Synergistic inhibition between tween 60 and NaCl on the corrosion of cold rolled steel in 0.5 M sulfuric acid

The corrosion inhibition of cold rolled steel in 0.5 M sulfuric acid in the presence of tween 60 and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The inhibition efficiency increases with increasing tween 60 concentration at the same temperature, but decreases with increasing temperature studied. A synergistic effect exists when tween 60 and chloride ions are used together to prevent cold rolled steel corrosion in 0.5 M sulfuric acid at every experimental temperature. The polarization curves show that tween 60 is a cathodic inhibitor, while the complex of tween 60 and NaCl is a mixed-type inhibitor. The experimental results suggest that the presence of chloride ions in the solution stabilizes the adsorption of tween 60 molecules on the metal surface and improves the inhibition efficiency of tween 60. The adsorption of single tween 60 follows the Temkin adsorption isotherm, but the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy has been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed.     

Synergistic influence of iodide ions on the inhibition of corrosion of C-steel in sulphuric acid by some aliphatic amines

The synergistic influence caused by iodide ions on the inhibition of corrosion of C-steel in 1 M H₂SO₄ in the presence of some aliphatic amines has been studied using weight loss, potentiodynamic polarization, linear polarization and a.c. impedance techniques. Aliphatic amines used inhibit the corrosion of C-steel and the inhibition efficiency increases by increasing the concentration of the additives and also by addition of iodide ions. The adsorption of these compounds is found to obey Frumkin’s adsorption isotherm. The increase in surface coverage in the presence of iodide ions indicates that iodide ions enhance the adsorption of these aliphatic amines on the metal surface. Defines and evaluates synergism parameter (S_θ). Values of the parameter which are more than unity indicate the fact that the enhanced inhibition efficiency in the presence of iodide ions is only due to synergism and there is a definite contribution from the inhibitors molecules, which are adsorbed by coulombic interaction on the metal surface, where iodide ions are already adsorbed and thus reduces the corrosion rate.     

Adsorption properties and inhibition of mild steel corrosion in sulphuric acid solution by ketoconazole: Experimental and theoretical investigation

Ketoconazole (KCZ) has been evaluated as a corrosion inhibitor for mild steel in aerated 0.1 M H₂SO₄ by gravimetric method. The effect of KCZ on the corrosion rate was determined at various temperatures and concentrations. The inhibition efficiency increases with increase in inhibitor concentration but decrease with rise in temperature. Adsorption followed the Langmuir isotherm with negative values of , suggesting a stable and a spontaneous inhibition process. Quantum chemical approach was further used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of ketoconazole.     

Stress corrosion cracking of type 304 austenitic stainless steel in sulphuric acid solution including sodium chloride and chromate

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 304 was investigated as functions of chloride concentration, chromate concentration and test temperature under a constant applied stress condition in 0.82 kmol/m³ sulphuric acid solution by using a constant load method. From the dependence of the three parameters (, steady state elongation rate; t_ss, transition time; t_f, time to failure) obtained from corrosion elongation curve on chloride/chromate concentrations and test temperature, a parameter for predicting time to failure and critical values of chromate concentration and test temperature, below which little SCC takes place, were estimated. In addition, a transgranular SCC mechanism was qualitatively inferred and then the effect of chromate and chloride on SCC behavior was discussed.     

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.     

Stress corrosion cracking susceptibility of sensitized type 316 stainless steel in sulphuric acid solution

The stress corrosion cracking (SCC) of a commercial austenitic stainless steel type 316 was investigated as a function of sensitizing temperature (800-1300 K) and test temperature (333-373 K) in 0.82 kmol/m³ sulphuric acid solution by using a constant load method, to compare with that already obtained in 0.82 kmol/m³ hydrochloric acid solution. The three parameters (l_ss, steady state elongation rate, t_ss, transition time, t_f, time to failure) were obtained from corrosion elongation curve and were divided into three regions of applied stress, irrespective of sensitizing temperature, which are dominated by either stress, SCC or corrosion. In the SCC-dominated region, the logarithm of l_ss was a linear function of the logarithm of t_f regardless of applied stress and test temperature for each sensitized specimens, showing that l_ss became a useful parameter for prediction of t_f, although the slope depended upon sensitizing temperature. The maximum applied stress, the minimum applied stress and the value of t_ss/t_f in the SCC-dominated region depended upon sensitizing temperature. Specifically, at a sensitizing temperature of around 950 K the maximum applied stress was smaller at a test temperature of 353 K, but larger at a test temperature of 333 K than that of the solution annealed specimens. In addition, sulphate ions were found to become more aggressive than chloride ions for the SCC susceptibility of the specimens with the most severe sensitization. On the basis of the results obtained, the effect of sensitization on SCC, the role of sulphate ions and an intergranular mechanism were discussed in comparison to the results of the sensitized specimens obtained in 0.82 kmol/m³ HCl solution.     

