Tungstate inhibitors are seldom used alone in open recirculating cooling water systems due to their low oxidising ability and high cost. The objective of the present work was to…
Abstract
Tungstate inhibitors are seldom used alone in open recirculating cooling water systems due to their low oxidising ability and high cost. The objective of the present work was to develop efficient synergistic inhibitor combinations comprising sodium silicate and very low concentration of sodium tungstate, keeping in view of their application in industrial cooling water system. It was demonstrated in the present study that all the combinations of the inhibitors exhibited synergistic benefit and higher inhibition efficiencies than did either of the individual inhibitors. It was also established that a 4:1 ratio of sodium silicate to sodium tungstate (total 1,000 ppm) was the best overall combination. The FTIR spectra also suggest that tungstate and silicate ions were incorporated in the passivating metal oxide layer formed on the surface of carbon steel in the inhibitor solutions. The effects of excess and depleted concentrations of the individual inhibitor components on overall inhibition behaviour are also discussed.
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Athira Krishnan and S.M.A. Shibli
This paper aims to evaluate the inhibitive action of different concentrations of Sesbania grandiflora leaf extract on the mild steel corrosion in an aggressive HCl medium under…
Abstract
Purpose
This paper aims to evaluate the inhibitive action of different concentrations of Sesbania grandiflora leaf extract on the mild steel corrosion in an aggressive HCl medium under different experimental conditions.
Design/methodology/approach
Weight loss investigation, open-circuit voltage analysis, Tafel polarisation, AC impedance analysis, etc. were used for the evaluation of inhibition efficiency. The influence of immersion period on inhibition efficiency was evaluated. The mechanism of action of the inhibitor is also discussed. Infrared (IR) spectroscopy and energy-dispersive X-ray spectroscopy analysis were used to characterise the passive film.
Findings
The results suggested that 10,000 ppm solution has maximum inhibition efficiency of 98.01 per cent at room temperature, while 1,000 ppm solution also exhibited a better efficiency of about 96.16 per cent. Efficiency of inhibitor solution was found to increase with an increase in its concentration. Polarisation study proposed the solution as an anodic inhibitor. Impedance study confirmed the formation of a protective layer over the surface of the specimen, and the constituents of the film were identified using IR spectroscopy. Stability of the film adsorbed on the steel was cleared from the steady open-circuit potential value. Study on action of the inhibitor under accelerated conditions revealed the fact that the efficiency of extract in preventing corrosion is good under stimulated conditions also.
Practical implications
The action of inhibitor sustains for a sufficient time period and could sustain under stimulated conditions. Hence, its application is practically possible in industries. The proposed inhibitor is widely available and is environmentally safe.
Originality/value
HCl is an industrially important chemical used for acid cleaning, acid pickling, etc. HCl was used as an aggressive corrosion environment. As the chances for mild steel to be in contact with HCl were very high, it was important to develop an efficient, economical and eco-friendly inhibitor for corrosion.
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Younes El Kacimi, Mouhsine Galai, Khaoula Alaoui, Rachid Touir and Mohamed Ebn Touhami
The purpose of this paper is to study the effect of silicon and phosphorus content in steel suitable for galvanizing on its corrosion and inhibitor adsorption processes in…
Abstract
Purpose
The purpose of this paper is to study the effect of silicon and phosphorus content in steel suitable for galvanizing on its corrosion and inhibitor adsorption processes in steels/cetyltrimethylammonium bromide combined and KI (mixture)/5.0 M hydrochloric acid systems has been studied in relation to the temperature using chemical (weight loss), Tafel polarization, electrochemical impedance spectroscopy (EIS), scanning electronic microscope (SEM) analysis and Optical 3D profilometry characterization. All the methods used are in reasonable agreement. The kinetic and thermodynamic parameters for each steels corrosion and inhibitor adsorption, respectively, were determined and discussed. Results show that the adsorption capacity for Steel Classes A and B are better than Steel Class C surfaces depending on their silicon and phosphorus content. Surface analyses via SEM and Optical 3D profilometry was used to investigate the morphology of the steels before and after immersion in 5.0 M HCl solution containing mixture. Surface analysis revealed improvement of corrosion resistance of Steels Classes A and B in the presence of mixture more than Classes C. It has been determined that the adsorbed protective film on the steels surface heterogeneity markedly depends on steels compositions, that is, the heterogeneity increases with decreasing silicon and phosphorus content.
