Some investigations into hydrogen sulphide adsorption by lead

The adsorption of very low concentrations of H₂ ³⁵S from air on to thin foil samples of lead was investigated using a continuous flow technique. The H²S uptake rate was constant at r.t. over the r.h. range 40–80% but increased markedly from 80–100% r.h. Autoradiography revealed a non-uniform adsorption in the low relative humidity range changing to a uniform uptake from 80–100% r.h. The possible nature of the adsorption sites, and the role of water vapour in the adsorption process is discussed.     

The atmospheric corrosion of copper by hydrogen sulphide in underground conditions

The atmospheric corrosion of copper by hydrogen sulphide has been followed during field tests using different sulphide concentrations, for 77 days, and during exposure to a well-defined synthetic atmosphere in a test chamber. The main components formed at the surface of the samples are copper oxides and sulphide. We show that exposure tests performed for short times in synthetic atmospheres cannot be extrapolated to long time exposure in real conditions, since three successive phases of film growth are observed. The mechanism of film growth is discussed, assuming that cationic diffusion through the cuprous oxides and sulphide is the rate-determining step.     

硫化锌精矿常压富氧直接浸出行为

借助工艺矿物学分析对常压富氧直接浸出条件下锌精矿中主要硫化物的浸出行为进行研究。结果表明,除黄铁矿外,其他硫化矿均会明显溶解。基于对浸出渣中单质硫与反应残余硫化物之间关系的分析,认为闪锌矿、黄铜矿、铜蓝、方铅矿的溶出可能遵循间接氧化方式,即硫化物首先酸溶,生成的H2S脱离矿物表面并迁移至溶液本体中进而氧化成单质硫。上述硫化矿的浸出过程可能受界面化学反应控制。对于磁黄铁矿的溶出,直接电化学氧化可能起主导作用,其浸出过程可能受产物层单质硫的扩散控制。     

Stress-induced failure of high-strength steels in environments containing hydrogen sulphide

Abstract

The pre-cracked cantilever beam test is a sensitive means of evaluating the relative susceptibilities of different steels to stress-Induced failure in H₂S-containing environments. This, test indicated that a 12Ni 5Cr.3Mo maragmg stee1 is considerably more resistant to stress-induced crackining than the low-alloy steels 0Ni 1Cr 2Mo and 2Ni 1Cr 3Mo. For low-alloy steels with no applied potential the failure appears to be caused predominantly by hydrogen embrittlement. Impressed anodic or cathodic potentials have no effect on the time to Failure of low-alloy steels where as a zone of immunity exists for maraging steel with Impressed potentials Within the approximate range ?0·6 to ?1·0 V. This suggests that the maraging steel is less susceptible to hydrogen embrittlement than the quenched and tempered low-alloy steels. Permeability studies indicate that stress-induced failure is related to the ability of the steel to transmit hydrogen and to the nature of hydrogen traps in the steel.     

Effect of hydrogen sulphide on The corrosion behaviour of titanium

In this paper the effect of hydrogen sulphide on the electrochemical and corrosion behaviour of VT 1–0 commercial titanium has been studied in acidic solutions containing polarization and analytical methods. Neither in the presence of sulphate nor chloride ions hydrogen sulphide affected electrochemical corrosion parameters in less acidic solutions but in 1 M sulphuric and hydrochloric acid where the increase of the corrosion rate can be attributed first of all to the decrease of the hydrogen overvoltage. The interpretation of the results is based on considerations including the role of titanium hydrides formed during the processes.     

多金属硫化精矿中铜、锌和铁的生物浸出(英文)

利用嗜温混合菌Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans和Leptospirillum ferrooxidans对低品位复杂Cu-Zn-Pb-Fe-Ag-Au硫化精矿在曝气生物浸出反应器中进行生物浸出。该菌种为从塞尔维亚Bor地下铜矿的酸性溶液中筛选出一种嗜热嗜酸菌。营养液为p H 1.6的9K营养液。87%的矿物粒度大于10μm,矿浆密度为8%(w/v)。在测试条件下,锌、铜和铁的浸出率分别达到89%、83%和68%。动力学分析表明,浸出过程与Spencer-Topley模型相符,受局部反应扩散控制。     

Brass sulphidation by hydrogen sulphide and sulphur vapour at low pressure: Morphological and kinetic aspects

The effect of alloy composition on the sulphidation of brass in H₂S/H₂ mixtures and sulphur vapour is shown. In all cases the corrosion rate is determined by cationic diffusion through one of the sulphide layers formed. The different morphologies observed at the end of sulphidation are explained on the basis of zinc content of the alloys.     

Some investigations on vibratory tapping process

This paper reports the results of an experimental program to study the influence of torsional vibrations on the tapping process. An attachment has been designed and developed to produce controlled torsional vibrations on the tap while tapping. Investigations have been carried out to study the influence of different process conditions, such as tap size, work material, vibration amplitude and frequency, etc., on the tapping torque and thrust during machining. Optimal process conditions which enhance the tap life are reported.     

