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The use of corrosion inhibitors is one of the most common methods to combat acid corrosion. The current studies aim to apply natural products as corrosion inhibitors, once the most used compounds are mostly toxic to the environment and to humans. The present paper purposes the application of an aqueous extract of agro-industrial waste (AEAW) to inhibit the corrosion of stainless steel AISI 304 in sulfuric acid. Gravimetric and electrochemical experiments were performed. The gravimetric experiments revealed that the extract acts as an inhibitor for stainless steel, showing inhibitory efficiency up to 81.6%. The electrochemical tests show that the AEAW makes the steel surface more noble. The extract acts by adsorption in the metallic surface, following a Temkin isotherm. The results indicate that the AEAW is a promising substitute of conventional organic compounds as a corrosion inhibitor to AISI 304 stainless steel in sulfuric acid.

Based on Lemaitre’s strain equivalence hypothesis theory, it is assumed that the strength of acid-etching rock microelements under the coupling effect of temperature and confining pressure follows the Weibull distribution. Under the hypothesis that micro-element damage meets the D-P criterion and based on continuum damage mechanics and statistical theory, chemical damage variables, thermal damage variables and mechanical damage variables were introduced in the construction of damage evolution equations and constitutive models for acid-etching rocks considering the coupled effects of temperature and confining pressure. The required model parameters were obtained by theoretical derivation, and the model was verified based on the triaxial compression test data of granite. Comparing the experimental stress-strain curve with the theoretical stress-strain curve, the results show that they were in good agreement. By selecting reasonable model parameters, the damage statistical constitutive model can accurately reflect the stress-strain curve characteristics of rock in the process of triaxial compression. The comparison between the experimental and theoretical results also verifies the reasonableness and reliability of the model. This model provides a new rock damage statistical constitutive equation for the study of rock mechanics and its application in engineering, and has certain reference significance for rock underground engineering.

The performance of 1‐vinyl‐3‐allyl imidazolium bromide ([VAIM][Br]) for inhibiting the corrosion of carbon steel in 1 M HCl solution from 298 K to 338 K was assessed. Electrochemical impedance spectroscopy (EIS) measurements proved that the inhibition efficiency (η) of [VAIM][Br] was as high as 95 %, and after immersion of 144 h, η still kept more than 90 %. Polarization curve verified that [VAIM][Br] acted as a mixed‐type inhibitor and adsorption of [VAIM][Br] was found to obey Langmuir adsorption isotherm. Molecular dynamic simulations suggested that the addition of vinyl group increased interaction energy between [VAIM]+ and (0 0 1) plane of Fe from 43.92 kcal mol−1 to 71.98 kcal mol−1. Liquid chromatography‐mass spectrometry (LC‐MS) and UV‐vis spectrum demonstrated that [VAIM][Br] and Fe atom can form stable complex (Fe2(VAIM)2Br4), which hindered the corrosion of carbon steel. [ABSTRACT FROM AUTHOR]

The inhibition performance of ionic liquids, abbreviated as [(CH 2)COOHMIm][HSO 4 , [(CH 2) 2 COOHMIm][HSO 4 , and [(CH 2) 3 SO 3 HMIm][HSO 4 was investigated for carbon steel in 0.5 M HCl solution. Results indicated that these ionic liquids could act as effective inhibitors by adsorption onto the steel surface, and the inhibition efficiency increases with cation alkyl chain length and concentration up to a limit. The inhibition efficiency of a sulfonate-type ionic liquid with a longer alkyl chain is higher than those of the carboxylate-type ionic liquids. Besides, the order of inhibition efficiency was verified by both computational calculation and electrochemical experimental observations. [ABSTRACT FROM AUTHOR]

The inhibition of (3ar,6ar)-3a,6a-di-p-tolyltetrahydroimidazo[4,5-d]imidazole-2,5(1 h,3h)-dithione (TTHIIDT) for carbon steel was full characterized in a 1 M hydrochloride acid environment at various inhibitor concentrations and temperatures by the gravimetric, electrochemical, surface and quantum chemical analyses. The obtained results confirmed that the inhibition efficiency of TTHIIDT was over 95–97% and nearly stable in the rise of temperature and concentration; TTHIIDT was mixed type inhibitor and effectively influenced both anodic and cathodic corrosion reactions; a protective hydrophobic thin layer of this inhibitor on the carbon steel surface is more stable and non soluble in 1 M HCl medium; this inhibitor adsorbed endothermically on the carbon steel surface by the chemical and physical adsorption processes. The quantum chemical calculations supported the experimental results and showed that the inhibition efficiency is depends on the structure of inhibitor. [ABSTRACT FROM AUTHOR]