Design/methodology/approach
The effect of silicon and phosphorus content in Steels Classes A, B and C on its corrosion and inhibitor mixture adsorption processes in 5.0 M HCl solution has been studied by weight loss, potentiodynamic polarization, EIS and surface analysis.
Findings
The inhibition efficiency of mixture follows the order: (Steel Class A) > (Steel Class B) > Steel Class C) and depends on their compositions in the absence of mixture according on their silicon and phosphorus content, that is, the corrosion rate increases with increasing of the silicon and phosphorus content. A potentiodynamic polarization measurement indicates that the mixture acts as mixed-type inhibitor without changing the mechanism of corrosion process for the three classes of mild steels.
Originality/value
Corrosion rate mild steels in 5.0 M HCl depends on their compositions in the absence of mixture according to their silicon and phosphorus content, that is, the corrosion rate increases with increasing silicon and phosphorus content. The adsorbed protective film on the steels surface heterogeneity markedly depends on steels class’s compositions, that is, the heterogeneity increases with decreasing silicon and phosphorus content.
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Mohammad yaghoub Abdollahzadeh Jamalabadi
The purpose of this paper is to find the time dependent thermal creep stress relaxation of a turbine blade and to investigate the effect thermal radiation of the adjacent turbine…
Abstract
Purpose
The purpose of this paper is to find the time dependent thermal creep stress relaxation of a turbine blade and to investigate the effect thermal radiation of the adjacent turbine blades on the temperature distribution of turbine blade and creep relaxation.
Design/methodology/approach
For this analysis, the creep flow behavior of Moly Ascoloy in operational temperature of gas turbine in full scale geometry is studied for various thermal radiation properties. The commercial software is used to pursue a coupled fields analysis for turbine blades in view of the structural force, materials kinematic hardening, and steady-state temperature field.
Findings
During steady-state operation, the thermal stress was found to be decreasing, whereas by considering the thermal radiation this rate was noticed to increase slightly. Also by increase of the distance between stator blades the thermal radiation effect is diminished. Finally, by decrease of the blade distance the failure probability and creep plastic deformation decrease.
Research limitations/implications
This paper describes the effect of thermal radiation in thermal-structural analysis of the gas turbine stator blade made of the super-alloy M-152.
Practical implications
Blade failures in gas turbine engines often lead to loss of all downstream stages and can have a dramatic effect on the availability of the turbine engines. There are many components in a gas turbine engine, but its performance is highly profound to only a few. The majority of these are hotter end rotating components.
Social implications
Three-dimensional finite element thermal and stress analyses of the blade were carried out for the steady-state full-load operation.
Originality/value
In the previous works the thermal radiation effects on creep behavior of the turbine blade have not performed.
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Mobin Salasi, Taghi Shahrabi and Emad Roayaei
To study and compare the inhibition effects of eco‐friendly inhibitors of sodium silicate and 1‐hydroxyethylidene 1,1 diphosphonic acid (HEDP) in corrosion control and prevention…
Abstract
Purpose
To study and compare the inhibition effects of eco‐friendly inhibitors of sodium silicate and 1‐hydroxyethylidene 1,1 diphosphonic acid (HEDP) in corrosion control and prevention of soft water discolouration (red water) in carbon steel pipelines.
Design/methodology/approach
Electrochemical impedance and Tafel polarization measurements were used to study corrosion inhibition properties. The experiments were carried out under different concentration ratios of inhibitors. Different hydrodynamic conditions were applied to simulate pipeline fluid flow. Scanning electron microscopy (SEM) and EDAX analysis were used for surface studies.
