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Due to strict environmental regulations, the use of toxic chemicals as corrosion inhibitors for the oil-well acidizing is restricted. Environmentally benign Vanillin-modified chitosan (Van-Cht) is synthesized using a microwave-induced green synthetic protocol and thoroughly characterized by FTIR and NMR spectroscopy. The inhibitor has been evaluated for the first time for carbon steel in 15% HCl. The corrosion inhibition performance was assayed using weight loss and electrochemical methods complemented with the surface analysis of the corroded carbon steel samples without and with the inhibitor immersed in the corrosive medium. Results obtained showed that the Van-Cht acted by adsorption on the surface of carbon steel to inhibit corrosion and exhibited a mixed-type behavior with cathodic predominance. The adsorption of Van-Cht on the carbon steel surface obeyed the Langmuir isotherm. The excellent corrosion inhibition efficiency of > 98% observed at a concentration of 500 mg L−1. Surface analysis using SEM and FTIR-ATR measurements supported the adsorption of Van-Cht inhibitor on the carbon steel surface. The pKa analysis proved that the inhibitor Van-Cht exists mainly in the protonated form at the experimental pH. The density functional theory (DFT) analysis proved that the protonated form of the Van-Cht inhibitor behaves better compared to that of the Van and neutral Van-Cht.

The potential of an environmentally friendly novel synthesized and characterized isoxazolidine derivative namely 5-(4-dodecyloxy-3-methoxybenzyl)-2-methylisoxazolidine (DMBMI) as anticorrosion agent for carbon steel in 1 mol/L HCl solution was investigated using gravimetric and electrochemical techniques. Kinetics parameters of the corrosion process and the thermodynamic data of adsorption of the organic molecule on the carbon steel surface was also assessed in order to characterize the performance of the studied compound as a corrosion inhibitor. The solubility, toxicity and the state of the molecule at the acidic pH (1 mol/L HCl) was predicted. It was found that the synthesized compound is green (environmentally friendly) with an optimum solubility of 23.8 mg/L. Also the molecule exists 100 percent in protonated form in 1 mol/L HCl (pH = 0). The molecule possesses anticorrosion property against steel corrosion in acid environment. Corrosion retardation efficacy is dependent on concentration and temperature. DMBMI exhibited concentration dependent corrosion inhibition ability influencing mainly anodic metal dissolution based on potentiodynamic polarization data. Addition of KI through the mechanism of competitive adsorption enhanced the inhibition efficiency considerably. The active sites for the interaction of DMBMI with steel surface was calculated using quantum chemical method while the adsorption energy between the inhibitor and steel surface was derived via Monte Carlo simulations. Results from theoretical studies and surface analysis are in conformity and reveal that the O and N heteroatoms in the synthesized molecule are the interaction centers. Keywords: Isoxazolidine compounds, Theoretical studies, Corrosion inhibitor, Acid corrosion, Steel

A novel random copolymer 4, containing diallylmethylamine and N1,N1-diallyl-N1-methyl-N6,N6,N6-tripropylhexane-1,6-diammonium dibromide units in a 1:1 ratio (polymer 4) was synthesized via Butler's cyclopolymerization technique. Characterization was accomplished by 1H NMR, elemental analysis, and Fourier-transform infrared spectroscopy (FTIR). Polymer 4 was tested as corrosion inhibitor for low carbon steel in 15% HCl solution via gravimetric and electrochemical approaches. The analysis of the metal specimen surfaces was done using scanning electron microscope (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDAX), and X-ray photoelectron spectroscopy (XPS) methods. Polymer 4 is inhibitor for the substrate particularly at elevated temperatures. Corrosion mitigation is by chemisorption mechanism and can be best described with the Langmuir and El-Awady et al. kinetic-thermodynamic adsorption isotherms. Polymer 4 corrosion mitigation capacity can be improved by the addition of a minute amount of I− ions. Inhibition efficiency of 92.99% has been achieved with 500 ppm polymer 4 + 1 mM KI mixture at 25 °C. Surface analysis results support the claim of adsorption of additive molecules on steel surface. From XPS results, corrosion products on steel surface exposed to the free acid solution are mixtures of chlorides, carbonates, oxides, and hydroxides. In polymer 4 + KI system, polymer 4 molecules are adsorbed on triiodide and pentaiodide ions layer. The improved corrosion inhibition of polymer 4 by I− ions is synergistic in nature according to calculated synergism parameter. Polymer 4 is a promising corrosion inhibitor for oil well acidizing purpose.

Corrosion defined as the deterioration of a material when it interacts with its environment is a global problem. Among the different strategies employed to combat corrosion, the use of coatings and corrosion inhibitors are the most popular. Coatings or corrosion inhibitors form a layer over the metallic substrate and protect it against corrosion. Polymers, both naturally occurring and synthetic have been tested for metal corrosion protection as replacement for the toxic inorganic and organic corrosion inhibitors. Interest in them stems from their availability, cost effectiveness, and eco-friendliness (especially for natural polymers) in addition to the inherent stability and multiple adsorption centers. However, it is found that most polymeric materials studied are moderate corrosion inhibitors. Several attempts such as copolymerization, addition of substances that exert synergistic effect, cross linking, blending, and most recently incorporation of inorganic substances in nano size into the polymer matrix have been made to improve the inhibition ability of polymers. In this review, the application of conducting polymers, polymer composites and nanocomposites for corrosion protection of different industrial metal substrates are explored based on reported experimental data and their mechanism of inhibition explained. Some identified drawbacks and future direction in this area have also been highlighted.

