Synergistic inhibitive effect of tartarate and tungstate in preventing steel corrosion in aqueous media

The inhibitive effect of tartarate was studied as a coinhibitor with tungstate in preventing carbon steel corrosion in aqueous solutions. Open circuit potential measurements, weight-loss measurements and polarization studies were conducted to understand the domains of corrosion and passivation. Tartarate ions, even at low concentration, showed excellent synergistic corrosion inhibition characteristics. A mixture of 500 ppm each of the inhibitors was found to be optimum inhibitor combination. This inhibitor combination showed inhibition efficiency as high as 98%. Tartarate in the synergistic inhibitor combination did not reveal any dominant role in shifting the surface potential, even though it showed substantial passivation effect. The present study explores and evaluates the synergistic combination as a potential inhibitor system in combating corrosion on carbon steel surface.     

The inhibited effect of some tetrazolic compounds towards the corrosion of brass in nitric acid solution

The effect of the addition of some tetrazolic type organic compounds: 1-phenyl-5-mercapto-1,2,3,4-tetrazole (PMT), 1,2,3,4-tetrazole (TTZ), 5-amino-1,2,3,4-tetrazole (AT) and 1-phenyl-1,2,3,4-tetrazole (PT) on the corrosion of brass in nitric acid is studied by weight loss, polarisation and electrochemical impedance spectroscopy (EIS) measurements. The explored methods gave almost similar results. Results obtained reveal that PMT is the best inhibitor and the inhibition efficiency (E%) follows the sequence: PMT > PT > AT > TTZ. Polarization measurements also indicated that tetrazoles acted as mixed-type inhibitors without changing the mechanism of the hydrogen evolution reaction. Partial π-charge on atoms has been calculated. Correlation between the highest occupied molecular orbital energy E_HOMO and inhibition efficiencies was sought. The adsorption of PMT on the brass surface followed the Langmuir isotherm. Effect of temperature is also studied in the (25-50 °C) range.     

Synergistic effect of iodide ions on the corrosion inhibition of steel in 0.5 M H2SO4 by new chalcone derivatives

The effect of addition of 4′,4-dihydroxychalcone (P₁), 4-aminochalcone (P₂) and 4-bromo, 4′-methoxychalcone (P₃) 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.     

Investigation of the inhibitive effect of triphenyltin 2-thiophene carboxylate on corrosion of steel in 2 M H3PO4 solutions

A new organic compound was synthesised and tested as corrosion inhibitor of steel in phosphoric acid medium using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that the inhibitor studied is a good cathodic inhibitor. EIS results show that the change in the impedance parameters (R_T and C_dl) with concentration of triphenyltin 2-thiophene carboxylate (TTC) is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of steel. The effect of the temperature on the steel corrosion in 2 M H₃PO₄ and with addition of various concentrations of TTC in the range of temperature 298-348 K was studied. The associated apparent activation corrosion energy has been determined.     

Pyridine–pyrazole compound as inhibitor for steel in 1 M HCl

The influence of 3,5-dimethyl-1H-pyrazole (P1), pyridine (P2) and 2-(3-methyl-1H-pyrazol-5-yl) pyridine (P3) on the corrosion inhibition of steel in molar hydrochloric acid solution is studied using weight-loss, potentiodynamic and EIS measurements. Results obtained shows that P3 is the best inhibitor and its inhibition efficiency increases with the increase of concentration to attain 89% since 10⁻³ M. Potentiodynamic polarisation studies clearly reveal that it acts essentially as a cathodic inhibitor. The inhibitor studied reduces the corrosion rates. E (%) values obtained from various methods used are in good agreement. Adsorption of P3 on steel surface has an S-shaped adsorption isotherm.     

