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.     

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.     

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.     

Effect of hexamethylpararosaniline chloride (crystal violet) on mild steel corrosion in acidic media

The corrosion inhibition of mild steel in 0.5 M H₂SO₄ and 1 M HCl by hexamethylpararosaniline chloride (HMPC) was investigated using the gravimetric technique in the temperature range 303–333 K. The results indicate that HPMC inhibited the corrosion reaction in both acid media at all temperatures and inhibition efficiency increased with HMPC concentration. The inhibiting action is attributed to general adsorption of protonated and molecular HPMC species on the corroding metal surface. Adsorption followed a modified Langmuir isotherm and the Temkin isotherm, with very high negative values of the free energy of adsorption (). An increase in temperature reduced the inhibition efficiency of HPMC in 0.5 M H₂SO₄ but increased efficiency in 1 M HCl. Activation parameters such as activation energy (E_a), activation enthalpy (ΔH^∗) and activation entropy (ΔS^∗) as well as the adsorption heat (Q_ads) were evaluated from the effect of temperature on corrosion and inhibition processes.     

The inhibitive effect of 5‐amino‐indole on the corrosion of mild steel in acidic media

The inhibitor performance of 5‐aminoindole (5‐AI) on mild steel corrosion in 0.5 M HCl was investigated in relation to the inhibitor concentration using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization (LPR) methods. The effect of immersion time on the corrosion behavior of mild steel was also studied. The impedance data obtained were fitted and modeled using an equivalent circuit model. The results show that 5‐AI is an effective inhibitor and has an inhibition efficiency of 90% at 1 × 10^?2 M additive concentration. The adsorption behavior of 5‐AI was also investigated. For this purpose, the adsorption equilibrium constant (K_ads), and the free energy of adsorption (ΔG_ads) were calculated and discussed. It was found that 5‐AI acts as mixed‐type inhibitor and obeys Langmuir adsorption isotherm with a free energy of adsorption of ?27.71 kJ/mol.     

Synergistic inhibition effect of rare earth cerium(IV) ion and anionic surfactant on the corrosion of cold rolled steel in H2SO4 solution

The synergistic inhibition effect of rare earth cerium(IV) ion and anionic surfactant of sodium oleate (C₁₇H₃₃-COONa, SO) on the corrosion of cold rolled steel (CRS) in H₂SO₄ solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that SO had a moderate inhibitive effect, and the adsorption of SO obeyed the Freundlich adsorption isotherm. For the cerium(IV) ion, it had a negligible effect. However, incorporation of Ce⁴⁺ with SO significantly improved the inhibition performance, and produced strong synergistic inhibition effect. Depending on the results, the synergism mechanism was proposed.     

Inhibiting effects of some quinolines and organic phosphonium compounds on corrosion of mild steel in 3M HCl solution and their adsorption characteristics

Abstract

The inhibiting effects of quinoline, 8-hydroxyquinoline, benzo(f)quinoline, quinoline-2-thiol, triphenylbenzyl, and tetrabenzyl phosphonium chloride on the corrosion of mild steel (0.26 wt-%C) in deaerated 3M HCl solution have been studied using the determination of polarisation curves as well as linear polarisation measurements. Adsorption isotherms and thermodynamic parameters for the adsorption process of the inhibitors were also determined and are discussed. Except for benzo(f)quinoline, which acts as an accelerator of corrosion, the other quinolines act as corrosion inhibitors. The inhibition was found to be predominantly anodic with quinoline and 8-hydroxyquinoline, while quinoline-2-thiol is a mixed inhibitor. The increase in inhibition efficiency with temperature, the resulting Langmuir adsorption isotherm and the high negative values of the standard free energy of adsorption ΔG_a° denoted chemisorption. Triphenylbenzyl and tetrabenzyl phosphonium compounds were found to be inhibitors of the mixed type. High negative values of the standard free energy of adsorption and the resulting Temkin isotherm indicated chemisorption of the phosphonium compounds. The positive values of the standard enthalpy and entropy of adsorption indicated that adsorption of the inhibitors is associated with the desorption of H₂O molecules from the electrode surface. High values of the standard energy of activation E_a* of the inhibited corrosion process were interpreted in terms of deactivating coverage.     

Adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl) (phenyl)methyl)urea on the carbon steel corrosion in hydrochloric acid media

The adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl)(phenyl)methyl)urea (HNPU) on corrosion behavior of carbon steel in 1 M hydrochloric acid solution was investigated using weight loss, potentiostatic polarization, and infrared spectroscopy methods. Surface morphology was studied by scanning electron microscopy (SEM). The experimental results, suggest that HNPU inhibited the corrosion of carbon steel in acid solution and the inhibition efficiencies increased as the concentration of the compound in the solution was increased. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Potentiostatic polarization measurements indicate that HNPU acts as a mixed‐type inhibitor. The adsorption of the inhibitor on the carbon steel surface obeys Langmuir adsorption isotherm. The values of activation energy and the thermodynamic parameters, such as adsorption equilibrium constant (K_ads), adsorption free energy (ΔG_ads), adsorption heat (ΔH_ads), and adsorption entropy (ΔS_ads) values were calculated and discussed. The results obtained from infrared spectra, confirmed the adsorption of inhibitor on the alloy surface after immersion in acidic solution containing HNPU. The SEM analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acidic solution containing HNPU than that in blank.     