A novel tetrapolymer (TP) consisting of carboxylate, sulphonate, phosphonate and sulfur dioxide based co-monomers was synthesized using Butler cyclopoymerization technique. The synthesized tetrapolymer was characterized using FTIR, 1H-NMR, 13C NMR and elemental analysis. The performance of the tetrapolymer as a corrosion inhibitor for St37 carbon steel in 15% HCl and 15% H2SO4 acid media was assessed using electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), potentiodynamic polarization (PDP) and electrochemical frequency modulation (EFM) techniques. The influence of addition of a small amount of KI on the corrosion inhibition efficiency of TP was also assessed. Results obtained showed that the tetrapolymer moderately inhibited the corrosion of St37 steel in the acid media with protection efficiency of 79.5% and 61.1% at the optimum concentration of 1000 mg·L− 1 studied in HCl and H2SO4 media respectively. On addition of 5 mmol·L−1 KI to the optimum tetrapolymer concentration, the protection efficiency was upgraded to 90.6% and 93.5% in HCl and H2SO4 environment, respectively. The enhanced performance of the polymer in the presence of KI is due to synergistic action deduced from synergism parameter (S1) which was found to be greater than unity. The tetrapolymer afforded the corrosion inhibition of St37 steel in the acid media by virtue of adsorption of the polymer molecules on the steel surface which was confirmed by ATR-FTIR analysis of the adsorbed film extracted from the steel surface. TP + KI formed complex with St37 steel surface in H2SO4 solution but not in HCl solution.

s Investigation into amitriptyline (AMI) as a corrosion inhibitor for different grades of pipeline steels (X80, J55 and mild steel) was undertaken under static conditions in 3.7% and 15% HCl solution and temperature ranging from 30 to 90 °C using electrochemical, gravimetric, and surface screening approaches. AMI is adjudged an effective steel corrosion inhibitor in 3.7% HCl at 30 °C but poor inhibitor at high temperatures and in 15% HCl. The values of enthalpy of adsorption and variation of protection efficacy with temperature point to physical interaction between AMI molecules and the steel surface. Evidence of formation of adsorbed film on the specimen surface has been found via Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDAX) screening. Various formulations consisting of AMI as the base component and other additives (potassium iodide, glutathione and N-acetyl cysteine) have been developed. The formulations were tested at different experimental conditions and inhibition performance compared with that of a commercial corrosion inhibitor. Results obtained show that AMI based formulations can compete favorably with commercial inhibitor even at severe conditions. In 15% HCl solution and temperature of 90 °C, inhibition efficiency of 94% is recorded for commercial inhibitor and 92% for AMI based formulation. AMI based formulation can be utilized as effective corrosion inhibitor in oil and gas production.

The quest to replace toxic chemicals in the nearest future is revolutionizing the corrosion inhibitor research world by turning its attention to plant biomaterials. Herein, we report the corrosion inhibiting potential of butanolic extract of date palm leaves (BUT) on the corrosion of API 5L X60 carbon steel in 15 wt.% HCl solution. The mass loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization (LPR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), and atomic force microscopy (AFM) techniques were employed in the investigation. We also report the effect of intensifier additives, namely formic acid (FA), potassium iodide (KI), and zinc nitrate (Zn(NO3)2) as well as temperature on the corrosion inhibiting performance of BUT. BUT exhibits inhibiting ability but the extent of inhibition is dependent on concentration, temperature, and intensifiers’ concentration. At 25 °C, 200 mg/L BUT and 700 mg/L BUT protected the carbon steel surface by 50% and 88%, respectively. The addition of 3 mM FA and 5 mM KI to 200 mg/L upgraded the extract performance to 97% and 95%, respectively. Zn(NO3)2 performs poorly as an intensifier for BUT under acidizing conditions. The adsorption of BUT + FA and BUT + KI is synergistic in nature whereas that of BUT + Zn(NO3)2 drifts towards antagonistic behavior according to the calculated synergism parameter. Increase in the system temperature resulted in a slight decline in the inhibition efficiency of BUT + FA and BUT + KI but with efficiency of above 85% achieved at 60 °C. The SEM and AFM results corroborate results from the electrochemical techniques.

Corrosion is a critical problem that can be found in all industries worldwide. Corrosion is particularly serious in the petroleum industry, due to the large amounts of metallic based assets located throughout the entire supply chain. Annual costs of corrosion and its consequences are estimated to be 3 – 5 % of GDP for developed countries of the world. Corrosion mitigation strategies adopted by some industries include materials selection, coatings and linings, cathodic protection and the use of corrosion inhibitors amongst others. The use of biopolymers for corrosion protection of industrial metal substrates particularly as corrosion inhibitors has generated interest globally because they are considered as environmentally friendly in addition to the possession of multiple adsorption centres. However, it is found that most biopolymers studied function as moderate corrosion inhibitors. Some of the steps taken to offset this drawback include copolymerization, addition of substances to exert synergistic action as well as the incorporation of inorganic substances in nano-size into the biopolymer matrix in order to improve the corrosion inhibition performances of the biopolymers. The application of biopolymer composites and nanocomposites as anticorrosion materials has shown promising results and is believed to form metal chelate which could block metal surfaces from aggressive ions present in corrosive media. In this chapter, the application of composites and nanocomposites of biopolymers such as chitosan, carboxyl methylcellulose, gum Arabic, Xanthan gum for corrosion protection of industrial metal substrates in different corrosive media is discussed.

A novel palmitic imidazoline compound, N-(2-(2-pentadecyl-4,5-dihydro-1H-imidazol-1-yl)ethyl)palmitamide (NIMP) has been successfully synthesized and characterized with Fourier transform spectroscopy (FTIR), Proton nuclear magnetic resonance (1H NMR), and Carbon-13 nuclear magnetic resonance (13C NMR). NIMP has been tested as corrosion inhibitor for N80 steel in 15% HCl solution at low and elevated temperatures using weight loss measurements, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), linear polarization (LPR), and electrochemical frequency modulation (EFM) techniques. The experimental investigation was supported with surface examination using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDAX), and Fourier transform spectroscopy (FTIR). NIMP is found to be effective in retarding N80 steel dissolution in 15% HCl solution at studied temperatures. The optimum concentration of NIMP is 300 ppm and this concentration afforded corrosion protection efficiency of 97.92% and 95.59% at 25 °C and 60 °C respectively from weight loss measurements. Chemisorption is proposed as the mechanism of adsorption of NIMP molecules onto N80 steel surface based on the value of standard enthalpy of adsorption (100.34 kJ/mol). PDP results disclosed that NIMP acted like a mixed type corrosion inhibitor but with principal effect on cathodic corrosion reactions. Surface screening results are in agreement with experimental results that NIMP molecules adsorbed on N80 steel surface. NIMP can be utilized as an acidizing corrosion inhibitor.

In this study, Kola nut extract (KE) was evaluated for inhibiting ability towards low carbon steel corrosion in 1 M HCl solution using weight loss and electrochemical techniques. The surface of the corroded carbon steel was examined by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM). Elemental composition of the corrosion products and/or adsorbed inhibitor film on the carbon steel surface was determined with the aid of an energy-dispersive X-ray spectroscopy (EDX). The ultraviolet-visible (UV-vis) experiments were also performed to get information about the interaction of KE with the carbon steel surface. It was found that KE exhibited good corrosion protection property. From weight loss technique, corrosion rate was reduced from 0.387 to 0.054 mm/year by 700 ppm of KE at room temperature after 24 h immersion and this corresponded to inhibition efficiency (IE) of 86%. The IE however depreciated with rise in temperature. FTIR results reveal that KE interacted with the carbon steel surface through the O and N heteroatoms of its phytoconstituents. FTIR spectroscopy, UV-vis, SEM, AFM, and EDX data provided proof of KE adsorption on the steel surface as reason for the corrosion inhibition.