• DM drug was introduced as a novel corrosion inhibitor. • Polarization measurements signify that DM drug acted as a mixed mode inhibitor. • Adsorption mode best reflect in Langmuir isotherm. • MD-simulation reveals the vital role of active sites of DM molecule in their adsorption. • ANFIS best predicted the interactive effects between the input and output response. In this research, the effect of Dexamethasone drug (DM) on mild steel corrosion in 2 M HCl was analyzed using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and MD-simulation. In addition, Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), Energy dispersive x-ray spectroscopy (EDX), and atomic force microscopy (AFM) were employed to inspect the mild steel surface in the blank and inhibited medium. For the optimization tool, adaptive neuro-fuzzy inference system (ANFIS) model was developed to predict the inhibition efficiency. The experimental data was categorized into two different sections for training and testing the ANFIS model. The developed model aimed to evaluate the fitness between the experimental and predicted values. From the results generated, optimum value (IE%) of DM was recorded as 80%, 81% and 83% at concentration of 0.4 g/L for weight loss, EIS and PDP respectively. Potentiodynamic polarization results reveal that Dexamethasone functions as a mixed-type inhibitor, whereas studies of EIS show that the inhibition mechanism is by the transfer of charges. Mild steel surface examination confirmed the presence of a protective adsorbed film on the mild steel surface. Thermodynamic parameters obtained imply that Dexamethasone is adsorbed on the steel surface by a physiochemical process and obeys Langmuir adsorption isotherm. Also the MD-simulation results evidenced that DM forms a metallic surface adsorbed film on the steel surface. From the ANFIS model, the sensitivity analysis shows that time and inhibitor concentration were the most important input variable while other input variables could not be neglected. ANFIS model coefficient of determination (R 2 0.993) was found between the observed and predicted values. ANFIS model gave optimum prediction (80%) with high degree accuracy and robustness. The outcomes of this investigation provide more information, simulation, and prediction about inhibition of metal corrosion. [ABSTRACT FROM AUTHOR]

A polyacrylamide with capsaicin‐derived monomers (AM–MAA–AMPS–HMBA–SMA; AMAHS) was synthesized and investigated as a novel environment‐friendly polymer inhibitor for Q235 mild steel at 25°C in 1 M HCl solution. The inhibition efficiency was evaluated by weight loss measurements, electrochemical experiments, and surface investigation methods as well as by theoretical calculations. Experimental results indicated that the efficiency of AMAHS was up to 94.86% at the concentration of 2 g/L. Electrochemical tests and surface morphology analysis showed that AMAHS served as a mixed‐type corrosion inhibitor, which could be adsorbed and self‐assembled on the surface of mild steel forming a highly hydrophobic protective film (contact angle of 172°). Density functional theory calculations revealed that heteroatoms in AMAHS, such as O, N, S, are active sites in forming coordination bonds with surface iron atoms. In addition, hydrophobic groups played an important role in protecting the metal surfaces from corrosion media. [ABSTRACT FROM AUTHOR]

The role of Echium angustifolium Mill extract for advancing corrosion resistance of carbon steel in 1.0 M H2SO4 solution was discussed in this research. Weight loss (WL), open circuit potential (OCP), potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS) methods were applied to monitor the corrosion behavior of carbon steel in 1.0 M H2SO4 solution. The influence of temperature was studied from 25–45°C and some thermodynamic parameters were computed. The Surface morphology of the carbon steel surface was examined via different techniques. These measurements confirmed that the existence of Echium angustifolium Mill extract reduces the corrosion rate (CR), corrosion current densities (icorr), and double layer capacities (Cdl), simultaneously increase the polarization resistance (Rp) values. Tafel plots observed that the Echium angustifolium Mill extract play as a mixed type inhibitor. Electrochemical impedance confirmed that the existence of the applicable extract reduced the double layer capacitance and enhanced the charge transfer resistance. The extract molecules adsorbed on the metal surface follow Langmuir adsorption isotherm. The gained data confirmed that the inhibition efficiency (η%) increase with the increase of extract concentration. [ABSTRACT FROM AUTHOR]

The inhibitive action of cysteine was investigated against the corrosion of aluminium alloy 6061-T6 (AA6061-T6) in a 0.5 M hydrochloric acidic medium in the temperatures range of 303–323 K using potentiodynamic polarization as well as electrochemical impedance spectroscopy methods. The electrochemical results of the former were validated by the latter. Cysteine showed mixed inhibitor behavior and exhibited good inhibition performance. The thermodynamic properties indicated mixed adsorption behavior of cysteine, which satisfied the Langmuir adsorption isotherm. The surface morphological investigation of both corroded and inhibited specimens was performed using a scanning electron microscopy and atomic force microscope, which revealed the adsorption of cysteine onto the alloy surface. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper deals with a review of the inhibition activity of various reported Schiff bases on the deterioration of mild steel in hydrochloric acid and sulfuric acid media. Mild steels find wide applications in structural, automobile and petrochemical industry, where acid solutions such as hydrochloric acid, sulfuric acid are commonly being used as pickling or descaling agents. The undue deterioration of metal during pickling can be controlled by adding a suitable inhibitor to the pickling solution. Schiff bases are widely being employed in such applications. This paper highlights the influence of structure–inhibition activity relationship of Schiff base compounds on their performance as corrosion inhibitors of mild steel in acid media. The information provided finds a useful practical application for different industrial fields in the selection of best-performing inhibitors and also for the researchers involved in the development of new novel corrosion inhibitors for mild steel in acid media. [ABSTRACT FROM AUTHOR]

