Synthesis of poly(p‐phenylene diamine) and its corrosion inhibition effect on iron in 1M HCl

Water‐soluble poly(p‐phenylene diamine) was chemically synthesized. Its corrosion inhibition performance was evaluated for iron corrosion in 1M HCl at various concentrations, and the results were compared with that of the monomer. The corrosion inhibition properties were evaluated by polarization techniques and electrochemical impedance spectroscopy. The results showed that poly(p‐phenylene diamine) was a more efficient corrosion inhibitor than the monomer and gave an 85% inhibition efficiency at a concentration of 50 ppm, whereas the monomer gave an efficiency of 73% at 5000 ppm. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The inhibitive effect of poly(p‐toluidine) on corrosion of iron in 1M HCL solutions

In recent years, polymer amines have been recognized as an excellent corrosion inhibitors for iron in acid solutions. In this work, the inhibitive effect of p‐toluidine and poly(p‐toluidine) on corrosion of iron in 1M HCl has been studied by the electrochemical methods such as impedance, linear polarization, Tafel polarization techniques. The effectiveness of poly(p‐toluidine) was found to be high in comparison with that of monomer. The results showed that p‐toluidine and poly(p‐toluidine) suppressed both cathodic and anodic processes of iron dissolution in 1M HCl. The inhibition efficiency of both p‐toluidine and poly(p‐toluidine) were found to increase with the inhibitor concentrations. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Synthesis and characterization of poly(o-ethoxyaniline): A processable conducting polymer

The synergic effect of the substituentlike ethoxy group on the electronic properties of conducting polyaniline was investigated. The presence of substituents affects not only the electrochemical polymerization window but also brings about changes in optical and electronic properties of the parent polymer polyaniline. The study indicates that electrochemical polymerization of (o-ethoxyaniline) yields a conducting polymer that shows a multiple color transition (yellow → green) on switching the potential between the reduced and oxidized states with an electrochromic response time of 40 ms in addition to its solubility in dimethyl sulfoxide, N-methyl pyrrolidinone, etc. However, the chemical polymerization of the monomer yields a crimson red polymer that is less conducting but has solubility in ethanol/methanol. Evaluation of this alcohol soluble polymer as a corrosion inhibitor for iron in acidic medium shows that it offers corrosion inhibition efficiency of 90%. © 1995 John Wiley & Sons, Inc.     

Influence of H+ and Cl− ions on inhibitive performance of poly(aniline) for iron corrosion in acid

The inhibition effect of poly(aniline) on pure iron corrosion in 1M HCl and with various H⁺ ions and Cl^? ions concentrations was investigated by the polarization and electrochemical impedance spectroscopy methods. The results showed that poly(aniline) suppressed both cathodic and anodic processes of iron dissolution in 1M HCl by its adsorption on the iron surface according to Langmuir's adsorption isotherm. The inhibition efficiency of poly(aniline) was found to increase with the inhibitor concentrations. Further, it was observed that, there was no significant variation in corrosion potential (E_corr) values in the presence of inhibitors suggesting that, this polymer behaved as mixed type inhibitor. Similar studies for the inhibitor at 500 ppm in various concentrations of H⁺ and Cl^? ions, have shown that the inhibition efficiency decreases with decrease in concentrations of H⁺ ions and Cl^? ions in aqueous solution. It reveals that, the adsorption of inhibitor on iron surface is by more cationic form of inhibitor and higher efficiency at higher H⁺ and Cl^? ions is due to enhanced adsorption of cat ionic form of inhibitor molecules. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Corrosion protection of iron by benzoate doped polyaniline containing coatings

Polyaniline containing organic coatings based on vinyl and acrylic resins are found to protect iron in acid and neutral media. Since dopants play an important role in forming salts with iron, a study has been made on the effect of benzoate doped polyaniline on the corrosion protection of iron by polyaniline–vinyl coatings in acid and neutral media. EIS studies have been made on the corrosion protection performance of vinyl coating on steel with 1% polyaniline in 0.1N HCl and 3% NaCl up to 100 days of exposure. It has been found that benzoate doped polyaniline containing coating has found to offer more protection in neutral media than that in acidic media due to passivating ability of benzoate ions in neutral solution, along with iron–polyaniline complex.     