Oil well acidizing, although a stimulation process, induces the corrosion of metallic equipment and well tubing. There is, at present, a high demand for effective and less toxic high-temperature corrosion inhibitors for the acidizing process due to the failing of the existing inhibitors at high temperatures occasioned by increases in the well depths. In this study, aspartame (ASP), a commercially available natural compound, is examined as a corrosion inhibitor for T95 carbon steel in 15 wt.% HCl solution at 60, 70, 80, and 90 °C using the weight loss, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), scanning electron microscope (SEM), energy dispersive spectroscopy (EDX), and optical profilometry (OP) techniques. It was found that ASP possesses a corrosion inhibiting effect at the studied conditions. Inhibition efficiency increased with increases in temperature. With 2000 ppm ASP, inhibition efficiency of 86% was achieved from the weight loss method at 90 °C after 4 h of immersion. Results from the electrochemical techniques are in good agreement with the weight loss results. PDP results reveal that ASP acted as a mixed-type corrosion inhibitor under the investigated conditions. The inhibition ability of ASP is due to adsorption on the steel surface and has been confirmed by the SEM, OP, and EDX results. ASP is a promising active compound for the formulation of acidizing corrosion inhibitors.

The study was aimed at establishing the possibility of using eco-friendly natural polymers to formulate corrosion inhibitors for sweet oil field environment. Against this background, the performance of two natural polymers; chitosan and carboxymethyl cellulose (CMC) as single component corrosion inhibitors in comparison with a commercial inhibitor formulations, on API 5L X60 pipeline steel in CO2 saturated 3.5% NaCl solution were investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques; complemented with surface morphology characterization of the corroded steel samples without and with inhibitors using scanning electron microscope (SEM). The results indicate that there is a remarkable difference in inhibition efficiency of each inhibitor on the API 5L X60 steel and the commercial inhibitor formulations. Inhibition efficiency increased with the increase of inhibitors' concentrations. Immersion time was found to have a profound effect on the corrosion inhibition performance of all the inhibitors. Also the inhibition efficiency was found to decrease with the increase in temperature. Potentiodynamic polarization results reveal a mixed-type inhibition for all inhibitors. The adsorption of each inhibitor on the steel surface obeys Langmuir's isotherm.

YILDIZ, MESUT/0000-0001-6964-6705; KAYA, ERTUGRUL/0000-0003-1579-6411; Gerengi, Husnu/0000-0002-9663-4264; Solomon, Moses/0000-0002-3251-8846; Umoren, Saviour/0000-0002-8564-4897 WOS: 000425767400010 The efficacy of 1-butyl-1-methylpiperidinium tetrafluoroborate (BMPTFB) in retarding St37 steel corrosion in HCl environment has been examined using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), dynamic-EIS (DEIS), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques. Results from all applied methods reveal that BMPTFB is effective in suppressing St37 dissolution in the studied corrosive medium. Inhibition efficiency of 88% has been achieved by 4mM BMPTFB. From DEIS results, BMPTFB is found to perform better as corrosion inhibitor at longer immersion time. The charge transfer resistance of the metal is raised in the presence of 4mM BMPTFB from 378 to 744 cm(2) at 1h and further increased to 867 cm(2) at 4h. BMPTFB, according to PDP result behaves as mixed-type corrosion inhibitor. Corrosion inhibition by BMPTFB is via adsorption which can best be explained using El-Awady kinetic/thermodynamic adsorption isotherm. K-ads and values indicate that physisorption is the mechanism of adsorption of BMPTFB molecules onto St37 surface. The presence of BMPTFB molecules on St37 surface has been verified by SEM and FTIR. Duzce University Research Council for Science and Technology (BAP) [2016.06.05.492] The authors acknowledge the following: (i) Dr Kazimierz Darowicki and Pawel Slepski for providing the DEIS software and (ii) Duzce University Research Council for Science and Technology (BAP) for the financial support (Project No. 2016.06.05.492).

Activated carbon obtained from plantain peels was applied to the optimization of the adsorption process parameters for abstraction of colour from simulated dye effluent. The activated carbon was prepared and characterized using nitrogen adsorption, X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FTIR). Equilibrium isotherms were modelled using the Langmuir, Freundlich, Dubinin–Radushkevich and Temkin models; the Temkin and Dubinin–Radushkevich models provided the best fit for the sorption process, with a correlation coefficient greater than 0.95. The D–R model suggested a chemical process. The pseudo second-order kinetic model agreed well for fitting experimental data with the calculated adsorption capacity, qe, (46.5mg/g), which was reasonably close to the experimental value (47.3mg/g). Optimization of the process parameters was achieved using response surface methodology (RSM) – Box–Behnken design, where factors considered are represented on three levels: (−1), (0) and (+1) for high, mean and low levels, respectively. ANOVA fits a quadratic model with prob>F less than 0.05 (

KAYA, ERTUGRUL/0000-0003-1579-6411; Solomon, Moses/0000-0002-3251-8846; Gerengi, Husnu/0000-0002-9663-4264; WOS: 000394145500035 The inhibiting ability of chitosan alone and in combination with KI for St37 steel in 15% H2SO4 solution has been studied using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), dynamic electrochemical impedance spectroscopy(DEIS), and weight loss (WL) complemented by surface morphological examination with the aid of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The effect of immersion time on inhibition efficiency has been examined for 15 h and the influence of temperature studied over the temperature range of 25-60 A degrees C. Results obtained from all the applied methods portray chitosan as a moderate inhibitor for St37 steel in the studied acid environment. Addition of KI is found to remarkably enhance the inhibition efficiency of the polymer above 92%. DEIS results show that the adsorbed chitosan-KI film on the metal surface is more stable at longer immersion time and performs more effectively. The inhibition efficiency of chitosan decreases with increasing temperature, while that of the chitosan-iodide combination increases with a rise in temperature reaching an optimum value of 99.72% at 60 A degrees C. PDP results show that both chitosan and chitosan + KI behave as a mixed type inhibitor. A calculated synergism parameter confirms that the improved performance of chitosan is due to a synergistic effect. EDS results confirm the adsorption of inhibitor molecules on the metal surface. Scientific and Technological Research Council of Turkey (TUBITAK) under the TUBITAK 2216-Postdoctoral Research Fellowship [TUBITAK 21514107-115.02-56312]; Duzce University, TurkeyDuzce University Moses M. Solomon acknowledges the financial support by The Scientific and Technological Research Council of Turkey (TUBITAK) under the TUBITAK 2216-Postdoctoral Research Fellowship (TUBITAK 21514107-115.02-56312) and Duzce University, Turkey, for providing the facilities.

