Inhibition of copper corrosion in aerated hydrochloric acid solution by amino-acid compounds

The effect of two amino-acid compounds, dl-alanine and dl-cysteine, on copper corrosion in an aerated 0.5 mol l⁻¹ HCl solution was studied by weight-loss measurements, potentiodynamic polarisation curves, and electrochemical impedance spectroscopy. A conventional benzotriazole (BTA) inhibitor was also tested for comparison. dl-cysteine was shown to be the most effective inhibitor among those tested inhibitors. Potentiodynamic polarisation results revealed that both the dl-alanine and dl-cysteine acted as an anodic inhibitor; however, dl-cysteine, in particular, was more effective, as it strongly suppressed anodic current densities. The improved inhibition efficiency of dl-cysteine in the 0.5 mol l⁻¹ HCl solution was due to its adsorption on the copper surface via the mercapto group in its molecular structure.     

Eco friendly corrosion inhibitors: Inhibitive action of quinine for corrosion of low carbon steel in 1 m HCl

Quinine, a natural product, was investigated as a corrosion inhibitor for low carbon steel in 1.0 m HCl solution. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization were used to study the inhibition action in the temperature range 20–50 °C. The corrosion of steel was controlled by a charge transfer process at the prevailing conditions. The electrochemical results showed that quinine is an efficient inhibitor for low carbon steel and an efficiency up to 96% was obtained at 20 °C. The inhibition efficiency increases with inhibitor concentration and reaches a near constant value in the concentration range 0.48 mM and above. Application of the Langmuir adsorption isotherm enabled a study of the extent and the mode of adsorption.     

Effectiveness of some non ionic surfactants as corrosion inhibitors for carbon steel pipelines in oil fields

The ability of new synthesized non ionic surfactants (I and II) to protect carbon steel in acid chloride solution was investigated using potentiostatic polarization, open circuit potential, weight loss and surface tension measurements. The experimental results showed that these inhibitors revealed a very good corrosion inhibition even at low concentrations. The percentage inhibition efficiency (η%) increases by increasing the inhibitor concentration until the critical micelle concentration (cmc) is reached. It was found that, the adsorption ability of the surfactant molecules on carbon steel surface increased with the increase of the molecular size of the surfactant. Potentiostatic polarization curves indicate that the inhibitors under investigation act as mixed type. Finally, the mechanism of carbon steel dissolution in acidic medium was discussed both in absence and presence of the inhibitor molecules.     

Thiophene derivatives as effective inhibitors for the corrosion of steel in 0.5 <Emphasis Type="SmallCaps">m</Emphasis> H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

The influence of thiophene and five of its substituted derivatives on the corrosion inhibition of steel in 0.5 m H₂SO₄ solution was studied using weight-loss, electrochemical polarisation, and impedance measurements. 5-tert-butoxythiophene-2-carbaldehyde phenylhydrazone (TBCP) is the best inhibitor and its inhibition efficiency increases with increase in concentration to attain 87% at 5×10⁻³ m. Potentiodynamic polarisation studies clearly reveal that it acts essentially as a cathodic inhibitor. The partial π-charge on atoms has been calculated. A correlation between the highest occupied molecular orbital E _HOMO and inhibition efficiencies was sought. The inhibition efficiency of TBCP is not affected by rise in temperature in the range 298–353 K. E% values obtained from weight-loss and electrochemical methods were in good agreement. Adsorption of TBCP on steel has an S-shaped adsorption isotherm.     

Corrosion inhibition of mild steel in 1 M HCl using Tamarindus indica extract: electrochemical,surface and spectroscopic studies

