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A study is carried out on the resistance to corrosion of mild steel in 5 per cent H₂SO₄ solutions at temperatures between 30 and 60°C. The effectiveness of quaternary ammonium salt used as corrosion inhibitor under the same experimental conditions was also investigated. Weight loss results and electrochemical data showed the good inhibiting action of the inhibitor, acting as anodic type. Thermodynamic parameters for adsorption of the compound are calculated using the Temkin adsorption isotherm.

The purpose of this paper is to evaluate the performance of polypropylene glycol (PPG), as a corrosion inhibitor for aluminium corrosion in 0.5 M H₂SO₄ solution at 303-333 K and the effect of addition of iodide ions on the corrosion inhibition efficacy of PPG.

The corrosion inhibition performance of PPG alone and on addition of iodide ions in the acid medium was evaluated using weight loss and electrochemical [electrochemical impedance spectroscopy (EIS), linear polarisation resistance (LPR) and potentiodynamic polarization (PDP)] methods as well as surface analysis approach at 303-333 K. The morphology of the corroding aluminium surface without and with the additives was visualised using scanning electron microscopy (SEM). The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption.

Results obtained showed that PPG moderately retarded the corrosion of Al in 0.5 M H₂SO₄ solution. Addition of KI to PPG is found to synergistically improve the inhibitive ability of PPG. From the variation of inhibition efficiency, K_ads, and E_a, with rise in temperature, physisorption mechanism is proposed for the adsorption of PPG and PPG + KI onto the Al surface in 0.5 M H₂SO₄ solution. Polarisation results showed that PPG and PPG + KI acted as mixed type inhibitor. The adsorption of PPG and PPG + KI, respectively, onto the metal surface followed El-Awady et al. adsorption isotherm model. SEM and water contact angle analysis confirmed the adsorption of PPG and PPG + KI on Al surface.

The research is limited to aqueous acid environment in aerated condition, and all tests were performed under static conditions.

The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal.

The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal.

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

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.

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 (ΔG_ads⁰,ΔH_ads⁰,ΔS_ads⁰) for the adsorption process and kinetic parameters for the metal dissolution (or hydrogen evolution) reaction were determined.

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

The inhibiting effect of cationic surfactant N, N, N‐dimethyl 4‐methylbenzyl dodecyl ammonium chloride on mild steel in hydrochloric acid solutions was investigated by surface and thermodynamic measurements, weight loss tests, polarization measurements and EDS techniques. The data obtained from surface and thermodynamic measurements with the inhibitor indicate that the area per molecule slightly increases with increasing temperature and both absorption and micellization processes are spontaneous. Weight loss measurement showed that the inhibition efficiencies increased with increasing surfactant concentration and attained a maximum around their critical micelle concentration. Polarization studies reveal that the inhibitor behaves as a mixed type in hydrochloric acid solutions and acted on the cathodic reaction without modifying the mechanism of the hydrogen evolution reaction. EDS measurement showed high coverage of surfactant on the mild steel surface.

The pitting corrosion of copper in chloride solution has been studied using potentiostatic polarisation and surface analysis techniques. X‐ray photoelectron spectroscopy (XPS) results enabled conclusions to be drawn about the nature of the film formed in different chloride concentrations. In dilute chloride solutions (C≤10⁻³ M), XPS proved the existence of Cu₂O film on the copper surface. It was found that, depending on the chloride content, pitting of copper was evident only after the formation of a protective film of Cu₂O. A current‐time trend plot showed the onset of fluctuations, which were dependent on the NaCl content. On the other hand, introduction of O₂ into the solution during prepolarisation time period increased the current value of the fluctuations at the same concentration of NaCl in comparison with the freely aerated solution. These results, together with the surface analysis, confirm the role of chloride ion on the mechanism of pitting attack on copper metal.

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 (ΔG_ads^o, ΔH_ads^o, ΔS_ads^o), 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.

The purpose of this paper is to investigate the inhibition effect of 2‐aminoethane thiol hydrochloride, 2‐cystamine dihydrochloride, 2,3‐dimercapto‐1‐propanol, 1,2‐ethanedithiol, and the synergistic effect of these compounds with halide ions (Cl⁻, Br⁻, I⁻) and with some metal cations (Co^2 +, Ni^2 +, Cu^2 +, Zn^2 +).

The inhibiting effect of the studied thiols on the corrosion of carbon steel in 0.5 M H₂SO₄ solution were investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy and linear polarisation methods.

The inhibition action of thiols depends mainly on the type of the heteroatom present in the inhibitor molecule. The increase in inhibition efficiencies with increase in inhibitor concentration revealed that the studied compounds were adsorbed onto steel surfaces and the adsorption mechanism obeyed the Langmuir adsorption isotherm. Polarisation curves indicated that thiols containing both N and S atoms in their structure behaved as mixed type inhibitors, while thiols containing only an S atom in their structure acted essentially as anodic inhibitors. The increase in the inhibition efficiencies of thiols with the addition of halide ions indicates that halides play important role in the adsorption process. The synergistic effect of the studied metal cations could be explained by the adsorption of complex ions formed from thiol molecules and metal cations.

This paper provides useful information about the relationship between inhibition efficiencies and the structures of thiols and clarifies the mechanism of the synergistic effects of some halides and some metal cations.

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 E_corr value, together with change in anodic and cathodic Tafel slopes (b_a, b_c), 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.

The effectiveness of bisquaternary ammonium salt N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐ pentanediammonium dichloride used as corrosion inhibitor for carbon steel in 1.0 M HCl was investigated by weight loss and electrochemical techniques. Surfaces were characterised by scanning electron microscopy. The performance of the bisquaternary ammonium salt was also compared with that of urotropine, a commercial corrosion inhibitor for acid media in industry practice. The results showed good inhibiting action of the inhibitor. The inhibition efficiency increases with the inhibitor concentration but is temperature–independent. N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐pentanediammonium dichloride acts mainly as a mixed‐type inhibitor. The inhibition of this bisquaternary ammonium compound was assumed to occur via adsorption of the inhibitor molecule on the metal surface without affecting the corrosion mechanisms. The adsorption of the inhibitor on the metal surface in HCl solution was found to obey Frumkin's isotherm.