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1 – 10 of 270
Article
Publication date: 18 September 2007

P.C. Okafor, V.I. Osabor and E.E. Ebenso

This paper aims to investigate the inhibitive effect of ethanol extracts of Garcinia kola (EXG) for the corrosion of mild steel in H2SO4 solutions. The study is another…

Abstract

Purpose

This paper aims to investigate the inhibitive effect of ethanol extracts of Garcinia kola (EXG) for the corrosion of mild steel in H2SO4 solutions. The study is another trial to find a cheap and environmentally safe inhibitor for mild steel corrosion.

Design/methodology/approach

The inhibition efficiency has been evaluated using the hydrogen evolution technique at 30‐60°C. The mechanism of adsorption inhibition and type of adsorption isotherm were proposed based on the trend of inhibition efficiency and kinetic data.

Findings

The results obtained indicate that EXG inhibits the corrosion of mild steel in acidic medium and that the inhibition efficiency increases with an increase in the concentration of ethanol extracts and decreasing temperature. The inhibition efficiency increased on addition of potassium iodide to EXG, indicating synergism. The experimental data obeyed the Langmuir adsorption isotherm as well as the El‐Awady et al. thermodynamic‐kinetic model. The activation energy of inhibition of 6.8508 KJ/mol calculated for the corrosion process suggests that the EXG molecules are physically adsorbed on the metal surface.

Research limitations/implications

Further investigations involving electrochemical studies such as polarization method will provide further enlightenment on the mechanistic aspect of the corrosion inhibition.

Originality/value

This paper provides new information on the possible application of EXG as an environmentally friendly corrosion inhibitor under the specified conditions. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

Details

Pigment & Resin Technology, vol. 36 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 23 March 2010

N.O. Eddy and E.E. Ebenso

The purpose of this paper is to study the inhibitive and adsorptive characteristics of ethanol extract of Gongronema latifolium (GL) as a corrosion inhibitor for mild…

Abstract

Purpose

The purpose of this paper is to study the inhibitive and adsorptive characteristics of ethanol extract of Gongronema latifolium (GL) as a corrosion inhibitor for mild steel in H2SO4.

Design/methodology/approach

The inhibition efficiencies were evaluated using thermometric and hydrogen evolution techniques.

Findings

The inhibition efficiency of ethanol extract of GL vary with concentration of the extract, period of immersion and with temperature. The extract acts as an inhibitor because of its phytochemical and amino acid composition. The extract is adsorbed spontaneously on the surface of mild steel according to Langmuir adsorption isotherm. The mechanism of physical adsorption is proposed from the trend of the inhibition efficiency with temperature and the values of some kinetic and thermodynamic parameters obtained.

Research limitations/implications

The study provides information on the use of ethanol extract of GL as a corrosion inhibitor. Electrochemical studies such as polarisation and alternating current impedance spectra will throw more light on the mechanistic aspects of the corrosion inhibition.

Practical implications

Ethanol extract of GL can be used as an environmentally friendly inhibitor for the corrosion of mild steel in H2SO4.

Originality/value

This environmentally friendly inhibitor could find possible applications in metal surface anodising and surface coatings.

Details

Pigment & Resin Technology, vol. 39 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 September 2006

S.A. Umoren, I.B. Obot, E.E. Ebenso, P.C. Okafor, O. Ogbobe and E.E. Oguzie

To investigate the inhibitive effect of gum arabic (GA) for the corrosion of aluminium in alkaline (NaOH) medium and determine its adsorption characteristics. The present…

1215

Abstract

Purpose

To investigate the inhibitive effect of gum arabic (GA) for the corrosion of aluminium in alkaline (NaOH) medium and determine its adsorption characteristics. The present work is another trial to find a cheap and environmentally safe inhibitor for aluminium corrosion.