Co‐effect of bis(cyclohexanone) oxalyldihydrazone and copper(II) ion on the corrosion of cold rolled steel in 0.5 M hydrochloric acid solution

Effects of bis(cyclohexanone) oxalyldihydrazone (BCO) and copper(II) ion (Cu²⁺) on the corrosion of cold rolled steel (CRS) in 0.5 M hydrochloric acid (HCl) solution were investigated using Tafel polarization curve and electrochemical impedance spectroscopy (EIS) at 20 °C. Results elucidate that the inhibition efficiency increases with increase in BCO concentration, and the addition of 10^?5 M Cu²⁺ significantly enhances the inhibition efficiency of BCO. Polarization curve results elucidate that the single BCO acts as a mixed‐type inhibitor while the combination of Cu²⁺ and BCO acts as cathodic inhibitor. Ultraviolet and visible spectrophotometer (UV–Vis) results show that BCO molecules do not interact with Cu²⁺ and Fe²⁺ in 0.5 M HCl solution. Atomic force microscope (AFM) result indicates that a protective layer forms on CRS surface after immersion in 0.5 M HCl containing BCO in the absence and presence of Cu²⁺. The adsorption of BCO is found to follow the Langmuir adsorption isotherm in the presence and absence of Cu²⁺. The mechanism of typically chemical adsorption is proposed via the value of free energy of adsorption (ΔG) in the presence of BCO and Cu²⁺.     

Strychnos nux‐vomica an eco‐friendly corrosion inhibitor for mild steel in 1 M sulfuric acid medium

The inhibition efficiency of the extract of Strychnos nux‐vomica for the corrosion of mild steel in 1 M sulfuric acid was investigated using weight loss test (carried out at 303–323 K), electrochemical measurement, and scanning electron microscope (SEM). The results of weight loss studies indicated that the inhibition efficiency increased with inhibitor concentration and the temperature of the system (following Temkin adsorption isotherm). Electrochemical studies proved that the inhibitor acts through mixed mode of inhibition and the inhibitor molecules adsorb on the metal–solution interface. SEM studies supported the adsorption of the inhibitor over the metal surface. The possible active ingredient responsible for the anticorrosion effect is identified as brucine which is isolated and screened for the anticorrosion effect using electrochemical studies and quantum chemical studies. The possible mode of corrosion inhibition of brucine is also derived using FT‐IR studies.     

Thermodynamics and kinetics of fluoride removal from simulated zinc sulfate solution by La(III)-modified zeolite

To understand the mechanism of fluoride removal from the simulated zinc sulfate solution by the La(III)-modified zeolite, the adsorbent was characterized by XRD, SEM and EDS. The effects of absorbent dose and contact time, the adsorption isotherms and the sorption kinetics were investigated. The experimental results were compatible with the Langmuir isotherm model. The theoretical maximum adsorption capacities are 20.83 and 23.04 mg/g at 303 and 313 K, respectively. And the physisorption is revealed using the Temkin isotherm model and the D–R isotherm model. The sorption process is more suitable by the pseudo-second-order kinetic models. Thermodynamic parameters such as standard free energy change (ΔG^Θ<0 kJ/mol), standard enthalpy change (ΔH^Θ=8.28 kJ/mol) and standard entropy change (ΔS^Θ=0.030 kJ/(mol·K)) indicate the spontaneity of adsorption and endothermic physical sorption. Furthermore, the fluoride concentration in the industrial zinc sulfate solution decreases from 98.05 to 44.09 mg/L with the adsorbent dosage of 15 g/L.     

Lignin terpolymer for corrosion inhibition of mild steel in 10% hydrochloric acid medium

Lignin terpolymer has been obtained by grafting copolymerization of both dimethyl diallyl ammonium chloride (DMDAAC) and acrylamide (AM) onto lignin. The corrosion inhibition properties of the terpolymer were tested. The results showed that the highest corrosion inhibition percentage was over 95% in 10% HCl acid medium at 25 °C and 80 °C. The lignin terpolymer inhibitor adsorption followed Temkin isotherm at 25 °C and 80 °C, and the adsorption capability was in reverse proportion to the temperature according to −ΔG_ads. The effects of corrosion inhibition are the comprehensive synergistic effect through the graft reaction among lignin, AM and DMDAAC.     

