Effect Of Halide Ions Research Articles

A Comparative Study of the Corrosion Inhibitive Properties of Pyrimidine Derivatives for Mild Steel

The influence of pyrimidine derivatives on the corrosion inhibition of mild steel in 1 M H2SO4 was studied using weight loss and electrochemical techniques. These compounds act as good corrosion inhibitors even at low concentration and the inhibition efficiency increased with the increase in inhibition concentration. The corrosion rates have been determined at various temperatures (303‐333K) by weight loss measurements. The Rt values obtained from EIS method increased with increase in inhibitor concentration. The potentiostatic polarization results clearly revealed that the inhibitors behave as a mixed type but slightly anodic in nature. The adsorption process was found to obey the Langmuir adsorption isotherm. The synergistic effect of halide ion on the inhibition efficiency increase with increase concentration.

Shape-Controlled Syntheses of Gold Nanoprisms and Nanorods Influenced by Specific Adsorption of Halide Ions

This paper describes the effect of halide ions during the seed-mediated growth of gold nanoparticles employing cetyltrimethylammonium bromide (CTAB) as a cationic surfactant system. With the addition of a small amount of iodide ion (∼20 μM) in a growth solution, the major product of the gold nanostructures formed were notably changed into triangular nanoprisms in the presence of excessive bromide ion (∼0.1 M); otherwise, in its absence, nanorods with an aspect ratio of ∼11 were the main products. The major role of the iodide ion was in retarding the overall rate of crystal growth, and the iodide adsorption appeared to repress the crystal growth along Au(111) direction, resulting in Au(111)-faced triangular nanoprisms. When the counteranions of the surfactant were replaced with chloride ions, a novel nanostructure (i.e., nanorice) was manufactured, which demonstrates the effectiveness of the adsorption of halide ions. However, this finding is quite contrasted with the work of the Sastry group (J. Nanosci. ...

Effect of halide ions on the corrosion inhibition of aluminium in alkaline medium using polyvinyl alcohol

AbstractThe corrosion inhibition of aluminum in NaOH in the presence of polyvinyl alcohol (PVA) at 30 and 40°C and the effect of addition of halides (KCl, KBr, KI) were studied using weight loss and hydrogen evolution methods. Results obtained showed that PVA acts as a corrosion inhibitor in the alkaline environment. The inhibition efficiency increased with increase in concentration of PVA and synergistically increased on the addition of the halides but however decreased with rise in temperature. The phenomenon of physical adsorption is proposed from the obtained Ea and Qads values. PVA was found to obey Freundlich and Frumkin adsorption isotherms. The increase in inhibition efficiency I (%), surface coverage θ values as well as synergistic parameter, SI were found to be in the order I− > Br− > Cl−, which clearly indicates that the radii and electronegativity of the halides play a significant role in the adsorption process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2810–2816, 2007

Effect of halide ions on the corrosion inhibition of mild steel in acidic medium using polyvinyl alcohol

PurposeTo investigate the effect of halide ions on the corrosion inhibition of mild steel using polyvinyl alcohol (PVA) in H2SO4 at 30‐60°C and to study the mechanism of action.Design/methodology/approachThe corrosion rates were determined using the gravimetric (weight loss) and gasometric (hydrogen evolution) techniques. The results obtained in the absence and presence of PVA, halides, PVA – halides combination were used to calculate the inhibition efficiency (%I), degree of surface coverage and to propose the mechanism of inhibition and type of adsorption.FindingsResults obtained showed that inhibition efficiency (%I) increased with the increase in concentration of PVA, on the addition of halides and with the increase in temperature. Phenomenon of chemical adsorption was proposed and PVA was found to obey Langmuir, Flory‐Huggins and Freundlich adsorption isotherms. The synergism parameter, S1, evaluated was found to be greater than unity and the values of Ea, ΔH°, ΔS° and ΔG° obtained revealed that the adsorption process was spontaneous.Research limitations/implicationsElectrochemical studies such as polarization and AC impedance spectra will enlighten more on the mechanistic aspects of the corrosion inhibition and more polymers need to be evaluated as corrosion inhibitors.Practical implicationsPVA can be used as corrosion inhibitor and the addition of halides to PVA improves the inhibition efficiency considerably.Originality/valueThis paper provides new information on the effects of halides on the corrosion inhibition using PVA as an inhibitor for mild steel in acidic medium. Such a study had not been reported elsewhere.