Corrosion inhibition of mild steel in 1 M H 2 SO 4 by leaves and stem extracts of Sida acuta was studied using chemical (weight loss and hydrogen evolution) and spectroscopic (AAS, FTIR and UV-V) techniques at 30–60 °C. It was found that the leaves and stem extracts of S. acuta inhibited the acid induced corrosion of mild steel. The inhibition efficiency increases with increase in concentration of the extracts but decrease with rise in temperature. Inhibitive effect was afforded by adsorption of the extracts’ components which was approximated by Freundlich adsorption isotherm. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency and also from spectroscopic results.

Purpose The purpose of this paper is to evaluate the performance of polypropylene glycol (PPG), as a corrosion inhibitor for aluminium corrosion in 0.5 M H2SO4 solution at 303-333 K and the effect of addition of iodide ions on the corrosion inhibition efficacy of PPG. Design/methodology/approach The corrosion inhibition performance of PPG alone and on addition of iodide ions in the acid medium was evaluated using weight loss and electrochemical [electrochemical impedance spectroscopy (EIS), linear polarisation resistance (LPR) and potentiodynamic polarization (PDP)] methods as well as surface analysis approach at 303-333 K. The morphology of the corroding aluminium surface without and with the additives was visualised using scanning electron microscopy (SEM). The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption. Findings Results obtained showed that PPG moderately retarded the corrosion of Al in 0.5 M H2SO4 solution. Addition of KI to PPG is found to synergistically improve the inhibitive ability of PPG. From the variation of inhibition efficiency, K_ads, and E_a, with rise in temperature, physisorption mechanism is proposed for the adsorption of PPG and PPG + KI onto the Al surface in 0.5 M H2SO4 solution. Polarisation results showed that PPG and PPG + KI acted as mixed type inhibitor. The adsorption of PPG and PPG + KI, respectively, onto the metal surface followed El-Awady et al. adsorption isotherm model. SEM and water contact angle analysis confirmed the adsorption of PPG and PPG + KI on Al surface. Research limitations/implications The research is limited to aqueous acid environment in aerated condition, and all tests were performed under static conditions. Practical implications The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal. Originality/value The use of PPG as corrosion inhibitor for Al corrosion in acidic medium were reported for the first time. The results suggest that iodide ions could be used to enhance corrosion protection ability of PPG which could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the synergistic effect of iodide ions addition to polymer to control acid-induced corrosion of metal.

Polypropylene glycol (PPG) was investigated as a corrosion inhibitor for typical × 60 pipeline steel in 15% HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), linear polarization resistance (LPR) and potentiodynamic polarization (PDP) techniques. Water contact angle measurements and scanning electron microscopy (SEM) were employed for surface morphology characterization. Results obtained show that polypropylene glycol acts as a good corrosion inhibitor for × 60 pipeline steel in the strong acid environment. Inhibition efficiency increased with an increase in PPG concentration and temperature up to 55 °C but decreased as immersion time was prolonged. Optimum inhibition efficiency of 90.5% was obtained at 55 °C with 1000 ppm PPG concentration from weight loss method. Potentiodynamic polarization studies revealed that PPG functions as a mixed-type inhibitor. The corrosion inhibition effect of PPG could be related to the adsorption of PPG molecules on the metal surface which follows Langmuir adsorption isotherm model and a protective film formation.

The corrosion inhibition efficiency of 2-Thiobarbituric acid (TBA) for metal substrate (API X60 steel) in 3.5% NaCl solution saturated with CO2 gas was probed using various techniques namely, LPR (linear polarization resistance), EIS (electrochemical impedance spectroscopy), and PDP (potentiodynamic polarization). The effects of TBA concentration (25–100 ppm), solution pH (4 and 6), temperature (25–80 °C), and immersion time (2–72 h) on the inhibition efficiency were examined. SEM (scanning electron microscopy) and XPS (X–ray photoelectron spectroscopy) were deployed to explore the corrosion retardation mechanism. TBA exhibited protection efficiencies exceeding 90% for all experimental conditions considered. The excellent anticorrosion performance by TBA was retained up to 72 hours of immersion time. PDP results exhibited that TBA behaved as a mixed type inhibitor. Results from kinetics and thermodynamics analyses indicate that TBA chemically adsorbed on the steel surface following Langmuir isotherm model. The composition of the adsorbed TBA film has been analyzed by XPS.

A benzimidazole derivative, 2-(2-bromophenyl)-1-methyl-1H-benzimidazole (2BPB) has been studied as a corrosion inhibitor for Cu-Ni 70/30 and 90/10 alloys in 1 mol/dm3 HCl solution at low and high temperatures using the weight loss, electrochemical (potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), & cyclic voltammetry (CV)), and surface characterization (scanning electron microscopy (SEM) & Fourier-transform infrared spectroscopy (FTIR)) techniques. The effect of immersion time (up to 72 h) and addition of iodide ions on the inhibition efficiency of 2BPB have also been investigated. At low temperature, 1.0 g/L 2BPB inhibits Cu-Ni 70/30 and 90/10 alloys by 88.9 ± 4.8% and 57.5 ± 1.3%, respectively. The performance of 2BPB improves with increase in immersion time and addition of iodide ions but slightly depreciates with rise in temperature. 2BPB acts as a mixed type corrosion inhibitor and adsorbs on the alloys surfaces through physical adsorption mechanism. SEM and FTIR results confirm the adsorption of 2BPB on the alloys surfaces. 2BPB is a potential low toxic candidate for the formulation of acid corrosion inhibitor for Cu-Ni alloys.

