Cluster type molecule as novel corrosion inhibitor for steel in HCl solution

The MOF [Ag (qox) (4-hb)] 1, was obtained at room temperature by the reaction of AgNO₃, quinoxaline (qox) and 4-hydroxy benzoate (4-hb). A cluster molecule containing two silver atoms, two qox and two 4-hb ligands is considered the basic building block of the structure of 1. 3D-network structure is created via H-bonds and π-π stacking. The MOF 1 was tested as corrosion inhibitor for carbon steel in 1 M HCl solution using potentiodynamic polarization and electrochemical impedance techniques (EIS). The polarization measurements indicated that the MOF 1 is of mixed type. The adsorption of MOF 1 obeyed Langmuir adsorption isotherm. The inhibition efficiency increased with increase in MOF 1 concentration but decreased with increase in temperature. The activation and thermodynamic parameters were calculated and discussed. Mechanism of inhibition is explained on the basis of molecular structure of the inhibitor.     

New thio-compounds as corrosion inhibitor for steel in 1 M HCl

Some S-containing compounds newly synthesised have been tested as inhibitors for the corrosion of steel in 1 M HCl solution. Weight loss measurements, potentiodynamic polarisation and impedance spectroscopy (EIS) methods are used. The inhibiting action increases with the concentration of the compounds tested. The highest efficiency 95% is obtained at 10⁻⁴ M of [(11-hydroxyundecyl)thio]acetic acid (3 and 4). We note good agreement between gravimetric and electrochemical methods (potentiodynamic polarisation and EIS). Polarisation measurements show also that 3 and 4 act as mixed inhibitors. The cathodic curves indicate that the reduction of proton at the steel surface happens with an activating mechanism. 3 adsorbs on the steel surface according to Langmuir adsorption model. Effect of temperature is also studied between 308 K and 353 K.     

Cobalt(III) complexes of macrocyclic-bidentate type as a new group of corrosion inhibitors for iron in perchloric acid

A new class of corrosion inhibitors for iron demonstrated by group of cobalt complex compounds, of the general formula [Co^III(Rdtc)cyclam](ClO₄)₂ (1)-(4) where cyclam is 1,4,8,11-tetraazacyclotetradecane and Rdtc⁻ refer to piperidine-, 2-, 3- or 4-methylpiperidine-dithiocarbamates, respectively, has been studied. Investigation of inhibiting properties of the ligands themselves as well as their corresponding complexes with Co(III) ion, was performed in 0.1 M HClO₄ by potentiodynamic polarization and EIS measurements. Cobalt complexes inhibit the corrosion of iron better than the uncomplexed ligands. Polarization curves suggest that complexes and amino-ligands are mixed-type and cathodic-type inhibitors, respectively. The impedance of the inhibited substrate increased with increasing concentration of inhibitor. An equivalent circuit is suggested, based on the analysis of EIS spectra. Using molecular modeling calculations, the complex compounds were characterized in terms of their structural properties and inhibition activity.     

Study of inhibition effect of pyridinium salt derivative on corrosion of C1010 carbon steel in saline solution

In this work, pyridinium dibromide (2) was synthesized and its structure was confirmed using spectroscopic techniques. Compound (2) was successfully applied as a corrosion inhibitor for C1010 carbon steel in 3.5% NaCl solution at 25°C. Different electrochemical measurements such as potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) were used to evaluate different concentrations of the suggested inhibitor (2). The results showed that inhibition efficiencies obtained from EIS curves are in consistence with the results of PDP at higher concentration 4.5 × 10^–4 M. Semi-empirical calculations with PM3 method was used to find relationship between molecular structure and inhibiting effect of suggested inhibitor (2).     

N-Aminorhodanine as an effective corrosion inhibitor for mild steel in 0.5 M H2SO4

The corrosion inhibition effect of N-aminorhodanine (N-AR) on mild steel (MS) in 0.5 M H₂SO₄ was studied in both short and long immersion duration using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), chronoamperometry and hydrogen gas evolution. The surface morphology of MS was examined with scanning electron microscopy (SEM) in absence and presence inhibitor. The inhibitor adsorption process on MS surfaces obeys the Langmuir adsorption isotherm. The results show that NAR is a good inhibitor for MS in the acidic medium. The inhibition efficiency obtained from potentiodynamic polarization, EIS and LPR up to 98% is determined.     

