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Article
Publication date: 1 April 2002

A. Dafali, B. Hammouti, R. Touzani, S. Kertit, A. Ramdani and K. El Kacemi

The inhibition of the copper corrosion in aerated 3 per cent sodium chloride solution was studied by using electrochemical polarisation, weight loss and impedance…

Abstract

The inhibition of the copper corrosion in aerated 3 per cent sodium chloride solution was studied by using electrochemical polarisation, weight loss and impedance measurements in the presence of different concentration of synthesised bipyrazolic compounds: N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) butylamine (bipy1); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) allylamine (bipy2); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) ethanolamine. (bipy3); N,N‐bis (3,5‐dimethylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy4); N,N‐bis (3‐carbomethoxy‐5‐methylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy5); N,N‐bis(3‐carboethoxy‐5‐methylpyrazol‐1‐ylmethyl) cyclohexylamine (bipy6). The inhibition efficiencies obtained from cathodic Tafel plots, polarisation resistance and weight loss are in good agreement with electrochemical impedance spectroscopy (EIS) measurements. All these additives were found to be excellent inhibitors of copper corrosion. The difference in inhibition efficiencies of these inhibitors was not big, but the optimum concentration for maximum efficiency was slightly dependent on the substitution of each molecule. The studied molecules act as mixed‐type inhibitors. Detailed study of bipy1 shows that the maximum inhibition efficiency revolves around 99 per cent from 5×10−4 M of inhibitor. This latter adsorbs on the copper surface according to the Frumkin isotherm model. The inhibition efficiency of bipy1 decreases with the rise of temperature in the range 25 – 60°C.

Details

Anti-Corrosion Methods and Materials, vol. 49 no. 2
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 December 2003

F. Bensajjay, S. Alehyen, M. El Achouri and S. Kertit

1‐phenyl 5‐mercarpto 1,2,3,4‐tetrazole (PMT) was tested as an inhibitor for the corrosion of steel in 0.5 M H2SO4 and 1/3 M H3PO4 by weight‐loss and electrochemical…

Abstract

1‐phenyl 5‐mercarpto 1,2,3,4‐tetrazole (PMT) was tested as an inhibitor for the corrosion of steel in 0.5 M H2SO4 and 1/3 M H3PO4 by weight‐loss and electrochemical methods. Results obtained showed that the inhibition efficiency of PMT increased with the increase of inhibitor concentration and reached an optimum value (98 per cent) at 10−3 M in H2SO4 and H3PO4 solutions. The effect of the temperature on the kinetic parameters of corrosion of steel in the aqueous solutions of H2SO4 and H3PO4 with and without addition of PMT has been studied and the associated parameters were determined.

Details

Anti-Corrosion Methods and Materials, vol. 50 no. 6
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 1 May 2006

M. Mihit, R. Salghi, S. El Issami, L. Bazzi, B. Hammouti, El. Ait Addi and S. Kertit

To evaluate the effect of some tetrazole compounds as corrosion inhibitors of copper in HNO3 at various temperatures.

Abstract

Purpose

To evaluate the effect of some tetrazole compounds as corrosion inhibitors of copper in HNO3 at various temperatures.

Design/methodology/approach

1‐phenyl‐5‐mercapto‐1,2,3,4‐tetrazole (PMT) was selected as the best inhibitor among the tetrazole compounds tested. Gravimetric and electrochemical techniques were conducted.

Findings

PMT was an excellent inhibitor for copper in acid. Its efficiency attained 97.5 per cent and decreased slightly with temperature.

Research limitations/implications

The inhibition efficiency increased with the concentration of PMT to reach 97.5 per cent at 10−3 M. Good agreement between the various methods explored was observed. Polarisation measurements also showed that PMT acted as a mixed inhibitor.

Practical implications

The efficiency of PMT increased with the concentration but decreased with rise of temperature in the 298‐333 K range. As such, PMT could be used in chemical cleaning and pickling processes.

Originality/value

The originality of this work was the finding of an efficient inhibitor (PMT) having a nearly 100 per cent efficiency.