Pyrazine is an important diazine with the nitrogen atoms occupying the 1,4-positions within an aromatic ring. Pyrazine and its derivatives find great importance in food and medicine courtesy of their chemical characteristics functionality, namely the chemistry of their nitrogen atoms. Based on the known ability of some nitrogen-based compounds to function as excellent corrosion inhibitors for metallic materials in aqueous solutions, pyrazine and its derivatives have been reported as effective corrosion inhibitors. However, these reports are relatively scarce and limited. Herein, we have attempted a review of the known literature investigating the corrosion inhibition properties of pyrazine and its derivatives. They were reported to function as mixed-type inhibitors for steel and Al and Mg alloys. Their adsorption follows the Langmuir isotherm with steel and deviated in the case of Al and Mg alloys. The adsorption of the pyrazine derivatives on steel may be physical or chemical but is purely chemical on Al and Mg alloys. Theoretical correlations with molecular dynamic simulation have also been reviewed. We have also provided future considerations and direction of research on this important multifunctional chemistry.

A novel polypropylene glycol/silver nanoparticles (PPG/AgNPs) composite was prepared in-situ using natural honey as the reducing and capping agent. Characterization of the composite was done by UV-Vis spectroscopy, FTIR, TEM, XRD, and EDS. The TEM results reveal that the nanoparticles are spherical in shape. XRD and EDS results confirm the presence of elemental silver in the polymer matrix. The influence of the prepared composite on the corrosion inhibition of mild steel in 0.5M H2SO4 solution was studied by weight loss, electrochemical, SEM, EDS, and water contact angle measurements. Results show that PPG/AgNPs is effective inhibitor for mild steel in 0.5M H2SO4 solution and adsorbs onto the metal surface via chemisorption mechanism. Maximum inhibition efficiency of 94% is afforded by the highest studied concentration of PPG/AgNPs at 333K from weight loss measurements. Potentiodynamic polarization results reveal that the composite acts as a mixed-type corrosion inhibitor. Adsorption of PPG/AgNPs composite onto the mild steel surface follows Temkin adsorption isotherm. The SEM, EDS, and water contact angle images confirm the formation of PPG/AgNPs protective film on the mild steel surface.

Poly(methacrylic acid)/silver nanoparticles (PMAA/AgNPs) composite was prepared in-situ and characterized by UV–vis spectroscopy, FTIR, TEM, XRD, and EDS. The anticorrosion performance of the composite was investigated by gravimetric, electrochemical, SEM, EDS, and water contact angle measurements. Results obtained show that PMAA/AgNPs act as corrosion inhibitor for mild steel in 0.5 M H2SO4 solution. Inhibition efficiency increased with increase in concentration and temperature. PMAA/AgNPs composite behaved as a mixed-type corrosion inhibitor and adsorption onto the metal surface followed Temkin adsorption isotherm model. Results from all the surface analyses confirm the formation of PMAA/AgNPs protective film on the mild steel surface.

The corrosion inhibition of Al in 0.5 M H2SO4 solution by poly (methacrylic acid) (PMAA) alone and in combination with iodide ions was studied at 303–333 K 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.

The inhibiting action of polyethylene glycol and imidazole (PEG/IMZ)) complexes prepared by a simple deprotonation procedure on carbon steel corrosion in 0.5 mol/L sulphuric acid was evaluated using the weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques complemented by surface analysis using scanning electron microscopy. The inhibiting effect of the PEG/IMZ complexes on carbon steel corrosion was compared with the non-complex forms. Results obtained show that PEG/IMZ complex is a very effective corrosion inhibitor of carbon steel in the acid environment. The inhibition efficiency increased with the increase in the temperature and also with increasing percentage of imidazole in the complex. Corrosion inhibition occurs by virtue of adsorption of PEG/IMZ complexes on the steel surface which was found to follow the Temkin adsorption isotherm model. The PEG/IMZ complexes function as a mixed-type inhibitor. Results from all the methods employed are in a reasonably good agreement.

The performance of 1-[(2-hydroxyethyl) amino]-2-(salicylideneamino)ethane (HAS) as a corrosion inhibitor for carbon steel in CO2-saturated 3.0% NaCl solution under aerated and deaerated conditions was studied using weight loss and potentiodynamic polarization methods at different temperatures. The results obtained show that in aerated environment, HAS acts as an effective corrosion inhibitor for carbon steel in CO2-saturated brine solution and accelerate corrosion under deaerated condition. Inhibition efficiency (IE%) increased with increase in HAS concentration but decreased with increase in temperature. Corrosion inhibition action was via the adsorption of HAS on the metal’s surface which follows the Langmuir adsorption isotherm model. Polarization curves indicate that HAS functions as a mixed-type inhibitor.

Admixture of polypropylene glycol and 1 mM AgNO3 together with natural honey as reducing and stabilizing agent was employed to prepare in situ polypropylene glycol/silver nanoparticle (PPG/AgNPs) composite. The prepared PPG/AgNPs composite was characterized by UV-Vis spectroscopy, FTIR, XRD, and EDS, while the morphology of the Ag nanoparticles in the composite was obtained by TEM. TEM results revealed that the Ag nanoparticles were spherical in shape. The anticorrosion property of PPG/AgNPs composite was examined by electrochemical, weight loss, SEM, EDS, and water contact angle measurements. Results obtained show that PPG/AgNPs are effective in retarding the dissolution of Al in an acid-induced corrosive environment. Inhibition efficiency increased with the increasing composite concentration but decreased with the increasing temperature. Potentiodynamic polarization results revealed that PPG/AgNPs functions as a mixed-type corrosion inhibitor. The adsorption of the composite onto Al surface was found to follow El-Awady et al. adsorption isotherm model. SEM, EDS, and water contact angle results confirmed the adsorption of PPG/AgNPs films onto Al surface.

The corrosion inhibition effect of polypropylene glycol (PPG) without and with addition of iodide ions at mild steel/0.5 M H2SO4 solution interface was investigated using chemical, electrochemical, and surface analysis methods at different temperatures. Results obtained showed that PPG inhibited the corrosion of mild steel in the acid environment. Addition of iodide ions to PPG is found to synergistically enhance the corrosion inhibitive ability of PPG with efficiency in the vicinity of 98.4%. Temperature–inhibition efficiency relationship suggest physisorption of PPG onto mild steel surface and chemisorption when PPG was combined with iodide ions. Potentiodynamic polarization results showed that PPG behaved as mixed type inhibitor but under anodic control when combined with iodide ions. The adsorption of PPG and PPG–iodide ions mixtures onto the metal surface followed Temkin adsorption isotherm model.