Design/methodology/approach

The inhibition efficiency (%I) has been evaluated using the hydrogen evolution (via the gasometric assembly) and the thermometric methods at 30 and 40°C. The concentrations of GA (inhibitor) used were 0.1‐0.5 g/l and the concentrations of NaOH (the corrodent) were 0.1‐2.5 M. The mechanism of adsorption inhibition and type of adsorption isotherms were proposed from the trend of inhibition efficiency with temperature, Ea, ΔGads and Qads values.

Findings

GA inhibited the corrosion of aluminium in NaOH solutions. The inhibition efficiency increased with increase in GA concentration and with increase in temperature. Phenomenon of chemical adsorption is proposed for the inhibition and the process followed the Langmuir and Freundlich adsorption isotherms. The results obtained in this study for the %I were comparable for the two methods used and were corroborated by kinetic and thermodynamic parameters evaluated from the experimental data.

Research limitations/implications

Further investigations involving electrochemical studies such as polarization method will enlighten more on the mechanistic aspect of the corrosion inhibition.

Originality/value

This paper provides new information on the possible application of GA as an environmentally friendly corrosion inhibitor even in highly aggressive alkaline environments. It has not been published elsewhere.

Details

Anti-Corrosion Methods and Materials, vol. 53 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 January 2006

E.E. Oguzie and E.E. Ebenso

To investigate the efficacy of Congo red dye (CR) as an inhibitor of the acid corrosion of mild steel and aluminium alloy (AA 1060) and to assess the influence of halide…

Abstract

Purpose

To investigate the efficacy of Congo red dye (CR) as an inhibitor of the acid corrosion of mild steel and aluminium alloy (AA 1060) and to assess the influence of halide ions on the inhibition efficiency.

Design/methodology/approach

Corrosion rates were estimated by monitoring the weight losses of the metal specimen as a function of time at different temperatures. Inhibition efficiency was determined by comparing the corrosion rates in the acid medium in the absence and presence of the additive.

Findings

CR dye reduced the corrosion rates of mild steel and aluminium in the acidic environment. Better inhibition was observed with the mild steel specimen. Protection efficiency was sensitive to inhibitor concentration as well as temperature and generally increased with an increase in CR dye concentration. The halide additives improved the inhibition efficiency in the order KCl < KBr < KI.

Research limitations/implications

The inhibiting effect of CR dye was studied within a fixed concentration range, which could be expanded for further studies. The same applies to the CR+halide systems. Also, the dye structure could be modified by introducing different functional groups, and the effect on inhibition efficiency investigated.

Practical implications

The research findings could find practical application in corrosion control in aqueous acidic environments.

Originality/value

This paper provides new information on the inhibiting characteristics of CR dye under the specified conditions, as a guide to possible applications in metal surface anodizing and surface coatings.

Details

Pigment & Resin Technology, vol. 35 no. 1
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 23 May 2008

S.A. Umoren and E.E. Ebenso

The purpose of this paper is to investigate the effect of Raphia hookeri exudate gum and halide ions on the corrosion inhibition of aluminium in HCl solutions at 30‐60°C…

Abstract

Purpose

The purpose of this paper is to investigate the effect of Raphia hookeri exudate gum and halide ions on the corrosion inhibition of aluminium in HCl solutions at 30‐60°C and to study the mechanism of action.

Design/methodology/approach

The corrosion rates were determined using the gravimetric (weight loss), gasometric (hydrogen evolution) and thermometric techniques. The results obtained in the absence and presence of Raphia hookeri, halides and Raphia hookeri – halides combination were used to calculate the inhibition efficiency (%I), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption.

Findings

Results obtained showed that the Raphia hookeri exudates gum acted as an inhibitor for aluminium corrosion in acidic environment. Inhibition efficiency (%I) increased with increase in concentration of the Raphia hookeri exudates gum and synergistically increased to a considerable extent on the addition of halide ions. The increase in inhibition efficiency (%I) and surface coverage (θ) in the presence of the halides was found to be in the order I > Br > Cl which indicates that the radii as well as electronegativity of the halide ions play a significant role in the adsorption process. Raphia hookeri exudates gum obeys Freundlich, Langmuir and Temkin adsorption isotherms. Phenomenon of physical adsorption is proposed from the values of kinetic/thermodynamic parameters obtained. The values of synergism parameter (SI) obtained for the halides are greater than unity suggesting that the enhanced inhibition efficiency of the Raphia hookeri caused by the addition of the halide ions is only due to synergistic effect.

