Search results

1 – 10 of over 5000
Article
Publication date: 1 January 2006

Dong Youp Ryu and Michael L. Free

To evaluate mild steel corrosion using a new surfactant‐inhibition model which was derived, in part, from the concept of intermolecular energy and molecular separation distance.

Abstract

Purpose

To evaluate mild steel corrosion using a new surfactant‐inhibition model which was derived, in part, from the concept of intermolecular energy and molecular separation distance.

Design/methodology/approach

A Gamry potentiostat was used for polarization resistance tests to determine corrosion rate and the level of adsorption of surfactant at the solution‐metal interface was determined using UV‐spectroscopy. The relationship between inhibition and surfactant adsorption as well as metal corrosion was investigated using a traditional surfactant‐inhibition model, which assumes inhibition is directly proportional to surfactant coverage and new model.

Findings

The comparison of adsorption data and corrosion inhibition data shows inhibition was not directly proportional to physical coverage as assumed by the traditional inhibition model. Instead, it was found that coverage was related to inhibition through a power‐law dependency that is similar to that used to determine molecular interaction energies.

Research limitations/implications

The new model was evaluated only for dodecyl pyridinium chloride mild steel system. The evaluation of the new model for various surfactant‐metal systems is suggested for future research.

Originality/value

The new model was found to more accurately predict the relationship between inhibition and coverage rather than traditional models for dodecyl pyridinium chloride‐mild steel system.

Details

Anti-Corrosion Methods and Materials, vol. 53 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 26 August 2014

S.A. Umoren, U.M. Eduok and M.M. Solomon

The purpose of this paper is to investigate the effect of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and blended formulations on the corrosion inhibition of aluminium…

Abstract

Purpose

The purpose of this paper is to investigate the effect of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and blended formulations on the corrosion inhibition of aluminium in HCl solutions at 30-60°C and to study the mechanism of action.

Design/methodology/approach

The inhibitive effect of the homopolymers and polymer blend was assessed using weight loss and hydrogen evolution methods at 30 and 60°C. The morphology of the corroding aluminium surface without and with the additives was visualized using atomic force microscopy. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption.

Findings

Results obtained show that inhibition efficiency (η%) increases with increase in concentration of the polymers but decreases with increase in temperature. The inhibition efficiency of the homopolymers and their blends decreased with rise in temperature. Inhibition efficiency was found to be synergistically enhanced on blending the two homopolymers with highest inhibition efficiency obtained for (PEG:PVP) blending ratio of 1:3. The phenomenon of physical adsorption is proposed from the trend of inhibition efficiency with temperature.

Research limitations/implications

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

Originality/value

Studies involving the use of polymer blends/mixtures as corrosion inhibitor for metals in corrosive environments are scarce. The results suggest that the mixture could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the use of polymer–polymer mixtures to control acid-induced corrosion of metal.

Details

Pigment & Resin Technology, vol. 43 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 18 September 2007

Lu Zhaoling, Fu Chaoyang and Guo Xingpeng

This paper seeks to investigate the different inhibition performance and adsorption behaviour of dodecylamine in acidic and neutral environments and to understand further the…

Abstract

Purpose

This paper seeks to investigate the different inhibition performance and adsorption behaviour of dodecylamine in acidic and neutral environments and to understand further the inhibition mechanism of dodecylamine in CO2‐saturated brine solution.

Design/methodology/approach

The inhibition performance and adsorption behaviour of dodecylamine on N80 steel in CO2‐saturated brine solution in acidic and neutral environments were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy and the attenuated total reflection‐Fourier transform infrared spectroscopy.

Findings

Corrosion potentials exhibited a pronounced shift in the positive direction at higher concentrations of dodecylamine. The inhibition efficiency of dodecylamine was shown to be pH‐dependent. The effective inhibition concentration of dodecylamine decreased from pH 4.9 to 7.4. In a neutral environment, the inhibitor was shown to affect the deposition of the corrosion products and provide more active sites to bond with the inhibitor. More alkaline environments made the electron cloud density of dodecylamine much higher, which was more favourable to the interaction of dodecylamine and the naked metal base, and hence dodecylamine had a much better inhibition performance in a neutral environment than in acidic environments.

Originality/value

This paper provides information regarding the inhibition performance and adsorption behaviour of dodecylamine on N80 steel and probes the inhibition mechanism of dodecylamine in acidic and neutral environments. The results of the work contribute to an understanding of the inhibition mechanism of the inhibitor in different environments, which will be useful for effective design and choice of inhibitors in CO2 corrosion.

Details

Anti-Corrosion Methods and Materials, vol. 54 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 March 2006

H.S. Awad

Zn‐Al alloys are widely used as coatings for corrosion protection of steel. These alloys provide long‐term protection to steel in several aqueous media; however, little attention…

Abstract

Purpose

Zn‐Al alloys are widely used as coatings for corrosion protection of steel. These alloys provide long‐term protection to steel in several aqueous media; however, little attention has been paid to their behaviour in acidic media. The aim of this investigation is to study the corrosion and inhibition of 90 per cent Zn‐10 per cent Al alloy in hydrochloric acid.

