Synergistic Effect Of Iodide Ions Research Articles

Corrosion Inhibition of Mild Steel In (1 M Hcl) Solution Using Plant Extract and The Synergistic Effect of Iodide Ions

The corrosion inhibitive impacts of a mixture (4:1) of Citrus Limon leaf (CLL) extract and potassium iodide additives when the mild steel was exposed to the corrosive solution (1M HCl) were evaluated using the weight-loss method at temperatures of )303, 313, 323, and 333( K. It was noted that the mixture acts as an inhibitor of mild steel corrosion at concentrations of )1.25, 2.5, 3.75, 5, and 6.25( ml/L. It was observed also that the inhibition efficiency (%I) of the mixture increased with an increase in temperature in the presence of the synergistic effect of the iodide ion. It was found that at the highest mixture concentrations and temperatures, the inhibition competence increased to 95.20%. Inhibitor adsorption characteristics were reached by the Langmuir isotherm and were compatible. The adsorption thermodynamic parameters that were calculated supported the mixed-adsorption of the mixture on a mild steel surface. A surface analysis technique (SEM) used to confirm the occurrence of an adsorption process on the surface.

Synergistic effect of iodide ions on the corrosion inhibition of mild steel in 1 M HCl by Cardaria Draba leaf extract

In pickling or descaling processes, plant extracts have the potential to operate as corrosion inhibitors due to their low impact on the environment, high rate of renewable availability, and plenty of available resources. It was found that mild steel in 1 M HCl can be protected from corrosion by the application of Cardaria Draba leaves (CDL) and potassium iodide (KI). The weight loss method was adopted to study the influences of temperature and blend concentration. Using a CDL-KI blend, the results reveal that the inhibitory efficacy increases with the concentration and temperature of the inhibitor. At higher concentrations and temperatures, 96 % inhibition efficiency was obtained. The Langmuir isotherm model predicted that the mixture would form a monolayer on the metal surface upon adsorption. It was discovered that the adsorption-free energy ranged from 20 to 40 kJ/mol, demonstrating the presence of chemical adsorption. Antagonism was indicated by synergistic parameter (SΘ) values lower than unity. Weight loss data is verified using FTIR and SEM.

Experimental and Theoretical Insights into the Synergistic Effect of Iodide Ions and 1-Acetyl-3-Thiosemicarbazide on the Corrosion Protection of C1018 Carbon Steel in 1 M HCl.

Experimental insights into the synergistic effect of 1-acetyl-3-thiosemicarbazide (AST) and iodide ions on the corrosion of C1018 carbon steel in 1 M HCl solution were investigated using open-circuit potential (OCP), linear polarization resistance (LPR), electrochemical frequency modulation (EFM), potentiodynamic polarization (PDP) measurements and electrochemical impedance spectroscopy (EIS). Theoretical studies were further undertaken using ACD/LABS Percepta software, density functional theory (DFT) calculations and Monte Carlo simulation to understand the mechanism of the corrosion inhibition process and interpret the experimental results at the atomic and molecular levels. The electrochemical results obtained showed that AST alone inhibited the acid-induced corrosion of C1018 carbon steel. The inhibition efficiency increases with a concentration reaching up to 72.27% at 750 ppm of AST. The addition of 5 mM KI to 250 ppm of AST improved the inhibition efficiency to 81.64%. The solubility and protonated state results predicted using the ACD/LABS Percepta software showed that AST was highly soluble in the aqueous acidic medium and approximately 95% of AST exists in the neutral form in 1 M HCl (pH = 0). DFT calculations and a Monte Carlo simulation were utilized to predict the active reactivity sites of AST and calculate the lowest adsorption energy and configuration of AST alone and AST + iodide on/Fe (110)/water interface.

Synergistic effect of iodide ions and bark resin of Schinus molle for the corrosion inhibition of API5L X70 pipeline steel in H2SO4

AbstractThe synergistic effect of bark resin of Schinus molle (BRSM) and iodide ions in 0.5 M sulfuric acid has been studied for the first time by potentiodynamic polarization and electrochemical impedance spectroscopy measurements; also, the surface morphology has been analyzed by scanning electron microscopy–energy‐dispersive X‐ray spectroscopic analysis in the present work. The results show that the BRSM and iodide ions have an evident synergistic inhibition effect in a 0.5‐M sulfuric acid solution. The adsorption of the BRSM/iodide ion system follows the Langmuir adsorption isotherm and acts as a mixed‐type inhibitor in sulfuric acid. The BRSM/iodide ion system is an effective inhibitor for API5L X70 pipeline steel in the 0.5‐M sulfuric acid solution. The maximum percentage inhibition efficiency is equal to 99% at 1 g/L BRSM + 2 mM KI.