Abstract

We report, here, the corrosion inhibition of mild steel specimen in 1?M HCl by tamarind fruit pulp aqueous (TFPA) extract. The inhibition property in the presence of TFPA extract is studied using weight loss, polarization measurement and electrochemical impedance spectroscopy (EIS). The inhibitor efficiency is found to vary from 74% to 88% (weight loss method) with TFPA concentration of 100–600?ppm. The reduction in Tafel slopes shows that TFPA acts as a mixed-type inhibitor. The adsorption of the inhibitor on the metal surface follows Langmuir isotherm. The standard Gibbs free energy of adsorption value of –40?kJ/mol suggests the chemisorption of inhibitor molecules via coordinate bond. AFM results exhibit a decrease in the surface roughness of mild steel, exposed to 1?M HCl from 299?±?12 to 154?±?6.6?nm, with increasing concentration of inhibitor from 0 to 600?ppm due to the uniform coverage of inhibitor molecules on the metal surface. X-ray photoelectron spectroscopy de-convoluted high resolution profiles of C 1?s (carbon) for mild steel exposed to 1?M HCl with 600?ppm inhibitor show major peaks corresponding to sp³ C–C/C–H (284.9?eV) and oxygen bondings in C–OH, C=O, COOH with a binding energy of 285.9, 286.9, 288.5?eV, respectively, thereby confirming the adsorption of organic moieties on mild steel surface. Fourier transform infrared spectroscopy further confirms the adsorption of inhibitor molecules on the metal surface. Therefore, tamarind fruit pulp extract is a potential corrosion inhibitor for mild steel, which is cost-effective, green and non-toxic.     

Influence of H+ and Cl− ions on inhibitive performance of poly(aniline) for iron corrosion in acid

The inhibition effect of poly(aniline) on pure iron corrosion in 1M HCl and with various H⁺ ions and Cl^? ions concentrations was investigated by the polarization and electrochemical impedance spectroscopy methods. The results showed that poly(aniline) suppressed both cathodic and anodic processes of iron dissolution in 1M HCl by its adsorption on the iron surface according to Langmuir's adsorption isotherm. The inhibition efficiency of poly(aniline) was found to increase with the inhibitor concentrations. Further, it was observed that, there was no significant variation in corrosion potential (E_corr) values in the presence of inhibitors suggesting that, this polymer behaved as mixed type inhibitor. Similar studies for the inhibitor at 500 ppm in various concentrations of H⁺ and Cl^? ions, have shown that the inhibition efficiency decreases with decrease in concentrations of H⁺ ions and Cl^? ions in aqueous solution. It reveals that, the adsorption of inhibitor on iron surface is by more cationic form of inhibitor and higher efficiency at higher H⁺ and Cl^? ions is due to enhanced adsorption of cat ionic form of inhibitor molecules. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

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.     

Adsorption and inhibitive corrosion properties of thiourea derivatives on cold rolled steel in 1 M HClO<Subscript>4</Subscript> solutions

Thiourea derivatives namely, phenylthiourea (PTU), N, N′-diphenylthiourea (DPTU) and N-naphtyl N′-phenylthiourea (NPTU) synthesised in our laboratory, were tested as inhibitors for the corrosion of cold rolled steel in 1 M HClO₄ using polarisation and electrochemical impedance measurements. At 30 °C, PTU and DPTU stimulated corrosion at low concentrations while addition of NPTU caused inhibition at all concentrations. The best protection (93%) was obtained by adding NPTU at 2.5 × 10⁻⁴ M. Polarisation curves showed that NPTU acted as a mixed inhibitor. The degree of surface coverage of the adsorbed inhibitors was determined by the ac impedance technique. The adsorption of NPTU on the cold rolled steel surface obeyed the Langmuir adsorption isotherm. Corrosion behaviour in the presence of NPTU at various concentrations was studied in the temperature range 20–50 °C. Both the corrosion rate of cold rolled steel and protection efficiency increased with increasing temperature. Activation energies with and without NPTU were obtained from the temperature dependence of corrosion current. The thermodynamic functions of the adsorption processes were calculated from the polarisation data and were used to analyse the inhibitor adsorption mechanism.     

