion of the polyfurcated Kirkendall plane is derived by the thermodynamic extremal principle. The degrees of freedom of the system are discussed rigorously. The model is demonstrated on simulations of kinetics in binary three-phase and ternary four-phase systems.     

HIPIMS制备Cr-B涂层及摩擦学性能

为研究Cr-B涂层在多测试环境(干摩擦、蒸馏水和海水环境)下摩擦磨损行为,采用高功率脉冲磁控溅射沉积技术制备Cr-B涂层,分析涂层成分、结构、微观形貌和力学性能,重点考察涂层在不同环境下的摩擦磨损性能。结果表明:制备的Cr-B涂层,B/Cr的原子比为1.8,结构主要由CrB2和自由Cr相组成,硬度和弹性模量分别为(26.9±1.0)GPa和(306.7±6.0)GPa。摩擦测试结果显示:涂层在干摩擦时具有较高的摩擦因数为0.75,发生严重磨损失效,归因于摩擦过程中涂层剥落而导致严重的磨粒磨损;与干摩擦相比,涂层在蒸馏水和海水环境中的摩擦因数均显著降低,分别为0.26和0.22,这主要由于蒸馏水和海水的边界润滑作用所导致,在蒸馏水中摩擦的磨损机制为磨粒磨损,而在海水中的磨损机制为磨粒磨损和腐蚀磨损的协同作用。     

Metal Protection with Volatile Corrosion Inhibitors under Heat-Transfer Conditions

The influence of heat transfer on metal protection with volatile corrosion inhibitors (VCIs), the mechanisms of corrosion initiation, and methods for its prevention were analyzed. It was found that effective VCIs can be prepared from substances that form azeotropic mixtures with water. The theoretical conclusions are illustrated by corrosion tests carried out under intense moisture condensation.     

Galvanic corrosion of A1 alloys — II. Effect of solution composition

Galvanic corrosion of the A1 alloys 1100, 2024, 2219, 6061 and 7075 coupled to Cu, stainless steel 304L, Ti-6A1-4V, 4130 steel or zinc has been studied in 3·5% MaCl, tapwater and distilled water using electrochemical and weight loss data. In 3·5% NaCl the galvanic effect decreases in the order Cu > 4130 steel > SS304L > Ti-6A1-4V for A1 alloys coupled to one of these metals, while in tapwater and distilled water the ranking is Cu > SS304L ～ Ti-6A1-4V > 4130 steel. Zinc, although being the anode in all galvanic couples, can sometimes accelerate corrosion rates of A1 alloys. Dissolution rates of A1 alloys coupled to a given dissimilar material are higher in 3·5% NaCl than in tapwater and distilled water where they are found to be comparable. In assessing galvanic corrosion behaviour of a given A1 alloy as a function of environment, one has to consider the effect of the dissimilar metal. The dissolution rate of A1 6061 is, for example, higher in tapwater with Cu as cathode than in 3·5% NaCl with SS304L or Ti-6A1-4V as cathode.     

Rapid solvent extraction of gold(III) with high molecular weight amine from organic acid solution

A novel solvent extraction separation method has been developed for the determination of gold in real samples. It involves selective and quantitative extraction of gold by N-n-octylaniline, a high molecular weight amine (HMWA), in xylene from aqueous sodium malonate medium at pH 1.0. The effects of concentration of malonate, extractant, metal ion, and pH and of various diluents, stripping agents and other substances on the quantitative extraction of gold have been assessed. The applicability of the method to binary mixtures, synthetic mixtures, alloys and pharmaceutical samples is discussed.     