Synthesis, characterization and the inhibition activity of 3-(4-cyanophenylazo)-2,4-pentanedione (L) on the corrosion of carbon steel, synergistic effect with other halide ions in 0.5 M H2SO4

3-(4-cyanophenylazo)-2,4-pentanedione (L) was synthesized and characterized by several spectral techniques. The synergistic effect of iodide ions on the inhibition of carbon steel corrosion in 0.5 M H2SO4medium by (L) was studied by experimental and theoretical methods. It was found that the addition of potassium iodide (KI) to acidic solution having L stabilized the adsorption of L molecules on the metal surface. The optimal mass ratio was found to be [L]/[KI] = 1 while the values of the synergy parameter (Sθ) are found to be greater than unity in all cases. There is a perfect approval between the experimental results and the theoretical calculation.

The synergistic corrosion inhibition study of different chain lengths ionic liquids as green inhibitors for X70 steel in acidic medium

For this study, three corrosion inhibitors with different anionic carbon chain lengths, 1-vinyl-3-methylimidazolium iodide ([VMIM]I), 1-vinyl-3-proplylimidazolium iodide ([VPIM]I) and 1-vinyl-3-butylimidazolium iodide ([VBIM]I) were studied on the corrosion of X70 steel in 0.5 M H2SO4 solution at 298 K by electrochemical measurements, weight loss methods, scanning electron microscope (SEM), FTIR spectra, atomic force microscopy (AFM) and theoretical calculation. Three inhibitors with synergistic effect of iodide ions are mixed-type inhibitors with excellent inhibition efficiency. The order of corrosion inhibition efficiency is: [VMIM]I < [VPIM]I < [VBIM]I according to theoretical and experimental study, indicating the inhibition performance was improved with the increase of alkyl chain length attached to imidazolium ring, owing to its electron-donating effect of alkyl groups. The adsorption of three inhibitors including physisorption and chemisorption obeyed Langmuir adsorption isotherm.

Electrochemical and gravimetric measurements of inhibition of aluminum corrosion by poly (methacrylic acid) in H2SO4 solution and synergistic effect of iodide ions

The corrosion inhibition of Al in 0.5M H2SO4 solution by poly (methacrylic acid) (PMAA) alone and in combination with iodide ions was studied at 303–333K using gravimetric, electrochemical impedance spectroscopy, potentiodynamic polarization, scanning electron microscopy and water contact angle measurements techniques. Results obtained show that PMAA moderately inhibited the dissolution of Al in the corrosive medium. Addition of Iodide ions synergistically upgrades the inhibition efficiency of PMAA to a maximum value of 82.6%. From polarization results, PMAA and PMAA+KI can be classified as mixed-type corrosion inhibitor. Thermodynamic parameters namely Gibbs free energy of adsorption, activation energy and enthalpy of activation revealed that the adsorption processes of PMAA and PMAA+KI are endothermic reactions mainly by a physisorption mechanism and followed El-Awady et al. thermodynamic–kinetic adsorption isotherm.

Some Phthalocyanine and Naphthalocyanine Derivatives as Corrosion Inhibitors for Aluminium in Acidic Medium: Experimental, Quantum Chemical Calculations, QSAR Studies and Synergistic Effect of Iodide Ions.

The effects of seven macrocyclic compounds comprising four phthalocyanines (Pcs) namely 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (Pc1), 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine (Pc2), 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (Pc3) and 29H,31H-phthalocyanine (Pc4), and three naphthalocyanines namely 5,9,14,18,23,27,32,36-octabutoxy-2,3-naphthalocyanine (nPc1), 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine (nPc2) and 2,3-naphthalocyanine (nP3) were investigated on the corrosion of aluminium (Al) in 1 M HCl using a gravimetric method, potentiodynamic polarization technique, quantum chemical calculations and quantitative structure activity relationship (QSAR). Synergistic effects of KI on the corrosion inhibition properties of the compounds were also investigated. All the studied compounds showed appreciable inhibition efficiencies, which decrease with increasing temperature from 30 °C to 70 °C. At each concentration of the inhibitor, addition of 0.1% KI increased the inhibition efficiency compared to the absence of KI indicating the occurrence of synergistic interactions between the studied molecules and I− ions. From the potentiodynamic polarization studies, the studied Pcs and nPcs are mixed type corrosion inhibitors both without and with addition of KI. The adsorption of the studied molecules on Al surface obeys the Langmuir adsorption isotherm, while the thermodynamic and kinetic parameters revealed that the adsorption of the studied compounds on Al surface is spontaneous and involves competitive physisorption and chemisorption mechanisms. The experimental results revealed the aggregated interactions between the inhibitor molecules and the results further indicated that the peripheral groups on the compounds affect these interactions. The calculated quantum chemical parameters and the QSAR results revealed the possibility of strong interactions between the studied inhibitors and metal surface. QSAR analysis on the quantum chemical parameters obtained with B3LYP/6-31G (d,p) method show that a combination of two quantum chemical parameters to form a composite index provides the best correlation with the experimental data.