Interaction of organic molecules with the surface of metals plays important role in many applications. In particular, surface protective applications need much explanation from both experimental and theoretical point of view. Herein, we have investigated the surface adsorption characteristics and corrosion inhibition behavior of two new benzimidazole derivatives namely 2-(2-Bromophenyl)-1H-benzimidazole (BPBA) and 2-(2-Bromophenyl)-1-methyl-1H-benzimidazole (BPMA) on mild steel in 0.5 M HCl solution using experimental and theoretical approach. Electrochemical and weight loss experiments were used to elucidate the corrosion inhibition potentials of BPBA and BPMA. Attenuated total reflectance-Fourier transform infrared spectroscopy, contact angle, scanning electron microscopy, and X-ray photoelectron spectroscopy measurements were performed to confirm the adsorption of BPBA and BPMA on mild steel surface. Computer simulations were further employed to provide additional insights into the mechanism of interac...

The corrosion inhibition effect of pectin (a biopolymer) for X60 pipeline steel in HCl medium was investigated using weight loss, electrochemical, water contact angle measurements, and scanning electron microscopy techniques. The results obtained show that pectin acts as a good corrosion inhibitor for X60 steel. Inhibition efficiency increased with increase in pectin concentration and temperature. Potentiodynamic polarization results reveal that pectin could be classified as a mixed-type corrosion inhibitor with predominant control of the cathodic reaction. The effective corrosion inhibition potential of pectin could be related to the adsorption of pectin molecules at the metal/solution interface which is found to accord with the Langmuir adsorption isotherm model and a protective film formation. Quantum chemical calculations provided insights into the active sites and reactivity parameters governing pectin activity as a good corrosion inhibitor for X60 steel.

The inhibition performance of poly (methacrylic acid) (PMAA) and the effect of addition of iodide ions on the inhibition efficiency for mild steel corrosion in 0.5 M H2SO4 solution were investigated in the temperature range of 303–333 K using electrochemical, weight loss, scanning electron microscopy (SEM), and water contact angles measurements. The results show that PMAA is a moderate inhibitor for mild steel in 0.5 M H2SO4 solution. Addition of small amount of KI to PMAA significantly upgraded the inhibition efficiency up to 96.7%. The adsorption properties of PMAA and PMAA + KI are estimated by considering thermodynamic and kinetic parameters. The results reveal that PMAA alone was physically adsorbed onto the mild steel surface, while comprehensive adsorption mode characterized the adsorption of PMAA + KI. Adsorption of PMAA and PMAA + KI followed Temkin adsorption isotherm. The SEM and water contact angle images confirmed the enhanced PMAA film formation on mild steel surface by iodide ions.

Three agro-waste products namely; watermelon rind extract (WMRE), watermelon seed extract (WMSE) and watermelon peel extract (WMPE) were investigated for their corrosion inhibition potentials for mild steel in HCl solution using electrochemical techniques at 25 °C. All the extracts inhibited acid-induced corrosion of mild steel in the order WMSE > WMRE > WMPE. Corrosion inhibition effect was found to be dependent on extracts’ concentrations. Inhibitive action of the extracts could be attributed to adsorption of the extracts’ components on mild steel surface by physisorption mechanism according to Langmuir adsorption isotherm model and functions as mixed-typed inhibitors as revealed by potentiodynamic polarization studies.

The corrosion and corrosion inhibition of St37 steel in 0.1 M HCl solution by 1-ethyl-3-methylimidazolium tetrafluoroborate (EMITFB) and the effect of addition of KI on the inhibitive performance of EMITFB have been examined by electrochemical [electrochemical impedance spectroscopy, potentiodynamic polarization, and dynamic electrochemical impedance spectroscopy (DEIS)] and surface examination [scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS)] techniques. Results show that EMITFB could only afford the protection of St37 steel in HCl medium on an average scale. The highest studied concentration of EMITFB (4 mM) affords optimum inhibition efficiency of 78.86% from DEIS method. Addition of iodide ions to EMITFB has beneficial effect on the inhibition efficiency; 86.10% has been achieved by addition of 1 mM KI to 4 mM EMITFB. Adsorption of EMITFB molecules onto the metal surface is via physical adsorption mechanism and follows El Awady et al. kinetic/thermodynamic adsorption isotherm model. SEM and EDS results confirm the improvement of corrosion inhibiting ability of EMITFB by iodide ions. EMITFB and EMITFB + KI behave as mixed-type corrosion inhibitor in the studied environment. © 2018, Springer International Publishing AG, part of Springer Nature. Türkiye Bilimsel ve Teknolojik AraÅŸtirma Kurumu: TUBİTAK-114M933 Funding Husnu Gerengi thanks the Scientific and Technological Research Council of Turkey for the financial support under the TUBİTAK-114M933 coded project. Moses M. Solomon is grateful to King Fahd University of Petroleum and Minerals, Saudi Arabia for accepting him as a Postdoctoral Research Fellow.

KAYA, ERTUGRUL/0000-0003-1579-6411; Solomon, Moses/0000-0002-3251-8846; WOS: 000418661000006 PubMed: 29253993 A green anticorrosive composite (GA-AgNPs) has been formulated for steel in 15% HCl and 15% H2SO4 media. Characterization of GA-AgNPs is achieved via FTIR, UV-vis, EDAX, and SEM. Gravimetric, electrochemical (EIS, EFM, DEIS, & TP), and surface assessment (SEM, EDAX, AFM, & XPS) techniques have been deployed in the anticorrosion studies. Results from all applied methods potray GA-AgNPs as effective anticorrosive agent. Inhibition is by adsorption mechanism and follows Langmuir isotherm. GA-AgNPs acts as mixed type inhibitor in 15% H2SO4 solution but as anodic type in 15% HCl solution. Results from surface techniques confirm adsorption of GA-AgNPs molecules on specimen surface. Oxides, hydroxides, carbonates, and sulphates (H2SO4 medium) or chlorides (HCl medium) are the corrosion products in the free corrodent according to XPS results. In the presence of composite, both ionic and neutral forms of GA-AgNPS are adsorbed. AgNPs are present on the surface in the form: Ag degrees, Ag2O, and AgO. Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK 2216, TUBITAK 21514107-115.02-56312] Moses M. Solomon expresses his appreciation to The Scientific and Technological Research Council of Turkey (TUBITAK) for financial support under the TUBITAK 2216-Postdoctoral Research Fellowship (TUBITAK 21514107-115.02-56312) programme and Duzce University, Turkey for making available the facilities used in this work.