Corrosion Inhibition Efficiency,Electrochemical and Quantum Chemical Studies of Some New Nonionic Surfactants for Carbon Steel in Acidic Media

In this work, three types of nonionic surfactant as corrosion inhibitors were synthesized. The chemical structure of the prepared inhibitors was confirmed using FT‐IR and ¹H‐NMR spectroscopy. The surface tension and thermodynamic properties of these inhibitors were investigated. The corrosion inhibition efficiency of these surfactants was investigated on a carbon steel surface in 1 M HCl solution by weight loss and electrochemical measurements. Untreated and treated steel surfaces were characterized by scanning electron microscopy. Results show that the inhibition efficiency of the prepared inhibitors increases with increasing the ethylene oxide units. Also, the potentiodynamic polarization curves indicated that the investigated inhibitors behave as a mixed type inhibitor. Adsorption of these surfactants on the carbon steel surface was found to obey Langmuir's adsorption isotherm. The computed quantum chemical properties viz., electron affinity (EA), highest occupied molecular orbital (E_HOMO), the lowest unoccupied molecular orbital (E_LUMO), energy gap ΔE = E_HOMO ? E_LUMO, dipole moment (μ), polarizability and total energy (E_T) show good correlation with experimental inhibition efficiency.     

Ceftriaxone: a novel corrosion inhibitor for mild steel in hydrochloric acid

Corrosion inhibition of mild steel in 1 N HCl by Ceftriaxone was studied by polarization resistance, Tafel polarization, EIS, and weight loss measurement. The inhibitor showed more than 90% inhibition efficiency at optimum concentration of 400 ppm. Results obtained revealed that inhibition occurs through adsorption of the drug on the metal surface without a modification of the mechanism of the corrosion process. Potentiodynamic polarization suggests that this is a mixed type of inhibitor. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Thermodynamic parameters such as E _a, ΔH, ΔS, ΔG and Q were calculated to investigate the mechanism of inhibition. All the investigations suggested that the compound follows the Langmuir adsorption isotherm.     

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.     

Effect of Schiff Bases Containing Pyridyl Group as Corrosion Inhibitors for Low Carbon Steel in 0.1 M HCl

The inhibiting effect of four newly synthesised Schiff bases containing pyridyl group was investigated on the corrosion of low carbon steel in 0.1 M hydrochloric acid solution under various conditions by potentiodynamic polarisation method and impedance measurements. The Schiff bases used were 2-((1Z)-1-aza-2-(2-pyridyl)vinyl)benzene-1-thiol, (1Z)-1-aza-1,2- di(2-pyridyl)ethene, [((1Z)-1-aza-2-(2-pyridyl)vinyl)amino]benzene-1-thione and 2-((1Z)-1-aza-2-(2-pyridyl)vinyl)benzothiazole. All the Schiff bases inhibit corrosion of low carbon steel and their inhibition efficiencies increase with decrease in temperature and increase in concentration. The difference in protection actions of the inhibitors can be attributed to the presence of substituents in the structures that increase or decrease the electron density on the azomethine (–C=N–) group. Polarisation curves indicate that the Schiff bases act as anodic inhibitors. AC impedance and potentiodynamic polarisation measurements reveal that the compounds are adsorbed on the steel surface and the adsorption obeys the Temkin isotherm. Activation parameters (E_a, ΔH*, ΔS*) for the corrosion of low carbon steel in 0.1 M HCl were calculated and showed that corrosion was much reduced in the presence of inhibitors.     

Novel calixarene derivatives as inhibitors of mild C-38 steel corrosion in 1 M HCl

Calixarenes CA1–CA4 containing one to four 4-imidazolylethylamidocarbonyl groups were synthesized and tested as inhibitors for the corrosion of mild steel in 1 M HCl at 308 K. The study was made using Tafel polarisation and weight-loss methods. In contrast to CA1, calixarenes CA2–CA4 were good inhibitors, reaching inhibition efficiencies (E%) of 94 to 100% at 10⁻⁴ M. The values of the inhibition efficiency calculated by the two techniques were in acceptable agreement. E% increased with the number of 4-imidazolylethylamidocarbonyl groups attached to the calixarene. Polarisation curves showed that CA2–CA4 act as mixed-type inhibitors. Their adsorption on the steel surface followed a Langmuir isotherm. Thermodynamic parameters of adsorption were also deduced.     

