Newly synthesized pyrimidine compound as CO2 corrosion inhibitor for steel in highly aggressive simulated oilfield brine

A newly synthesized pyrimidine–based compound, 5-(4-hydroxy-3-methoxyphenyl)-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d]pyrimidin-4(1H)-one (PP), was evaluated as a promising inhibitor for the CO₂ corrosion of API X60 steel in NACE 1D196 brine solution. Under rotation speed of 1000?rpm, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were complemented with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Attenuated total reflectance infrared (ATR-IR) techniques to assess the corrosion inhibition performance. PP provided inhibition efficiency up to 90% at 20?ppm. It adsorbs on the Fe (110) phase on the steel using its heteroatoms and aromatic rings. Its adsorption greatly reduces the steel surface pitting corrosion.     

Surface analysis of inhibitor films formed by 1-aminoanthraquinones on API 5L-X60 steel in diesel-water mixtures

Three long chain fatty acid substituted aminoanthraquinone (AAQ) were synthesized in the laboratory and evaluated as corrosion inhibitors for steel (API 5L-X60) in diesel-water mixtures at room temperature by weight loss and electrochemical studies. Potentiodynamic polarization studies carried out at room temperature on steel (API 5L-X60) in diesel with water containing 120 ppm of chloride and 50 ppm of aminoanthraquinone (AAQ) derivative showed that all the investigated compounds are of anodic type. The results obtained indicate that 1-aminoanthraquinone derivatives are good corrosion inhibitors in diesel-water mixtures. Oleic acid substituted aminoanthraquinone was found to be the best corrosion inhibitor. It exhibited 92% inhibition efficiency against the corrosion of API 5L-X60 steel in diesel-water mixtures. The surface analysis by AFM indicates the adsorption of synthesized inhibitors on the metal surface.     

Enhancing of Corrosion Inhibition and the Biocidal Effect of Phosphonium Surfactant Compounds for Oil Field Equipment

It is well known that tetra hydroxymethyl phosphonium sulfate (THPS) is commonly used in oil fields as a biocide for sulfate-reducing bacteria (SRB), but it has low corrosion inhibition. In this study, four phosphonium surfactant compounds were synthesized via a coupling reaction between THPS and different fatty acids namely: decanoic, dodecanoic, palmitic and stearic acids to produce the corresponding surfactants. The chemical structure of the synthesized surfactants was confirmed using FTIR and ¹H-NMR spectroscopy. The surface activity of the prepared compounds was determined by surface tension measurements. The critical micelle concentration (CMC) of each surfactant compound was determined. The corrosion inhibition of the synthesized compounds on carbon steel in 0.5 M HCl was studied by weight loss measurements, potentiodynamic and electrochemical impedance spectroscopy. The effect of the inhibitor concentration and hydrophobic chain length on the their efficiency was also studied. It was found that the CMC of each compound depends on its chemical structure. It was also found that the corrosion inhibition efficiency depends on both of concentration and molecular structure of the inhibitors. Polarization curves revealed that the inhibitors used represent mixed-type inhibitors, which hinder the cathodic and anodic parts of the corrosion reaction in acidic media. Adsorption of used inhibitors leads to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Also the biocidal effect of these compounds was enhanced.     

Adsorption and corrosion inhibition of amphiphilic compounds on steel pipeline grade API 5L X52 in sulphuric acid 1 M

The effect of seven amphiphilic compounds, on steel API 5L X52 corrosion in sulphuric acid 1 M solution was studied by potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization curves indicated that these compounds acted mainly as cathodic type inhibitors. The EIS spectrums showed that the mechanism of corrosion inhibition is mainly a faradic process, the spectra were fitted with one electrical equivalent circuit (EEC) using a constant phase element (CPE). Double layer capacitance associated with CPE was also obtained. Langmuir, Temkin, and Henry adsorption isotherm described the experimental findings. This information suggested that organic molecules were adsorbed on active sites on metal surface avoiding contact of corrosive media with steel surface, having adsorbate molecules low molecular interaction between them even with the presence of more amphiphilic molecules on the steel surface as concentration got higher values.     