Inhibition of mild steel corrosion in H2SO4 solution by coconut coir dust extract obtained from different solvent systems and synergistic effect of iodide ions: Ethanol and acetone extracts

Weight loss and electrochemical (open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy) techniques were used to assess the effectiveness of ethanol and acetone extracts of coconut coir dust as corrosion inhibitor for mild steel in 0.5 M H2SO4 solution at 30–60 °C. It was found that both ethanol and acetone extracts of coconut coir dust retard the dissolution of mild steel in 0.5 M H2SO4 solution, but a pronounced effect was noted with ethanol extract. The inhibition efficiency increased with increase in extract concentration but decreased with rise in temperature, which is suggestive of physical adsorption mechanism. Addition of KI was found to synergistically enhance the protective ability of coconut coir dust extracts obtained from both solvent systems investigated. The synergistic effect was confirmed from the synergism parameter (S0) which was found to be greater than unity. Potentiodynamic polarization result suggests that coconut coir extracts functioned as mixed-type inhibitor. The adsorption of coconut coir dust extracts onto the mild steel surface followed Freundlich adsorption isotherm model. The mechanism of physisorption of the extracts onto the steel surface is proposed from the trend of inhibition efficiency with temperature which is corroborated by the values of activation parameters obtained from the experimental data.

Study of Synergistic Effect of Iodide on the Corrosion Antagonistic Behaviour of a Heterocyclic Phenylhydrazone in Sulphuric Acid Medium on Carbon Steel

