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This paper aims to investigate the influence of temperature and lignin concentration on the inhibition of carbon steel corrosion in 1 M HCl.

Weight loss corrosion tests were performed at different temperatures in the range of 30-70°C (303-343 K).

It was found that the corrosion inhibition efficiency (IE) of lignin on the carbon steel decreased when the temperature was increased from 60 to 70°C. However, at lower temperatures ranging from 30 to 50°C, the IE improved, due to occurrence of lignin adsorption on the surface of metal specimens. The IE was higher with increasing lignin concentration, thus reducing the weight loss of the carbon steel. The adsorption phenomenon involved exothermic processes because the value of enthalpy of adsorption (ΔH°_ads) < 0 and Gibbs free energy of adsorption (ΔG°_ads) were less negative with increase in temperature. The entropy of adsorption (ΔS°_ads) had negative values, representing the decrease in disorder of adsorption. The adsorption of lignin on the carbon steel surface in 1 M HCl was comprehensive, as deduced from kinetic and thermodynamic parameters. However, physisorption was the major contributor in the inhibition mechanism. The inhibitive features of carbon steel surfaces showed less damage once the steel was treated in lignin, as evident from macroscopy images.

The use of lignin as an acid corrosion inhibitor at high temperature is practical in metal surface treatment process.

The use of organic compounds gives an advantage to the environment, universal health and save cost, as the compounds can be found in nature.

Lignin can act as a flexible corrosion inhibitor within the temperature range of 30-70°C in 1 M HCl because it exhibits comprehensive adsorption (i.e. a combination of both physisorption and chemisorption) at specific concentrations.

This paper aims to evaluate the inhibition efficiency of norfloxacin on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions.

Evaluation was carried out by electrochemical techniques such as electrochemical impedance spectroscopy and potentiodynamic polarization studies. Scanning electron microscopy was used, and it finally confirmed the existence of the adsorbed film.

The electrochemical measurements showed that norfloxacin has good inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The inhibition action of norfloxacin in both of the corrosive media was observed to be of mixed type but with more of cathodic nature. The temperature dependence of the corrosion rate was studied in the temperature range from 35 to 55°C and the activation energy (E_a) was calculated. The adsorption of norfloxacin molecules on copper surface obeyed Langmuir adsorption isotherm. Studies on the potential of zero charge have been carried out to establish the mechanism of adsorption of the inhibitor onto the metal surface. The thermodynamic parameters such as the adsorption equilibrium constant (K_ads) and the free energy of adsorption (ΔG_ads) were calculated. The value of free energy of adsorption very close to −40 kJmol⁻¹ indicates that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in value of E_a with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface.

This paper indicates that norfloxacin can act as a good inhibitor for the corrosion of copper in both the acid media.

The inhibition mechanism and the relationship between the inhibition efficiency of para‐chlorobenzene nitriles on carbon steel in hydrochloric acid, and their molecular structure, were studied by microscopy and quantum chemistry calculations. The inhibition of carbon steel was achieved by chemisorption of the para‐chlorobenzene nitriles onto the surface of the carbon steel. The greater was the σ_N (absolute value) and the less the E_LUMO value, the greater was the inhibition efficiency.

This study aims to characterize the composition of the tribo-layer formed during sliding of steel in the presence of crude jatropha oil (CJO) and epoxidized jatropha oil (EJO) under boundary lubricant application.

CJO was obtained from a local market and used as received. EJO was obtained by epoxidation process with peroxyformic acid catalyzed by acidic ion exchange resin. The tribological test was conducted by the four ball method according to ASTM 4192. Wear scars generated on the lower balls were used to characterize the tribo-layer. Energy-dispersive X-ray and X-ray photo spectroscopy analysis were conducted to characterize the tribo-layer composition.

EJO shows a lower friction coefficient compared to CJO. Moreover, EJO also shows better wear preventive properties compared to CJO. The oxidation of CJO and EJO has lead chemisorption of the oil to steel surface to cause formation of protective layers for the steel surface. The layers were constructed from inorganic oxide in the form of iron oxides and silicon oxide together with organic layers in form of aldehyde, ketone and carboxylic acid. The formation and removal of this layer from rubbing sites are considered to affect wear-preventive and friction behaviour of steel lubricated with CJO and EJO.

This works highlights friction and anti-wear characteristics of CJO and EJO. This work also presents the composition of the tribo-layer that formed because of the sliding of steel lubricated with CJO and EJO. The method and result can be used for further investigation and development of lubricant.

The purpose of this study is to evaluate the effect of the four tautomeric forms of 2-amino-5-mercatpo-1,3,4-thiadizole (AMT) absorbed on copper surface by the polar or non-polar groups. Polar group of AMT is mostly electronegative with larger N and S atoms as central atoms. 5-amino-1,3,4-thiadiazole-2(3H)-thion (AMT-c) has the highest adsorption energy and is easy to react with copper. The interaction between AMT-c and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement.

Adsorption behavior of AMT as corrosion inhibitor on copper surface in oil field was studied by weight loss measurement, and the corrosion inhibition mechanism was analyzed. Reactive sites and distributions of tautomeric forms of AMT as inhibitor on Cu(100) crystal plane were calculated by density functional theory.

