Synergistic inhibition effect of rare earth cerium(IV) ion and 3,4-dihydroxybenzaldehye on the corrosion of cold rolled steel in H2SO4 solution

The synergistic inhibition effect of rare earth cerium(IV) ion and 3,4-dihydroxybenzaldehye (DHBA) on corrosion of cold rolled steel (CRS) in H₂SO₄ solution was first investigated by weight loss and potentiodynamic polarization methods. Effects of inhibitor concentration, temperature, immersion time and acid concentration on synergism are discussed in detail. The results reveal that DHBA has moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. For the cerium(IV) ion, it has negligible effect. However, incorporation of Ce⁴⁺ with DHBA improves the inhibition performance significantly, and produces strong synergistic inhibition effect.     

Synergistic inhibition effect of rare earth cerium(IV) ion and sodium oleate on the corrosion of cold rolled steel in phosphoric acid solution

The synergistic inhibition effect of rare earth cerium(IV) ion (Ce⁴⁺) and sodium oleate (SO) on the corrosion of cold rolled steel (CRS) in 3.0 M phosphoric acid (H₃PO₄) has been investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The results reveal that SO has a moderate inhibitive effect and its adsorption obeys Temkin adsorption isotherm. Ce⁴⁺ has a poor effect. However, incorporation of Ce⁴⁺ with SO improves the inhibition performance significantly, and exhibits synergistic inhibition effect. SO acts as a cathodic inhibitor, while SO/Ce⁴⁺ mixture acts as a mixed-type inhibitor.     

Synergistic inhibition effect of 6-benzylaminopurine and iodide ion on the corrosion of cold rolled steel in H3PO4 solution

The synergistic inhibition effect of 6-benzylaminopurine (BAP) and iodide ion (I⁻) on the corrosion of cold rolled steel (CRS) in 1.0 M H₃PO₄ solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that BAP has a moderate inhibitive effect. However, incorporation of BAP with I⁻ improves the inhibition performance significantly. The adsorption of BAP in the absence and presence of I⁻ obeys Langmuir adsorption isotherm. BAP and BAP/I⁻ mixture act as mixed-type inhibitors. A probable synergism mechanism is proposed.     

Synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel in 1.0 M HCl solution

The synergism between rare earth cerium(IV) ion and vanillin on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution was first investigated by weight loss, potentiodynamic polarization, ultraviolet and visible spectrophotometer (UV–vis), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). The results revealed that vanillin had a moderate inhibitive effect, and the adsorption of vanillin obeyed the Temkin adsorption isotherm. For rare earth Ce⁴⁺, it had a negligible effect. However, incorporation of Ce⁴⁺ with vanillin significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed.     

Synergism between red tetrazolium and uracil on the corrosion of cold rolled steel in H2SO4 solution

The synergism between red tetrazolium (RT) and uracil (Ur) on the corrosion of cold rolled steel (CRS) in H₂SO₄ solution is first investigated by weight loss, potentiodynamic polarization, and atomic force microscope (AFM). Effects of inhibitor concentration (25-500 mg l⁻¹), temperature (20-50 °C), and acid concentration (1.0-5.0 M) on synergism are discussed systematically. The results reveal that RT has a moderate inhibitive effect, and its adsorption obeys the Freundlich adsorption isotherm. For Ur, it has a poor effect. However, incorporation of RT with Ur significantly improves the inhibition performance, and produces synergistic inhibition effect.     

Electrochemical study of corrosion inhibition and adsorption behaviour for pure iron by polyacrylamide in H2SO4: Synergistic effect of iodide ions

Corrosion inhibition and adsorption behaviour for pure iron in 0.5 M H₂SO₄ by polyacrylamide (PA) were investigated using electrochemical techniques. The effect of iodide ion additives was also studied. It was found that inhibition efficiency increased with PA concentration. Corrosion inhibition was afforded by adsorption of PA onto the metal following El-Awady kinetic-thermodynamic adsorption isotherm model via chemisorption mechanism. A mixed inhibition mechanism is proposed for the inhibitive effects of PA as revealed by potentiodynamic polarization technique. A synergistic effect was observed between PA and KI as evident from the values of synergism parameter found to be greater than unity.     

N-Aminorhodanine as an effective corrosion inhibitor for mild steel in 0.5 M H2SO4

The corrosion inhibition effect of N-aminorhodanine (N-AR) on mild steel (MS) in 0.5 M H₂SO₄ was studied in both short and long immersion duration using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), chronoamperometry and hydrogen gas evolution. The surface morphology of MS was examined with scanning electron microscopy (SEM) in absence and presence inhibitor. The inhibitor adsorption process on MS surfaces obeys the Langmuir adsorption isotherm. The results show that NAR is a good inhibitor for MS in the acidic medium. The inhibition efficiency obtained from potentiodynamic polarization, EIS and LPR up to 98% is determined.     