Investigation of corrosion inhibition effect of 3-[(2-hydroxy-benzylidene)-amino]-2-thioxo-thiazolidin-4-one on corrosion of mild steel in the acidic medium

The corrosion behavior of mild steel (MS) in 0.5 M H₂SO₄ was studied using 3-[(2-hydroxy-benzylidene)-amino]-2-thioxo-thiazolidin-4-one (HBTT) as inhibitor using the conventional potentiodynamic polarization studies, linear polarization studies (LPR), electrochemical impedance spectroscopy studies (EIS). SEM was utilized for surface characterization. The results showed that HBTT posses excellent inhibition effect towards MS corrosion. The inhibitor molecules were first adsorbed on the MS surface and blocking the reaction sites available for acid attack. Adsorption of inhibitor was found to obey Langmuir isotherm and was more chemical than physical.     

Electrochemical investigation of inhibitory of new synthesized 3-(4-iodophenyl)-2-imino-2,3-dihydrobenzo[<Emphasis Type="Italic">d</Emphasis>]oxazol-5-yl 4-methylbenzenesulfonate on corrosion of al in acidic medium

3-(4-Iodophenyl)-2-imino-2,3-dihydrobenzo[d]oxazol-5-yl 4-methylbenzenesulfonate (4-IPhOXTs) was synthesized and its inhibiting action on the corrosion of Aluminum 1005 in sulfuric acid was investigated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results of the investigation show that this compound has excellent inhibiting properties for Al corrosion in sulfuric acid. Inhibition efficiency increases with increase in the concentration of the inhibitor. The adsorption of 4-IPhOXTs onto the Al surface followed the Langmuir adsorption model with the free energy of adsorption ΔG_ads⁰ of?9.18 kJ mol^–1. Quantum chemical calculations were employed to give further insight into the mechanism of inhibition action of 4-IPhOXTs.     

The corrosion inhibition of copper in hydrochloric acid solutions by a tripeptide compound

The efficiency of glutathione as a non-toxic corrosion inhibitor for copper in 0.5 M HCl has been studied by using the weight-loss technique, cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. Maximum protection efficiency reaches about 92.7% for glutathione at 10 mM concentration level. Results obtained from potentiodynamic polarization and impedance measurements are in good agreement. The adsorption of glutathione on copper surface follows Langmuir isotherm. The adsorption free energy of glutathione on copper (−32 kJ mol⁻¹) reveals a strong physical adsorption of the inhibition on the metal surface.     

<Emphasis Type="Italic">Sinapis alba</Emphasis> as an anti-rusting agent for corrosion of stainless steel in hydrochloric acid medium

Protection against corrosion using Sinapis alba was studied for the corrosion control of stainless steel in 0.5 M HCl. The electrochemical techniques such as potentiodynamic polarization measurements and electrochemical impedance spectroscopy were used for the stainless steel protection studies. Surface morphology studies were done using scanning electron microscopy/energy dispersive X-ray analysis. Kinetic and thermodynamic parameters were evaluated and discussed. The mechanism for the corrosion inhibition was proposed. The obtained results showed that Sinapis alba acted as a mixed-type inhibitor, with the maximum inhibition efficiency of 88% for the concentration of 0.1 g L^–1 at 323K. It was chemically adsorbed on stainless steel and obeyed the Langmuir adsorption isotherm. Sinapis alba emerged as an effective eco-friendly corrosion inhibitor for the corrosion control of stainless steel in the HCl acid medium. Surface morphology studies confirmed the adsorption of this inhibitor onto the surface of the metal. The results obtained via potentiodynamic polarisation and electrochemical impedance spectroscopy was in agreement with each other.     

Polyaspartic acid as a green corrosion inhibitor for carbon steel

The inhibitor effect of the environmentally friendly corrosion inhibitor polyaspartic acid (PASP) on the corrosion of carbon steel in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Polarization curve results clearly reveal the fact that PASP is a good anode‐type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing PASP concentration, and the maximum inhibition efficiency was 80.33% at 10 °C. SEM reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Freundlich adsorption isotherm. A mechanism is proposed to explain the inhibitory action of the corrosion inhibitor.     

