Effect of cationic surfactant and inorganic anions on the electrochemical behavior of carbon steel in formation water

Corrosion behavior of carbon steel in formation water associated crude oil from Egyptian western desert was studied at various concentrations of dodecyl dimethyl ammonium chloride (CS) as a cationic surfactant. Polarization curves indicate that CS has a good inhibition efficiency for carbon steel in formation water and behaves as cathodic inhibitor. The inhibition efficiency was found to increase with increase in CS concentration until reaches a maximum constant value corresponding to the critical micelle concentration of CS and decrease with increase in solution temperature. The adsorption of CS follows the kinetic thermodynamic model and Flory-Huggins isotherm. Thermodynamic parameters obtained indicate that that the presence of the CS increases the activation energy. Polarization and Impedance measurements indicate that the addition of KI has a significant synergistic effect with CS and results in increase the inhibition efficiency of CS in formation water.     

Carbon steel corrosion inhibition in hydrochloric acid solution using a reduced Schiff base of ethylenediamine

The behavior of the Schiff base N,N′-bis(salicylidene)-1,2-ethylenediamine (Salen), its reduced form (N,N′-bis(2-hydroxybenzyl)-1,2-ethylenediamine) and a mixture of its preceding molecules, ethylenediamine and salicylaldehyde, as carbon steel corrosion inhibitors in 1 mol L⁻¹ HCl solution was studied by corrosion potential measurements, potentiodynamic polarization curves, electrochemical impedance spectroscopy and spectrophotometry measurements. The experimental results showed that the reduced Salen presented the highest efficiency among the inhibitors studied. The results obtained in the presence of Salen were similar to those obtained in the presence of the salicylaldehyde and ethylenediamine mixture, showing that in acid medium the Salen molecule undergoes hydrolysis, regenerating its precursor molecules.     

Influence of pH on the nitrite corrosion inhibition of reinforcing steel in simulated concrete pore solution

Measurements of corrosion rate of reinforcing steels have been carried out in solutions simulating electrolytic chloride environments in corrosion pits in the propagation period with sodium nitrite. A significant corrosion inhibition has been observed at relatively low chloride contents of 0.045 M due to the presence of nitrite in these systems, but its efficiency decreases when the pH is reduced. The corrosion intensity seems to be related to the [Cl⁻]/[OH⁻] ratio. Three different pH regions from acid to alkaline have been observed in terms of corrosion activity. An explanation on the behaviour of nitrite at different pH is given.     

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.     

Adsorption and corrosion inhibition of phytic acid calcium on the copper surface in 3 wt% NaCl solution

The adsorption and corrosion protection effect of phytic acid calcium (PAC) film on the copper surface in 3 wt% NaCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. Polarization curves indicate that PAC is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The inhibition efficiency of PAC film reached 92.53% at an optimized condition. Adsorption of PAC molecules on the surface followed Langmuir adsorption isotherm and the standard Gibbs energy of −37.32 kJ mol⁻¹ indicated a chemisorptive way. Raman studies suggested that PAC molecule chemically anchored at the surface via PO groups.     

Photoelectron spectroscopy study of the inhibition of mild steel corrosion by molybdate and nitrite anions

Passive films formed on mild steel in aqueous 8.6 mM NaCl solutions (pH 8), containing either or , have been studied with X-ray photoelectron spectroscopy. For either anion these films are ∼5 nm deep, and the primary chemical state of iron is Fe³⁺. Following exposure to , the film consists of a sub-layer (∼4.1 nm) composed largely of ferric oxide/hydroxide, overlaid by Fe₂(MoO₄)₃ (∼0.6 nm). As regards , spectra are consistent with the film being closely related to γ-Fe₂O₃. Furthermore, a reduction product of , potentially N₂, is present, displaying a depth profile comparable to that of molybdate.     

Study of the corrosion inhibition effect of sodium silicate on AZ91D magnesium alloy

The poor corrosion resistance of magnesium alloys is a major impediment to their applications in many fields. In this paper, sodium silicate as a corrosion inhibitor is studied on the inhibition effect of AZ91D magnesium alloy. From the results of the corrosion tests, sodium silicate could effectively improve the corrosion resistance of alloy at the optimum concentration 10 mmol/L, while the pH value range from 10.5 to 12.5 is preferable. The corrosion inhibition mechanism of the protective layers is also discussed. These results can provide a guide for the protection of magnesium alloy in the cooling water systems, etc.     

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.     