Synergistic effect of halide ions on the corrosion inhibition of aluminum in acidic medium by some polymers

AbstractThe corrosion inhibition of aluminum in H2SO4 in the presence of polyvinyl alcohol (PVA) and polyethylene glycol (PEG) and the effect of addition of halides (KCl, KBr, KI) was studied using the hydrogen evolution technique at 30 and 40°C. Inhibition efficiency (%I) increases with concentration of PVA and PEG—‐but with PEG having higher %I. The %I decrease with increase in temperature from 30 to 40°C in the absence and presence of inhibitor and halides. PVA and PEG were found to obey Freundlish adsorption isotherm. Phenomenon of physical adsorption is proposed from the obtained Ea, ΔGads, and Qads values obtained. The synergism parameters (SI) obtained were found to be greater than unity for both PVA and PEG, which indicates that the enhanced inhibition efficiency caused by the addition of halides is only due to synergism. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2889–2894, 2006

Role of Halide Ions and Temperature on the Morphology of Biologically Synthesized Gold Nanotriangles

In this paper, we demonstrate the effect of halide ions on the formation of biogenically prepared gold nanotriangles using the leaf extract of lemongrass (Cymbopogon flexuosus) plant. We have also studied the effect of halide ions on the morphology of biogenic nanotriangles. It has been shown that iodide ions have a greater propensity to transform flat gold nanotriangles into circular disk-like structures as compared to other halide ions. The study also suggests that the presence of Cl- ions during the synthesis promotes the growth of nanotriangles, whereas the presence of I- ions distorts the nanotriangle morphology and induces the formation of aggregated spherical nanoparticles. The change in the morphology of gold nanotriangles has been explained in terms of the ability of the halide ions to stabilize or inhibit the formation of (111) faces to form [111] oriented gold nanotriangles. Last, we have also shown that the temperature is an important parameter for controlling the aspect ratio and the relative amounts of gold nanotriangles and spherical particles. The results show that, by varying the temperature of reaction condition, the shape, size, and optical properties of anisotropic nanoparticles can be fine-tuned.

The inhibition of aluminium corrosion in potassium hydroxide by “Congo Red” dye, and synergistic action with halide ions

PurposeTo investigate the inhibitive effect of Congo red dye (CR) for aluminium corrosion in strong alkaline solutions and evaluate the synergistic effect of halide ions on the inhibition efficiency.Design/methodology/approachCorrosion rates of aluminium test coupons were determined by gravimetric technique at 30 and 60°C. Inhibition efficiencies of the additives (0.01‐5.0 mM CR and 5.0 mM CR+0.5 mM halides) were evaluated by comparing corrosion rates of the test coupons in 2 M KOH solution in the absence and presence of the additives.FindingsCR inhibited aluminium corrosion in 2 M KOH by physical adsorption of the dye molecules on the corroding metal surface. Maximum efficiency at 30 and 60°C was 31.72 and 19.32 per cent, respectively. Dye adsorption was enhanced in the presence of halides in the order KCl < KBr < KI, with KI increasing efficiency up to 48.63 and 41.70 per cent at 30 and 60°C, respectively.Research limitations/implicationsFurther studies to involve variation of dye and halide concentrations for CR+halide systems to determine the best combination for optimum inhibition synergism.Originality/valueThis paper forms part of an extensive database on the inhibition characteristics of organic dyes for corrosion of different metals in various aggressive environments. This is to serve as a guide to possible applications in metal‐surface anodizing and as additives in surface coatings for service in different environments.

Electrochemical behavior of tin in sodium borate solutions and the effect of halide ions and some inorganic inhibitors