Synergistic effect of halide ions on improving corrosion inhibition behaviour of benzisothiozole-3-piperizine hydrochloride on mild steel in 0.5 M H2SO4 medium

The synergistic effect of iodide ions and benzisothiozole-3-piperizine hydrochloride (BITP) on corrosion inhibition of mild steel in 0.5 M H₂SO₄ solution has been studied by both chemical and electrochemical methods. The corrosion performance of BITP in 1.0 M HCl and 0.5 M H₂SO₄ media was examined and compared. The adsorption of BITP and its combination with iodide ions on mild steel surface followed Langmuir adsorption isotherm via chemisorption mechanism. The calculated values of synergism parameter (S_θ) were found to be greater than unity. This result clearly showed the existence of synergism between iodide ions and BITP molecules.     

Inhibition effect of 6-benzylaminopurine on the corrosion of cold rolled steel in H2SO4 solution

The inhibition effect of 6-benzylaminopurine (BAP) on the corrosion of cold rolled steel (CRS) in 1.0-7.0 M H₂SO₄ at 25-50 °C was studied by weight loss and potentiodynamic polarization methods. Fourier transform infrared spectroscopy (FTIR) and atomic force microscope (AFM) were used to characterize the CRS surface. The results showed that BAP was a good inhibitor in 1.0 M H₂SO₄, and the adsorption of BAP obeyed the Temkin adsorption isotherm. Polarization curves showed that BAP acted as a mixed-type inhibitor in sulfuric acid. Depending on the results, the inhibitive mechanism was proposed.     

Alizarin violet 3B as a novel corrosion inhibitor for steel in HCl, H2SO4 solutions

The inhibition effect of alizarin violet 3B (AV3B) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl and 0.5 M H₂SO₄ solutions was investigated for the first time by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that AV3B is a good inhibitor, and exhibits more efficient in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of AV3B on CRS surface obeys Langmuir adsorption isotherm in both acids. Polarization curves reveal that AV3B acts as a mixed-type inhibitor.     

Triazolyl blue tetrazolium bromide as a novel corrosion inhibitor for steel in HCl and H2SO4 solutions

The inhibition effect of triazolyl blue tetrazolium bromide (TBTB) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl and 0.5 M H₂SO₄ solution was investigated for the first time by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy (EIS) methods. The results show that TBTB is a very good inhibitor, and is more efficiency in 1.0 M HCl than 0.5 M H₂SO₄. The adsorption of TBTB on CRS surface obeys Langmuir adsorption isotherm. Polarization curves reveal that TBTB acts as a mixed-type inhibitor in both acids.     

Synergistic effect of polyaspartic acid and iodide ion on corrosion inhibition of mild steel in H2SO4

The inhibition effect of polyaspartic acid (PASP) and its synergistic effect with KI on mild steel corrosion in 0.5 M H₂SO₄ solution are studied by weight loss and electrochemical methods. The inhibition efficiency increases with the concentration of PASP and increases further with the presence of 1 mM KI. Result of the zero charge potential measurement shows that iodide ion promotes the film formation of PASP greatly. The mild steel surfaces after immersion test were analyzed using scanning electron microscopy and X-ray photoelectron spectroscopy. An adsorption model is proposed to elucidate the synergistic mechanism of synergistic effect.     

Synergism between protocatechualdehyde and rare earth cerium(IV) ion on the corrosion of cold rolled steel in hydrochloric acid solution

The synergism between protocatechualdehyde (PAL, 3,4‐dihydroxy‐benzaldehye) and rare earth cerium(IV) ion (Ce⁴⁺) on the corrosion of cold rolled steel (CRS) in 1.0 M hydrochloric acid (HCl) solution has been investigated by weight loss and potentiodynamic polarization methods. The results reveal that PAL has a moderate inhibitive effect, while Ce⁴⁺ has a poor effect. Incorporation of PAL with Ce⁴⁺ improves the inhibition performance significantly, and exhibits synergistic inhibition effect. The adsorption of individual PAL obeys the Temkin adsorption isotherm, and the adsorption of the complex of PAL and Ce⁴⁺ accords with the Temkin adsorption isotherm too. The thermodynamic parameters of adsorption heat (ΔH⁰), adsorption free energy (ΔG⁰), and adsorption entropy (ΔS⁰) are calculated and discussed. Polarization curves show that individual PAL acts as a mixed‐type inhibitor, while Ce⁴⁺ slightly inhibits the corrosion reaction. The complex of PAL and Ce⁴⁺ acts as a mixed‐type inhibitor, which drastically inhibits both anodic and cathodic reactions. Depending on the results, the synergism mechanism is proposed from the viewpoint of adsorption theory.     