Potent inhibition of copper corrosion in neutral chloride media by novel non-toxic thiadiazole derivatives

Inhibiting effect of two novel non-toxic thiadiazole derivatives on copper were investigated in 3.5% NaCl solution using weight loss and electrochemical measurements. Presence of inhibitors and increase of concentration greatly decrease corrosion rate, parameters determined from polarization curves and EIS plots show that inhibitors decrease both cathodic and anodic current densities, suppressing charge transfer process by adsorption on copper surface. Thermodynamic calculation indicates chemisorption obeys Langmuir isotherm. Surface layers were characterized by SEM coupled with EDX. Raman micro-spectroscopy reveals that inhibitor molecules suppress copper corrosion via formation of thiadiazole–Cu complex. Relationships between inhibition efficiency and molecular orbital were also evaluated.     

2-Amino-5-(4-pyridinyl)-1,3,4-thiadiazole monolayers on copper surface: Observation of the relationship between its corrosion inhibition and adsorption structure

Corrosion inhibition behavior of 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole (4-APTD) monolayers on copper surface were investigated by electrochemical impedance spectroscopy (EIS), electrochemical polarization measurement and surface-enhanced Raman scattering (SERS) experiment. The EIS mechanism of the copper surface with 4-APTD monolayers fitted to the mode of R(Q(R(QR))). The electrochemical polarization measurements indicated high inhibition efficiency of about 90.4%. SERS results suggested that 4-APTD molecules anchored at copper surface in a tilted orientation directly via N³ and N¹² atoms. The transition adsorption states of 4-APTD on the copper surface were observed as the potential applied from 0 to −1.6 V vs. SCE.     

Chlorhexidine digluconate as corrosion inhibitor for carbon steel dissolution in emulsified diesel fuel

Nitrogen oxide (NO_x) and particulate matter (PM) emissions from diesel engines are reduced by mixing water in the diesel fuel in the form of water-in-diesel emulsion. The results of experiment showed that blend of span 80 and tween 80 at HLB 6 was found to be the most suitable emulsifier for water/diesel emulsion. The effect of chlorhexidine digluconate on the corrosion of carbon steel electrode in aerated stagnant water/diesel emulsion solution has been studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiency was found to increase with increasing inhibitor concentration. The inhibition is attributed to adsorption of the inhibitor on the carbon steel surface. The adsorption behavior of chlorhexidine digluconate on the carbon steel surface follows Temkin-type isotherm. The standard free energies of adsorption are lower than 40 kJ mol⁻¹ confirming the physical adsorption of chlorhexidine digluconate on the electrode surface. Chlorhexidine digluconate has a significant inhibiting effect on the growth of micro-organisms in the liquid fuel and protection efficiencies up to 99.9% were measured.     

The effect of synthetic zinc corrosion products on corrosion of electrogalvanized steel. II. Zinc reactivity and galvanic coupling zinc/steel in presence of zinc corrosion products

The reactivity of zinc under synthetic zinc patinas and the galvanic coupling in steel/patina/Zn are studied. Zn₅(OH)₆(CO₃)₂ and Na₂Zn₃(CO₃)₄⋅3H₂O inhibit zinc anodic dissolution in NaCl, while Zn₅(OH)₈Cl₂ H₂O and Zn₄(OH)₆SO₄ nH₂O do not. The galvanic current in steel/patina/NaCl/Zn is smaller as compared to steel/NaCl/Zn. The inhibiting effect decreases with time for Na₂Zn₃(CO₃)₄⋅3H₂O or Zn₄(OH)₆SO₄ nH₂O due to the transformation into Zn(OH)₂. In NaHCO₃, the polarity between zinc and steel can reverse. The effect of confinement on the cathodic current is stronger than the initial effect of patina which is explained by the instability of the patinas under rapid pH-increase.     

Synergistic effect of potassium iodide with phthalazone on the corrosion inhibition of mild steel in 1.0 M HCl

The effects of phthalazone (PTO) and its synergistic effect with KI on the corrosion of mild steel in 1.0 M HCl solution were studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The inhibition efficiency increases with the concentration of the inhibitor and increased further with the presence of 6.02 mM KI. The synergistic effect of 6.02 mM KI at different concentrations of PTO was determined by calculating the synergism parameters, which showed that a cooperative mechanism exists between the iodide anion and PTO cations.     

