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Article

M. Mobin and S.K. Hasan

The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr2O3 and Al2O3 with Na2SO4 in flowing SO2 (g) at 1,100 and 1,200 K.

Abstract

Purpose

The purpose of this paper is to present the results of studies on the reaction of metal oxides such as Cr2O3 and Al2O3 with Na2SO4 in flowing SO2 (g) at 1,100 and 1,200 K.

Design/methodology/approach

The oxides chosen for the studies were initial scaling products during the oxidation of industrial alloys and invariably are involved in hot‐corrosion reactions in the presence of molten salts. The thermo‐gravimetric studies for the system were carried out as a function of Na2SO4 in the mixture. The different constituents in the reaction products were identified by XRD analysis and morphologies of the reaction products were discussed on the basis of optical metallography and scanning electron microscopic studies. The pH and conductivity of the aqueous solutions of reaction products were measured and an attempt made to functionalize these parameters with Na2SO4 concentration in the mixture. Quantitative estimation of the soluble metal was carried out using an atomic absorption spectrophotometer. The formation of products was investigated by thermodynamic computation of free energies of the reactions and the study of relevant phase stability diagrams.

Findings

Looking at the complex nature of the reactions, it is difficult to generalize the conductance studies, as many complex species are liable to hydrolyze in the aqueous solution. However, the break in few curves at certain mole fraction of Na2SO4 indicates the presence of soluble complex species.

Originality/value

The paper provides information regarding the reaction between a pertinent oxide and Na2SO4 and proper identification of reaction products, useful for understanding the occurrence and importance of fluxing reactions and in the interpretation of hot corrosion mechanism and the development of new protective materials.

Details

Anti-Corrosion Methods and Materials, vol. 55 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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Article

Anh Thi Le and Swee-Yong Pung

This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB).

Abstract

Purpose

This paper aims to investigate the reusability of metal/metal oxide-coupled ZnO nanorods (ZnO NRs) to degrade rhodamine B (RhB).

Design/methodology/approach

ZnO NRs particles were synthesized by precipitation method and used to remove various types of metal ions such as Cu2+, Ag+, Mn2+, Ni2+, Pb2+, Cd2+ and Cr2+ ions under UV illumination. The metal/metal oxide-coupled ZnO NRs were characterized by scanning electron microscope, X-ray diffraction and UV-Vis diffuse reflectance. The photodegradation of RhB dye by these metal/metal oxide-coupled ZnO NRs under UV exposure was assessed.

Findings

The metal/metal oxide-coupled ZnO NRs were successfully reused to remove RhB dye in which more than >90% of RhB dye was degraded under UV exposure. Furthermore, the coupling of Ag, CuO, MnO2, Cd and Ni particles onto the surface of ZnO NRs even enhanced the degradation of dye. The dominant reactive species involved in the degradation of RhB dye were OH- and O2-free radicals.

Research limitations/implications

The coupling of metal/metal oxide onto the surface of ZnO NRs after metal ions removal could affect the photocatalytic performance of ZnO NRs in the degradation of organic pollutants in subsequent stage.

Practical implications

A good reusability performance of metal/metal oxide-coupled ZnO NRs make ZnO NRs become a desirable photocatalyst material for the treatment of wastewater, which consists of both heavy metal ions and organic dyes.

Originality/value

Metal/metal oxide coupling onto the surface of ZnO NRs particles improved subsequent UV-assisted photocatalytic degradation of RhB dye.

Details

Pigment & Resin Technology, vol. 50 no. 1
Type: Research Article
ISSN: 0369-9420

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Article

Zhiping Zhu, Hui Zhang, Linlin Jing, Shuhua Xiong and Zhenghui Tan

The purpose of this paper is to research the morphologies of the oxide films formed on the internal surfaces of water wall tubes in a 600 MW furnace at 300° while using…

Abstract

Purpose

The purpose of this paper is to research the morphologies of the oxide films formed on the internal surfaces of water wall tubes in a 600 MW furnace at 300° while using CPT, CT, AVT(R) and AVT(O) water chemistry. In these water chemistry conditions, a layer of oxide film spontaneously forms in the furnace wall which could prevent corrosions in boiler water directly contact with the inner tube and reduce the probability of tube perforation.

Design/methodology/approach

The different morphologies, specific functions and distribution in the oxide film were identified by electrochemical workstation, XRD, SEM and EDAX.