Activated carbon has been prepared from plantain peels unripe, a biowaste from confectioneries for investigation of its adsorption efficiency in binary system of lead (II) and 3,7-Bis(dimethylamino)-phenothiazin-5-ium chloride as common water pollutants. The prepared carbons were characterized using nitrogen adsorption, FTIR spectroscopy, and XRD. Batch adsorption experiments were conducted to determine most probable conditions of adsorption maximum via varying adsorbent concentration, initial pollutants concentration, and pH of adsorption. Adsorption was found to be dependent on the factors studied. Favorable adsorption was recorded at initial concentration of 300 mg/dm3 after 30 min. Equilibrium and kinetic data were modeled using well-known isotherm and kinetic models. Results deviated largely from Langmuir monolayer, Freundlich multilayer and extended Langmuir isotherm models suggesting a mutual interaction of the adsorbates in solution which is shown with data obtained from competitive adsorp...

The corrosion inhibition effect of red apple (Malus domestica) fruit extract for mild steel in hydrochloric acid was investigated by gravimetric and electrochemical methods at 30–60°C. Inhibition efficiency increased with the increase in concentration and temperature. Polarization curves indicate that the extract functions as mixed-type inhibitor. The adsorption of the extract onto mild steel surface followed Langmuir adsorption isotherm model. Chemisorption mechanism is proposed based on the trend of inhibition efficiency with temperature. Quantum chemical calculations and molecular dynamics simulations have been used to provide insights into the mechanism of interaction of the major extract components with mild steel.

Purpose – The purpose of the paper was to investigate the use of aqueous extract of date palm (Phoenix dactylifera) leaf as a green inhibitor for corrosion of carbon steel in 1M hydrochloric acid (HCl) solution. Design/methodology/approach – Extracts from the date palm were used as the main component of an environmentally friendly corrosion inhibitor for use in HCl pickling processes. Inhibition behavior on carbon steel in HCl was investigated using weight loss measurements, linear and potentiodynamic polarization curves, electrochemical impedance spectroscopy and scanning electron microscopy. Findings – The results show that the extract exhibited good inhibition performance in 1M HCl. The inhibition efficiency increased with increase in the concentration of the inhibitor but decreased with increase in temperature. Inhibition efficiency also was found to increase as immersion time increased. The inhibitive action was due to adsorption of the date palm leaf components on the steel, which was consistent with the Langmuir isotherm. Practical implications – Date palm leaf extract (DPLE) is an effective inhibitor at room temperature and can be used to protect plain carbon steel from corrosion in HCl solution. Originality/value – This study provides new information on the inhibiting characteristics of DPLE under specified conditions. The environmentally friendly inhibitor could find possible applications in metal surface anodizing and acid pickling processes.

Corrosion inhibition potentials of two imidazole derivatives namely, vinylimidazole (VI) and allylimidazole (AI) for carbon steel in 1 M HCl at 25 °C were predicted theoretically using quantum chemical calculations and molecular dynamics (MD) simulations. DFT calculations indicated that VI is more reactive towards steel surface than AI. Equilibruim adsorption behaviour of VI and AI molecules on Fe 2 O 3 (0 1 0) surface was investigated using molecular dynamics (MD) simulations. The equilibrium adsorption energy followed the order: VI > AI. Theoretical conclusions were subsequently validated experimentally using potentiodynamic polarization, linear polarization resistance, electrochemical impedance spectroscopy, and surface analytical techniques (SEM and AFM).

Electrochemical techniques were used to investigate the efficacy of watermelon rind extract (WMRE) as corrosion inhibitor for mild steel in HCl and H 2 SO 4 solutions. The inhibition efficiency increased as the concentration of the extract increases. Potentiodynamic polarization results indicate that WMRE act as a mixed-type inhibitor. The values of effective capacitance obtained by utilizing the impedance parameters in both acidic media are in the range of double layer capacitance. Corrosion inhibition effect of WMRE can be attributed to the adsorption of constituents of WMRE onto the mild steel surface which can be approximated by Temkin adsorption isotherm model.

Two isoxazolidine derivatives namely 5-(benzo[d][1,3]dioxol-5-ylmethyl)-2-tetradecyl isoxazolidine (BDMTI) and 5-(4-hydroxy-3-methoxybenzyl)-2-tetradecyl isoxazolidine (HMBTI) were synthesized and characterized using FTIR, C-NMR, H-NMR, and elemental analysis. The synthesized compounds were evaluated as corrosion inhibitors for API 5L X60 steel in 1 M HCl in the temperature range of 25–60 °C using gravimetric and electrochemical (Electrochemical Impedance Spectroscopy (EIS), Potentiodynamic Polarization (PDP) and Linear Polarization Resistance (LPR)) techniques. The effect of addition of a small amount of iodide ions on the corrosion inhibition performance of the compounds was also assessed. In addition, quantum chemical calculations and Monte Carlo simulations were employed to correlate the electronic properties of the compounds with the corrosion inhibition effect as well as to evaluate the adsorption/binding of the inhibitor molecules on the steel surface. Experimental results show that the two compounds inhibited the corrosion of carbon steel in an acid environment with HMBTI showing superior performance. The corrosion inhibition effect was found to be dependent on the inhibitors' concentration and temperature. Addition of iodide ions improves the inhibition efficiency considerably due to co-adsorption of the iodide ions and the inhibitors on the steel surface which was competitive in nature as confirmed from the synergistic parameter (S1) which was less than unity at higher temperature. Experimental and theoretical results are in good agreement.

Seven natural polymers namely, chitosan (CHI), dextran (Dex), carboxymethyl cellulose (CMC), sodium alginate (ALG), pectin (PEC), hydroxylethyl cellulose (HEC), and Gum Arabic (GA) were screened for anticorrosion property towards AZ31 Mg alloy in 3.5 wt.% NaCl solution. CHI, Dex, CMC, PEC, and GA accelerated the corrosion while ALG and HEC moderately inhibited the corrosion of the alloy. HEC and ALG (1 g/L) protected the alloy by 64.13 % and 58.27 %, respectively. Two inhibitor cocktails consisting of either HEC or ALG, KI, and Date palm seed oil have been formulated. HEC- and ALG-formulations inhibited the alloy corrosion by 80.56 % and 77.43 %, respectively from EIS technique. Surface observation studies using SECM, AFM, SEM, and EDX agreed with other experimental results revealing effective corrosion inhibition by the formulations. X-ray photoelectron spectroscopy, FTIR, and UV–vis results disclose that Mg(OH)2 co-existed with adsorbed inhibitor complexes.