Inhibition of mild steel corrosion in groundwater by pyrrole and thienylcarbonyl benzotriazoles

The inhibition efficiency of Zn²⁺, 3-phosphonopropionic acid (3-PPA), benzotriazole (BTA) and two synthesized benzotriazole derivatives namely 1-(2-pyrrole carbonyl) benzotriazole (PCBT) and 1-(2-thienylcarbonyl) benzotriazole (TCBT) were evaluated as inhibitors for the corrosion of mild steel in ground water. The inhibition efficiencies of PCBT and TCBT in combination with Zn²⁺ and 3-PPA were also investigated and the results were compared with BTA. In order to study the corrosion rate and inhibition efficiency we employed potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Further characterization using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) demonstrates the adsorption of inhibitor and the formation of corrosion products on the mild steel surface, respectively. Combination of PCBT along with Zn²⁺ and 3-PPA shows better corrosion inhibition efficiency than other inhibitor combinations and the individual inhibitors.     

Inhibition Effects of a Synthesized Novel 4-Aminoantipyrine Derivative on the Corrosion of Mild Steel in Hydrochloric Acid Solution together with Quantum Chemical Studies

1,5-Dimethyl-4-((2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-one (DMPO) was synthesized to be evaluated as a corrosion inhibitor. The corrosion inhibitory effects of DMPO on mild steel in 1.0 M HCl were investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, open circuit potential (OCP) and electrochemical frequency modulation (EFM). The results showed that DMPO inhibited mild steel corrosion in acid solution and indicated that the inhibition efficiency increased with increasing inhibitor concentration. Changes in the impedance parameters suggested an adsorption of DMPO onto the mild steel surface, leading to the formation of protective films. The novel synthesized corrosion inhibitor was characterized using UV-Vis, FT-IR and NMR spectral analyses. Electronic properties such as highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy (EHOMO and ELUMO, respectively) and dipole moment (μ) were calculated and discussed. The results showed that the corrosion inhibition efficiency increased with an increase in the EHOMO values but with a decrease in the ELUMO value.     

Thiazoles as corrosion inhibitors for mild steel in formic and acetic acid solutions

2-(N,N-dimethylamino) benzylidene imino-4-(4-methyl phenyl)-1,3-thiazole (DIMPT), 2-benzylidene imino-4-(4-methyl phenyl)-1,3-thiazole (BIMPT), 2-salicylidene imino-4-(4-methyl phenyl)-1,3-thiazole (SIMPT) and 2-cinnamylidene imino-4-(4-methyl phenyl)-1,3-thiazole (CIMPT) were synthesized in the laboratory and their influence on the inhibition of corrosion of mild steel in 20 formic acid and 20 acetic acid was investigated by weight loss and potentiodynamic polarization techniques. The inhibition efficiency of these compounds was found to vary with their nature and concentration, temperature, immersion time and acid concentration. The values of activation energy and free energy of adsorption of the thiazoles were calculated to investigate the mechanism of corrosion inhibition. The adsorption of all the thiazoles on mild steel surface was found to obey Langmuir adsorption isotherm. The potentiodynamic polarization result revealed that the compounds studied are mixed type inhibitors. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition.     

Biomaterials for corrosion protection: evaluation of mustard seed extract as eco-friendly corrosion inhibitor for X60 steel in acid media

The toxic nature of most organic and inorganic corrosion inhibitors has necessitated the search for corrosion inhibitors with an excellent environmental profile. The present work is focused on the widening utilization of plant extracts for metallic corrosion control and reports on the corrosion inhibition effect of mustard seed extract (MSE) for typical X60 pipeline steel in 2 M HCl and 1 M H₂SO₄ solutions. Gravimetric and electrochemical (electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization) methods were employed. The effect of immersion time and temperature on the corrosion inhibition effect of the plant extract was also studied. Results obtained show that MSE inhibited the corrosion of steel in both media which was more pronounced in H₂SO₄ than in HCl environment. Inhibition efficiency increased with increase in the concentration of the extract but decreased with increase in temperature. The potentiodynamic polarization studies revealed that MSE functions as a mixed-type inhibitor. The corrosion inhibition is assumed to occur via adsorption of the components of the extract on the steel surface which was found to obey Langmuir adsorption isotherm model. The morphology of the corroding steel surface in the absence and presence of the MSE was visualized using scanning electron microscopy.     