Findings

It is concluded that metal surface was rugged and had deep corrosion in CPT. Ions penetrated into the oxides of large particles with gaps and intergranular corrosion occurred in CT conditions. In AVT(R), the oxide film uniformly covered on the metal surface played a protective role, but could be easily washed away by solution. The oxide film formed in AVT(O) was similar to AVT(R), but the difference is that large solid particles of Fe2O3 cover the outermost oxide film, which prevents the oxide film from being taken away by the flowing solution. In consequence, the degree of corrosion sustained by the tube walls is lowest in the case of AVT(O).

Originality/value

The results can provide reference for reducing the high temperature corrosion of metal in the actual operation.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

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Article

Lun‐Chen Hsu, Thermpon Ativanichayaphong, Hung Cao, Jeongsik Sin, Mason Graff, Harry E. Stephanou and J.‐C. Chiao

Selection of a gas sensor requires consideration of environmental effects that can significantly affect performance and cause false alarms. Metaloxide sensors have high…

Abstract

Purpose

Selection of a gas sensor requires consideration of environmental effects that can significantly affect performance and cause false alarms. Metaloxide sensors have high sensitivity due to the specific interactions of gas molecules with thin metaloxide films, however, the films can also be sensitive to variations in temperature and humidity and some oxidizing and deoxidizing gases. The purpose of this paper is to evaluate the environmental effect on metaloxide nitrogen dioxide (NO2) sensors quantitatively.

Design/methodology/approach

Three commercial metaloxide NO2 sensors and one electrochemical sensor were tested simultaneously under controlled gas concentrations and various environmental conditions. For this test, a customized sensor testing setup was prepared including a gas mixer, heating module, gas chamber, electronics, and data acquisition units.

Findings

Based on the test results for NO2 gas concentrations ranging from 0 to 10 ppm, the metaloxide sensors showed significant signal variations at elevated temperatures and humidity. The results provide overall sensor performance. Linearity, repeatability, selectivity and sensitivity of the metaloxide sensors were measured and compared to an electrochemical sensor.

Originality/value

A systematic evaluation to characterize metaloxide NO2 sensors is presented, and their comparison regarding sensitivity, selectivity, linearity, and dependence on humidity and temperature is reported. The result provides sensor performance data and guideline for sensor evaluation.

Details

Sensor Review, vol. 27 no. 2
Type: Research Article
ISSN: 0260-2288

Keywords

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Article

Studere Corrosion has been described as a transformation process in which a metal passes from its elementary form to a combined condition. It includes wet and dry…

Abstract

Studere Corrosion has been described as a transformation process in which a metal passes from its elementary form to a combined condition. It includes wet and dry corrosion; the former requires an aqueous environment and the latter is oxidation. Deterioration of the metal due to physical causes is not called corrosion, but is known as erosion, galling, wear, etc, depending upon the material and the conditions. Corrosion is the result of the metal chemical or an electrochemical reaction with its environment. Sometimes the chemical reaction is accompanied by physical deterioration, as in fretting corrosion. It should be noted here that the term corrosion is only applied to metals; non‐metals rot, crack or erode. Also it should be appreciated that only ferrous metals can ‘rust’, i.e. form hydrous ferric oxides.

Details

Anti-Corrosion Methods and Materials, vol. 19 no. 8
Type: Research Article
ISSN: 0003-5599

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Article

P.L. Hurricks

The first part of this paper appeared in our November/December issue and dealt with fretting wear behaviour of mild steel from room temperature to 600°C in air. The…

Abstract

The first part of this paper appeared in our November/December issue and dealt with fretting wear behaviour of mild steel from room temperature to 600°C in air. The general mechanism for fretting is discussed at all temperatures where normal oxidative processes become involved. The nature of fretting wear is also covered and the effects of temperature are described. In this part of the paper, the discussion is continued to include triboxidation, delamination theory, atmospheric environment, transition temperatures, activitation energy and other factors affecting the influence of temperature on fretting.

Details

Industrial Lubrication and Tribology, vol. 28 no. 1
Type: Research Article
ISSN: 0036-8792

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Abstract

Purpose

This paper aims to analyse the surface evolution of pure recycled titanium subjected to isothermal and cyclic oxidation conditions using dry air as oxidant gas. It is important to mention that the cyclic oxidation behaviour of pure titanium is a process that has been barely studied.