Synergistic effect of KI on the corrosion inhibition efficiency of 3-acetylpyridine phenylhydrazone (3APPH) on carbon steel (CS) in 0.5&#x2009;M sulphuric acid solution has been investigated using gravimetric studies, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. Gravimetric corrosion studies revealed that 3APPH showed moderate corrosion inhibition efficiency up to 8&#x2009;h and beyond this period it showed corrosion accelerating behavior. This antagonistic effect of 3APPH is due to the hydrolysis of the molecule in acidic medium. A very high percentage of inhibition efficiency at 24&#x2009;h was obtained on the addition of KI due to the synergistic effect of iodide ions. The adsorption of 3APPH and 3APPH&#x2009;+&#x2009;KI on the surfaces of the corroding metal obey Langmuir isotherm as obtained by impedance measurements. Polarization studies revealed that 3APPH act as a mixed type inhibitor. Thermodynamic parameters (<svg style="vertical-align:-3.39064pt;width:76.224998px;" id="M1" height="20.0625" version="1.1" viewBox="0 0 76.224998 20.0625" width="76.224998" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x1D43E" d="M764 650l-7 -26q-61 -10 -91.5 -22.5t-76.5 -48.5l-235 -184q104 -152 208 -276q31 -37 54.5 -48.5t68.5 -16.5l-7 -28h-156q-138 170 -213 284q-19 29 -33.5 35t-33.5 -7l-29 -173q-15 -75 -5.5 -90.5t74.5 -20.5l-5 -28h-260l7 28q58 5 74 21.5t30 89.5l70 378&#xA;q12 68 2 83t-72 22l6 28h257l-7 -28q-62 -7 -76 -21.5t-27 -83.5l-32 -172q29 11 78 46q112 84 217 179q18 16 23.5 25.5t-1 14.5t-26.5 8l-30 4l5 28h249z" /></g> <g transform="matrix(.012,-0,0,-.012,13.25,19.863)"><path id="x61" d="M433 39l-85 -51q-27 0 -47 20q-16 16 -24 44q-5 -3 -24 -16.5t-27 -18.5t-23 -13.5t-25 -12t-19 -3.5q-52 0 -86 36.5t-34 85.5q0 71 81 99q128 43 155 65v17q0 54 -23 83.5t-62 29.5q-28 0 -45 -19t-29 -66q-7 -23 -29 -23q-15 0 -29 13t-14 30t31 40q25 19 68.5 40.5&#xA;t81.5 29.5q49 0 82 -27q45 -39 45 -123v-185q0 -60 35 -60q18 0 36 11zM275 84v156q-12 -6 -49 -23t-41 -19q-31 -14 -46 -31t-15 -43q0 -35 22.5 -55.5t48.5 -20.5q19 0 42 10.5t38 25.5z" /></g><g transform="matrix(.012,-0,0,-.012,18.474,19.863)"><path id="x64" d="M517 51v-25q-101 -18 -155 -38v65l-61 -36q-50 -29 -78 -29q-68 0 -126.5 58t-58.5 155q0 103 77 175.5t180 72.5q36 0 67 -12v143q0 48 -11.5 58.5t-65.5 14.5v25q79 9 156 34v-597q0 -38 7.5 -48t36.5 -13zM362 85v275q-35 51 -103 51q-20 0 -40.5 -8.5t-42 -28&#xA;t-35 -57.5t-13.5 -89q0 -83 42 -130t96 -47q51 0 96 34z" /></g><g transform="matrix(.012,-0,0,-.012,24.756,19.863)"><path id="x73" d="M319 325l-25 -7q-33 99 -103 99q-29 0 -47 -19.5t-18 -49.5t22 -49.5t62 -36.5q63 -26 95 -57t32 -79q0 -64 -50 -101t-115 -37q-35 0 -67.5 10.5t-46.5 23.5q-5 11 -11 51t-6 67l27 5q14 -53 46.5 -88.5t75.5 -35.5q29 0 50 19.5t21 50.5t-19.5 51.5t-59.5 39.5&#xA;q-28 12 -46 22.5t-38.5 27t-30.5 38.5t-10 49q0 54 42.5 92t109.5 38q48 0 88 -18q6 -15 13 -50.5t9 -55.5z" /></g> <g transform="matrix(.017,-0,0,-.017,29.75,15.775)"><path id="x2C" d="M95 130q31 0 61 -30t30 -78q0 -53 -38 -87.5t-93 -51.5l-11 29q77 31 77 85q0 26 -17.5 43t-44.5 24q-4 0 -8.5 6.5t-4.5 17.5q0 18 15 30t34 12z" /></g><g transform="matrix(.017,-0,0,-.017,36.448,15.775)"><path id="x394" d="M600 0h-557v24l268 633l28 8l261 -641v-24zM497 50l-194 489l-196 -489h390z" /></g><g transform="matrix(.017,-0,0,-.017,47.344,15.775)"><path id="x1D43A" d="M713 296l-5 -25q-47 -7 -59 -20t-23 -72l-15 -79q-9 -48 -3 -74q-15 -3 -55 -13t-63 -15t-59.5 -10t-70.5 -5q-149 0 -243 80t-94 220q0 169 127.5 276.5t336.5 107.5q91 0 206 -36l-10 -165l-29 -1q1 85 -47.5 126t-146.5 41q-153 0 -243.5 -97t-90.5 -242&#xA;q0 -122 68.5 -198.5t188.5 -76.5q121 0 139 75l20 86q13 58 -1.5 70.5t-99.5 20.5l5 26h267z" /></g> <g transform="matrix(.012,-0,0,-.012,59.663,7.613)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105&#xA;q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g> <g transform="matrix(.012,-0,0,-.012,59.663,19.863)"><use xlink:href="#x61"/></g><g transform="matrix(.012,-0,0,-.012,64.886,19.863)"><use xlink:href="#x64"/></g><g transform="matrix(.012,-0,0,-.012,71.169,19.863)"><use xlink:href="#x73"/></g> </svg>) were derived from the adsorption isotherms. Surface morphology of the corroding metal was investigated by SEM analysis.