Inhibition of mild steel corrosion in sulfuric acid solution by thiadiazoles

Four heterocyclic compounds namely 2-amino-1,3,4-thiadiazoles (AT), 5-Methyl-2-amino-1,3,4-thiadiazoles (MAT), 5-Ethyl-2-amino-1,3,4-thiadiazoles (EAT) and 5-Propyl-2-amino-1,3,4-thiadiazoles (PAT) were synthesized and their influence on the inhibition of corrosion of mild steel (MS) in 0.5 M H₂S0₄ was investigated by weight loss and potentiodynamic polarization techniques. The values of activation energy, free energy of adsorption, heat of adsorption, enthalpy of activation and entropy of activation were also calculated to investigate the mechanism of corrosion inhibition. Potentiodynamic polarization studies were carried out at room temperature, and showed that all the compounds studied are mixed type inhibitors causing blocking of active sites on the metal. The inhibition efficiency of the compounds was found to vary with concentration, temperature and immersion time. Good inhibition efficiency was evidenced in the sulfuric acid solution. The adsorption of the compounds on mild steel for sulfuric acid was found to obey Langmuir’s adsorption isotherm. FT–IR spectroscopic studies were also used to investigate the purity of compounds synthesized.     

Synthesis and application of phenylcarbamodithioate compound for steel protection

Phenyldithiocarbamate compound has been synthesized and studied as corrosion inhibitor for steel. Dithiocarbamate (DTC) compounds with linear alkyl groups are good inhibitors, but their stability is quite low in acidic solutions. It should be noted that long-term stability is important for practical applications, in order to avoid excess use of chemicals. So, we have synthesized phenyl substituted DTC which offers strong inhibition efficiency and extra stability. This new inhibitor is chemically adsorbed on steel through its DTC group, while the aromatic ring provides extra stability and long-term efficiency. For the assessment of corrosion kinetics, we have utilized potentiodynamic and ac impedance studies; also solution assay analysis was realized with atomic absorption spectroscopy. It was revealed that inhibitor exhibits remarkably high efficiency, even under elevated temperature conditions. At 55 °C temperature conditions, i_corr value decreased from 5050 to 154 μA cm^?2, with the addition of 500 ppm inhibitor. The long-term stability of inhibitor was also tested and 85.93% efficiency was obtained after three days of exposure period for 500 ppm concentration.     

Fatty acid oxadiazoles as corrosion inhibitors for mild steel in formic acid

Selected oxadiazoles of fatty acids; namely 2-hepta decene-5-mercapto-1-oxa-3,4-diazole (HMOD); 2-undecane-5-mercapto-1-oxa-3,4-diazole (UMOD); and 2-decene-5-mercapto-1-oxa-3,4-diazole (DMOD), were synthesized. Their influence on the inhibition of corrosion of mild steel in 20% formic acid (HCOOH) was investigated by weight loss and potentiodynamic polarization techniques. The inhibition efficiency of the compounds was found to vary with concentration, immersion time and temperature. All the compounds showed good inhibition efficiency (e _IE) in formic acid solution. Adsorption on mild steel obeyed the Langmuir adsorption isotherm. Potentiodynamic polarization revealed that all three inhibitors, HMOD, UMOD, and DMOD are mixed inhibitors. Electrochemical impedance spectroscopy was also used to investigate the inhibition mechanism.     

Hector bases – a new class of heterocyclic corrosion inhibitors for mild steel in acid solutions

Three heterocyclic compounds namely 3-anilino-5-imino-4-phenyl-1, 2,4-thiadiazoline (AIPT), 3-anilino-5-imino-4-tolyl-1, 2,4-thiadiazoline (AITT), and 3-anilino-5-imino-4-chlorophenyl-1, 2,4-thiadiazoline (AICT) were synthesized and their influence on the inhibition of corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ was investigated by weight loss and potentiodynamic polarization techniques. The values of activation energy and free energy of adsorption of these compounds were also calculated. Potentiodynamic polarization studies were carried out at room temperature, and showed that all the compounds were mixed type inhibitors causing blocking of active sites on the metal. The inhibition efficiency of the compounds was found to vary with concentration, temperature and immersion time. Good inhibition efficiency was evidenced in both acid solutions. The adsorption of the compounds on mild steel for both acids was found to obey the Langmuir adsorption isotherm. Electrochemical impedance spectroscopy was also used to investigate the mechanism of corrosion inhibition.     