Preparation and properties of polyimide–clay nanocomposite materials for anticorrosion application

A series of polymer–clay nanocomposite (PCN) materials that consist of organosoluble polyimide and layered montmorillonite clay were prepared by the solution dispersion technique. The organosoluble polyimide containing non‐coplanar moiety in diamine monomer and flexible bridging linkages in dianhydride monomer was synthesized by chemical imidization. The as‐synthesized PCN materials were characterized by infrared spectroscopy, wide‐angle powder X‐ray diffraction, and transmission electron microscopy. The organosoluble polyimide showed better corrosion resistance compared to polyaniline, poly(o‐ethoxyaniline) and poly(methyl methacrylate) by using a series of standard electrochemical corrosion measurements of corrosion potential, polarization resistance, and corrosion current in 5 wt % aqueous NaCl electrolyte. Polyimide–clay nanocomposite materials incorporated with low loading of clay were found to further improve corrosion inhibition over pure polyimide. Effects of the material composition on the O₂/H₂O molecular permeability, optical clarity, and thermal properties of polyimide–clay nanocomposite materials were studied by molecular permeability analysis, UV–visible transmission spectra, thermogravimetric analysis, and differential scanning calorimetry, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3573–3582, 2004     

Mechanistic study of adsorption of cetyltrimethyl ammonium bromide on high purity iron using contact angle, polarization resistance and XPS

The mechanism of inhibition of carbon dioxide (CO₂) corrosion of high purity iron by cetyl trimethyl ammonium bromide (CTAB) was investigated by contact angle, polarization resistance and X-ray photoelectron spectroscopy (XPS). The wetting properties, corrosion inhibitor performance and the adsorption of the inhibitor on a high purity iron surface were investigated. Test conditions during corrosion testing were 25 °C, 3 wt% NaCl brine, initial pH 3.9 and 1 bar CO₂ partial pressure. The samples were precorroded for 5 h before inhibitor was added.The inhibitor performance data showed that addition of CTAB significantly reduced the corrosion rate of high purity iron. The decreased corrosion rate seems to be caused by a blocking effect, where the CTAB forms a surface structure on the iron surface. Chemisorption of the CTAB molecules, which could lead to gradually increasing inhibitor efficiency, might be the reason for the slowly decreasing corrosion rate. The XPS data confirmed a gradual accumulation of inhibitor on the surface but did not show any distinct change between different mechanisms at different exposure times. The contact angle measurements showed that the iron was water wet, with a contact angle higher than 160°, at all CTAB concentrations.     

Corrosion inhibition of mild steel in acidic medium by poly (aniline-co-<Emphasis Type="Italic">o</Emphasis>-toluidine) doped with <Emphasis Type="Italic">p</Emphasis>-toluene sulphonic acid

The corrosion behaviour of mild steel in 0.5 M H₂SO₄ solution containing various concentrations of a p-toluene sulphonic acid doped copolymer formed between aniline and o-toluidine was investigated using weight loss, polarization and electrochemical impedance techniques. The copolymer acted as an effective corrosion inhibitor for mild steel in sulphuric acid medium. The inhibition efficiency has been found to increase with increase in inhibitor concentration, solution temperature and immersion time. Various parameters like E _a for corrosion of mild steel in presence of different concentrations of inhibitor and ΔG _ads, ΔH ⁰, ΔS ⁰ for adsorption of the inhibitor, revealed a strong interaction between inhibitor and mild steel surface. The adsorption of this inhibitor on the mild steel surface obeyed the Langmuir adsorption equation.     