The effect of some Schiff bases on the corrosion of aluminum in hydrochloric acid solution

The inhibition effect of Schiff bases benzylidene-(2-methoxy-phenyl)-amine (A), (2-methoxy-phenyl)-(4-methyl-benzylidene)-amine (B), (4-chloro-benzylidene)-(2-methoxy-phenyl)-amine (C) and (4-nitro-bezylidene)-(2-methoxy-phenyl)-amine (D) on the corrosion of aluminum in 1 M HCl has been studied by polarization, electrochemical impedance spectroscopy (EIS) and weight loss measurements. It has been found that all the studied Schiff bases are excellent inhibitors. Maximum inhibition was obtained for 0.01 M Schiff base A. Results show that the inhibition efficiency increases with decreasing in temperature and increasing in concentration of Schiff base. Polarization curves reveal that the used inhibitors are mixed type inhibitors. The surface adsorption of the Schiff bases leads to a decrease of double layer capacitance as well as an increase of polarization resistance. The inhibitor performance depends strongly on the type of function groups substituted on benzene ring. The adsorption of used compounds on the aluminum surface obeys a Langmuir isotherm and has a physical mechanism. Thermodynamic parameters for both dissolution and adsorption processes were determined. The quantum chemical study of the corrosion inhibition efficiency of the Schiff bases on Al in molar HCl was carried out.     

Inhibition of steel pitting corrosion in HCl by some inorganic anions

The effect of Mn and V content on corrosion behavior of mild steel in different concentration of HCl was investigated. The increase of Mn and V content in the steel sample leads to increasing corrosion resistance. The effect of phosphate, molybedate and chromate anions on the corrosion of steel in HCl solution has been studied using weight loss, potentiodynamic and scanning electron microscope (SEM) techniques. The addition of increasing concentrations of phosphate, molybedate and chromate anions causes a shift of the pitting potential (E_pit) in the positive direction, indicating the inhibitive effect of the added anions on the pitting attack. The phosphate anion has a stronger inhibitive effect of the pitting corrosion. The inhibition efficiency (IE) of different inhibitors increases with the increasing of phosphate concentration and decreases with the increasing the concentration of molybedate and chromate anions. The presence of these anions inhibits the pitting corrosion of steel samples in the order phosphate > molybedate > chromate. The effect of different inorganic anions on the corrosion behavior of two different composition steel samples was also studied in HCl solution.     

Inhibiting effects of some oxadiazole derivatives on the corrosion of mild steel in perchloric acid solution

The efficiency of 3,5-bis(n-pyridyl)-1,3,4-oxadiazole (n-POX, n = 1, 2, 3), as corrosion inhibitors for mild steel in 1 M perchloric acid (HClO₄) have been determined by weight loss measurements and electrochemical studies. The results show that these inhibitors revealed a good corrosion inhibition even at very low concentrations. Comparison of results among those obtained by the studied oxadiazoles shows that 3-POX was the best inhibitor. Polarisation curves indicate that n-pyridyl substituted-1,3,4-oxadiazoles are mixed type inhibitors in 1 M HClO₄. The adsorption of these inhibitors follows a Langmuir isotherm model. The electronic properties of n-POX, obtained using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies using the linear resistance model (LR).     

Establishment of equivalent circuits from electrochemical impedance spectroscopy study of corrosion inhibition of steel by pyrazine in sulphuric acidic solution

This paper describes the use of the electrochemical impedance spectroscopy technique (EIS) in order to study the corrosion inhibition process of steel in 0.5 M H₂SO₄ solution at the open circuit potential (OCP). Diethyl pyrazine-2,3-dicarboxylate (Prz) as a non-ionic surfactant (NS) inhibitor has been examined. The Nyquist diagrams consisted of a capacitive semicircle at high frequencies followed by a well-defined inductive loop at low frequency values. The impedance measurements were interpreted according to suitable equivalent circuits. The results obtained showed that the Prz is a good inhibitor. The inhibition efficiency increases with an increase in the surfactant concentration to attain 80% at the 5 × 10⁻³M. Prz is adsorbed on the steel surface according to a Langmuir isotherm adsorption model.     

Corrosion inhibition of steel in sulphuric acid by pyrrolidine derivatives

Novel corrosion inhibitors, namely 1-{2-[(2-hydroxyethyl)thio]ethyl}pyrrolidin-2-one (P5) and {[2-(2-oxopyrrolidin-1-yl)ethyl]thio}acetic acid (P4), were synthesised and tested as corrosion inhibitors for steel in 0.5 M H₂SO₄. The effects of P4 and P5 are also compared to their initial reactants 1-vinylpyrrolidin-2-one (P1), 2-mercaptoethanol (P2) and mercaptoacetic acid (P3). The study was carried out by weight loss measurements, potentiodynamic polarisation, linear polarisation resistance (R_p) and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency increases with the concentration of P5 to attain 89% at 5 × 10⁻³ M. We note good agreement between the various methods explored. Polarisation measurements show also that the pyrrolidones act essentially as cathodic inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface is an activating mechanism. P4 and P5 adsorb on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied in the 298-353 K range. Efficiency is explained by the theoretical studies.     