The inhibiting effect of the expired meloxicam on the corrosion of mild steel (MS) in 1 M HCl was tested by the weight loss, electrochemical frequency modulation, potentiodynamic polarization (PP) and electrochemical impedance spectroscopy techniques. The PP curves showed that this drug acts as mixed type inhibitor. This drug was adsorbed chemically on the MS surface following the Temkin adsorption isotherm. Some thermodynamic parameters were computed and discussed. The results indicated that the protection efficiency increases by raising both the doses of the inhibitor and the temperature of the medium. The morphology of the MS surface was analyzed by scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy. All of the obtained results from different techniques are similar. [ABSTRACT FROM AUTHOR]

Two types of polymer latexes and one expansive agent were employed to investigate their effects on the resistance of cement asphalt (CA) pastes to sulfuric acid. Mercury intrusion porosimetry, a thermogravimetric analysis, and scanning electron microscopy were performed to analyze the microstructure of the CA pastes. Anticorrosion coefficients were calculated by comparing the compressive strength before and after corrosion. Results show that the chemical attack by sulfuric acid on the CA pastes begins from the neutralization reaction, accompanied by the crystalline expansion of calcium sulfate in pores and the decompositions of C-S-H gel and asphalt. At a mass ratio of asphalt to cement (A/C) of 0.2, Latex I enhances the anticorrosion coefficients of the CA pastes at low dosages but reduces them at high dosages. In contrast, Latex II results in a completely inverted effect on the anticorrosion coefficients. At an A/C of 0.6, the addition of both Latex I and II visibly increases the anticorrosion coefficients, owing to the binding effect of latex on hydrates. Compared to Latex I, Latex II results in a more obvious increase in the anticorrosion coefficients. With the inclusion of the expansive agent, the anticorrosion coefficients of the CA pastes at the A/C of 0.2 sharply decrease, while the ones at the A/C of 0.6 significantly increase. It is concluded that the precipitation of calcium sulfate crystals in a compact structure produces expansion stress and microcracks, thereby decreasing the strength and anticorrosion coefficients of CA pastes at low A/C values. In the case of high A/C values, the paste structure is difficult to be damaged, owing to the binding effects of asphalt membranes. Hence, the anticorrosion coefficients are increased by adding the expansive agent. [ABSTRACT FROM AUTHOR]

The aim of this research is evaluation of the performance of Pistacia khinjuk aerial part extract (PKAPE) on the corrosion of carbon steel in 2.0 M hydrochloric acid and 1.0 M sulfuric acid solutions and comparing the differences in the behavior of the extract in these two acidic environments. For this study, the classical method of weight loss and electrochemical methods [open-circuit potential (OCP) time, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS)] were used. Based on weight loss experiments, the maximum inhibition efficiencies of 92.8% and 90.3% were obtained at 2.0 g/L of extract in 2.0 M HCl and 1.0 M H2SO4 solutions, respectively. Potentiodynamic polarization results revealed that PKAPE in both examined acidic solutions act as mixed-type inhibitor. Polarization measurements in the temperature range of 25–65 °C were carried out for different concentration to define the effect of temperature on the behavior of the extract. At all investigated temperatures, adsorption of PKAPE on the surface for both acidic media follows the Langmuir adsorption isotherm. Thermodynamic and activation parameters were calculated, and the results inferred that the adsorption of PKAPE on the surface for both acidic solutions is physisorption. Quantum chemical parameters were calculated using the density functional theory (DFT) method for main components of PKAPE to predict their adsorption on the surface. [ABSTRACT FROM AUTHOR]

The inhibitive ability against mild steel corrosion of pharmacologically active compound Bexol towards acid was valued by gravimetric experiments and electrochemical experiments. The results of the weight loss studies indicated inhibition efficiency was boosted with increased concentration of Bexol from 5 mg/L to 45 mg/L in the acid environment. Potentiodynamic polarization behaviour of the metal specimen in presence of Bexol exposed the mixed style inhibitive action. EIS results established that Bexol adsorb at the metal/acid junction by mere electrostatic physical adsorption mechanism to inhibit the corrosion process. Epoxy coated mild steel without and with the studied bexol was used for electrochemical studies in 3.5% of NaCl for different time intervals. The Density Functional -theory was employed to scrutinize inhibition property of the considered inhibitor. Experimental measurement obtained shows perfect fit to the theoretical calculations. [ABSTRACT FROM AUTHOR]