Design/methodology/approach

Pyridine and a number of its methyl‐containing derivatives were applied in controlling the corrosion of 90 per cent Zn‐10 per cent Al alloy. The inhibitive action and mechanism of these compounds were investigated by weight loss tests, linear polarisation resistance measurements, galvanostatic polarisation tests and electrochemical impedance spectroscopy.

Findings

It was found that the corrosion rate of this alloy was much higher than that of either Zn or Al alone. Pyridine and its derivatives exhibited good inhibition for the corrosion of 90 per cent Zn‐10 per cent Al alloy, their inhibition efficiency increased in the order: I < II < III < IV. Potentiodynamic polarisation studies revealed that the investigated pyridine derivatives were mixed‐type inhibitors and functioned by adsorption on reactive sites on the alloy surface through the influence of the nucleophilic nitrogen atom forming a good physical barrier to prevent access of aggressive ions to the alloy surface. This was supported by the impedance measurements which showed a change in the charge transfer resistance and double layer capacitance indicating adsorption on the alloy surface. It was shown that the introduction of the methyl group(s) into the pyridine ring enhanced the effectiveness of pyridine inhibition. The improvement was attributable to the electron‐donating tendency of this group that gives rise to the increase in the electron density at the adsorption site. All the investigated substituents showed negative values of the Hammett constant (σ), indicating their electron‐donating property. The negative value of this constant increased according to the order: I < II < III < IV, the greater the negative value of σ being consistent with the greater degree of corrosion inhibition. It also was revealed that the presence of these inhibitors increased the value of activation energy for corrosion with a ranking order that was consistent with that of their inhibition effectiveness.

Research limitations/implications

The evaluated inhibitors assured significant corrosion inhibition of the Zn‐Al alloy in HCl, however, their behaviour in different acid media was ambiguous.

Originality/value

This paper makes significant contibution to understanding the corrosion and inhibition of one of the widely apply coatings for steel protection in one of the most widely used aqueous mineral acids in industry.

Details

Anti-Corrosion Methods and Materials, vol. 53 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

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 trial to…

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: 1 April 1998

A.M.S. Abdennabi, A.I. Abdulhadi and S. Abu‐Orabi

Corrosion inhibitors represent the most cost effective and flexible means of controlling internal corrosion associated with oil and gas production. Tests were carried out to…

445

Abstract

Corrosion inhibitors represent the most cost effective and flexible means of controlling internal corrosion associated with oil and gas production. Tests were carried out to demonstrate the structure/effect relationships which are effective in controlling the inhibition efficiency. To illustrate this approach, the substituent field effect at the paraposition of 1(Benzyl)1‐H‐4,5‐Dibenzoyl‐1,2,3‐ Triazole (BDBT) on corrosion inhibition has been investigated. Mild steel rotating cylinder electrode in acid media was used in conjunction with Tafel polarization technique, AC impedance measurements and continuous linear polarization resistance method. The nitro group was found to cause a considerable decrease in the corrosion inhibition of the parent compound BDBT. Owing to the induction effects of Br on the aromatic ring the bromo derivative has better inhibition protection than the methyl derivative. The corrosion rate profiles obtained from on‐line polarization technique showed that the inhibition capacity of the studied substituents at the para‐position increases as follows: NO2 < CH3 < Br < H.

Details

Anti-Corrosion Methods and Materials, vol. 45 no. 2
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 7 November 2008

Qun‐jie Xu and Guo‐ding Zhou

The purpose of this paper is to provide useful information pertaining to the corrosion inhibition mechanism of BTA and its derivatives on copper.

Abstract

Purpose

The purpose of this paper is to provide useful information pertaining to the corrosion inhibition mechanism of BTA and its derivatives on copper.

Design/methodology/approach

The photoelectrochemical behavior of copper electrodes in buffered borax solutions (pH 9.2) containing BTA and its derivatives was comparatively studied by using a photoelectrochemical technique. It was possible to analyze the inhibition mechanism of the derivatives of BTA for copper corrosion from the photoelectrochemical results. The photoresponse of the Cu electrode in buffered borax solutions containing BTA and its derivatives was measured. Different concentrations and different kinds of inhibitors may result in different photoresponses on the Cu electrode in buffered borax solutions.