Electrochemical and theoretical investigation on the corrosion of aluminium in acidic solution containing some Schiff bases

The effect of newly synthesised three Schiff bases—2-[2-aza-2-(5-methyl(2-pyridly))vinyl]phenol, 2-[2-aza-2-(5-methyl(2-pyridly))vinyl]-4-bromophenol, 2-[2-aza-2-(5-methyl(2-pyridly))vinyl]-4-chlorophenol—on the corrosion behaviour of aluminium in 0.1 M HCl were investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy and linear polarisation methods. Polarisation curves indicate that all studied Schiff bases were acting as mixed type inhibitors. All measurements show that inhibition efficiencies increase with increase in inhibitor concentration. This reveals that inhibitive actions of inhibitors were mainly due to adsorption on aluminium surface. Adsorption of these inhibitors follows Langmuir adsorption isotherm. Thermodynamic parameters of adsorption (K_ads, ΔG_ads) of studied Schiff bases were calculated using Langmuir adsorption isotherm. The variation in inhibition efficiency values depends on the type of functional groups substituted on benzene ring. It was found that the presence of bromine and chlorine atoms in the molecular structure of studied Schiff bases facilitate the adsorption of molecule on aluminium surface.The correlation between the inhibition efficiencies of studied Schiff bases and their molecular structure has been investigated using quantum chemical parameters obtained by MNDO semi-empirical SCF-MO methods. These results indicate that adsorption of studied Schiff bases depends on the charge density of adsorption centres and dipole moments.     

Inhibition of steel corrosion in 2 M H3PO4 by artemisia oil

Artemisia oil (Ar) is extracted from artemisia herba alba collected in Ain es-sefra-Algeria, and tested as corrosion inhibitor of steel in 2 M H₃PO₄ using weight loss measurements, electrochemical polarisation and EIS methods. The naturally oil reduces the corrosion rate. The inhibition efficiency was found to increase with oil content to attain 79% at 6 g/l. Ar acts as a cathodic inhibitor. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance decreases with the rise of temperature. The adsorption isotherm of natural product on the steel has been determined.     

The roles of hydrochloric acid and polyethylene glycol in magnetic fluids

Increasing interest has been drawn to the studies of magnetic fluids due to their multiple applications from industry to medicine. However, further exploration is still required for the techniques of preparing satisfying, convenient and stable magnetic fluids. We explored characteristics of magnetic liquids prepared by employing co-precipitation techniques of hydrochloric acid (HCl) and polyethylene glycol (PEG), and the functions of HCl and PEG in the magnetic liquid. According to the improved technique, after preparing Fe₃O₄ by a co-precipitation method, hydrochloric acid and PEG2000 react with magnetic particles at a certain temperature to generate the anticipated magnetic nanoparticles. The process could be under an air atmosphere rather than a N₂ atmosphere. Compared with traditional techniques, the magnetic nanoparticles prepared by this method have smaller size, better dispersion and stability, with the average hydrodynamic diameter adjustable between 8 and 50 nm. This study revealed that reduction of nanoparticles size is not mainly due to a [Cl⁻] coating over the magnetic nanoparticles, but that HCl reacts with Fe₃O₄ particles after being heated. Meanwhile, PEG can stabilize or coat Fe₃O₄ nanoparticles as a dispersing and stabilizing agent.     

Influence of poly(aminoquinone) on corrosion inhibition of iron in acid media

The inhibitor performance of chemically synthesized water soluble poly(aminoquinone) (PAQ) on iron corrosion in 0.5 M sulphuric acid was studied in relation to inhibitor concentration using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. On comparing the inhibition performance of PAQ with that of the monomer o-phenylenediamine (OPD), the OPD gave an efficiency of 80% for 1000 ppm while it was 90% for 100 ppm of PAQ. PAQ was found to be a mixed inhibitor. Besides, PAQ was able to improve the passivation tendency of iron in 0.5 M H₂SO₄ markedly.     