Inhibition investigation and determination of some quantum chemical parameters of 1‐(4‐(dimethylamino)benzylidene)thiosemicarbazide on steel alloys in sulfuric acid medium

The inhibition effect of 1‐(4‐(dimethylamino)benzylidene)thiosemicarbazide (DBT) on the corrosion behavior of 304 stainless steel and mild steel in 0.5 M sulfuric acid solution was investigated using weight loss and potentiostatic polarization methods. The experimental results suggest that DBT inhibits the corrosion of the steels in acid solution. The inhibition efficiencies increased as the concentration of the compound was increased. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Potentiostatic polarization measurements indicate that DBT acts as a mixed type inhibitor for both alloys. The adsorption of inhibitor on the steel surfaces obeys Langmuir adsorption isotherm. The structure of DBT was optimized using PM3 semi‐empirical method. Highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), energy levels, E_LUMO ? E_HOMO (energy gap), dipole moment (µ), and Mulliken charge densities for this molecule were computed and the adsorption mechanism was discussed. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize the surfaces of the alloys.     

Inhibition of mild steel corrosion in acidic medium using synthetic and naturally occurring polymers and synergistic halide additives

The corrosion inhibition of mild steel in H₂SO₄ in the presence of gum arabic (GA) (naturally occurring polymer) and polyethylene glycol (PEG) (synthetic polymer) was studied using weight loss, hydrogen evolution and thermometric methods at 30-60 °C. PEG was found to be a better inhibitor for mild steel corrosion in acidic medium than GA. The effect of addition of halides (KCl, KBr and KI) was also studied. Results obtained showed that inhibition efficiency (I%) increased with increase in GA and PEG concentration, addition of halides and with increase in temperature. Increase in inhibition efficiency (I%) and degree of surface coverage (θ) was found to follow the trend Cl⁻ < Br⁻ < I⁻ which indicates that the radii and electronegativity of the halide ions play a significant role in the adsorption process. GA and PEG alone and in combination with halides were found to obey Temkin adsorption isotherm. Phenomenon of chemical adsorption is proposed from the trend of inhibition efficiency with temperature and values obtained. The synergism parameter, S_I evaluated is found to be greater than unity indicating that the enhanced inhibition efficiency caused by the addition of halides is only due to synergism.     

Inhibitive properties, thermodynamic and quantum chemical studies of alloxazine on mild steel corrosion in H2SO4

Alloxazine (ALLOX) was tested as corrosion inhibitor for mild steel in 0.5 M H₂SO₄ solution using non-electrochemical technique (gravimetric and UV–Visible spectrophotometric measurements) at 303–333 K. ALLOX acts as inhibitor for mild steel in acidic medium. Inhibition efficiency increases with increase in concentration of ALLOX but decrease with rise in temperature. The adsorption of ALLOX was found to follow Temkin adsorption isotherm model. Both the activation and thermodynamic parameters governing the adsorption process were calculated and discussed. The adsorption follows a first-order kinetics. DFT study gave further insight into the mechanism of inhibition action of ALLOX.     

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.     

The corrosion inhibitory property of N,N‐bis(2‐benzimidazolylmethyl)amine for Q235 steel

The main purpose of this paper is to systematically evaluate the anti‐corrosion property of N,N‐bis(2‐benzimidazolylmethyl)amine (IDB), which is a novel good thermal stabilized inhibitor in acidic medium. Results obtained from electrochemical tests and corrosion surface morphology analyses reveal that IDB performs excellently as corrosion inhibitor for Q235 steel in 1 mol/L hydrochloric acid corrosive solution. Potentiodynamic polarization measurements show that IDB inhibits both the anodic and cathodic processes of corrosion and exhibits as a mixed‐type inhibitor. Besides, the inhibiting efficiency (IE%) and consequently the degree of surface coverage (θ) increase with the inhibitor concentration rising. And when the concentration is 20 × 10^?5 mol/L, the corrosion inhibition effect is best to reach 96.39%. The adsorption of inhibitor on Q235 steel is found to obey the Langmuir adsorption isotherm, and the calculated Gibbs free energy demonstrates that IDB spontaneously adsorbs and forms a protective chemisorbed film on Q235 steel to restrain its corrosion. Hereby, IDB will become a promising corrosion inhibitor in further.     

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.     

Sodium tungstate as a corrosion inhibitor of cold rolled steel in peracetic acid solution

Sodium tungstate (Na₂WO₄) as a corrosion inhibitor of cold rolled steel (CRS) in peracetic acid (PAA) solution was investigated by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). All the data obtained from the experiments indicate that Na₂WO₄ is capable of inhibiting the corrosion of CRS in PAA solution. Polarization data show that Na₂WO₄ behaves as an anodic type inhibitor in PAA solution. Adsorption of Na₂WO₄ is found to follow the Temkin adsorption isotherm. The calculated free energy of adsorption (ΔG_ads) probably indicates that both physical adsorption and chemical adsorption may take place in the adsorption process.     

The corrosion of mild steel in 0.01M, 1M and 3M HCl

The corrosion of mild steel has been studied in HCl of concentrations 3M, 1M and 0.01M. The anodic reaction order with respect to OH^? ion is 0.5 ± 0.2. A reaction mechanism with an intermediate following the Temkin adsorption isotherm has been proposed to explain the observed kinetic parameters