Mild steel corrosion modelling in presence of hydrogen sulphide in aqueous solutions

Abstract

Corrosion of mild steel in aqueous solutions containing hydrogen sulphide was modelled under the condition that an iron sulphide film was formed on the steel surface. In the present model, the iron sulphide forms on the steel surface as a result of a solid state reaction between iron and hydrogen sulphide which has several steps. First a very thin film of iron sulphide nucleates on the steel surface. Then, due to further growth of the initial thin layer, a more porous layer of iron sulphide forms on the initial film. In the present model, it is assumed that mass transfer through the thin iron sulphide layer (i.e. adjacent to the steel substrate) controls the corrosion rate of steel in H₂S aqueous solutions, and as a result electrochemical reactions were not considered. The model was verified against the published experimental data and effects of some parameters such as hydrogen sulphide partial pressure were investigated. The results show that increase in partial pressure of hydrogen sulphide leads to an increase in the corrosion rate of mild steel at the primary stages of the reaction, but as a consequence of formation of iron sulphide scales on the steel surface, it drops with respect to time.     

Crystallographic, optical and electrical properties of low zinc content cadmium zinc sulphide composite thin films for photovoltaic applications

In this paper a screen-printing method has been employed for the deposition of low zinc content cadmium zinc sulphide (Cd_0.9Zn_0.1S) composite thin films on ultra clean glass substrate. Cadmium sulphide, zinc sulphide and cadmium chloride have been used as the basic source material. With these basic source materials, the optimum conditions for preparing good quality screen-printed films have been found. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal) structure with strong preferential orientation of grains along the (1 0 1) direction. SEM/EDAX analysis confirms the formation of ternary compound. The optical band gap (E_g) of the films has been studied by using reflection spectra in wavelength range 350-600 nm. The DC conductivity of the films has been measured in vacuum by a two probe technique.     

Surface analysis, hydrogen adsorption and electrochemical performance of alkali-reduce treated hydrogen storage alloy

The hydrogen storage alloy powders (M1Ni4.0Co0.6Al0.4, M1 = rich-La mischmetal) were treated in a hot 6 mol/L KOH 0.02 mol/L KBH4 solution, the surface compositions and chemical states of the treated and untreated alloys were analyzed by XPS and EDX, the hydrogen adsorption on the surface of these alloys was evaluated by thermal desorption spectroscopy (TDS), the effects of the surface treatment on the electrochemical performances of the alloy electrodes were investigated. The results show that the hydrogen adsorption is greatly strengthened by the surface modification, and hence leads to marked improvement in the electrocatalytic activity, the treated alloy exhibits higher exchange current density and lower apparent activation energy for the hydrogen electrode reaction than the untreated alloy.     

Electrochemical evidence of caffeine adsorption on zinc surface in ethanol

Several electrochemical methods were employed to confirm the ability of caffeine (1,3,7-trimethylxanthine) to adsorb on zinc surface in aerated ethanol solutions. The interaction between the organic compound and the electrode surface was dependent on the electrode potential. Adsorption on the electrode surface was confirmed by comparing the voltammograms, Tafel plots and EIS curves of a zinc electrode in the absence and presence of dissolved caffeine. The calculated standard free energy of adsorption confirms a spontaneous chemical adsorption step.     

Effect of immersion time on the hydrogen content and tensile properties of A350LF2 steel exposed to hydrogen sulphide environments

The effect of immersion time on the hydrogen content and tensile properties of A350LF2 steel exposed to hydrogen sulphide environments was investigated by immersion tests, hydrogen content measurements and tensile tests. The results show that both hydrogen content and relative tensile strength and plasticity loss increased first and then decreased with increasing immersion time. High mass transfer resistance of corrosion films can be responsible for that hydrogen content decreased after 240 h immersion. A probable mechanism is proposed to interpret the reason for hydrogen content result. The tensile property loss and embrittled region were closely associated with hydrogen content.     

Multianalytical in-situ investigations of the early stages of corrosion of copper, zinc and binary copper/zinc alloys

A new experimental infrared reflection absorption spectroscopy (IRRAS) set-up for in-situ investigation of corrosion phenomena occurring in the metal–atmosphere interface was developed. It was applied in combination with in-situ tapping-mode atomic force microscopy (TM-AFM) and phase detection imaging (PDI) to study the early stages of corrosion of pure copper and pure zinc as well as to determine the influence of increasing zinc contents in brass. Additionally, ex-situ secondary ion mass spectrometry (SIMS) investigations were carried out on the samples after exposure.The investigations were accomplished in synthetic air with 80% relative humidity (RH) and synthetic air with 80% RH and 250 ppb SO₂. The experiments showed that an increase of the zinc content in the brass alloy yields to an increase of the dimension of the corrosion features formed on the metal surface during weathering. Large features on top of smaller features were observed with TM-AFM on the surfaces exposed to SO₂-containing humidified air, which could be identified by IRRAS as metal sulphur compounds. Furthermore, an increased amount of physisorbed water on the metal surfaces was determined with IRRAS in dependence of the increasing zinc content in the brass samples.     

