Piperazine derivatives as inhibitors of the corrosion of mild steel in 3.9 M HCl

The inhibitory action of two piperazine derivatives, 1-benzyl piperazine (P1) and bis(1-benzylpiperazine) thiuram disulfide (P2) on the corrosion of mild steel in 3.9 M HCl at different concentrations has been investigated in the temperature domain 298–333 K. Both weight loss measurements and potentiodynamic polarization methods showed that P2 was the best inhibitor and that its inhibition efficiency increased with concentration to a value >92% at 10⁻³ M. Potentiodynamic polarization studies clearly revealed that P2 acts as cathodic-type inhibitor. The activation energy for the corrosion rates was evaluated in the temperature range 298–333 K. Adsorption of P2 on the mild steel surface in 3.9 M HCl followed a Langmuir isotherm model. A physical adsorption phenomenon is proposed.     

Influence of tramadol [2-[(dimethylamino)methyl]-1-(3-methoxyphenyl) cyclohexanol hydrate] on corrosion inhibition of mild steel in acidic media

Tramadol[2-[(dimethylamino)methyl]-1-(3-methoxyphenyl)cyclohexanol hydrate], a drug, was tested as a corrosion inhibitor for mild steel in 0.5 M HCl and 0.25 M H₂SO₄ separately at 300, 310 and 320 K using mass loss and galvanostatic polarization techniques. The percentage protection efficiencies were evaluated at different concentrations of the inhibitor at different temperatures. The protection efficiency increased with increase in inhibitor concentration and decreased with increase in temperature in both the acid solutions. Galvanostatic polarization studies showed that the inhibitor is of mixed type with a slight predominance of cathodic character. The inhibitor was more active in HCl than in H₂SO₄. The maximum protection efficiency approached 82.6% in the presence of 2.16 × 10⁻³ M inhibitor. Some samples of mild steel were examined by scanning electron microscopy. The inhibitor was found to adsorb on the mild steel surface according to the Langmuir adsorption isotherm. The thermodynamic functions of dissolution and adsorption processes were evaluated.     

Joint effect of halides and ethanol extract of <Emphasis Type="Italic">Lasianthera africana</Emphasis> on inhibition of corrosion of mild steel in H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

Inhibitive and adsorption properties of ethanol extract of Lasianthera africana for inhibition of corrosion of mild steel in H₂SO₄ were studied using gravimetric, thermometric, gasometric, and infrared (IR) methods. The extract was found to be a good inhibitor of corrosion of mild steel in H₂SO₄. Inhibitive properties of the extract were attributed to enhancement in adsorption of the inhibitor on mild-steel surface by saponin, alkaloid, tannin, flavanoid, cardiac glycoside, and anthraquinone (present in the extract). Also, adsorption of the inhibitor was found to be exothermic, spontaneous, and consistent with assumptions of Langmuir and Temkin adsorption isotherms. Synergistic study revealed that, of the investigated halides, only KCl may enhance adsorption of the inhibitor, whereas KBr and KI antagonized its adsorption. Based on the decrease in efficiency of the inhibitor with temperature, with values of activation energy and free energy of adsorption below the threshold values of −40 and 80 kJ mol⁻¹, respectively, a physical adsorption mechanism has been proposed for adsorption of ethanol extract of Lasianthera africana on the surface of mild steel.     

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.     

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.     

Corrosion inhibition of mild steel in acidic medium by poly (aniline-co-<Emphasis Type="Italic">o</Emphasis>-toluidine) doped with <Emphasis Type="Italic">p</Emphasis>-toluene sulphonic acid

The corrosion behaviour of mild steel in 0.5 M H₂SO₄ solution containing various concentrations of a p-toluene sulphonic acid doped copolymer formed between aniline and o-toluidine was investigated using weight loss, polarization and electrochemical impedance techniques. The copolymer acted as an effective corrosion inhibitor for mild steel in sulphuric acid medium. The inhibition efficiency has been found to increase with increase in inhibitor concentration, solution temperature and immersion time. Various parameters like E _a for corrosion of mild steel in presence of different concentrations of inhibitor and ΔG _ads, ΔH ⁰, ΔS ⁰ for adsorption of the inhibitor, revealed a strong interaction between inhibitor and mild steel surface. The adsorption of this inhibitor on the mild steel surface obeyed the Langmuir adsorption equation.     

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.     