Findings
It was observed that corrosion inhibitor combinations under static conditions showed synergistic effects at low concentrations. The inhibition efficiency and synergistic behaviours of inhibitors were enhanced as the electrolyte turbulence was increased. In addition, the inhibitor concentration value required to reach maximum inhibition decreased. It was found that at 20 ppm sodium silicate and 5 ppm HEDP, co‐inhibition efficiencies increased significantly to more than 90 per cent and the corrosion rate decreased far below 1 mpy as the electrode rotational speed was increased. Surface studies using SEM revealed the formation of a compact and uniform film of co‐inhibitors.
Practical implications
The results of this paper can be used for the development of effective, non‐toxic and economically attractive corrosion inhibitor formulations for soft water transmission pipelines.
Originality/value
The observed synergistic behaviour can be due to the incorporation of the silicate gel‐like network through organic phosphorous bonds. The hydrodynamic condition of the electrolyte leads to enhancement of inhibition efficiency, which indicates that the corrosion inhibition was mass transfer controlled.
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Jun Yang, Pei Zhang, Lihuizi Su, Fuan Yan and Zhou Yong
The aim of this work was to propose a method to prepare composite phosphate conversion coating (CPCC), including ternary phosphate conversion coating (TPCC) and binary phosphate…
Abstract
Purpose
The aim of this work was to propose a method to prepare composite phosphate conversion coating (CPCC), including ternary phosphate conversion coating (TPCC) and binary phosphate conversion coatings (BPCC), with one-step chemical conversion and to reveal and compare the corrosion resistance between TPCC and BPCC.
Design/methodology/approach
In this work, a calcium–manganese–zinc (Ca–Mn–Zn) TPCC was prepared on the surface of magnesium alloy (MA) AZ91D with one-step chemical conversion method; for Ca-Mn-Zn@TPCC, its microstructure was characterized with scanning electron microscope observation and scanning tunneling microscope detection, and its composition was characterized with energy dispersion spectroscopy and X-ray photoelectron spectroscopy analyses. Particularly, the corrosion resistance of Ca-Mn-Zn@TPCC and its comparison with Ca–Mn, Ca–Zn and Mn–Zn BPCCs were clarified with electrochemical and immersion measurements.
Findings
Ca-Mn-Zn@TPCC, which was composed of Ca, Mn, Zn, P and O, exhibited a mud-shaped with cracks microstructure, and the average crack width, terrain fluctuation and coating thickness were 0.61 µm, 23.78 nm and 2.47 µm, respectively. Ca-Mn-Zn@TPCC provided good corrosion resistance to MA AZ91D; in NaCl solution, the total degradation of Ca-Mn-Zn@TPCC consumed eight days; corrosion products with poor adhesion peeled out from Ca-Mn-Zn@TPCC-coated MA AZ91D spontaneously. Besides, the corrosion resistance of Ca-Mn-Zn@TPCC was better than that of Ca-Mn@BPCC, Ca-Zn@BPCC or Mn-Zn@BPCC.
Originality/value
The successful preparation of Ca-Mn-Zn@TPCC on MA AZ91D surface confirmed the proposed method to prepare CPCC with one-step chemical conversion was feasible; at the same time, it was further confirmed that for phosphate conversion coating, ternary coating had better corrosion resistance than binary coating did.
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M.N. Boucherit, Sid‐Ahmed Amzert, Fahd Arbaoui, Salah Hanini and Abdennour Hammache
The purpose of this paper is to illustrate the usefulness of inhibitors for the prevention of localised corrosion of carbon steel in a low‐aggressive medium. The efficiencies of…
Abstract
Purpose
The purpose of this paper is to illustrate the usefulness of inhibitors for the prevention of localised corrosion of carbon steel in a low‐aggressive medium. The efficiencies of two inorganic non‐toxic inhibitors are compared, associated with an oxidant.
Design/methodology/approach
Many experiments were conducted. For each experiment, a solution was prepared with different concentrations of pitting agent, inhibitor and oxidant. The performance was then estimated by the pitting potential taken from the voltammograms of carbon steel obtained with each solution.
Findings
The results show that the efficiency of molybdate and tungstate were comparable. The presence of iodate, which plays an oxidizing role, can be synergistic to the inhibitor but harmful if the concentration ratio is not adequate.