All atoms of AMT are in the same plane, and AMT is an aromatic ring structure by large p-chain adsorbed on the metal surface by a plane configuration. AMT-c has the highest adsorption energy and also the most stable isomerized product. The determinate locations of AMT on the Cu(100) surface are the bridge and the hollow sites using molecular dynamics. Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Inhibition efficiency is increased with the increase in the concentration of the inhibitor. The maximum efficiency of 92 per cent is obtained for 50 ppm AMT concentration at 373 K, which is attributed to the presence of extensively delocalized electrons of the phenyl rings, planarity and the presence of lone pair of electrons on N and S atoms, which favored a greater adsorption of inhibitors on copper surface.

Corrosion of copper can be effectively inhibited by AMT, which is a kind of excellent corrosion inhibitor, and this property is attributed to the polar groups and non-polar groups of AMT that play a role as absorption and shielding on copper surface, respectively. Adsorption of AMT as corrosion inhibitor on copper surface obeys Langmuir isotherm. The interaction between AMT and copper conforms to chemisorption, which is to be further verified by the experiment on the weight loss measurement.

The purpose of this paper is to study the corrosion inhibition performance of an eco-friendly drug clozapine on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions.

The corrosion inhibition nature of inhibitor molecule was evaluated by weight loss, electrochemical impedance spectroscopy and potentiodynamic polarization studies. An attempt was made to correlate the molecular properties of neutral and protonated forms of inhibitor molecule using quantum chemical calculations. The effect of temperature on the corrosion inhibition efficiency was also studied using electrochemical impedance spectroscopy. The potential of zero charge was determined to explain the mechanism of corrosion inhibition.

The studies on corrosion inhibition performance of clozapine showed that it has good corrosion inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The adsorption of clozapine molecules onto the copper surface obeyed the Langmuir adsorption isotherm. The value of free energy of adsorption calculated is very close to −40 kJmol⁻¹, indicating that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in the value of energy of activation with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface. The potential of zero charge and quantum chemical studies confirmed that the protonated molecules also get involved in the corrosion inhibition process through physisorption.

The present work indicates that clozapine can act as a good corrosion inhibitor for the corrosion of copper in acid media.

Plant development and use as green corrosion inhibitors are already recognized as one of the most environmentally friendly and effective protocols. In recent years, efforts have been made to find green corrosion inhibitors as an alternative to synthetic inhibitors for metals in acid medium. This paper aims to report the investigation of use of aqueous extracts of Tamarindus Indica as green inhibitors for corrosion of metals within different circumstances.

The use of Tamarindus Indica extracts (leaves, stem, fruit pulp and fruit husk) as corrosion inhibitors for mild steel and aluminum in different mediums (HCl, H2SO4, formic acid and citric acid) at different temperatures was investigated.

The inhibitory efficiency of Tamarindus Indica extracts increases with increasing concentration and decreases with increasing temperature. Langmuir is the adsorption isotherm, and the extract (inhibitor) is a mixed-type inhibitor (physisorption and chemisorption).

Tamarindus extracts (leaves, stem, fruit pulp and fruit husk) are effective inhibitors and can be used to protect metals from corrosion at different circumstances.

To the best of the authors’ knowledge, this is the first review that discusses the use of Tamarindus Indica extracts as corrosion inhibitors for metals.

To investigate the capability of a series of nitrogen‐based heterocyclic organic compounds in inhibiting corrosion of iron in HCl and elucidate the dominant active form of the applied compounds during the adsorption process to explore the mechanism of their action.

The tested compounds were pyrimidine containing compounds, which were selected, based on molecular structure considerations. Gravimetric method has been applied with various electrochemical techniques (polarisation resistance, polarisation curves and electrochemical impedance spectroscopy) to investigate inhibition efficiency and mechanism.

The inhibiting action of the investigated pyrimidine containing compounds depends primarily on their concentration and molecular structure. These compounds act as mixed type inhibitors and function via adsorption on the surface, which follows Frumkin adsorption isotherm. The inhibition by the tested pyrimidine derivatives could be attributed to their chemisorption on the metal surface forming donor/acceptor type of bond between the inhibitor molecules and the vacant d orbitals of the surface iron atoms. Contribution from electrostatic adsorption, via interaction between the protonated form of the inhibitor and the charged metal surface, is also possible.

The applied inhibitors were tested in the presence of chloride ions as a corrosive medium. Whether these inhibitors will function well in the presence of other ions that are typically present in natural corrosive environment is unknown.

This paper provides useful information regarding inhibition effect of pyrimidine and series of its derivatives. The outcome of this work contributes to better understanding of the mechanism of inhibition by this class of N‐based heterocyclic organic compounds.

The inhibition of sweet gas corrosion of carbon steel in high pressure CO₂ saturated brine by rosin amine has been studied by weight‐loss, electrochemical polarisation and electrochemical impedance spectrum measurements. The results obtained revealed that rosin amine compound is a good inhibitor. The inhibition efficiency increased with the increase of inhibitor concentration. Rosin amine acts mainly as a adsorptive mixed‐type inhibitor. The adsorption of the inhibitor on the metal surface in high pressure CO₂ saturated brine obey Langmuir isotherm. The adsorption mechanism of inhibitor was both electrostatic‐adsorption and chemisorption.

The work described in this paper is part of a current programme that has two objects: (1) to investigate further the reasons for the different scaling behaviour of steel in steam and carbon dioxide, although these gases have similar oxygen potentials; (2) to provide background information for an investigation into the effect of variations in re‐heating furnace atmospheres upon scaling and scale adhesion.