Corrosion inhibition of pipeline steel grade API 5L X52 immersed in a 1 M H2SO4 aqueous solution using heterocyclic organic molecules

The effect of the concentration of four types of inhibiting heterocyclic molecules on the corrosion susceptibility of steel pipeline samples grade API 5L X52 in 1 M H₂SO₄ was studied by electrochemical testing and SEM analysis. The compounds used were: 2-mercaptobenzoimidazole (MBI), 5-mercapto-1-tetrazoleacetic sodium salt (MTAc), 1-hydroxybenzotriazole (HBT) and benzimidazole (BIA). The results showed that there was an optimum inhibitor concentration at which the maximum inhibiting efficiency, IE, was reached. Further, the MBI displayed the best inhibiting characteristics for this system, with a maximum IE of approximately 99% having added only 25 ppm. It is shown that this compound can affect both the anodic and cathodic processes, thus it can be classified as a mixed-type inhibitor for API 5L X52 steel corrosion in sulphuric acid. Moreover, this compound follows an adsorption mechanism, which can be adequately described by the Langmuir isotherm with an adsorption standard free energy difference (ΔG°) of −28.5 kJ mol⁻¹.     

Influence of substituted benzothiazoles on corrosion in acid solution

Compounds such as 2-aminobenzothiazole (ABT), 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methyl benzothiazole (AMEBT) and 2-amino-6-methoxy benzothiazole (AMEOBT) have been synthesized and their inhibitive action on the corrosion of mild steel in 1 m HCl has been evaluated using weight loss, potentiodynamic polarization studies and hydrogen permeation measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that ACLBT shows the best performance, even at a temperature as high as 60°C. Potentiodynamic polarization studies reveal the fact that ABT and its derivatives act as cathodic inhibitors. All these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. The adsorption of these compounds on mild steel from HCl solutions obeys Temkin's adsorption isotherm. The adsorption of 2-amino benzothiazole on the mild steel has been substantiated by Auger electron spectroscopy.     

Corrosion Inhibition and Adsorption Behavior of Sodium Lauryl Ether Sulfate on L80 Carbon Steel in Acetic Acid Solution and Its Synergism with Ethanol

The application of sodium lauryl ether sulfate (SLES) as an anionic surfactant and its synergistic combination with ethanol for inhibition of corrosion of L80 carbon steel in acetic acid solutions were investigated by means of potentiodynamic polarization measurements, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and energy‐dispersive X‐ray (EDX) investigations. The inhibition efficiency increases with an increase in concentration of SLES. The adsorption of SLES on the surface of L80 carbon steel obeys the Freundlich isotherm. SLES acts predominately as an anodic inhibitor. XRD, EDX, and SEM examinations of the electrode surface confirmed the adsorption of SLES on the electrode surface. The addition of ethanol with SLES significantly enhances the inhibition effectiveness and generates a strong synergistic effect.     

Inhibition of mild steel corrosion in the presence of fatty acid triazoles

The influence of some fatty acid triazoles namely, 4-Phenyl-5-undecyl-4H- [1,2,4] triazole-3-thiol (PUTT), 5-Heptadec-8-enyl-4-phenyl-4H- [1,2,4] triazole-3-thiol (HPTT), and 5-Dec-9-enyl-4-phenyl-4H- [1,2,4] triazole-3-thiol (DPTT) on the corrosion of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulfuric acid (H₂SO₄) was studied by weight loss and potentiodynamic polarization methods. The values of activation energy and free energy of adsorption of all the triazoles were calculated to investigate the mechanism of corrosion inhibition. The potentiodynamic polarization studies were carried out at room temperature, according to which all the compounds were mixed type inhibitors and inhibit the corrosion of mild steel by blocking the active sites of the metal. The adsorption of all the triazoles on mild steel surface in both the acid solutions was found to obey the Langmuir adsorption isotherm. All the compounds showed good inhibition efficiency in both acids. The inhibition efficiency of the compounds was found to vary with their nature and concentration, solution temperature and immersion time. Electrochemical impedance spectroscopy was also used to investigate the mechanism of the corrosion inhibition.     