Details

Pigment & Resin Technology, vol. 35 no. 3
Type: Research Article
ISSN: 0369-9420

Keywords

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Article
Publication date: 12 September 2008

R.F. Al‐Ghamdi, A.M. El‐Shareef, M.T. Saeed and S.A. Ali

The aim is to demonstrate corrosion inhibition capabilities of several isoxazolidines, containing hydrophobic substituents and having varying degree of steric congestion…

Abstract

Purpose

The aim is to demonstrate corrosion inhibition capabilities of several isoxazolidines, containing hydrophobic substituents and having varying degree of steric congestion around nitrogen.

Design/methodology/approach

A number of isoxazolidines were prepared. Corrosion inhibition efficiencies of these organic compounds were determined by gravimetric and electrochemical methods, using carbon steel as the substrate metal and 0.5 M H2SO4 at 40‐70°C as the corrosive environment. Concentration of inhibitor was varied between 5 and 400 ppm.

Findings

Increase in steric congestion around the nitrogen centre and hydrophobic chain lengths as well as increase in temperature (in the presence of the inhibitor in the higher concentration range 100‐400 ppm) were found to increase the corrosion inhibition efficiency of the isoxazolidines. Electrochemical measurements corroborated these results. Thermodynamic parameters (ΔGads0Hads0Sads0) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction were determined.

Originality/value

This is the first time the corrosion inhibition characteristics of isoxazolidines, an important class of readily accessible compounds, have been evaluated in H2SO4 medium.

Details

Anti-Corrosion Methods and Materials, vol. 55 no. 5
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 13 November 2007

M. Benabdellah, R. Souane, N. Cheriaa, R. Abidi, B. Hammouti and J. Vicens

To evaluate the effect of synthesised calixarenes as new inhibitors on the corrosion of steel in HCl media at various temperatures.

Abstract

Purpose

To evaluate the effect of synthesised calixarenes as new inhibitors on the corrosion of steel in HCl media at various temperatures.

Design/methodology/approach

Calixarenes have been synthesised and tested as corrosion inhibitors. Gravimetric technique and potentiodynamic polarisation and impedance spectroscopy methods were used.

Findings

Calixarenes exhibited a good inhibition. Their efficiency decreases slightly with temperature.

Research limitations/implications

It was found that the inhibition efficiency increases with the concentration of inhibitors to reach 92 per cent at 10−4M.

Practical implications

The efficiency of calixarene derivatives increases with the concentration and falls slowly with temperature to attain 84 per cent at 353 K range. Calixarenes can be used in chemical cleaning and pickling processes.

Originality/value

The originality of this work is to find an inhibitor to give protection close to 100 per cent.

Details

Pigment & Resin Technology, vol. 36 no. 6
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 December 2004

M. Tariq Saeed

The cycloaddition of cyclic nitrone1‐pyrroline‐1‐oxide with 1‐dodecene and 1‐hexadecene afford a bicyclic (isoxazolidines). These isoxazolidines were tested for corrosion…

Abstract

The cycloaddition of cyclic nitrone1‐pyrroline‐1‐oxide with 1‐dodecene and 1‐hexadecene afford a bicyclic (isoxazolidines). These isoxazolidines were tested for corrosion inhibition of carbon steel in 1N H2SO4 in the 30‐60°C temperature range by gravimetric and electrochemical methods. The compound isoxazolidines exhibited excellent inhibition efficiency in the acidic corrosion environment. The presence of heteroatoms such as N and O induce greater adsorption of the inhibitor molecules onto the surface of carbon steel and the long hydrocarbon chains ensure coverage of the metal surface. The values of activation energy and free energy of adsorption indicated the physical nature of the adsorption on the surface of the carbon steel. Thermodynamic parameters were determined for the adsorption process (ΔGadso, ΔHadso, ΔSadso), and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction in the presence of the isoxazolidines. The adsorption of inhibitors on the metal surface was found to obey the Langmuir adsorption isotherm. The isoxazolidines were found to be mixed‐type inhibitors. The isoxazolidine which had a tetradecyl hydrophobe was found to be a better inhibitor than was the decyl analogue.