The corrosion of tin electrode in sodium borate (Na 2B 4O 7) solutions was investigated using cyclic voltammetry and potentiostatic current transient techniques. In absence of halide ions, the E/ j response exhibits active/passive transition. The active region involves one anodic peak corresponding to the formation of Sn(OH) 2 and/or SnO. Addition of Cl −, Br − or I − (C ⩽ 0.01 M) ions inhibits the active dissolution of tin, but higher concentrations enhance the active dissolution and tend to breakdown the passive film and induce pitting attack. The effect of WO 4 2 - , MoO 4 2 - , NO 2 - and NO 3 - as inorganic inhibitors on the pitting corrosion of tin in (0.1 M Na 2B 4O 7 + 0.1 M NaCl) solution has also been studied. The presence of these anions (except NO 3 - ) inhibits pitting corrosion. Chronoamperometry measurements showed that nucleation of pit takes place after an incubation time ( t i). The rate of pit nucleation ( t i - 1 ) increases with increasing halide ions concentration and applied potentials, but decreases with increasing the concentration of the inorganic inhibitors (except NO 3 - ). The inhibition efficiency of these inhibitors decreases in the order: WO 4 2 − > MoO 4 2 − > NO 2 −

Co-adsorption effect of polyaniline and halide ions on the corrosion of iron in 0.5 M H 2SO 4 solutions

The synergistic effect of halide ions on the inhibition of corrosion of iron in 0.5 M H 2SO 4 solutions by polyaniline has been studied by polarization and impedance methods. Addition of 0.5 × 10 −3 M I − ions enhanced the inhibition efficiency of polyaniline at 10 ppm from 53% to 90%. However in the case of bromide and chloride ions, the inhibition efficiency of polyaniline at 50 ppm has been increased from 71% to 90%. The synergism parameter in all cases is found to be greater than 1. The synergistic effect is attributed to enhanced adsorption of polyaniline by the adsorbed halide ions.

Effect of oxygen substitution by halide ions on structure, thermal stability and upconversion fluorescence in Er 3+/Yb 3+-codoped germanium–bismuth glasses

For the first time, effect of halide ions (F −, Cl −, Br −, and I −) introduction on structure, thermal stability, and upconversion fluorescence in Er 3+/Yb 3+-codoped oxide–halide germanium–bismuth glasses has been systematically investigated. The results show that halide ions modified germanium–bismuth glasses have lower maximum phonon energy and phonon density, worse thermal stability, longer measured lifetimes of 4I 11/2 level, and stronger upconversion emission than germanium–bismuth glass. All these results indicate that halide ions play an important role in the formation of glass network, and have an important influence on the upconversion luminescence. The possible upconversion mechanisms of Er 3+ ion are also evaluated.

Photochemical oxidation of chrysene at the silica gel–water interface

The photolysis of chrysene at the silica–water interface proceeds more efficiently than when dissolved in solution. Loss of chrysene was apparently through self sensitized oxidation by singlet oxygen. The role of singlet oxygen in the system was probed by application of the 1 O 2 scavenger, 1,4-diazabicyclo[2,2,2]-octane (DABCO). The initial rate of chrysene loss exhibited a positive correlation with chrysene loading (μmol g −1) on silica gel supports. The system was subjected to model environmental conditions (simulating seawater) and the effects of halide ions on the photodegradation process were determined. Singlet oxygen steady state concentrations were measured under all experimental conditions by using 2,5-diphenylfuran as a singlet oxygen trapping agent, and varied from (3.73±0.37)×10 −12 to (1.43±0.14)×10 −11 M under our experimental conditions. [ 1 O 2 ] ss was a function of chrysene loading and salinity; high chrysene loading promoted high singlet oxygen concentrations, but high salinity suppressed it.

Electrochemical behavior of Sn–Ni nanostructured compound in alkaline media and the effect of halide ions

Tin–Nickel electrodeposits alloy of the approximate composition 34% Ni–66% Tin (wt.%) can be obtained from the chloride–fluoride bath. The potentiodynamic, cyclic voltammetry, and impedance spectroscopy techniques complemented by XRD and SEM (EDX) were used to study the corrosion behavior of Sn–Ni alloy in sodium carbonate solution (Na2CO3) at pH 11.9. The effect of different factors as concentration of the carbonate ion, the switching potential and the progressive addition of the halide ions on the electrochemical behavior of Sn–Ni alloy is discussed. The observed corrosion resistance of electrodeposited Sn–Ni alloy is due to the formation of a thin passive film, which is examined by X-ray spectroscopy, believed to be mainly nickel and tin oxides. The voltammogram are involving five anodic peaks. The first and second peaks are corresponding to the formation of SnO and SnO2 oxides. The third, fourth, and fifth peaks are related to the formation of nickel oxides. The data is indicating that the corrosion rate and the pitting corrosion of Sn–Ni alloy increases by the addition of the halide ions.