Investigation on the inhibition behavior of a pentaerythritol glycoside for carbon steel in 3.5% NaCl saturated Ca(OH)2 solution

A pentaerythritol glycoside (PG) was synthesized and then its corrosion inhibition for carbon steel in 3.5% NaCl saturated Ca(OH)₂ solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), as well as atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Results indicated that the PG compound acted as an anodic inhibitor by strong chemical interaction with the carbon steel surface according to the Langmuir adsorption isotherm. The inhibition efficiency and pitting potential on carbon steel increased with increasing concentrations of the inhibitor. Zero charge potential measurements and quantum chemical calculations provided insight into the inhibition mechanism, which are discussed.     

Mercaptopyrimidines as inhibitors of carbon dioxide corrosion of iron

The inhibition activity of 2-mercaptopyrimidine (I), 2-mercapto-4-methylpyrimidine hydrochloride (II), 2-mercapto-4,6-dimethylpyrimidine (III) and its hydrochloride (IV) upon carbon dioxide corrosion of iron has been studied in a wide range of concentrations at 40-90 °C using electrochemical and mass-spectrometry methods. High activity has been found for all compounds (P = 80-99%) at very low concentrations (0.02-5 mg/l). Adsorption of inhibitor by metal not only blocks its surface but changes the reaction mechanism as well. Charge transfer is the limiting stage of both cathode and anode reactions. The title compounds can be considered as inhibitors of what is a mixed type with prevailing effect on the anode reaction.     

Adsorption and corrosion inhibition of phytic acid calcium on the copper surface in 3 wt% NaCl solution

The adsorption and corrosion protection effect of phytic acid calcium (PAC) film on the copper surface in 3 wt% NaCl solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Raman spectroscopy. Polarization curves indicate that PAC is a mixed inhibitor, affecting both cathodic and anodic corrosion currents. The inhibition efficiency of PAC film reached 92.53% at an optimized condition. Adsorption of PAC molecules on the surface followed Langmuir adsorption isotherm and the standard Gibbs energy of −37.32 kJ mol⁻¹ indicated a chemisorptive way. Raman studies suggested that PAC molecule chemically anchored at the surface via PO groups.     

An electrochemical study of the effect of Li on the corrosion behavior of Ni3Al intermetallic alloy in molten (Li + K) carbonate

A study of the effect of lithium content (1, 3 and 5 wt.%) and heat treatment (400 °C during 144 h) on the corrosion behavior of Ni₃Al alloy has been carried out in a 62 mol.%Li₂CO₃-38 mol.%K₂CO₃ mixture at 650 °C using electrochemical techniques. Employed electrochemical techniques included potentiodynamic polarization curves, linear polarization resistance, LPR, electrochemical impedance spectroscopy, EIS, and electrochemical noise, measurements EN. Results have shown that the alloys exhibited an active-passive behavior regardless of the heat treatment. For alloys without heat treatment, the most corrosion resistant was the Ni₃Al base alloy, but when they were heat treated, the most corrosion resistant was the alloy containing 3%Li. EIS results showed that for short immersion tests, the corrosion process was under diffusion control, but for longer exposure times, the presence of a protective scale was evident. All the alloys were highly susceptible to a localized type of corrosion according to EN measurements and supported by SEM micrographs.     

Inhibition of Mild Steel Corrosion Using l-Histidine and Synergistic Surfactants Additives

The corrosion inhibition behavior of nitrogen-containing amino acid l-Histidine (LHS) on mild steel in 0.1 M H₂SO₄ solution in the temperature range of 30-60 °C was studied by weight loss measurements, and potentiodynamic polarization measurements. The effect of the addition of very small concentration of surfactants, sodium dodecyl sulfate (SDS), and cetyltrimethyl ammonium bromide (CTAB), respectively on the corrosion inhibition behavior of LHS was also studied. The surface morphology of the corroded steel samples was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). LHS significantly reduces the corrosion rates of mild steel, with the maximum inhibition efficiency (IE) being 71.09% at 30 °C in the presence of 500 ppm of LHS. The IE of LHS is synergistically increased in the presence of SDS and CTAB. The SEM and AFM photographs show a clearly different surface morphology in the presence of additives. LHS alone and in combination with surfactants obeys Langmuir adsorption isotherm from the fit of the experimental data of all concentration and temperature studied. The calculated thermodynamic parameters for adsorption reveal strong interaction between the inhibitors and the mild steel surface, and suggest physical adsorption. The results obtained by potentiodynamic polarization measurements are consistent with the results of the weight loss measurement. LHS acts more anodic than cathodic inhibitor.     