Inhibitive effect of polyacrylamide grafted with fenugreek mucilage on corrosion of mild steel in 0.5 M H2SO4 at 35°C

The inhibitive effect of polyacrylamide grafted with fenugreek mucilage, a natural grade polysaccharide, on the corrosion of mild steel in 0.5M H₂SO₄ has been investigated by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy. An inhibition efficiency of 78% has been obtained at a concentration as low as 1 ppm and efficiency as high as 96% at 100 ppm. The polarization studies reveal that it acts as a predominantly cathodic inhibitor. The adsorption of this inhibitor on the mild steel surface obeys a Langmuir adsorption isotherm. The deposited films on the electrode surface have been analyzed by using microscopic techniques. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Benzoic acid and substituted benzoic acids as interfacial corrosion inhibitors for copper in HClO4

Corrosion of copper in HClO₄ solution containing various concentrations (10^–7–10^–4 M) of benzoic acid,p-toluic acid,p-nitrobenzoic acid, phthalic acid and terephthalic acid has been studied at 30° C. These compounds inhibit corrosion effectively even in trace concentration. The corrosion rate is a function of temperature, concentration and nature of the inhibitor. The inhibitor efficiency calculated from weight loss and polarization methods are in good agreement. Thermodynamic parameters for adsorption of inhibitors have been evaluated by using the Bockris-Swinkels adsorption isotherm withn=5 as the configurational function. The corrosion inhibition is discussed from a view point of adsorption of inhibitor molecules at the metal-solution interface.     

High Performance Organic Coatings of Polypyrrole Embedded with Manganese Iron Oxide Nanoparticles for Corrosion Protection of Conductive Copper Surface

Herein, we report the formation of organic composite coating consists of epoxy (EP) reinforced para toluene sulphonic acid (PTSA) doped polypyrrole (PPy)–manganese iron oxide (MnFe₂O₂) as an efficient corrosion inhibitor for copper substrates. The PTSA doped PPy:MnFe₂O₂ nanocomposite was synthesized via in situ polymerization of PPy in the presence of MnFe₂O₂ nanoparticles. Structural features of the prepared samples were characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy and thermogravimetric analysis (TGA). The PTSA doped PPy:MnFe₂O₂ nanocomposite shows excellent conductivity and improved dielectric performance in comparison to pure PPy. The anti-corrosion performance of this organic composite coating was analyzed through Tafel polarization curves, open circuit potential (OCP), corrosion resistance, impedance spectroscopy and oxygen permeability barrier tests. The nanocomposite coating on copper substrate shows superior corrosion protection efficiency (99%) in comparison to pure epoxy (22%). Adhesion strength of the nanocomposite coating shows significant enhancement due to strong dispersions of MnFe₂O₂ nanoparticles in the host matrix. Owing to its improved conductivity, excellent anti-corrosion performance along with superior mechanical properties, the organic nanocomposite coating reported in this work can potentially be used to protect the conductive copper surfaces from harsh corrosive environments.

     

Corrosion protection of galvanized iron by polyaniline containing wash primer coating

Wash primer treatment of galvanized iron (GI) structure is widely used before painting in order to improve adhesion. Traditional wash primer contains zinc tetroxy chromate. Due to hazardous nature of chromate, alternate compounds for chromate replacements have been identified. In recent years polyaniline containing coating has been found to protect GI. In this study, a wash primer based on polyaniline has been formulated and its corrosion protection ability of GI has been compared with that of traditional chromate based wash primer by salt spray and EIS test. It has been found that the polyaniline based wash primer is able to protect GI and its corrosion protection performance is similar to chromate based wash primer coating.     

Influence of electrochemically prepared poly(pyrrole-co-N-methyl pyrrole) and poly(pyrrole)/poly(N-methyl pyrrole) composites on corrosion behavior of copper in acidic medium

Poly(pyrrole-co-N-methyl pyrrole) copolymer and poly(pyrrole)/poly(N-methyl pyrrole) bilayer composites were electrochemically synthesized on copper by cyclic voltammetry from aqueous solution of 0.3 M oxalic acid and 0.1 M monomer. Synthesis of copolymers were performed with different monomer feed ratios (pyrrole:N-methyl pyrrole, 8:2, 6:4, 5:5, 4:6 and 2:8) and in order to determine the copolymer, which has the best corrosion performance, anodic polarization was applied to copolymer coated samples. It was found that the performance of coatings was strongly dependent to the monomer feed ratio and the copolymer synthesized with 8:2 concentration ratio showed the most protective property compared to others. Bilayer of poly(pyrrole)/poly(N-methyl pyrrole) was also synthesized to compare the anticorrosive properties. Polymer films were characterized by ATR-FTIR spectroscopy and SEM techniques. Corrosion behavior of polymer composites was investigated in 0.1 M H₂SO₄ solution by anodic polarization and electrochemical impedance spectroscopy. Different approaches such as phase angle at high frequency and areas under Bode plots were used to evaluate corrosion performances of the coatings. Copolymer and bilayer coatings were found to have higher protection effect than single polypyrrole coatings. Moreover, bilayer coating exhibited better protection efficiency than copolymer coating against corrosion of copper when the obtained results were compared.     