Corrosion inhibition and adsorption behavior of triazoles derivatives on mild steel in 1 M H3PO4 and synergistic effect of iodide ions

Corrosion inhibition by 4-amino-1,2,4-triazole, 3-(2-pyridyl)-4-amino-1,2,4- triazole (2-PAT) and 3-(4-pyridyl)-4-amino-1,2,4-triazole (4-PAT) on mild steel in 1 M H3PO4 was investigated by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. The results indicate that these compounds act as inhibitors retarding the cathodic corrosion reaction. Adsorption of triazoles derivatives on mild steel surface was also studied to examine basic information on the interaction between the inhibitors and the metal surface. It was found that the inhibitors adsorb on the metal surface following the Langmuir isotherm model. In addition, a synergism effect with KI was studied. It was found that the inhibition efficiency of triazole derivatives increases with iodide ions concentration to achieve 97 % at 5 × 10−4 M of KI. The temperature effect on the corrosion behavior of mild steel in 1 M H3PO4 in the absence and presence of 4-PAT with KI (mixture) was studied in the temperature range from 293 to 333 K. It is noted that the mixture retains its performance in this range. Finally, an adsorption mechanism of triazoles molecules with KI has been proposed and is discussed.

Corrosion inhibition and adsorption behaviour of an amido-imidazoline derivative on API 5L X52 steel in CO2-saturated solution and synergistic effect of iodide ions

Corrosion inhibition of an amido-imidazoline derivative on API 5L X52 steel in CO2 saturated 3wt% NaCl solution was investigated. The effect of iodide ion additives was also studied by using electrochemical techniques. The results showed that amido-imidazoline derivative inhibited corrosion of steel and the extent of its inhibition was concentration dependent. Potentiodynamic polarization investigations revealed that amido-imidazoline acted as a mixed inhibitor showing anodic and cathodic behaviour. Furthermore, the inhibition efficiency of amido-imidazoline was enhanced by addition of iodide ions due to synergistic effect. It was also found that amido-imidazoline adsorbed chemically on the steel surface and followed the Langmuir adsorption isotherm.

Effect of aluminium microstructure on corrosion and inhibiting effect of polyacrylic acid in H2SO4 solution

The corrosion behaviour of a microcrystalline aluminium (mc-Al) coating fabricated from pure cast aluminium substrate by magnetron sputtering and the pure polycrystalline aluminium (pc-Al) were studied using electrochemical impedance spectroscopy and potentiodynamic polarization techniques in aerated 0.5 M H2SO4 at 30 ± 1 °C. The corrosion inhibiting effect of polyacrylic acid (PAA) and synergistic effect of iodide ions was also investigated. Results obtained show that surface microcrystallization increases the corrosion susceptibility of pure cast aluminium leading to decrease in interfacial impedance and an increase in the kinetics of the anodic dissolution. Introduction of PAA into the corrosive medium was observed to retard the corrosion rates of both specimens. The inhibition mechanism was affected by the microstructure of the sample. PAA functions as a mixed inhibitor but under cathodic control for pc-Al and under anodic control for mc-Al. Addition of iodide ions synergistically increased the inhibition efficiency of PAA and this effect was more pronounced with mc-Al.

Synergistic effect of halide ions on improving corrosion inhibition behaviour of benzisothiozole-3-piperizine hydrochloride on mild steel in 0.5 M H 2SO 4 medium

The synergistic effect of iodide ions and benzisothiozole-3-piperizine hydrochloride (BITP) on corrosion inhibition of mild steel in 0.5 M H 2SO 4 solution has been studied by both chemical and electrochemical methods. The corrosion performance of BITP in 1.0 M HCl and 0.5 M H 2SO 4 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.

Electrochemical study of corrosion inhibition and adsorption behaviour for pure iron by polyacrylamide in H 2SO 4: Synergistic effect of iodide ions

Corrosion inhibition and adsorption behaviour for pure iron in 0.5 M H 2SO 4 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.

Synergistic effect of iodide ions on inhibitive performance of 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole during corrosion of mild steel in 0.5 M sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M H2SO4 solutions by 2,5-bis(4-methoxyphenyl)-1,3,4-thiadiazole (4-MTH) has been studied using electrochemical impedance spectroscopy (EIS) and the Tafel polarisation method. The results showed that the inhibition efficiency increased with 4-MTH concentration while the potential of desorption (Ed) remained unchanged. The addition of potassium iodide (KI) in the acid solution stabilized the adsorption of 4-MTH molecules on the metal surfaces and, therefore, enhanced the inhibition efficiency of 4-MTH and increased the value of Ed. The synergistic effect was observed between KI and 4-MTH with an optimum mass ratio of [4-MTH]/[KI] = 5/5. The calculated values of synergism parameter (Sθ) from the coverage of the surface were found to be more than unity in most cases. This clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H2SO4 by 4-MTH. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir’s adsorption isotherm.