Investigation of the inhibiting effect of N-[(Z)-1-phenylemethyleidene]-N-{2-[(2-{[(Z)-1phenylmethylidene]amino}phenyl)disulfanyl]phenyl} amine and its derivatives on the corrosion of stainless steel 304 in acid media

The effect of newly synthesized S₂N₂-Schiff bases is investigated on stainless steel 304 corrosion in 15% hydrochloric acid. The Tafel curves of the steel in hydrochloric acid containing Schiff bases show inhibition for both cathodic and anodic processes. Moreover, double layer capacitance and charge transfer resistance values are derived from Nyquist plots. The inhibition efficiency of Schiff bases increases with the increase in inhibitor concentration and temperature. Moreover, Langmuir adsorption isotherm is suitable to fit experimental data of the studied inhibitors. Effect of temperature on the efficiency of the corrosion inhibition shows chemisorption of inhibitors on the surface of metal.     

EN, EIS and polarization studies to evaluate the inhibition effect of 3H-phenothiazin-3-one, 7-dimethylamin on mild steel corrosion in 1 M HCl solution

The corrosion inhibition effect of 3H-phenothiazin-3-one, 7-dimethylamin as a new inhibitor was studied using different electrochemical and weight loss methods. It was found that this compound acts as a strong inhibitor for mild steel in 1 M HCl even at very low concentration (1 ppm). Results showed that this compound acts as a mixed type inhibitor. As the inhibitor concentration increased, the charge transfer resistance of mild steel increased and double layer capacitance decreased. The results of EN measurements after trend removal were in good agreement with other methods results. It was found that this inhibitor acts through adsorption on the metal surface. Also, adsorption obeys the Langmuir isotherm.     

Benzyltrimethylammonium iodide as a corrosion inhibitor for steel in phosphoric acid produced by dihydrate wet method process

The inhibition effect of benzyltrimethylammonium iodide (BTAI) on the corrosion of cold rolled steel (CRS) in phosphoric acid produced by dihydrate wet method process (7.0 M H₃PO₄) solution was investigated for the first time by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) methods. The results show that BTAI is a good inhibitor, and the adsorption of BTAI obeys Langmuir adsorption isotherm. Polarization curves show that BTAI behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of BTAI is also evidenced by SEM images.     

Evaluation of the corrosion of UNS G10200 steel in aerated brines under hydrodynamic conditions

The influence of the flow velocity and the temperature on the corrosion of UNS G10200 in aerated brines had been evaluated by means of electrochemical techniques at the RCE. Increasing the flow velocity and the temperature enhances the corrosion kinetic of the system and changes the corrosion mechanism. This behaviour was adduced to the presence of a mixed control on the corrosion process related with the formation and stabilization of corrosion product layers on the electrode surface. The correlations of Wranglen and Silverman for the mass transfer and the wall shear stresses respectively were validated at the RCE for this system.     

Inhibition effect of methyl violet on the corrosion of cold rolled steel in 1.0 M HCl solution

The inhibition effect of methyl violet (MV) on the corrosion of cold rolled steel (CRS) in 1.0 M HCl solution at 20-50 °C was studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) methods. The results show that MV is an excellent inhibitor even with very low concentration, and the adsorption of MV on CRS surface obeys Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that MV behaves as a mixed-type inhibitor. EIS spectra exhibit one capacitive loop and confirm the inhibitive ability. The inhibition action of MV is also evidenced by SEM.     

Mechanisms of corrosion inhibition of AA2024-T3 by vanadates

The mechanisms of corrosion inhibition of AA2024-T3 by vanadates were studied using chronoamperometry, polarization curves and adsorption isotherms. The electrochemical behaviour of clear solutions containing metavanadates and orange solutions containing decavanadates was clearly distinctive. Metavanadates reduced the kinetics of oxygen reduction to an extent similar to chromates. Corrosion inhibition of AA2024-T3 by metavanadates was very rapid and it might occur by the formation of an adsorbed layer. Reduction of clear metavanadate solution was very slow. Approximately 35 min were required to develop a monolayer of a reduced vanadate species. The adsorption of the inhibitor likely blocked reactive sites on intermetallic particles, discouraging the oxygen reduction reaction (ORR). Adsorption of the inhibitor on the Al matrix could also displace Cl⁻ ions, increasing the stability of the passive film and reducing the breakdown of S-phase particles. In contrast, decavanadates were shown to be poor inhibitors of the ORR. A sharp current spike was observed after injection of decavanadates for both Cu and AA2024-T3 at various applied cathodic potentials. Integration of the current peaks suggested the formation of several monolayers of a reduced vanadate species. The formation of several monolayers was in line with the poor performance of decavanadates as inhibitors of AA2024-T3 corrosion.     

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.