Synergistic effect between cationic gemini surfactant and chloride ion for the corrosion inhibition of steel in sulphuric acid

Corrosion inhibition of cold rolled steel in 0.5 mol L⁻¹ sulphuric acid by a quaternary ammonium gemini surfactant, l,3-propane-bis(dimethyl dodecylammonium bromide) (designated as 12-3-12), in the absence and presence of chloride ions was investigated at different temperatures. The results revealed significant synergistic effect between gemini 12-3-12 and chloride ions for the corrosion protection of cold rolled steel in sulphuric acid, and that the novel composite inhibitor system containing cationic gemini surfactant and chloride ions was efficient and low-cost for steel corrosion inhibition in sulphuric acid medium, even when concentration of 12-3-12 was as low as 1 × 10⁻⁶ mol L⁻¹. By fitting the obtained experimental data with Langmuir adsorption model and Arrhenius equation, some thermodynamic and kinetic parameters such as adsorption free energy, the apparent activation energy, and the pre-exponential factor were estimated. The adsorption mechanism of the gemini surfactant onto steel surface in acid medium in the absence and presence of chloride ions was also discussed, respectively.     

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.     

Synergistic effect of chloride and sulfite ions on the atmospheric corrosion of bronze

The effect of chloride along with sulfite ions on the atmospheric corrosion of bronze was investigated by using periodic wet‐dry tests, surface tension tests and electrochemical impedance measurements. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were used to characterize the corrosion products. Both the electrochemical impedance measurements and surface tension tests agreed well with the results of weight loss measurements. Synergistic effect of chloride and sulfite ions was observed during the whole process. In addition, we found that the attack of anions on the metal at the initial corrosion stage showed good agreement with their surface activity. However, as the corrosion proceeded, the interaction among the corrosion products induced by chloride and HSO₃^? accelerated the corrosion process. A scheme was given to explain the whole corrosion process.     

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.     

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.     

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 between dodecylamine and potassium iodide on the corrosion of cold rolled steel in 0.1 M phosphoric acid

The corrosion inhibition of cold rolled steel in 0.1 M aerated phosphoric acid (H₃PO₄) in the presence of dodecylamine (DDA) and potassium iodide (KI) has been investigated by Tafel polarization curve and electrochemical impedence spectroscopy (EIS) at 20 °C. The results obtained from polarization curve show that the inhibition efficiency of DDA with and without KI increases with increase in concentration of DDA but the inhibition efficiency of DDA without KI is not too high. A synergistic effect exists when DDA and KI are combined together to prevent cold rolled steel corrosion in 0.1 M H₃PO₄. All impedance spectra in EIS tests exhibit one capacitive loop which indicates that the corrosion reaction is controlled by charge transfer process. Inhibition efficiencies obtained from Tafel polarization, transfer resistance (R_t) are consistent.     

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 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.     

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.     

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.     

Electrospun camphorsulfonic acid doped poly(o-toluidine)–polystyrene composite fibers: Chemical vapor sensing

The electrospinning technique was utilized to produce camphorsulfonic acid (HCSA) doped poly(o-toluidine) (POT)–polystyrene (PS) composite fibers in the non-woven mat form. HCSA doped POT–PS composite fibers were fabricated on an interdigited gold (Au) substrate for use as a chemical vapor sensor. The composite fiber sensor responded to volatile chemicals in different ways, depending on the polarity of sensing chemicals. The surface morphology of the non-woven composite fiber mat after chemical vapor sensing was unchanged. This study highlights that composite fibers comprised of polyaniline derivative and a spinnable polymer do have potential for use as chemical sensors due to their good solubility in common solvents and detectable electrical changes at low fiber contents.     

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.     

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.