Details

Anti-Corrosion Methods and Materials, vol. 51 no. 6
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 5 August 2019

Imad Jabbouri and Maryem Naili

The purpose of this paper is to explore how ownership concentration affects cost of debt (CoD) in one of the most important emerging markets in the Middle East and North…

Abstract

Purpose

The purpose of this paper is to explore how ownership concentration affects cost of debt (CoD) in one of the most important emerging markets in the Middle East and North Africa, Morocco.

Design/methodology/approach

The study employs panel data analysis using non-financial firms listed on Casablanca Stock Exchange (CSE) between 2004 and 2016. To unveil the hidden facets of the relationship between ownership concentration and CoD, and examine if this relationship changes with market conditions, we conduct a pre–post-crisis analysis.

Findings

The results demonstrate that controlling shareholders promote decent governance as long as they are able to generate appropriate returns. However, this behavior seems to change during the post-crisis period. In their attempts to increase their returns adversely affected by the financial crisis, controlling shareholders switch from guardians of decent governance and firm’s resources to a menace to creditors’ interests.

Practical implications

Our results expose the severity of agency problems in CSE. It is the duty of all market participants including regulators, board of directors, financial analysts, shareholders and creditors to scrutiny and reinforce governance mechanisms to alleviate expropriation by controlling shareholders. Improving country and firm-level governance mechanisms would enhance investors’ protection, attract international investors and boost the economic activity.

Originality/value

Prior research is inconclusive about the impact of ownership concentration on CoD. Hence, it is worthwhile to seek new evidence in a new market on the nature of this relationship.

Details

Review of Behavioral Finance, vol. 12 no. 3
Type: Research Article
ISSN: 1940-5979

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Article
Publication date: 4 November 2019

Omar Farooq and Mona A. ElBannan

The purpose of this paper is to document the impact of stock price synchronicity (SYNCH) on the dividend payout ratio.

Abstract

Purpose

The purpose of this paper is to document the impact of stock price synchronicity (SYNCH) on the dividend payout ratio.

Design/methodology/approach

The authors use data from India for the period between 2000 and 2012 and the panel regression approach to test their arguments.

Findings

This paper documents that the relationship between synchronicity and dividend payout ratio is positive until a turning point is reached. After that point, synchronicity has a negative impact on dividend payout ratio. The authors argue that firms with low synchronicity have higher information asymmetries. As a result, they have an incentive to develop a reputation as better-governed firms by paying high dividends. However, as synchronicity increases further, information asymmetries go down and as a result incentive to use dividend payouts as a mechanism to reduce information asymmetries goes down. Therefore, positive relationship between synchronicity and dividend payout ratios breaks down at high levels of synchronicity.

Originality/value

The authors provide evidence regarding the role played by SYNCH – a publicly available measure – on dividend polices adopted by firms within the context of emerging markets.

Details

Accounting Research Journal, vol. 32 no. 4
Type: Research Article
ISSN: 1030-9616

Keywords

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Article
Publication date: 19 May 2012

Hassan S. Emira, Alia A. Shakour, Sayed S. Abd El Rehim, Inas A. Saleh and Mohammed A. El‐Hashemy

The purpose of this paper is to report the use of zinc phosphate pigment as a chromate substitute for coatings on non‐ferrous metals (galvanized steel, pure aluminum…

Abstract

Purpose

The purpose of this paper is to report the use of zinc phosphate pigment as a chromate substitute for coatings on non‐ferrous metals (galvanized steel, pure aluminum, α‐brass and pure copper).

Design/methodology/approach

Paint systems based on zinc chromate and zinc phosphate pigments were prepared. The paints were tested for their physico‐mechanical properties. Testing of the anticorrosive properties of the zinc phosphate pigment in comparison with zinc chromate pigment was carried out by accelerated corrosion exposure, i.e. immersion in 3.5 percent salt solution and exposure for one year at five outdoor stations.

Findings

The possibility of replacing chromate pigment was assessed and the “gap“ observable between the performance of zinc chromate and zinc phosphate pigments was noted.

Originality/value

The non‐toxic inhibitive pigment, zinc phosphate, incorporated into a plasticized‐chlorinated rubber binder, could be applied successfully for the protection of non‐ferrous substrates.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

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