三唑化合物在0.5 mol/L硫酸中对Q235钢的缓蚀作用

合成了一种新型三氮唑化合物:1-苯次乙亚氨基-2-巯基-5-[1-(1,3,4-三氮唑)亚甲基]-1,3,4-三氮唑(PMT),并通过失重试验、动电位极化、电化学阻抗谱及扫描电镜方法研究了其在0.5mol/L硫酸溶液中对Q235碳钢的缓蚀作用。结果表明,该三唑化合物在硫酸中对Q235碳钢有较好的缓蚀效果,是混合型缓蚀剂。     

Inhibitive effect of diethylcarbamazine on the corrosion of mild steel in hydrochloric acid

Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss measurements and atomic force microscopy techniques were used to investigate the inhibitory effect of diethylcarbamazine (DECM) on corrosion of mild steel in HCl solution. The inhibitor showed >90% inhibition efficiency at 5.01 × 10⁻⁴ M. Results obtained revealed that inhibition occurs through adsorption of inhibitor molecules on metal surface without modifying the mechanism of corrosion process. Potentiodynamic polarization studies suggested that it is a mixed type inhibitor, predominantly controls cathodic reaction. Activation parameters (E_a, ΔH and ΔS) and thermodynamic parameters (, and ) were calculated to investigate mechanism of inhibition.     

The role of acid anion on the inhibition of the acidic corrosion of steel by lupine extract

The inhibitive effect of lupine (Lupinous albus L.) extract on the corrosion of steel in aqueous solution of 1 M sulphuric and 2 M hydrochloric acids was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization curves indicated that the lupine extract acts as a mixed-type inhibitor. EIS measurements showed that the dissolution process is under activation control. The inhibition efficiency of the extract obtained from impedance and polarization measurements was in a good agreement and was found to increase with increasing concentration of the extract. The obtained results showed that, the lupine extract could serve as an effective inhibitor for the corrosion of steel in acid media and the extract was more effective in case of hydrochloric acid. Theoretical fitting of the corrosion data to the kinetic-thermodynamic model was tested to show the nature of adsorption.     

Corrosion behavior of mild steel in the presence of scale inhibitor in sulfuric acid solution

Surfactants such as non-ionic polyethylene glycol tert-octylphenyl ether (Triton X-114) have been studied as efficient corrosion inhibitors in acid medium. In this study inhibition performance of Triton X-114 has been evaluated as corrosion inhibitor for mild steel in 0.5 mol l⁻¹ H₂SO₄. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and linear polarization (LPR) techniques has been applied to determine the electrochemical behaviour of Triton X-114. The maximum efficiency of Triton X-114 was found as 96% at the concentration 5.0 × 10⁻⁵ mol l⁻¹. The adsorption isotherm of inhibitor on the mild steel surface was found to be in a good agreement with the Langmuir and the standard free energy value (ΔG _ads^°) was calculated as −50.1 kJ mol⁻¹, which shows that adsorption of Triton X-114 on the mild steel surface improves the inhibition characteristics in 0.5 M H₂SO₄.     

Quinolin-5-ylmethylene-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide as an effective inhibitor of mild steel corrosion in HCl solution

Quinolin-5-ylmethylene-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propanohydrazide (QMQTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in 1 M and 2 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Polarization resistances calculated from the EIS measurements were in good agreement with those obtained from direct current (DC) polarization measurements. The mild steel samples were also analyzed by scanning electron microscopy (SEM). The results showed that QMQTPH is an excellent inhibitor for mild steel in acid medium. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. It acts as an anodic inhibitor. In the 30° to 60 °C temperature range, the QMQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration in the range 10⁻⁵ − 10⁻³ M, but slightly decreased with increasing temperature.