Cationic gemini surfactant as corrosion inhibitor for mild steel in 1 M HCl and synergistic effect of organic salt (sodium tosylate)

Synergistic result of cationic gemini surfactant (GS) 1,2-bis(N-hexadecyl-N,N-dimethylammonium) ethane dibromide (16-2-16) and organic salt (Sodium tosylate; NaTos) on mild steel corrosion in 1?M HCl solution at various temperatures (30, 40, 50 and 60?°C) has been examined using gravimetric, electrochemical and surface morphology measurement. Investigational result shows that the inhibition efficiency (η) of 16-2-16 GS enhanced in the existence of a set quantity of NaTos. The synergism parameter (S_θ) values are larger than unity, representing large inhibition efficiency, generated via the accumulation of NaTos to 16-2-16 GS is owing to adsorption supportive. The electrochemical results revealed that the 16-2-16 GS in the absence and presence of NaTos act as mixed-type inhibitors. The inhibitor adsorption on the mild steel surface in 1?M HCl solution obeys Langmuir adsorption isotherm. Surface morphology was studied using scanning electron microscopy (SEM).     

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.     

Effects of surfactants and their mixtures on inhibition of the corrosion process of ferritic stainless steel

The corrosion inhibition characteristics regarding mixtures of cationic/zwitterionic types of surfactant (Myristyltrimethylammonium bromide/Palmitylsulfo-betaineas), and non-ionic surfactant TRITON-X-405 mixed with 1 mM of KBr, as corrosion inhibitors for stainless steel (SS) (type X4Cr13) in aqueous solutions of 2 M H₂SO₄ were investigated using potentiodynamic polarisation measurements. The polarisation data showed that mixtures of the surfactants used in this study acted as mixed-type inhibitors, adsorbing on the stainless steel surface in agreement with the Flory-Huggins adsorption isotherm. The tensiometric results of this study suggest the existence of a second state of aggregation for zwitterionic/cationic surfactant mixtures. From these values of the free energy of adsorption, which in both mixtures decreased with respect to a single surfactant, we concluded that the adsorption in mixtures was stronger. The mixtures studied here showed good inhibition properties for ferritic stainless steel type X4Cr13 in 2 M H₂SO₄ solution.     

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.     

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.     

An investigation of mild carbon steel corrosion inhibition in hydrochloric acid medium by environment friendly green inhibitors

Inhibition effect of Brugmansia suaveolens (BS) and Cassia roxburghii (CR) on mild carbon steel in 1.0 M HCl solution was studied. Inhibition efficiency of plant extracts were carried out by using chemical (weight loss method) and electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy). The effect of temperature on the corrosion behavior of mild carbon steel in 1.0 M HCl with addition of plant extracts was studied in the temperature range of 300–320 ± 1 K. Inhibition efficiencies up to 94.69 for BS and 93.22 for CR can be obtained. The adsorption mechanism of inhibition was supported by FT-IR, surface analysis (SEM–EDS), and adsorption isotherms. The thermodynamic parameter values of free energy of adsorption (∆G _ads) reveal that inhibitor was adsorbed on the mild carbon steel surface via both physisorption and chemisorption mechanisms.     

Effects of structure of the ionic head of cationic surfactant on its inhibition of acid corrosion of mild steel

Two n-alkyl-quaternary ammonium compounds were studied as corrosion inhibitors for acid corrosion of mild steel using electrochemical and weight loss methods. The two compounds are hexadecylpyridinium bromide (HDPB) and hexadecyltrimethyl ammonium bromide (HDTB). The influence of the structure of the ionic head on the inhibition action of the two cationic surfactants was studied by analyzing the data at different concentrations and temperatures. The inhibition efficiency increases with the concentration. It increases with temperature in the case of HDPB but decreases in the case of HDTB. The apparent activation energy, E _a of corrosion in the presence of HDPB was found to be lower than in blank (0.5 m H₂SO₄). In the case of HDTB, E _a was larger than that of the blank. A larger extent of adsorption for HDPB on the metal surface was evident from the larger negative values of the free energy of adsorption. The results yielded the extent and mode of adsorption of the inhibitors on mild steel. The stronger adsorption of HDPB was attributed to the differences in the molecular structures of the inhibitors.