On the corrosion inhibition and adsorption behaviour of some benzotriazole derivatives during copper corrosion in nitric acid solutions: a combined experimental and theoretical study

Copper corrosion inhibition in 1 M HNO₃ solution by some benzotriazole derivatives, namely N-(2-thiazolyl)-1H-benzotriazole-1-carbothioamide (TBC), N-(furan-2-ylmethyl)-1H-benzotriazole-1-carbothioamide (FBC) and N-benzyl-1H-benzotriazole-1-carbothioamide (BBC), was investigated by ac impedance, dc polarization and weight loss techniques. A significant decrease in the corrosion rate of copper was observed in presence of the investigated compounds. The corrosion rate was found to depend on the concentration and type of the inhibitor. The degree of surface coverage of the adsorbed inhibitor was determined by weight loss technique, and it was found that the results obeyed Langmuir adsorption isotherm. Tafel polarization data indicated that the three selected inhibitors were of mixed type. The reactivities of the compounds under investigation were analyzed through Fukui indices, derived from density functional theory (DFT), to explain their inhibition performance.     

The Oil from Mentha rotundifolia as Green Inhibitor of Carbon Steel Corrosion in Hydrochloric Acid

The corrosion inhibition potentials of Mentha rotundifolia oil on carbon steel in 1 M HCl was studied at different concentrations via gravimetric, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Polarization curves reveal that Mentha rotundifolia oil is a mixed-type inhibitor. Changes in impedance parameters (charge transfer resistance R_t, and double-layer capacitance C_dl) were indicative of adsorption of Mentha rotundifolia on the metal surface, leading to the formation of a protective film. The effect of the temperature on the corrosion behavior with addition of the optimal concentration of Mentha rotundifolia oil was studied in the temperature range 308 and 338 K. Adsorption of oil on the carbon steel surface is found to obey the Langmuir adsorption isotherm. Attempts to explain the inhibitory action were carried out using density functional theory (DFT) at B3LYP/6-31G(d,p) level. Quantum chemical parameters most relevant to its potential action as corrosion inhibitor such as E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy), energy gap (ΔE), and Mulliken charges have been calculated and discussed. The theoretical results were found to be consistent with the experimental data.     

Conducting polyaniline-nano-TiO2 composites for smart corrosion resistant coatings

Coatings prepared from polyaniline-nano-TiO₂ particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polyaniline (PANI) in aggressive environments. The corrosion studies were carried out on steel plates coated with these formulations containing 10 wt% polyaniline prepared with different concentrations of nano-TiO₂. The electrochemical impedance spectroscopy was studied at periodic intervals during exposure to hot saline (65 °C) conditions for prolonged durations over a period of 90 h. The open circuit potential (OCP) was found to shift with time from −0.38 V SCE to more anodic side (−0.2 V SCE) much above that of bare steel (−0.5 V SCE). The presence of nano-TiO₂ was found to be vital in the prevention of corrosion and the shift of OCP to anodic side. From these data, one could envisage more than 100 times improvement in the corrosion resistance especially for polyaniline prepared with 4.18 wt% nano-TiO₂. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nano-size TiO₂, redox properties of polyaniline as well as very large surface area available for the liberation of dopant due to nano-size additive.     