Three pyrazine derivatives as corrosion inhibitors for steel in 1.0 M H2SO4 solution

The inhibition effect of three pyrazine derivatives of 2-methylpyrazine (MP), 2-aminopyrazine (AP) and 2-amino-5-bromopyrazine (ABP) on the corrosion of cold rolled steel (CRS) in 1.0 M H₂SO₄ solution was studied by weight loss, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) methods. The results show that all pyrazine compounds are good inhibitors, and inhibition efficiency follows the order: ABP > AP > MP. The adsorption of each inhibitor on CRS surface obeys Langmuir adsorption isotherm. For all these pyrazine derivatives, they act as mixed-type inhibitors. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

Quantum chemistry study on the effect of Cl ion on anodic dissolution of iron in H2S-containing sulfuric acid solutions

The effect of Cl⁻ ion on the anodic dissolution of iron in H₂SO₄ solutions containing low H₂S level has been studied by electrochemical polarization curve measurements. The total energy and binding energy of the competitive adsorption for Cl⁻ and HS⁻ ions have been calculated with CNDO/2 method, as well as the net charge distribution of iron atoms at an anodic potential. The results showed that certain concentration of Cl⁻ ion inhibit the anodic reaction of iron accelerated by HS⁻. However, when Cl⁻ ion reached saturated adsorption, it began to promote the anodic reaction of iron due to the increased negative charge of iron atoms.     

Sodium molybdate as a corrosion inhibitor for aluminium in H3PO4 solution

The inhibition effect of sodium molybdate (Na₂MoO₄) on the corrosion of aluminium in 1.0 M H₃PO₄ solution was studied by weight loss, potentiodynamic polarisation curves and electrochemical impedance spectroscopy (EIS) methods. The results show that Na₂MoO₄ is a good inhibitor, and the inhibition efficiency obtained by three methods is higher than 84% at 20 mM. The adsorption of Na₂MoO₄ obeys Freundlich isotherm at lower concentrations (1–7 mM), while Langmuir isotherm at higher concentrations (7–20 mM). Polarisation curves indicate that Na₂MoO₄ acts as an anodic inhibitor. EIS spectra exhibit three loops (two capacitive loops and one inductive loop).     

Synergistic effect of iodide ion and polyacrylic acid on corrosion inhibition of iron in H2SO4 investigated by electrochemical techniques

Corrosion inhibition of iron in H₂SO₄ by polyacrylic acid (PAA) was investigated using electrochemical techniques at 30 °C. Results obtained indicate that PAA inhibited the corrosion of iron in the acid medium. Inhibition efficiency increases with increase in PAA concentration and synergistically enhanced on addition of iodide ions. Potentiodynamic polarization results suggest that PAA functions as a modest cathodic inhibitor. The adsorption of PAA onto the iron surface followed Temkin adsorption isotherm. FTIR analysis revealed that the synergistic effect due to co-adsorption of iodide ions and PAA is co-operative in nature.     

A preliminary investigation of corrosion inhibition of mild steel in 0.5 M H2SO4 by 2-amino-5-(n-pyridyl)-1,3,4-thiadiazole: Polarization, EIS and molecular dynamics simulations

The efficiency, as steel corrosion inhibitors in 0.5 M H₂SO₄, of two thiadiazole derivatives, 2-amino-5-(3-pyridyl)-1,3,4-thiadiazole (3-APTD) and 2-amino-5-(4-pyridyl)-1,3,4-thiadiazole (4-APTD), was investigated by polarization and electrochemical impedance spectroscopy. The protection efficiency increases with increasing inhibitors concentration, but the temperature has hardly effect on the inhibition efficiency of APTD. The adsorption of APTD on iron surface obeys the Langmuir isotherm. The experimental results show that the inhibition efficiency of 4-APTD is higher than that of 3-APTD, and the molecular dynamics (MD) simulations show that the adsorption of 4-APTD on iron surface has the higher binding energy than that of 3-APTD.     

The investigation of synergistic inhibition effect of rhodanine and iodide ion on the corrosion of copper in sulphuric acid solution

The synergistic inhibition effect of rhodanine (Rdn) and iodide ion on the corrosion of copper in 0.5 M H₂SO₄ solution was studied using electrochemical techniques. The surface morphologies of the substrates were examined by scanning electron microscopy (SEM). Elemental analysis of electrode surface exposed to test solution was determined by energy dispersive X-ray spectroscopy (EDX). It was found that Rdn provided satisfactory inhibition on the corrosion of copper. Moreover, its inhibition efficiency further increased in the presence of iodide ions due to synergistic effect. Finally, a mechanism of inhibition is proposed and discussed.     

Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na3PO4

The corrosion inhibition behavior of benzotriazole, Na₃PO₄ and their mixture on carbon steel in 20 wt.% (0.628 mol l⁻¹) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l⁻¹ BTA and 2 g l⁻¹ SP showed optimum enhanced inhibition compared with their individual effects.