The beneficial influence of halide ions on the inhibition characteristics of nitrogen‐containing organic inhibitors to reduce the corrosion rate of carbon steel in HCl

The beneficial effect of halide ions on the inhibition of corrosion of carbon steel in 20 per cent HCl solution in the presence of some nitrogen‐containing compounds, cetyl pyridinium chloride, cetyl pyridinium bromide, and hexamine was investigated using potentiodynamic polarisation measurements. Potentiodynamic polarisation studies revealed that all the tested compounds were of anodic‐type inhibitors. All of the compounds were able to reduce the corrosion of carbon steel and their performance was enhanced by the addition of iodide ions. The increase in surface coverage in the presence of the iodide ions indicated that iodide ions enhanced the absorption of inhibitor compounds on the metal surface. Auger electron spectroscopic analysis confirmed the joint absorption of the compounds with KI.

Halides as activators of the local corrosion of brass

The resistance of Cu–Zn alloys against pitting in neutral halide-containing media is studied. It is shown that the resistance of brass against local depassivation is determined by the alloy nature, i.e., its chemical and phase composition, on one hand, and by the nature of activating anions, on the other hand. The mechanism of the depassivation effect of halide ions is discussed based on the concept of nucleophilic substitution of passivating species in the adsorption complexes on brass.

Synergistic effect of halide ions on the corrosion inhibition of aluminium in H 2SO 4 using 2-acetylphenothiazine

The corrosion inhibition of aluminium in H 2SO 4 in the presence of 2-acetylphenothiazine (2APTZ) at temperature range of 30–60 °C was studied using the weight loss and thermometric techniques. The effect of addition of halides (KCl, KBr, KI) is also reported. The inhibition efficiency ( I, %) increased with increase in concentration of 2APTZ. The addition of the halides increased the inhibition efficiency to a considerable extent. The temperature increased the corrosion rate and inhibition efficiency in the range 30–60 °C in the absence and presence of the inhibitor and halides. Phenomenon of chemical adsorption is proposed. Flory–Huggins adsorption isotherm equation was obeyed at all the concentrations studied. The decrease in inhibition efficiency (and surface coverage values) was found to be in the order I −>Br −>Cl − which clearly indicates that the radii and the electronegativity of halides play a significant role in the adsorption process. All the data acquired reveal that 2APTZ acts as an inhibitor in the acid environment from the two techniques used. The synergistic effect of 2APTZ and halide ions is discussed.

Regio‐ and Enantiospecific Rhodium‐Catalyzed Allylic Etherification Reactions Using Copper(I) Alkoxides: Influence of the Copper Halide Salt on Selectivity.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Regio- and enantiospecific rhodium-catalyzed allylic etherification reactions using copper(I) alkoxides: influence of the copper halide salt on selectivity.

The transition metal-catalyzed allylic etherification represents a fundamentally important cross-coupling reaction for the construction of allylic ethers. We have developed a new regio- and enantiospecific rhodium-catalyzed allylic etherification of acyclic unsymmetrical allylic alcohol derivatives using copper(I) alkoxides derived from primary, secondary and tertiary alcohols. This study demonstrates that the choice of copper(I) halide salt is crucial for obtaining excellent regio- and enantiospecificity, providing another example of the effect of halide ions in asymmetric transition metal-catalyzed reactions. Finally, the ability to alter the reactivity of the alkali metal alkoxides in this manner may provide a useful method for related metal-catalyzed cross-coupling reactions involving heteroatoms.

Investigation of the effects of halide ions on indirect UV detection in capillary zone electrophoresis

The use of halide salts in combination with sulfonated calixarenes has been recently demonstrated as a novel and effective approach for the indirect detection of a number of significant analytes, including amino acids, biogenic amines, and inorganic cations and anions in capillary zone electrophoresis (CZE). In this method, a sulfonated calixarene, such as p-sulfonic calix[6]arene (SCX6), was employed as the selectivity modifier as well as the UV-absorbing background electrolyte for the indirect detection of the sample ions, while the halide salt was supposed to serve as the ‘ionic strength adjuster’ in the run buffer. However, although halide ions are not commonly employed as UV-active chromophores in CZE for the indirect detection of various analytes, certain halide ions, especially Br– and I–, are capable of absorbing appreciable amounts of UV photons near 200 nm. Therefore, in a run buffer system containing a calixarene compound and a halide salt, the overall background absorbance can arise from both of these background electrolytes. In the present work, new insights into the influence of halide ions on the detector response patterns (both peak intensity and direction) were provided by examining the effects of the presence of SCX6 and/or halide ions in the run buffer on the indirect detection of various model analytes. The results indicated that halide ions played a significant role in governing detection sensitivity, while the cations of the halide salts were also found to influence the peak intensity, as well as the peak direction for the various analytes studied. These response patterns were briefly discussed in terms of mathematical treatments based on the Kohlrausch regulation function.