Research limitations/implications

Electrochemical studies such as polarization and AC impedance spectra will throw more light on the mechanistic aspects of the corrosion inhibition and more exudate gums need to be evaluated as corrosion inhibitors.

Practical implications

Raphia hookeri exudate gum can be used as corrosion inhibitor and the addition of halides to it improves the inhibition efficiency considerably.

Originality/value

This paper provides new information on the use of exudate gums as corrosion inhibitors and addition of halides in acidic medium. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

Details

Pigment & Resin Technology, vol. 37 no. 3
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 December 2003

E.E. Ebenso, P.C. Okafor and U.J. Ekpe

The inhibition of corrosion of aluminium in chloroacetic acids, namely monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) solutions…

Abstract

The inhibition of corrosion of aluminium in chloroacetic acids, namely monochloroacetic acid (MCA), dichloroacetic acid (DCA) and trichloroacetic acid (TCA) solutions, using 2‐acetylphenothiazine (2APTZ) at 30 and 40°C, at concentrations of 1×10−3M, 1×10−4M, 7.5×10−5M, 5×10−5M and 1×10−5M, was studied using the weight loss and hydrogen evolution techniques. At the highest concentration studied, using the hydrogen evolution technique, an inhibition efficiency of 86.16 per cent was obtained. The investigation revealed that 2APTZ inhibited the corrosion reaction. A physical adsorption mechanism is proposed on the basis of the obtained average Ea values of 76.05 kJ/mol for MCA, 70.75 kJ/mol for DCA and 68.52 kJ/mol for TCA. 2APTZ was confirmed to obey the Freundlish adsorption isotherm equation at the concentration studied. The two techniques employed revealed a first‐order kinetics.

Details

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

Keywords

Article
Publication date: 29 May 2007

P.C. Okafor and E.E. Ebenso

To evaluate the effect of different parts of Carica papaya (leaves (LV), seeds (SD), heart wood (HW) and bark (BK)) as eco‐friendly and non‐toxic mild‐steel corrosion…

1472

Abstract

Purpose

To evaluate the effect of different parts of Carica papaya (leaves (LV), seeds (SD), heart wood (HW) and bark (BK)) as eco‐friendly and non‐toxic mild‐steel corrosion inhibitors in H2SO4 at 30 to 60 oC.

Design/methodology/approach

Acid extracts of the different parts of Carica papaya were used as inhibitors in various corrosion tests. Gravimetric and gasometric techniques were used to characterise the mechanism of inhibition.

Findings

The LV, SD, HW and BK extracts were found to inhibit mild steel corrosion in H2SO4. The inhibition efficiencies of the plant's part extracts follow the trend: LV > SD > HW > BK. Inhibition efficiency increased with extracts concentration but decreased with temperature. Physical adsorption of the phytochemical components of the plant on the metal surface is proposed as the mechanism of inhibition. The experimental data fits well into the Langmuir and Temkin adsorption isotherms.

Practical implications

The plant extracts can be used in chemical cleaning and picking processes.

Originality/value

The research provides information on the possible use of the different parts of Carica papaya as sources of cheap eco‐friendly and non‐toxic corrosion inhibitors.

Details

Pigment & Resin Technology, vol. 36 no. 3
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 November 2006

S.A. Umoren, E.E. Ebenso, P.C. Okafor and O. Ogbobe

To determine the inhibition efficiency and adsorption characteristics of two water soluble polymers namely polyvinyl alcohol (PVA) and polyethyleneglycol (PGE) as…

Abstract

Purpose

To determine the inhibition efficiency and adsorption characteristics of two water soluble polymers namely polyvinyl alcohol (PVA) and polyethyleneglycol (PGE) as corrosion inhibitors of mild steel in H2SO4.