Relationship between chemical structure of imidazoline inhibitors and their effectiveness against hydrogen sulphide corrosion of steels

Abstract

Seven homologous imidazoline type inhibitors were synthesised, all being derivatives of cyclopentyl- and cyclohexylnaphthenic acids. The protective effectiveness of these compounds was investigated by applying the potential sweep method to the carbon steel St3S and austenitic steel 1H18N9T in a 2% solution of sodium chloride in contact with a hydrocarbon phase and saturated with hydrogen sulphide gas. It was found that the inhibitors investigated and their mixtures present high protective effectiveness at a concentration of 25 ppm, reaching values of 99% for carbon steel and 80% for austenitic steel at 40°C. This protective effectiveness was improved by increasing the length of the substituent chain. Consequently, the least effective compounds were those with the shortest chain substituted at the imidazoline ring. Inhibitors under study were chemisorbed on the electrode surface of the steel and this chemisorption process obeyed the Frumkin adsorption isotherm. Values of the Gibbs free energy of adsorption of inhibitors were determined, and also the equilibrium constants of adsorption and constants of attraction.     

Experimental investigations into ECSD process using various tool kinematics

Machining of electrically non-conducting materials, i.e. ceramics, composites, etc., is still a major problem. Electrochemical spark machining (ECSM) is found to be a potential process for machining these materials. However, ECSM has its own inherent problems too. So far, only non-rotational tools with gravity feed have been used 'by previous researchers, but the performance of such tools has been reported to be poor. In the present work, electrochemical spark drilling (ECSD) experiments have been conducted using various tool kinematics with a view to enhancing the process capabilities. Use of a rotational tool with controlled feed has been found to improve the process performance. Significant improvement in the “limiting value” of the machined depth during ECSD has been observed while using a tool with orbital motion. Geometrical parameters and surface integrity of the machined specimens have also been studied and presented.     

改性橘子皮对铜、铅和锌的吸附特性及吸附机制(英文)

将橘子皮经氢氧化钠和氯化钙处理,得到改性橘子皮生物吸附剂(SCOP)。用红外光谱(IR)、扫描电镜(SEM)和N2-吸附法对其形貌和特性进行表征;通过静态吸附实验,研究pH、起始金属离子浓度等因素对改性橘子皮SCOP吸附Cu2+、Pb2+和Zn2+的影响。等温吸附结果表明,SCOP对Cu2+、Pb2+和Zn2+的吸附符合Langmuir方程,根据Langmuir方程计算的SCOP对Cu2+、Pb2+和Zn2+的饱和吸附量分别为70.73,209.8和56.18mg/g。根据静态吸附实验结果,用动态柱吸附实现了水溶液中Pb2+和Zn2+的分离。吸附过程中离子交换发生了重要作用,重金属离子与吸附剂中的Ca2+离子发生离子交换。     

The effect of hydrogen sulphide on ammonium bisulphite when used as an oxygen scavenger in aqueous solutions

The effectiveness of ammonium bisulphite (ABS) as oxygen scavenger and the behaviour of H₂S in brine/ABS solutions are examined. Deionised water, 1 wt.% NaCl and 3.5 wt.% NaCl with different ABS concentrations are bubbled with H₂S gas, while the dissolved oxygen, sulphide, E_H and pH are measured. With the exception of natural seawater, ABS concentration much greater than 100 ppmw (parts per million by weight) is needed to completely scavenge dissolved oxygen in all the solutions considered. The reaction between ABS and H₂S leads to increase in sulphide. The implications of the results for environment assisted cracking of oil and gas production tubings are discussed.     

Experimental investigations into forces during magnetorheological fluid based finishing process

Magnetorheological fluid based finishing process is a fine finishing process that has been applied to a large variety of brittle materials, ranging from optical glasses to hard crystals. Under the influence of a magnetic field, the carbonyl iron particles (CIPs) and non-magnetic polishing abrasive particles remove material from the surface being polished. Knowledge of forces acting is important to understand the mechanism of material removal. A dynamometer and virtual instrumentation are used to on-line record the normal force and tangential force acting on the workpiece through the magnetorheological (MR) fluid. A full factorial design of experiments is used to plan the experiments and ANOVA to correlate the forces and process parameters. The selected process parameters (volume concentration of CIPs and abrasives, working gap, and wheel rotation) are varied over a range to measure forces during experimentation. The maximum contribution is made by a working gap on the forces developed on the workpiece surface followed by CIP concentration while the least contribution is noticed by the wheel speed.