Effect of molybdate ions as corrosion inhibitors of iron in neutral aqueous solutions

Abstract

The effect of molybdate ions on the corrosion of Fe in neutral solutions was investigated by electrochemical measurements (dc polarisation and impedance spectroscopy) together with gravimetric determinations. Studies were conducted in solutions containing sodium hydrogen/sodium sulphate salts with molybdate concentrations ranging between 10^?4 and 10^?2M at pH 8 and 9. Mass loss measurements indicated that about 10^?3M of molybdate was necessary in order to inhibit completely the corrosion of Fe at room temperature. The potentiodynamic polarisation and electrochemical impedance studies gave indications about the mechanism of action of the MoO^2?₄ ion. They also showed that the inhibiting effect of the oxyanion is increased in the presence of dissolved oxygen. Spontaneous passivation of the corroding Fe electrode could happen only in the presence of dissolved oxygen at concentrations greater than 10^?4M. However, passivity was also obtained under potentiodynamic polarisation conditions in deaerated solutions. The effect of the oxygen was attributed to displacement of the corrosion potential into the region of selfpassivation of the steel. Finally, the results indicated that the corrosion inhibition of Fe in neutral solutions by molybdate ions was largely insensitive to pH over the range from 8 to 9.     

2—HYGRAL CHANGES IN CURVATURE AND LENGTH IN SET KERATINS

The set developed in various wools and hairs when strained in boiling water or in monoethanolamine sulphite (MEAS) has been measured, together with the longitudinal swelling of set fibres on wetting. The changes in curvature of merino fibres on wetting are enhanced by setting in boiling water or in cold MEAS but diminished by setting in boiling 1% MEAS. The interpretation of these changes of curvature in terms of ortho–para differences throws into question the supposition that there is a specific para-type keratin (exemplified by human hair) and a specific ortho-type keratin (kid mohair). Some technological treatments diminish the hygral changes in curvature.     

31—THE HANDLE AND BENDING BEHAVIOUR OF FABRIC LAMINATES

Certain aspects of the handle of fabric laminates are related to properties of the component fabrics. Particular attention is paid to a theoretical prediction of the bending stiffness of a laminate from the bending and tensile properties of its components. This theoretical stiffness is a minimum value; if, in practice, the observed stiffness is much greater than this, it may generally be assumed that excess of adhesive or of melted foam is the cause. The paper also reports work on other features of the bending behaviour, such as the degree of recovery from bending, and on the shearing behaviour. The work is concluded by a brief study of some faulty laminates.     

Corrosion of porous iron electrodes containing metal additives in alkaline batteries

Abstract

Major problems currently associated with alkaline porous iron electrodes include the high rate of selfdischarge and the low utilisation efficiency of the active iron. The corrosion rates of porous iron electrodes electrodeposited with lead, mercury, silver, copper, or sulphur were analysed by the open circuit potential decay, cathodic potentiostatic polarisation, and gasometric methods. It was found that incorporation of elemental sulphur and copper produced the lowest corrosion rates.     

5—THE EFFECTS OF SOME PRE-CARDING CONDITIONS ON WOOL-COMBING

Combing performance, as assessed by the percentage of noil and the fibre length and nep count of the top, is better for alkaline than for neutral wool, and worse for wool stored in bales before being carded. These results are at variance with some previously reported by other workers.     

谐振接地系统单相接地故障DK法选线及其应用

谐振接地系统单相接地后 ,采用DK选线法的控制装置延时投切消弧线圈的并联电阻 ,利用微机采样并计算出系统和线路系数 ,准确地判明故障线路 ,可与继电保护配合快速切除永久性接地故障。电网应用和现场测试表明 ,DK法克服了以往微机小电流接地选线装置和其它选线法选线准确率不高的问题 ,提高了城市中压配电网络的供电可靠性、安全性和经济性     

Stress corrosion cracking of oil and gas pipelines in near neutral pH environment: review of recent research

Abstract

Since the discovery of transgranular stress corrosion cracking (SCC) on a Canadian gas transmission line in 1985, much research has been conducted in the past 20 years. Findings of the effects of operating conditions, metallurgical and the environmental factors have been useful in preventing and mitigating failures. Several overviews of this problem can be found in the literature and the purpose of this update is to review the research results produced since the turn of the century. The recent report of SCC under static stressing conditions confirms that the cracking is indeed a true SCC process, although the rate of which is low without dynamic loading. In contrast to the high pH pipeline stress corrosion cracking in the carbonate–bicarbonate solution, this forms of cracking in dilute near neutral environment takes much longer time to initiate. Once initiated, the crack growth rate is highly sensitive to the loading rate of the applied mechanical force.