Synthesis and corrosion protection study of poly(o-ethylaniline) coatings on copper

Poly(o-ethylaniline) coatings were synthesized on copper (Cu) by electrochemical polymerization of o-ethylaniline in an aqueous salicylate solution by using cyclic voltammetry. The characterization of these coatings was carried out by cyclic voltammetry, UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results of these characterizations indicate that the aqueous salicylate solution is a suitable medium for the electrochemical polymerization of o-ethylaniline to generate strongly adherent and smooth poly(o-ethylaniline) coatings on Cu substrates. The performance of poly(o-ethylaniline) as protective coating against corrosion of Cu in aqueous 3% NaCl was assessed by the potentiodynamic polarization technique and electrochemical impedance spectroscopy (EIS). The results of these studies demonstrate that the poly(o-ethylaniline) coating has ability to protect the Cu against corrosion. The corrosion potential was about 0.078 V versus SCE more positive in aqueous 3% NaCl for the poly(o-ethylaniline) coated Cu (∼ 15 μm thick) than that of uncoated Cu and reduces the corrosion rate of Cu almost by a factor of 70.     

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.     

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.     

Nitrotetrazolium blue chloride as a novel corrosion inhibitor of steel in sulfuric acid solution

The inhibition effect of nitrotetrazolium blue chloride (NTBC) on the corrosion of cold rolled steel (CRS) in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The results show that NTBC is a good inhibitor, and the adsorption of NTBC on CRS surface obeys Langmuir adsorption isotherm. Polarization curves show that NTBC acts as a mixed-type inhibitor. EIS spectra consist of large capacitive loop at high frequencies followed by a small inductive one at low frequency values, and charge transfer resistance increases with the inhibitor concentration.     

The inhibition activity of ascorbic acid towards corrosion of steel in alkaline media containing chloride ions

The activity of ascorbic acid towards steel corrosion in saturated Ca(OH)₂ solution containing chloride ions was investigated in this study. Concentration and time dependence of the protective properties of the passive film were acquired by electrochemical impedance spectroscopy. The best inhibitive performance, i.e. the longest pitting initiation time was obtained in the presence of 10⁻³ M ascorbic acid, while both lower and higher concentrations showed shortening of the pitting-free period. The overall behaviour of ascorbic acid was attributed to its ability to form chelates of various solubility having various metal/ligand ratios and oxidation states of the chelated iron. The assumption of ascorbic acid assisted reductive dissolution of the passive layer at higher inhibitor concentrations was confirmed by cyclic voltammetry and ATR FTIR spectroscopy. It is proposed that the overall inhibitive effect at lower concentrations is due to the formation of insoluble surface chelates and the effective blocking of the Cl⁻ adsorption at the surface of passive film. A pronounced inhibitive effect observed after the pitting had initiated was ascribed to the formation of a resistive film at the pitted area.     

Inhibitory action of Phyllanthus amarus extracts on the corrosion of mild steel in acidic media

The inhibitive action of leaves (LV), seeds (SD) and a combination of leaves and seeds (LVSD) extracts of Phyllanthus amarus on mild steel corrosion in HCl and H₂SO₄ solutions was studied using weight loss and gasometric techniques. The results indicate that the extracts functioned as a good inhibitor in both environments and inhibition efficiency increased with extracts concentration. Temperature studies revealed an increase in inhibition efficiency with rise in temperature and activation energies decreased in the presence of the extract. A mechanism of chemical adsorption of the plants components on the surface of the metal is proposed for the inhibition behaviour. The adsorption characteristics of the inhibitor were approximated by Temkin isotherm.     