Photochemical behavior of sitafloxacin, fluoroquinolone antibiotic, in an aqueous solution.

Sitafloxacin (STFX) hydrate, an antimicrobial agent, is photo-labile in aqueous solutions. The photodegradation rates (k) in neutral solutions were higher than those observed in acidic and alkaline solutions and maximum at the maximum absorption wavelength of STFX. The structures of photodegradation products were elucidated as 7-[7-amino-5-azaspiro[2.4]heptan-5-yl]-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid and 1-(1-amino-2-[16-fluoro-1-(2-fluoro-1-cyclopropyl)-1,4-dihydro-4-oxo-3-quinolin-7-yl]-amino]ethyl)cyclopropanecarbaldehyde. This implies that dechlorination is the key step in the photodegradation of STFX. The effect of halide ions on the photodegradation of STFX was estimated by observing the increments in the photostability of STFX with the addition of chloride ions. In contrast, in the presence of bromide ions, instead of increased photostability of the STFX rate, a new photodegradation product in the presence of bromide ion was observed. The structure of this new photodegradation product was an 8-bromo form of STFX, which was substituted for chlorine at the 8-position, so the dissociation of C-Cl bond at the 8-position of STFX was the rate-limiting step in the initial process of the photodegradation. STFX generated .C (carbon centered radical) and .OH (hydroxyl radical) in the process of photodegradation in a pH 4.0 buffer. On the contrary, STFX did not generate C in the presence of chloride ion in a pH 4.0 buffer. The .C was generated and then degraded into the above degradation products by photoirradiation in the absence of chloride ion, but the .C immediately reacted with chloride when it was present. As a result, the C-Cl bond was recovered leading to a possible increase in the apparent photostability.

Electrogenerated Chemiluminescence. 66. The Role of Direct Coreactant Oxidation in the Ruthenium Tris(2,2‘)bipyridyl/Tripropylamine System and the Effect of Halide Ions on the Emission Intensity

We describe the electrogenerated chemiluminescence (ECL) processes of the Ru(bpy)3(2+) (bpy = 2,2'-bipyridyl)/ tripropylamine (TPrA) system at glassy carbon, platinum, and gold electrodes. The electrochemical behavior of TPrA on different electrode materials and its influence on the ECL process are demonstrated. At glassy carbon electrodes, the direct oxidation of TPrA began at approximately 0.6 V vs SCE and exhibited a broad irreversible anodic peak. Two ECL waves were observed, one in the potential region more negative than 1.0 V vs SCE and one at more positive potentials. The first ECL process apparently occurs without the electrogeneration of Ru(bpy)3(3+), in contrast to that of the second ECL wave. At Pt and Au electrodes, however, the formation of surface oxides significantly blocked the direct oxidation of TPrA. An ECL wave below 1.0 V did not appear at Pt and was very weak at gold. The ECL peaks at potentials of 1.1-1.2 V were also much weaker than those observed at the glassy carbon electrode. These results showed that the direct oxidation of TPrA played an important role in the ECL processes. Therefore, the enhancement of the TPrA oxidation current might lead to an increase in the ECL intensity. Small amounts of halide species were found to inhibit the growth of surface oxides on Pt and gold electrodes and led to an obvious increase of TPrA oxidation current. The anodic dissolution of gold in halide-containing solution was also important in activating the gold electrode surface. The electrochemical catalytic effect of bromide further promoted the oxidation of TPrA. A halide effect on ECL at Pt and Au electrodes was also evident. The most effective enhancement of ECL was observed at Au electrode in a bromide-containing solution. This effect was also found in an commercial flow-through instrument (IGEN) and provided a simple way to improve the detection sensitivity at low concentrations of Ru(bpy)3(2+).