Synergistic inhibition between the gemini surfactant and bromide ion for steel corrosion in sulphuric acid

The inhibitive synergistic effect between a cationic gemini surfactant, 1,3-propane-bis(dimethyl dodecylammonium bromide) (12-3-12), and bromide ion for the corrosion inhibition of cold rolled steel in 0.5 mol L⁻¹ H₂SO₄ was investigated by weight loss, potentiodynamic polarization method and electrochemical impedance spectroscopy (EIS). The inhibition system composed by 12-3-12 and bromide ion is efficient. The adsorption mechanism of the 12-3-12 and bromide ion on steel in acidic medium is discussed on the basis of experimental data and an adsorption model is proposed. Adsorption of inhibitor system on the mild steel surface in acidic medium obeys Langmuir’s adsorption isotherm. In addition, potentiodynamic polarization studies show that the system acts as a mixed-type inhibitor. Electrochemical impedance spectroscopy also suggests the formation of a protective layer on the steel surface by the adsorption of surfactant molecules and bromide ions.     

Influence of 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole on corrosion inhibition of mild steel in acidic media

An example of a new class of corrosion inhibitors, namely, 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole (DAPT) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ at 30 °C was investigated by various corrosion monitoring techniques. A preliminary screening of the inhibition efficiency was carried out using weight loss measurements. At constant acid concentration, inhibitor efficiency increases with concentration of DAPT and is found to be more efficient in 0.5 M H₂SO₄ than in 1 M HCl. Potentiostatic polarization studies showed that DAPT is a mixed-type inhibitor. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of DAPT was studied in the temperature range from 25 to 60 °C. Its was shown that adsorption is consistent with the Langmuir isotherm for 30 °C. The negative free energy of adsorption in the presence of DAPT suggests chemisorption of thiadiazole molecules on the steel surface.     

Corrosion inhibition of mild steel in acidic media by Basic yellow 13 dye

The inhibition performance of Basic yellow 13 dye on mild-steel corrosion in hydrochloric acid solution was studied at 25 °C using weight loss and electrochemical techniques. The effect of inhibitor concentration on inhibition efficiency has been studied. Inhibition efficiency increased with increase of Basic yellow 13 concentration. The results showed that this inhibitor had good corrosion inhibition even at low concentrations (95% for 0.005 M Basic yellow 13) and its adsorption on mild-steel surface obeys Langmuir isotherm. ΔG _ads was calculated and its negative value indicated spontaneous adsorption of the Basic yellow 13 molecules on the mild-steel surface and strong interaction between inhibitor molecules and metal surface. The value of ΔG _ads was less than 40 kJmol⁻¹, indicating electrostatic interaction between the charged inhibitor molecules and the charged metal surface, i.e., physical adsorption.     

Dodigen 213-N as corrosion inhibitor for ASTM 1010 mild steel in 10% HCL

This article describes a study of the behavior of a mixture of amines and amides, commercially known as Dodigen 213-N (D-213 N), as a corrosion inhibitor for ASTM 1010 mild steel in 10% w/w HCl solution. The concentration range used was 1 × 10⁻⁵ M to 8 × 10⁻⁴ M. The weight loss and electrochemical techniques used were corrosion potential measurement, anodic and cathodic polarization curves, and electrochemical impedance spectroscopy (EIS). The solution temperature was 50 ± 1 °C and it was naturally aerated. The corrosion potential values shifted to slightly more positive values, thus indicating mixed inhibitor behavior. The anodic and cathodic polarization curves showed that D-213 N is an effective corrosion inhibitor, since both the anodic and the cathodic reactions were polarized in comparison with those obtained without inhibitor. For all concentrations the cathodic polarization curves were more polarized than the anodic ones. The inhibition efficiency was in the range 75–98%, calculated from values of weight loss and corrosion current density, i _corr, obtained by extrapolation of Tafel cathodic linear region.     

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.     

2-[(E)-{(1S,2R)-1-Hydroxy-1-phenylpropan-2-ylimino}methyl]phenol for Inhibition of Acid Corrosion of Mild Steel

2-[(E)-{(1S,2R)-1-hydroxy-1-phenylpropan-2-ylimino}methyl]phenol has been synthesized and its influence on corrosion of mild steel in 1?M HCl solution has been studied by means of weight loss and electrochemical measurements under various circumstances. The inhibitor showed a maximum of 91?% of inhibition efficiency at 100?ppm. Interestingly, the inhibition efficiency has decreased on increasing the inhibitor concentration. This abnormal behavior is attributed to the release of phenolic hydrogen from the molecule. The mechanism of corrosion inhibition follows Langmuir adsorption isotherm. The negative ?G _ads indicates the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies show that it is a mixed type inhibitor with predominant cathodic inhibition. UV?CVisible spectroscopy of the inhibitor and inhibitor adsorbed on the mild steel confirmed the chemical interaction of the inhibitor with the metal surface.     