Investigation of some oleochemicals as green inhibitors on mild steel corrosion in sulfuric acid

The inhibitive effect of four oleo chemicals (namely; 2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl-1,3-imidazoline (UDI), 2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI)), regarded as green inhibitors, were studied for the corrosion protection of mild steel in 0.5 M H₂SO₄. The methods employed were weight loss, potentiodynamic polarization and electrochemical impedance techniques. Scanning electron microscopy (SEM) was carried out on the inhibited and uninhibited metal samples to characterize the surface. The purity of synthesized inhibitors was checked by FT-IR and NMR studies. The inhibition efficiency increased with increase in inhibitor concentration, immersion time and decreased with increase in solution temperature. No significant change in IE values was observed with increase in acid concentration. The best performance was obtained for UDI possessing 96.2% inhibition efficiency at 500 ppm concentration. The adsorption of the compounds on the mild steel surface in the presence of sulfuric acid obeyed Langmuir’s adsorption isotherm. The values obtained for free energy of adsorption and heats of adsorption suggest physical adsorption. The addition of inhibitor decreased the entropy of activation suggesting that the inhibitors are more orderly arranged along the mild steel surface. The potentiodynamic polarization data indicate mixed control. The electrochemical impedance study further confirms the formation of a protective layer on the mild steel surface through the inhibitor adsorption.     

Synthesis and Evaluation of 4-Diethyl Amino Benzaldehyde Schiff Base Cationic Amphiphiles as Corrosion Inhibitors for Carbon Steel in Different Acidic Media

A novel series of cationic surfactants containing Schiff base groups were synthesized by condensation of fatty amines namely: dodecyl, tetradecyl, hexadecyl and octadecyl amine and 4-diethyl aminobenzaldehyde. The chemical structures of these surfactants were confirmed using elemental analysis, FTIR spectra, ¹H-NMR and atomic absorption spectroscopy. Surface properties of the synthesized compounds were determined using surface tension techniques. The results of the surface tension measurements showed good surface behaviors of these compounds in their aqueous solutions. The surface activities were found to be greatly influenced by the chemical structures of the synthesized compounds. The synthesized cationic Schiff bases were evaluated as corrosion inhibitors for carbon steel in different acidic media (HCl and H₂SO₄) at different doses (400, 200, 100, 50, 25 ppm). The corrosion inhibition efficiencies of these inhibitors were calculated using the corrosion rates of the carbon steel in the studied media and found in the acceptable range of the commercially used inhibitors. Also the chemical structure of these inhibitors was found of great influence on their inhibiting efficiency.     

Synthesis and Inhibition Effect of a Novel Tri-cationic Surfactant on Carbon Steel Corrosion in 0.5 M H2SO4 Solution

A novel Tri-cationic surfactant was synthesized, purified and characterized. The critical micelle concentration value of the prepared surfactant was determined by surface tension and conductivity measurements. The surface parameters were calculated by surface tension measurements. The relationship between the surface properties and the corrosion inhibition efficiency of the prepared surfactant was discussed. The inhibition effect of the novel Tri-cationic surfactant on carbon steel corrosion in 0.5 M H₂SO₄ was studied by potentiodynamic polarization, electrochemical impedance spectroscopy and weight loss techniques. Potentiodynamic polarization studies revealed that the inhibitor acted as a mixed-type inhibitor. The high inhibition efficiency was attributed to the blocking of active sites on the steel surface through the adsorption of inhibitor molecules. Inhibitor adsorption on the carbon steel surface was in accordance with the Langmuir adsorption isotherm model. Thermodynamic adsorption and kinetic parameters were obtained from weight losses at different temperatures (20–60 °C).     

Inhibiting effects of some synthesized organic compound on the corrosion of St-3 in 0.1N H2SO4 solution

The inhibiting properties of two synthesized metals (alkyl)-2-hydroxy benzene sulfonate compounds have been studied on the corrosion of steel (St-3) in aerated 0.1N H₂SO₄ solutions by potentiodynamic polarization (dc) technique and electrochemical impedance spectroscopy (ac). The polarization curves indicate that the inhibitors are mixed-type. The impedance increases with inhibitors concentration. Low difference in inhibition efficiencies of two compounds for the corrosion of St-3 steel could be explained by high similarities of their structures. Results obtained by both electrochemical methods are in relatively good agreement.