Quinoxaline derivatives as corrosion inhibitors for mild steel in hydrochloric acid medium: Electrochemical and quantum chemical studies

The corrosion inhibition potential of four quinoxaline derivatives namely, 1-[3-(4-methylphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Me-4-PQPB), 1-(3-(4-methoxyphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl)butan-1-one (Mt-4-PQPB), 1-[3-(3-methoxyphenyl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Mt-3-PQPB) and 1-[3-(2H-1,3-benzodioxol-5-yl)-5-(quinoxalin-6-yl)-4,5-dihydropyrazol-1-yl]butan-1-one (Oxo-1,3-PQPB) was studied for mild steel corrosion in 1 M HCl solution using electrochemical, spectroscopic techniques and quantum chemical calculations. The results of both potentiodynamic polarization and electrochemical impedance spectroscopic studies revealed that the compounds are mixed-type inhibitors and the order of corrosion inhibition efficiency at 100 ppm is Me-4-PQPB>Mt-3-PQPB>Oxo-1,3-PQPB>Mt-4-PQPB. Fourier transform infrared (FTIR) and ultraviolet–visible (UV–vis) spectroscopic analyses confirmed the presence of chemical interactions between the inhibitors and mild steel surface. The adsorption of the inhibitor molecules on mild steel surface was found to be both physisorption and chemisorption but predominantly chemisorption. The experimental data obey Langmuir adsorption isotherm. Scanning electron microscopy studies revealed the formation of protective films of the inhibitors on mild steel surface. Quantum chemical parameters obtained from density functional theory (DFT) calculations support experimental results.     

The corrosion behaviour of polypyrrole coating synthesized in phenylphosphonic acid solution

Electrochemical synthesis of polypyrrole (PPy) film was achieved on mild steel (MS), in monomer containing 0.1 M phenylphosphonic acid solution. The synthesis was carried out using cyclic voltammetry technique. It was found that the electrode surface could only become completely passive, after a few successive cycles in solution of 0.1 M pyrrole + 0.1 M phenylphosphonic acid. Then, the thickness of polymer film was increased with help of successive cycles in a relatively narrower potential range. The corrosion performance of polymer coating was investigated in 3.5% NaCl solution, using electrochemical impedance spectroscopy (EIS) and anodic polarization curves. It was shown that the coating had high stability and low permeability, under such aggressive conditions. The EIS results also showed that the coating exhibited important anodic protection behaviour on mild steel. The percent protection efficiency value (E%) was found to be 98.4% and the percent total porosity value (P%) was determined to be 0.752%, after 96 h exposure time to corrosive solution.     

Research of ultrasonic hydrochloric acid concentration meter

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Experimental and theoretical study for corrosion inhibition of mild steel in hydrochloric acid solution by some new hydrazine carbodithioic acid derivatives

The corrosion inhibition of mild steel in 0.5 M hydrochloric acid solutions by some new hydrazine carbodithioic acid derivatives namely N′-furan-2-yl-methylene-hydrazine carbodithioic acid (A), N′-(4-dimethylamino-benzylidene)-hydrazine carbodithioic acid (B) and N′-(3-nitro-benzylidene)-hydrazine carbodithioic (C) was studied using chemical (weight loss) and electrochemical (potentiodynamic and electrochemical impedance spectroscopy, EIS) measurements. These measurements show that the inhibition efficiency obtained by these compounds increased by increasing their concentration. The inhibition efficiency follow the order C > B > A. Polarization studies show that these compounds act as mixed type inhibitors in 0.5 M HCl solutions. These inhibitors function through adsorption following Langmuir isotherm. The electronic properties of these inhibitors, obtained using PM3 semi-empirical self-consistence field method, have been correlated with their experimental efficiencies using non-linear regression method.     

1,3-Bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane as corrosion inhibitor for steel in 0.5 M H2SO4 solution

The effect of addition of 1,3-bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane (M = 264 g). HMPP on steel corrosion in 0.5 M sulphuric acid is studied by weight-loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements at various temperatures. The results obtained showed that HMPP acts as a good corrosion inhibitor. The inhibition efficiency increases with the bipyrazole compound to attain 88%. It acts as a mixed-type inhibitor. Trends in the increase of charge-transfer resistance and decrease of capacitance values also show the adsorption of the molecule on the metal surface. The bipyrazole adsorbs on the steel surface according to the Langmuir isotherm adsorption model. Effect of temperature indicates that inhibition efficiency decreases with temperature between 25 and 85 °C.