1-(2-Hydroxyethyl)-2-imidazolidinone as corrosion inhibitor of mild steel in 0.5 M HCl solution: thermodynamic,electrochemical and theoretical studies

The inhibition effect of 1-(2-Hydroxyethyl)-2-imidazolidinone (2-HEI) on mild steel (MS) corrosion in 0.5?M HCl solution was investigated at different inhibitor concentration and temperature by electrochemical experiments, such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and quantum chemical calculations. The inhibitor adsorption process on mild steel in 0.5?M HCl system was studied at different temperatures (20?°C–50?°C). Furthermore, the surface morphology of MS was also investigated with SEM in the absence and the presence of inhibitor. The adsorption of 1-(2-Hydroxyethyl)-2-imidazolidinone on MS surface is an exothermic process and this process obeys the Langmuir adsorption isotherm. The Quantum chemical findings are good agreed with the empirical data.     

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.     

Inhibition by tween-85 of the corrosion of cold rolled steel in 1.0?M hydrochloric acid solution

The inhibition effect of tween-85 on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) was studied by weight loss and potentiodynamic polarization methods. The results show that tween-85 is a good inhibitor in 1.0 M HCl and its maximum inhibition efficiency (IE) is 92% at very low concentration. Its adsorption obeys the Langmuir adsorption isotherm equation. The thermodynamic parameters of adsorption enthalpy (ΔH ⁰), adsorption free energy (ΔG ⁰) and adsorption entropy (ΔS ⁰) were calculated and discussed. Polarization curves show that tween-85 acts as a mixed-type inhibitor in hydrochloric acid. IE values obtained from weight loss and polarization are consistent. The adsorbed film on a CRS surface containing an optimum dose of tween-85 was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). An inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

Corrosion inhibition and adsorption behavior of new Schiff base surfactant on steel in acidic environment: Experimental and theoretical studies

Synthesis, adsorption and corrosion inhibiting effect of new Schiff base surfactant named 4-hydroxy-3-(3-phenyl-allylideneamino)-benzene sulphonic acid2-[2-(2-{2-[2-(2-hydroxy-ethoxy)-ethoxy]-ethoxy}-ethoxy)-ethoxy]-ethyl ether (abbreviated as PAAB) on mild steel in 1.0 M HCl were investigated using weight loss, and potentiodynamic polarization techniques. The results revealed that this compound inhibited the corrosion reaction in HCl environment. The results indicated that this inhibitor was adsorbed on the metal/solution interface. Theoretical study of the adsorption behavior of this compound was carried out in the framework of the semiempirical (SE) and molecular dynamics (MD).     

Bis-Schiff bases of isatin as new and environmentally benign corrosion inhibitor for mild steel

Inhibition effect of three bis-Schiff bases of isatin namely (2-methoxybenzylidene) hydrazono) indolin-2-one (HZ-1), (2-hydroxybenzylidene) hydrazono) indolin-2-one (HZ-2) and (4-nitrobenzylidene) hydrazono) indolin-2-one (HZ-3) was studied on mild steel corrosion in 1.0 M HCl by gravimetric measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and quantum chemical study. The values of activation energy (E_a), equilibrium constant (K_ads), free energy of adsorption ΔG°_ads, activation enthalpy ΔH^* and activation entropy ΔS^*were discussed. The adsorption of inhibitors on metal followed Langmuir's adsorption isotherm. SEM and EDX observations confirmed the existence of protective inhibitor film on metal surface. Quantum chemical study supports the comparative inhibition effect of HZs.     

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.     

Synergistic effect of iodide ions on inhibitive performance of 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole during corrosion of mild steel in 0.5?M sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ solutions by 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole (4-MTH) has been studied using electrochemical impedance spectroscopy (EIS) and the Tafel polarisation method. The results showed that the inhibition efficiency increased with 4-MTH concentration while the potential of desorption (E _d) remained unchanged. The addition of potassium iodide (KI) in the acid solution stabilized the adsorption of 4-MTH molecules on the metal surfaces and, therefore, enhanced the inhibition efficiency of 4-MTH and increased the value of E _d. The synergistic effect was observed between KI and 4-MTH with an optimum mass ratio of [4-MTH]/[KI] = 5/5. The calculated values of synergism parameter (S _θ) from the coverage of the surface were found to be more than unity in most cases. This clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H₂SO₄ by 4-MTH. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir’s adsorption isotherm.