Design/methodology/approach

An isothermal and cyclic oxidation reactor was built for these purposes. This installation allows the oxidation of material under the action of any atmosphere and for temperatures up to 1,200°C. For this study, the oxidation behaviour of the material was studied at 850°C and 950°C.

Findings

Oxide growth under isothermal oxidation conditions in air follows a parabolic behaviour with an activation energy of 118 kJ/mol, and the oxide phase formed on the surface of the metal was rutile. The cyclic oxidation of the material indicates that oxide is spalled from the surface following linear behaviours; this phenomenon is controlled by the thermal stresses experienced by the samples during heating and cooling cycles.

Originality/value

The material is obtained from the production of electrolytic copper, and during its reprocessing practices at high temperature, it was thought that it could experience some abnormal oxidation. In addition, given that pure titanium is currently used for biomedical application, some surface degree can be given by means of oxidation and subsequent spallation process situation that is found during the cyclic oxidation experiments, which could be a low-cost method to engineer a surface for these purposes.

Details

Anti-Corrosion Methods and Materials, vol. 65 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

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Article

Osama A. G. Wahba, Ali M. Hassan, H. Abd El-wahab, A. Mohy-Eldin, A.M. Naser and Osama A. Fouad

The purpose of this paper is to investigate the synthesis of calcium-based group of mixed metal oxide (MMO) pigments. The evaluation of these pigments as heat and…

Abstract

Purpose

The purpose of this paper is to investigate the synthesis of calcium-based group of mixed metal oxide (MMO) pigments. The evaluation of these pigments as heat and corrosion resistant was also explored.

Design/methodology/approach

Two simple synthesis techniques, namely, co-precipitation and solid-state calcination method, were used to synthesise nanosized MMO pigments. And then the physico-chemical requirements according to standards for the synthesised pigments are investigated.

Findings

The prepared MMO pigments were mainly in the single phase double oxide forms. The prepared oxides exhibited good heat (up to 600°C) and corrosion resistance properties (in 5 per cent NaCl for 500 h).

Research limitations/implications

This paper investigates the physico-chemical properties of synthesised calcium-based group of MMO pigments. And then evaluate it as heat and corrosion resistant paints. The simple techniques used for synthesis of nanosized MMO pigments will significantly improve the research and development of pigments’ structure and performance.

Practical implications

Calcium-based MMO pigments can be used as heat and corrosion resistant pigments. The easy synthesis of the mixed oxide pigments will open the door for further vital special industrial uses and applications.

Originality/value

Low cost, simple techniques and using naturally abundant material can be used for mass production of some other low-cost nanosized materials.

Details

Pigment & Resin Technology, vol. 44 no. 6
Type: Research Article
ISSN: 0369-9420

Keywords

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Article

A method extensively used in the production of optically flat and finely finished surfaces is that of lapping the surface upon a plate using a loose abrasive mixed into a…

Abstract

A method extensively used in the production of optically flat and finely finished surfaces is that of lapping the surface upon a plate using a loose abrasive mixed into a slurry form with a carrying fluid. If the surfaces finished in this way are in continuous or intermittent sliding contact, it is the author's opinion that any abrasives retained in their surfaces will affect surface wear. This paper reported on some exploratory work to indicate the degree of embedment of abrasive in certain materials lapped by hand.

Details

Industrial Lubrication and Tribology, vol. 9 no. 12
Type: Research Article
ISSN: 0036-8792

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Article

Mayya Ziganshina, Sergey Stepin, Sergey Karandashov and Veronika Mendelson

The purpose of this paper is to search for toxic anticorrosive pigments’ substitute in protective coatings is one of the important tasks that the specialists in the field…

Abstract

Purpose

The purpose of this paper is to search for toxic anticorrosive pigments’ substitute in protective coatings is one of the important tasks that the specialists in the field of steel corrosion face.

Design/methodology/approach

One of the ways to solve the problem of metal corrosion is to use complex oxides as pigments, which are characterized as low-toxic compounds and possess the ability to inhibit corrosion.

Findings

In the production of ferrites, it is possible to use production waste as raw material, and that makes it possible to reduce the price of the resulting product and solve environmental problems simultaneously.

Originality/value

Permanent growth of world production is accompanied by the increasing environment corrosiveness, associated with the intensification of air, water basin and soil pollution by industrial waste. This, as well as the continuously increasing operated metal stock, has recently made the tendency of metals’ total loss from corrosion steadily increasing. All of this points to the importance of studying corrosion processes and the systematic and effective fight against metal corrosion.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

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