A comparative study of the corrosion inhibition of mild steel in sulphuric acid by 4,4-dimethyloxazolidine-2-thione

The corrosion protection of mild steel in a 2.5 M H₂SO₄ solution by 4,4-dimethyloxazolidine-2-thione (DMT) was studied at different temperatures by measuring changes in open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion current densities calculated from EIS data were comparable to those obtained from polarisation measurements. Results showed that DMT inhibited mild steel corrosion in a 2.5 M H₂SO₄ solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature. Polarisation curves showed that DMT is a mixed-type inhibitor. Changes in impedance parameters suggested the adsorption of DMT on the mild steel surface, leading to the formation of protective films. The DMT adsorption on the mild steel surface followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters for dissolution and adsorption were investigated. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the mild steel surface was suggested based on the thermodynamic adsorption parameters.     

Mechanical properties and corrosion resistance of nanocrystalline ZrNxOy coatings on AISI 304 stainless steel by ion plating

Transition metal oxynitrides have become emerging decorative coating materials due to their adjustable coloration and high hardness and corrosion resistance. This research studied the effect of oxygen content on the coloration, mechanical properties and corrosion resistance of ZrN_xO_y thin films deposited on AISI 304 stainless steel using hollow cathode discharge ion plating (HCD-IP). The Zr/N/O ratios of the ZrN_xO_y films were determined using X-ray photoelectron spectroscopy (XPS). The color of the ZrN_xO_y thin film changed from golden yellow to blue and then slate blue with increasing oxygen content. X-ray diffraction (XRD) patterns revealed that phase separation of ZrN and m-ZrO₂ occurred as the oxygen content reached 31.2 at.%. ZrN(O) (ZrN with dissolving oxygen) is dominant at oxygen content less than 18.1 at.%, while m-ZrO₂ phase was prevailed at oxygen content above 40.3 at.%. Phase separation lowered the hardness of the ZrN_xO_y films as the fraction of ZrO₂ was less than 40%. The residual stresses in ZrN phase was higher than that in ZrO₂, and the residual stress decreased for the specimen containing 30 to 37% ZrO₂. For the samples containing more than 44% ZrO₂, the average residual stress was close to that in ZrO₂ phase. The corrosion resistance was evaluated by salt spray test and potentiodynamic scan in two solutions: 0.5MH₂SO₄ + 0.05 M KSCN and 5% NaCl solutions. The results showed consistent trend in the two solutions. From the results of potentiodynamic scan, corrosion resistance increased as the packing density of the film increased, whereas the film thickness was not a crucial factor on corrosion current; moreover, the electrical conductivity of the film may be one of the significant factors in corrosion resistance. Results of salt spray tests suggested that the corrosion of ZrN_xO_y in NaCl may play an important role in corrosion resistance.     

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.     

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.     

The adsorption and corrosion inhibition of some cationic gemini surfactants on carbon steel surface in hydrochloric acid

The adsorption and corrosion inhibition of the gemini surfactants 1,2-ethane bis(dimethyl alkyl (C_nH_2n+1) ammonium bromide) (designated as n−2−n, n=10, 12 and 16) on the steel surface in 1 M hydrochloride acid were studied using the weight loss method. It was found that the adsorption of the gemini surfactants on the steel surface is the main reason to cause the steel corrosion inhibition in hydrochloride acid, and the inhibition efficiency increases with the increase of surfactant concentration and reaches the maximum value near the CMC. A possible adsorption model of gemini surfactant onto the metal surface was also discussed.     

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.     

Electrochemical polymerization of o-anisidine on low carbon steel from aqueous salicylate solution: Corrosion protection study

The electrochemical polymerization of o-anisidine was carried out on low carbon steel from an aqueous salicylate medium using cyclic voltammetry. The resulting poly(o-anisidine) coatings were uniform and adherent to the steel substrates. These coatings were characterized by cyclic voltammetry, UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction measurements and scanning electron microscopy. The ability of the poly(o-anisidine) coatings to protect low carbon steel in an aqueous 3% NaCl was evaluated by the potentiodynamic polarization measurements. The potentiodynamic polarization measurement reveals that the poly(o-anisidine) coating increases the corrosion potential and reduces the corrosion rate of low carbon steel almost by a factor of 15.