Corrosion Inhibition of Mild Steel in 1 M H2SO4 by Polyvinyl Pyrrolidone and Synergistic Iodide Additives

The corrosion inhibition of mild steel in 1M H 2SO 4 by polyvinyl pyrrolidone (PVP) and the synergistic effect of iodide ions were investigated using weight loss and hydrogen evolution methods in the temperature range of 30 – 60 o C. The corrosion rates of mild steel decreased with the increasing concentration of PVP, while the inhibition efficiency (%I) increased. The inhibition efficiency of PVP decreased with rise in temperature, suggesting a physical adsorption mechanism, which was found to follow Freundlich and Temkin adsorption isotherms. The inhibition mechanism was further collaborated by the values of kinetics/thermodynamic parameters obtained from the experimental data. The inhibiting action of PVP was considerably enhanced in the presence of iodide ions and values of the synergism parameter (S 1) obtained point to synergistic interactions between PVP and iodide ions.

Influence of halide ions on the adsorption of diphenylamine on iron in 0.5 M H 2SO 4 solutions

Halide ions are found to enhance the inhibition performance of amines due to enhanced adsorption of amines by the adsorbed halide ions on the metal surface. In this work, the synergistic action of halide ions on the corrosion inhibition of iron in 0.5 M H 2SO 4 by diphenylamine has been found out by electrochemical impedance and polarization methods. Analysis of impedance data has been made with equivalent circuit with constant phase angle element for calculation of double layer capacitance values. Experiments have been carried out in the concentration range of 100–1000 ppm of diphenylamine in the presence of 0.5–1.0 × 10 −3 M of halide ions. Diphenylamine is found to be a cathodic inhibitor and the inhibition efficiency of about 65% is obtained at 1000 ppm. The anodic and cathodic Tafel slopes in the presence of diphenylamine alone and with halide ions are 65 ± 5 and 105 ± 5 mV, respectively. Diphenylamine inhibits corrosion by adsorption and the surface coverage values are increased considerably in the presence of halide ions. In the presence of iodide ions, the inhibition efficiency of diphenylamine at 100 ppm is increased to more than 90%. In the case of other halide ions, the inhibition efficiency of diphenylamine in increased to 80% at 1000 ppm. The order of synergism of halide ions is I − ≫ Br − > Cl −. The highest synergistic effect of iodide ions is due to chemisorption with metal surface due to its larger size and ease of polarizability.

Synergistic effect of iodide ions on the corrosion inhibition of steel in 0.5 M H 2SO 4 by new chalcone derivatives

The effect of addition of 4′,4-dihydroxychalcone (P 1), 4-aminochalcone (P 2) and 4-bromo, 4′-methoxychalcone (P 3) on the corrosion of steel in 0.5 M sulphuric acid has been studied by weight loss measurements, potentiodynamic and EIS measurements. We investigate the synergistic effect of iodide ions on the corrosion inhibition of steel in the presence of chalcone derivatives. The corrosion rates of the steel decrease with the increase of the chalcones concentration, while the inhibition efficiencies increase. The addition of iodide ions enhances the inhibition efficiency considerably. The presence of iodide ions increases the degree of surface coverage. The synergism parameters S Θ and S I, calculated from surface coverage and the values of inhibition efficiency, in the case of chalcone derivatives are found to be larger than unity. 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. E (%) obtained from the various methods is in good agreement. Polarisation measurements show also that the compounds act as cathodic inhibitors.

Effect of iodide ions on corrosion inhibition of mild steel by 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole in sulfuric acid solution

The synergistic effect of iodide ions on the corrosion inhibition of mild steel in 0.5 M sulfuric acid (H2SO4) in the presence of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) was investigated using weight loss measurements and different electrochemical techniques such as potentiostatic polarization curves and electrochemical impedance spectroscopy (EIS). The inhibition efficiency (E, %) increased with 4-MTHT concentration, but the desorption potential (Ed) remained unchanged with increasing 4-MTHT concentration. The addition of potassium iodide (KI) enhanced E considerably and increased the value of Ed. A synergistic effect was observed between KI and 4-MTHT with an optimum mass ratio of [4-MTHT]/[KI] = 4 × 10−2. The synergism parameters (SΘ) calculated from surface coverage were found to be more than unity. This result clearly showed the synergistic influence of iodide ions on the corrosion inhibition of mild steel in 0.5 M H2SO4 by 4-MTHT. The adsorption of this inhibitor alone and in combination with iodide ions followed Langmuir's adsorption isotherm.