Enhancement of Corrosion Performance of Epoxy Coatings by Chemical Modification With GPTMS Silane Monomer

In this paper, commercial epoxy resin was chemically modified by different amounts of 3-glycidoxypropyltrimethoxysilane (GPTMS) monomer using an organotin compound as catalyst, aiming to improve the anti-corrosion performance of epoxy coatings on 2024-T3 aluminum alloy substrate. Electrochemical impedance spectroscopy (EIS) was used to evaluate the barrier properties against water permeation and protectiveness of silane-modified epoxy coatings. The results showed that all the modified coatings presented higher barrier performance and better corrosion performance than pure epoxy coating, which were characterized by higher charge transfer resistance (R _ct) and lower double-layer capacitance (C _dl) at the electrolyte/metal interface. The improvements in corrosion performance and wet adhesion of modified epoxy coatings were also observed by the Machu test and boiling water test, respectively. Interestingly, it was found that the glass-transition temperature (T _g) of silane-modified epoxy coatings decreased only slightly during immersion in 3.5 wt% NaCl solution, in contrast with pure epoxy coating, which was observed to decrease significantly after water permeation. The corrosion performance of epoxy coatings was, thus, improved when the amount of chemically grafted silane monomer increased in the content range investigated in the present work.     

Inhibition Performance of Novel Dissymmetric Bisquaternary Ammonium Salt with an Imidazoline Ring and an Ester Group

In this paper, the inhibition performance of a novel dissymmetric bis-quaternary ammonium salt with an imidazoline ring and an ester group (DBAS) for Q235 steel in 2 % NaCl solution saturated with CO₂ was investigated using weight loss, the polarization curve, electrochemical impedance spectroscopy methods and the quantum chemistry calculation. The results show that DBAS, which is good for the environment and have many activated centers and low E _LUMO, has a high inhibition performance for Q235 steel in 2 % NaCl solution saturated with CO₂. The inhibition efficiency of the studied corrosion inhibitor increased with increasing inhibitor concentrations. The inhibitor is a mixed-type inhibitor which inhibits both anodic and cathodic reactions.     

Adsorption and inhibitive properties of Apigenin derivatives as eco-friendly corrosion inhibitors for brass in nitric acid solution

Six apigenin derivatives were synthesized through Mannich reaction by using apigenin isolated from Hypericum perforatum as raw material. The inhibition performance of these apigenin derivatives were investigated as eco-friendly corrosion inhibitors for brass in 1.0 M HNO₃ solution by means of weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements. The obtained results show that the as-synthesized apigenin derivatives act as efficient inhibitors for brass in 1.0 M HNO₃. The inhibition efficiency increased with the increase in inhibitor concentration but decreased with a rise in temperature. The inhibition efficiency higher than 90% for these compounds was found even at a low concentration of 30?mg L^?1, which is superior to the commonly used synthetic organic corrosion inhibitors for brass in acidic media. Electrochemical studies indicate that the inhibitors are of mixed type but predominantly cathodic in HNO₃ solution. The inhibitor performance depends on the adsorption of the molecules on the metal surface. The thermodynamic parameters for inhibiting process were calculated according to the statistical model. The calculated thermodynamic parameters revealed that the adsorption of these inhibitors on brass surface was spontaneous, controlled by physiochemical processes. The adsorption behaviour of these apigenin derivatives on the surface of brass was analyzed utilizing SEM, AFM, XPS, and Raman spectroscopy measurements. The results confirmed that the apigenin derivatives prevented corrosion of brass by forming protective layer on its surface.     

Corrosion inhibitory action of Commiphora caudata extract on the mild steel corrosion in 1 M H2SO4 acid medium

Corrosion inhibitory action of Commiphora caudata extract on the mild steel corrosion in 1 M H₂SO₄ acid medium is investigated by weight loss and electrochemical studies. The weight loss method shows that the inhibition efficiency increases with the increase of inhibitor concentration, time, and temperature. The polarization studies reveal that the extract acts as a mixed type inhibitor. In electrochemical impedance measurement, the semicircle curves indicated that the charge transfer process controlled the corrosion of mild steel. Thermodynamic parameter such as free energy value was negative, that indicates spontaneous adsorption of inhibitor on mild steel surface. In the presence of inhibitor decreases the activation energy value which shows the chemical adsorption. The Commiphora caudata extract is found to obey Langmuir adsorption isotherm. Scanning electron microscopy, FTIR, and Quantum chemical studies confirmed that the mild steel protect from the corrosion by adsorption of the inhibitor molecules on surface of metal.