Practical implications
The interest in the use of an oxidant is that it makes it possible to reduce the inhibitor concentration, which limits the pH increase and prevents scale deposition.
Originality/value
This work provides useful guidance in the localised corrosion prevention of a semi‐open cooling circuit subject to seasonal sand‐storms. The obtained results from the many experiments carried out were compiled using neural networks for performance prediction.
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Shan Cao, Faqing He and Jinwei Gao
Important reserves of oil and gas, which are left to be discovered and produced, are mainly concentrated in challenging locations and under severe conditions such as high pressure…
Abstract
Purpose
Important reserves of oil and gas, which are left to be discovered and produced, are mainly concentrated in challenging locations and under severe conditions such as high pressure (HP)/high temperature (HT). The presence of aggressive environments including H2S, CO2 and chlorides plus HP/HT causes a series of corrosion problems, which cost the oil industry billions of dollars a year. Thus, there is an increasing challenge for tubes (i.e. oil country tubular goods, for short, OCTG) used in producing oil and gas. The purpose of this study is to summarize different kinds of corrosion problems and their mitigation, to more efficiently protect OCTG from corrosion.
Design/methodology/approach
To effectively select proper mitigation methods, the mechanism of corrosion must be understood, which can be classified into four categories: sweet corrosion, sour corrosion, galvanic corrosion and microbiologically induced corrosion. Also, the effects of environmental and material factors on the corrosion rate are presented. Subsequently, current technology of mitigating these corrosion problems has been discussed, including the development of materials, application of chemical inhibitors and application of protective layers.
Findings
It is stressed that limits exist for each individual mitigation method; therefore, a careful balance between economic life of OCTG and safety in operation is required.
Originality/value
The main purpose of this essay is to give a brief review and detailed introduction and analysis about those technologies.
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Dexin Chen, Hongyuan He, Zhixin Kang and Wei Li
This study aims to review the current one-step electrodeposition of superhydrophobic coatings on metal surfaces.
Abstract
Purpose
This study aims to review the current one-step electrodeposition of superhydrophobic coatings on metal surfaces.
Design/methodology/approach
One-step electrodeposition is a versatile and simple technology to prepare superhydrophobic coatings on metal surfaces.
Findings
Preparing superhydrophobic coatings by one-step electrodeposition is an efficient method to protect metal surfaces.
Originality/value
Even though there are several technologies, one-step electrodeposition still plays a significant role in producing superhydrophobic coatings.
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Mohamed Nadir Boucherit, Sid Ahmed Amzert, Fahd Arbaoui, Yakoub Boukhari, Abdelkrim Brahimi and Aziz Younsi
This paper aims to predict the localized corrosion resistance by the application of artificial neural networks. It emphasizes the importance to take into account the relationships…
Abstract
Purpose
This paper aims to predict the localized corrosion resistance by the application of artificial neural networks. It emphasizes the importance to take into account the relationships between the physical parameters before presenting them to the network.
Design/methodology/approach
The work was conducted in two phases. At the beginning, the authors executed an experimental program to measure pitting corrosion resistance of carbon steel in an aqueous environment. More than 900 electrochemical experiments were conducted in chemical solutions containing different concentrations of pitting agents, corrosion inhibitors and oxidant reagents. The obtained results were collected in a table where for a combination of the experimental parameters corresponds a pitting potential Epit obtained from the corresponding electrochemical experiment. In the second step, the authors used the experimental data to train different artificial neuron networks for predicting pitting potentials.
Findings
In this step, the authors considered the relationships that the chemical parameters are likely to have between them. Two types of relationships were taken into account: chemical equilibria which are controlled by the pH and the synergistic relationships that some corrosion inhibitors may have when they are in the presence of a chemical oxidant.
Originality/value
This comparative study shows that adjusting the input data by considering the physical relationships between them allows a better prediction of the pitting potential. The quality of the prediction, quantified by a regression factor, is qualitatively confirmed by a statistical distribution of the gap between experimental and calculated pitting potentials.