STATISTICAL THEORY OF MOLTEN SALT SOLUTIONS Ⅰ. ENERGY OF MIXING OF BINARY SYSTEMS

本文根据熔盐的径向分布函数理論,对于含一价离子的二元熔盐溶液,提出了三度空間的熔盐溶液統計模型。根据这一模型导出了計算二元熔盐系混合热、混合过剩自由能和某些二元相图液相线的公式,并利用这些公式对各种碱金属硝酸盐和卤化物的二元溶液作了計算,計算結果与实測值颇为符合。     

Ti-6Al-4V和Monel K500合金在海水环境中与316不锈钢对磨时的腐蚀磨损性能(英文)

研究Ti-6Al-4V和Monel K500合金在海水和纯水环境下的腐蚀磨损性能,对偶材料为316不锈钢,实验装置为环-块摩擦磨损试验机。研究结果表明,Ti-6Al-4V和Monel K500合金在海水中的摩擦因数明显小于在纯水中的摩擦因数,在海水中的磨损量明显大于纯水中的磨损量,这主要是由于摩擦作用破坏了金属表面的钝化膜,增加了摩蚀速度。磨损和腐蚀产生交互作用,交互作用量随着腐蚀速度的加快而增加。当和Monel K500配副时,316不锈钢的磨损严重,而和Ti-6Al-4V配副时磨损相对较小。     

Inhibition Effect of Binary Mixtures of Metal Salts on Aluminum Corrosion in Hydrochloric Electrolytes

The protection effects of tin, zinc, nickel, iron, and copper chlorides and their binary mixtures with cadmium chloride or thallium nitrate were compared, their effective concentrations being equal. In some cases, the mixtures proved to be better inhibitors than their constituents. Different approaches to the estimation of the mutual effects of the salts in their binary mixtures are discussed.     

含镉酸洗废液的治理研究

通过对某厂贵金属车间在生产过程中产生的含镉酸洗废液,进行治理试验研究,得出了通过蒸馏、电解的方法,可以实现含镉酸洗废液的回收利用,达到了闭路循环的目的。同时,对蒸馏液的回用以及电解电流、电解液浓度、酸度对电解的影响,进行了讨论,确定了工艺过程的最佳操作参数。     

Molecular models for the vapor-liquid equilibrium of simple binary mixtures

Simple analytical expressions are proposed for the calculation of the equilibrium pressure, as well as (for a given temperature and pressure) the mole fractions of both liquid and vapor phases at the vapor-liquid equilibrium of binary mixtures. They are based on a recently proposed molecular model for the vapor pressure of pure nonpolar fluids, which, for a given temperature, only requires as input the values of the two Lennard-Jones (LJ) molecular parameters and the acentric factor, which are parameters related to the molecular shape of each substance and whose values are readily available. The model for the equilibrium pressure of a binary mixture (which also permits one to obtain the liquid phase mole fraction) is similar to that derived from Raoult’s law, where a properly modified Lorentz-Berthelot mixing rule is used, the interaction parameters being given as simple functions of the temperature and composition with eight appropriate constants for each binary mixture. A different model is needed to calculate the vapor mole fraction in which five appropriate constants are needed for each mixture. Here, we show how the models reproduce accurately and straightforwardly the vapor liquid equilibrium properties (pressure, liquid mole fraction, and vapor mole fraction) of eight binary systems over a broad temperature range, including some data at or near the critical locus.     

Molecular models for the vapor-liquid equilibrium of simple binary mixtures

Simple analytical expressions are proposed for the calculation of the equilibrium pressure, as well as (for a given temperature and pressure) the mole fractions of both liquid and vapor phases at the vapor-liquid equilibrium of binary mixtures. They are based on a recently proposed molecular model for the vapor pressure of pure nonpolar fluids, which, for a given temperature, only requires as input the values of the two Lennard-Jones (LJ) molecular parameters and the acentric factor, which are parameters related to the molecular shape of each substance and whose values are readily available. The model for the equilibrium pressure of a binary mixture (which also permits one to obtain the liquid phase mole fraction) is similar to that derived from Raoult’s law, where a properly modified Lorentz-Berthelot mixing rule is used, the interaction parameters being given as simple functions of the temperature and composition with eight appropriate constants for each binary mixture. A different model is needed to calculate the vapor mole fraction in which five appropriate constants are needed for each mixture. Here, we show how the models reproduce accurately and straightforwardly the vapor liquid equilibrium properties (pressure, liquid mole fraction, and vapor mole fraction) of eight binary systems over a broad temperature range, including some data at or near the critical locus.