The adsorption and corrosion inhibition behavior of strawberry fruit extract at steel/1 M HCl and steel/0.5 M H2SO4 interfaces were investigated using gravimetric and electrochemical methods at 25 and 60 °C. Results obtained showed that the extract inhibited the acid-induced corrosion of mild steel which was more pronounced in HCl than H2SO4 medium. Inhibition efficiency increased with increase in the concentration of the extract but decreased with increase in temperature. The potentiodynamic polarization studies revealed that the extract functions as mixed-type inhibitors. The inhibition was assumed to occur via adsorption of the components of the extract on the mild steel surface which can be approximated by Langmuir adsorption isotherm model. Quantum-chemical calculations and molecular dynamics simulations have been used to provide insights into the mechanism of interaction of ascorbic acid as a major constituent of the extract with mild steel.

Corrosion inhibition of mild steel in H2SO4 by water and methanol extracts of coconut coir dust was studied using chemical and electrochemical techniques. It was found that the extracts inhibited the acid induced corrosion of mild steel. The inhibition efficiency increased with increase in extracts concentration but decreased with increase in temperature. Methanol extract was found to be a better inhibitor. The adsorption of the extracts’ components onto the mild steel surface follow Temkin and Freundlich adsorption isotherms for methanol and water extracts respectively. Polarization studies show that the extracts act as mixed typed inhibitor but under cathodic control.

Purpose – The purpose of this paper is to investigate the effect of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and blended formulations on the corrosion inhibition of aluminium in HCl solutions at 30-60°C and to study the mechanism of action. Design/methodology/approach – The inhibitive effect of the homopolymers and polymer blend was assessed using weight loss and hydrogen evolution methods at 30 and 60°C. The morphology of the corroding aluminium surface without and with the additives was visualized using atomic force microscopy. The trend of inhibition efficiency with temperature was used to propose the mechanism of inhibition and type of adsorption. Findings – Results obtained show that inhibition efficiency (η%) increases with increase in concentration of the polymers but decreases with increase in temperature. The inhibition efficiency of the homopolymers and their blends decreased with rise in temperature. Inhibition efficiency was found to be synergistically enhanced on blending the two homopolymers with highest inhibition efficiency obtained for (PEG:PVP) blending ratio of 1:3. The phenomenon of physical adsorption is proposed from the trend of inhibition efficiency with temperature. Research limitations/implications – The mechanistic aspect of the corrosion inhibition can be better understood using electrochemical studies such as potentiodynamic polarization and electrochemical impedance spectroscopy. Originality/value – Studies involving the use of polymer blends/mixtures as corrosion inhibitor for metals in corrosive environments are scarce. The results suggest that the mixture could find practical application in corrosion control in aqueous acidic environment. The data obtained would form part of database on the use of polymer–polymer mixtures to control acid-induced corrosion of metal.

The corrosion protection of carbon steel in 1 M HCl by 1-octadecanethiol (ODT) alone and in combination with iodide ions was investigated at ambient temperature using electrochemical impedance spectroscopy and potentiodynamic polarization techniques. Results obtained showed that ODT alone offered low corrosion protection ability at very low concentrations. However, on addition of iodide ions, the corrosion protection potential was enhanced due to synergistic effect. Potentiodynamic polarization data revealed that ODT acts as mixed-type inhibitor influencing both the cathodic hydrogen evolution and anodic metal dissolution reactions. Adsorption of ODT onto the carbon steel surface followed Langmuir adsorption isotherm model. The existence of synergism phenomenon between ODT and iodide ions was confirmed from synergism parameter, which was found to be greater than unity. Quantum chemical calculations provide greater insight into the mechanism of electron transfer and mechanistic aspects of ODT on steel surface.

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 H 2 SO 4 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 H 2 SO 4 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 ( S 0 ) 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.

The corrosion inhibition effect of date palm (Phoenix dactylifera) seed extracts for mild steel in 1 M HCl and 0.5 M H2SO4 solutions was investigated by weight loss and electrochemical methods. The inhibition efficiency increased with an increase in the extract concentration and decreased with an increase in the temperature. Extract concentrations of 2.5 and 1.5 g L–1 gave maximum inhibition efficiencies in 1 M HCl and 0.5 M H2SO4, respectively. The immersion time was also found to influence the corrosion inhibition effect in both acidic media. Polarization curves indicate that the extract functions as a mixed inhibitor, affecting both the anodic and cathodic partial reactions of the corrosion process. Adsorption of the extract onto a mild steel surface followed the Langmuir adsorption isotherm. The mechanism of physical adsorption has been proposed based on the trend of the inhibition efficiency with temperature. The date palm seed extract is a better corrosion inhibitor for mild steel in HCl than in a H...

Corrosion inhibition mechanism of aluminium in H2SO4 by polyacrylic acid (PAA) in the absence and presence of iodide ions was investigated using in-situ atomic force microscopy (AFM). Results indicate that PAA inhibited the corrosion of aluminium by adsorption onto the aluminium surface. Inhibition efficiency of PAA was found to enhance on addition of iodide ion which could be ascribed to synergistic effect. In-situ AFM morphology of the surface film suggests that PAA in the presence of iodide ion was adsorbed on aluminium surface after taking a more ordered arrangement, thus providing a more uniform coverage at potentials below and above potential of zero charge.

The inhibition of a substituted naphthol compound, 4-(4-nitrophenylazo)-1-naphthol (44NIN), on the corrosion of aluminium (Al) in a basic medium was studied by classical chemical (gravimetric) and spectrophotometric (UV–Vis and FTIR) methods at 303–333 K. 44NIN demonstrated an excellent inhibiting property to Al corrosion in the aerated binary alkaline solution as shown from the results. The inhibition efficiency was found to increase with the azo dye concentration but not with temperature. Thermodynamic and adsorption evaluation for this inhibition process were accessed and thoroughly discussed. The UV–visible absorption spectra of the solution containing this dye after the immersion of Al specimen indicate the possible formation of a 44NIN–Fe type complex. The FTIR was carried out of the dye and protective film formed on the surface of the metal in the electrolyte containing the dye after a 72 h immersion period. These results show a correlation between the inhibitive effect and molecular structural inf...

The inhibitive performance of chitosan and silver nanoparticles - chitosan (AgNPs-Chi) composite towards St37 steel corrosion in 15% H