Findings

The photoresponse for copper electrodes in solutions containing a certain amount of BTA exhibits an n‐type response during anodic polarization and, the greater the n‐type photoresponse, the better the performance of the inhibitor. The photoresponse for copper electrodes in solutions containing 4CBTA, or 5CBTA, or CBT‐1, always exhibited p‐type behavior during anodic polarization, but the photoresponse changed very evidently during cathodic polarization. The larger the maximum cathodic photocurrent, then the greater was the effectiveness of the corrosion inhibitor. In consequence, it is possible to evaluate inhibitors according to ΦV and iph at more negative potentials. The more negative the ΦV and iph, the better is the inhibition. It was shown that the inhibition mechanism of the derivatives of BTA with a −COOH group was different from that occurring with ester groups. The former could make the Cu2O film on the Cu electrode thicker. The photocurrent was observed to increase when the potential was scanned to more negative potentials in the presence of certain concentrated inhibitors. It is therefore possible to evaluate the performance of inhibitors according to the value of the cathodic photocurrent. The larger the cathodic photocurrent, the better is the inhibition effect of the compound. The latter could increase the density of the polymer film on the copper electrode and prevent O2− in the solution from entering the copper surface and changing the stoichiometric ratio of Cu2O. The photocurrent type could transfer from p‐ to n‐type according to the action of certain concentrated inhibitors when the potential was scanned to more positive potentials. The value of the anodic photocurrent can be used to evaluate the effectiveness of inhibition. The larger the anodic photocurrent, the greater is the inhibition effect.

Originality/value

The paper provides useful information pertaining to the corrosion inhibition mechanism of BTA and its derivatives on copper. The photoelectrochemical technique is an effective method with which to evaluate the effectiveness of corrosion inhibitors and to investigate the mechanism of corrosion inhibition on copper.

Details

Anti-Corrosion Methods and Materials, vol. 55 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 February 2005

Hayam S. Awad

The aim of the present work was to study the synergistic effect of HEDP and zinc on inhibition of the corrosion of carbon steel in neutral oxygen‐containing chloride solutions…

Abstract

Purpose

The aim of the present work was to study the synergistic effect of HEDP and zinc on inhibition of the corrosion of carbon steel in neutral oxygen‐containing chloride solutions, and to investigate the effect of zinc‐HEDP molar ratio on the effectiveness of the zinc‐HEDP inhibitive mixtures.

Design/methodology/approach

The inhibition of the corrosion of carbon steel by zinc‐HEDP mixtures in neutral oxygen‐containing solutions was investigated in the presence of 0.003 M (106 ppm) chloride.

Findings

It was shown that the inhibition by these mixtures depended not only on the zinc/HEDP molar ratio but also on the concentration of both zinc and HEDP. HEDP concentration appeared to be crucial where good inhibition was not achieved at low concentrations and aggressive nature is observed at high HEDP levels. The effectiveness of the zinc‐HEDP mixtures enhanced inhibition by increasing the zinc content of the mixture, but the mechanism was only effective to a certain level, above which the inhibition effect declined. The predominant corrosion control mechanism of the zinc‐HEDP mixture was on the anodic (metal dissolution) reaction, but it also affected the rate and mechanism of the oxygen reduction reaction.

Originality/value

Demonstrates how the effectiveness of the zinc‐HEDP mixtures can enhance inhibition by increasing the zinc content of the mixture.

Details

Anti-Corrosion Methods and Materials, vol. 52 no. 1
Type: Research Article
ISSN: 0003-5599

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 and to…

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 June 2002

G. Bereket and A. Yurt

Potentiodynamic polarisation studies were carried out on the inhibition of low carbon steel in 0.1M hydrochloric acid solution over the temperature range 20‐60°C at different…

Abstract

Potentiodynamic polarisation studies were carried out on the inhibition of low carbon steel in 0.1M hydrochloric acid solution over the temperature range 20‐60°C at different inhibitor concentrations by various quaternary ammonium salts and cationic surfactants. The inhibitors examined were tetraethyl ammonium chloride, tetrabutyl ammonium chloride, benzyltrimethyl ammonium chloride, benzyltriethyl ammonium chloride, benzyltributyl ammonium chloride, phenyltrimethyl ammonium chloride, alkylbenzyldimethyl ammonium chloride, tetradecyltrimethyl ammonium bromide and cetyltrimethyl ammonium bromide. Maximum inhibition efficiencies of cationic surfactants were observed around and above critical micelle concentration (cmc), while the inhibition efficiencies of the quaternary ammonium salts were found to increase with the increase in their concentrations. The degree of shift in Ecorr value, together with change in anodic and cathodic Tafel slopes (ba, bc), revealed that cationic surfactants behave as an anodic inhibitor, while quaternary ammonium salts behave as mixed type inhibitors. Inhibition efficiencies of studied inhibitors seem to be closely related with the chain length of the alkyl group as well as the presence of benzene ring in quaternary ammonium compounds. Thermodynamic and kinetic parameters for dissolution and adsorption were also calculated.

Details

Anti-Corrosion Methods and Materials, vol. 49 no. 3
Type: Research Article
ISSN: 0003-5599

Keywords

1 – 10 of over 5000