Design/methodology/approach

The inhibition efficiencies of PVA and PEG were evaluated using the weight loss and hydrogen evolution techniques at 30‐60°C.

Findings

The inhibition efficiency (I per cent) of the inhibitors increased with increase in concentration and temperature. The inhibitors (PVA and PEG) were found to obey Temkin, Freundlich and Langmuir adsorption isotherms from the fit of the experimental data at all concentrations and temperatures studied. The phenomenon of chemical adsorption is proposed from the activation parameters obtained. PEG was found to be a better inhibitor than PVA.

Research limitations/implications

The mechanistic aspect of the corrosion inhibition can be better understood using electrochemical studies such as polarization and AC impedance spectra.

Practical implications

The findings may be useful in cooling water systems in industries under simulated conditions.

Originality/value

This paper provides additional new information on the inhibiting characteristics of PVA and PEG as promising corrosion inhibitors.

Details

Pigment & Resin Technology, vol. 35 no. 6
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 September 2006

S.A. Umoren, O. Ogbobe, E.E. Ebenso and U.J. Ekpe

To investigate the effect of halide ions on the corrosion inhibition of mild steel using polyvinyl alcohol (PVA) in H2SO4 at 30‐60°C and to study the mechanism of action.

Abstract

Purpose

To investigate the effect of halide ions on the corrosion inhibition of mild steel using polyvinyl alcohol (PVA) in H2SO4 at 30‐60°C and to study the mechanism of action.

Design/methodology/approach

The corrosion rates were determined using the gravimetric (weight loss) and gasometric (hydrogen evolution) techniques. The results obtained in the absence and presence of PVA, halides, PVA – halides combination were used to calculate the inhibition efficiency (%I), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption.

Findings

Results obtained showed that inhibition efficiency (%I) increased with the increase in concentration of PVA, on the addition of halides and with the increase in temperature. Phenomenon of chemical adsorption was proposed and PVA was found to obey Langmuir, Flory‐Huggins and Freundlich adsorption isotherms. The synergism parameter, S1, evaluated was found to be greater than unity and the values of Ea, ΔH°, ΔS° and ΔG° obtained revealed that the adsorption process was spontaneous.

Research limitations/implications

Electrochemical studies such as polarization and AC impedance spectra will enlighten more on the mechanistic aspects of the corrosion inhibition and more polymers need to be evaluated as corrosion inhibitors.

Practical implications

PVA can be used as corrosion inhibitor and the addition of halides to PVA improves the inhibition efficiency considerably.

Originality/value

This paper provides new information on the effects of halides on the corrosion inhibition using PVA as an inhibitor for mild steel in acidic medium. Such a study had not been reported elsewhere.

Details

Pigment & Resin Technology, vol. 35 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 1 April 1967

W. Hunziker

Die Frage «Wie weit kann die öffentliche Hand den Fremdenverkehr fördern?» unterstellt bereits die vollzogene Tatsache der staatlichen Förderung des Fremdenverkehrs. Sie…

Abstract

Die Frage «Wie weit kann die öffentliche Hand den Fremdenverkehr fördern?» unterstellt bereits die vollzogene Tatsache der staatlichen Förderung des Fremdenverkehrs. Sie scheint diese hinzunehmen, ja sogar davon auszugehen, dass der Staat den Fremdenverkehr fördern soll, vielleicht sogar muss, wobei es dann, nur noch einen Schritt bis zur Untersuchung und zum Entscheid darüber bedeuten würde, wie weit er iiberhaupt zu gehen imstande ist, um das apodiktisch feststehende Gebot der staatlichen Unterstüzung maximal zu erfüllen.

Details

The Tourist Review, vol. 22 no. 4
Type: Research Article
ISSN: 0251-3102

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