Four quaternary ammonium cationic surfactants, cetyl-trimethyl ammonium fluorine (CTAF), cetyl-trimethyl ammonium chlorine (CTAC), cetyl-trimethyl ammonium bromine (CTAB) and cetyltrimethyl ammonium iodine (CTAI) were purchased as carbon steel corrosion inhibitors in HCl solution using weight-loss method. The correlation between inhibition efficiency and molecular structure of four inhibitors was studied. The experimental outcome showed that at the same concentration, solution temperature and HCl concentration, the inhibition efficiency of four inhibitors followed the order CTAI > CTAB > CTAC > CTAF, it seems to indicate that the type of halide ions of inhibitors greatly influence the inhibition efficiency. Based on weight loss results, the adsorption of studied inhibitors on the carbon steel surface in the HCl solution obeyed the Langmuir adsorption isotherm. The thermodynamic parameters including the standard adsorption free energy (ΔG° ads), the standard heat of adsorption (ΔH° ads) and the standard adsorption entropy (ΔS° ads) were calculated and discussed, which well explained that the synergistic effect between the quaternary ammonium cations and the halide anions greatly influenced the effective inhibiting tendency. [ABSTRACT FROM AUTHOR]

Corrosion inhibition effects of water-soluble peripheral substituted cobalt, copper and zinc metallophthalocyanines (CoPc (1), CuPc (2) and ZnPc (3)) on the copper metal in 0.1 N HCl were investigated by using gravimetric, electrochemical, SEM-EDS analysis and quantum chemical calculations. On the electrochemical investigations and gravimetric analysis the highest inhibitor efficiency was obtained with CoPc (1) at 1 × 10–2 mol/L concentration. SEM-EDS results indicated parallel results and oxygen atom content increased in the order of ZnPc (3), CuPc (2) and CoPc (1). According to the quantum chemical calculations, following corrosion inhibition efficiency ranking was obtained: CoPc (1) > CuPc (2) > ZnPc (3). [ABSTRACT FROM AUTHOR]

Nanoscale nickel is prepared from ethanol extracts of Allium cepa and characterized. Zerovalent face centred cubic (fcc) nickel nanoparticles oriented mainly at Ni (111) plane formed rapidly within 30–45 min. The nanoparticles are stabilized by negative surface potential, non-agglomerated, monodispersed, round-shaped and distributed between sizes of 39.5–53.1 nm. The nanoparticles are used to simultaneously regulate the rates of hydrogen gas production and X80 steel corrosion in 1 M HCl solution for the first time. The nanoparticles efficiently inhibit hydrogen gas evolution and X80 steel corrosion rates especially at increased concentration. Inhibition efficiency increases as temperature increases from 303 to 323 K, remains fairly constant from 323 to 343 K and decreases drastically from 343 to 363 K. By means of O–H, N–H and C=C sites, the nanoparticles are spontaneously physically adsorbed on X80 steel surface and act as mixed type corrosion inhibitor with dominant influence on cathodic reaction involving hydrogen gas evolution. In the presence of the nanoparticles, surface roughness (measured by AFM) reduces by 76.0% and heights of peaks from the mean plane reduces by 58.2%. Comparatively, even 100 ppm of the nanoparticles showed higher inhibition efficiency at all temperatures than 1000 ppm concentration of the crude extract. • Nickel nanoparticles (Et-OME-NiNPs) synthesized from onion mesocarp ethanol extract (Et-OME). • Et-OME-NiNPs are monodisperse, non-agglomerated with sizes between 39.5 and 53.1 nm. • Et-OME-NiNPs regulate hydrogen gas production rate and pipeline steel corrosion in 1 M HCl solution at 303–363 K. • Higher efficiency of corrosion inhibition obtained with Et-OME-NiNPs than the crude extract. [ABSTRACT FROM AUTHOR]

In order to study the change of static mechanical properties of heterogenous sell-piercing riveted joints in steel-aluminium lor salt and acid corrosion dry-wet periphery immersion accelerated corrosion test was carried out on self-piercing riveted specimens in DP590-5052 (DA). The weight loss failure mode and static load performance of joints at different corrosion times were analyzed by corrosion kinetics and static test The results show that in salt corrosion environment，the weight loss of steel-aluminium specimens (YDA) group shows an upward trend，while the corrosion rate decreases;in acid corrosion the weight loss of steel-aluminium specimens (SDA) group first increases and then decreases and the corrosion rate also shows the same trend. The effect of acid corrosion on joint failure mode is more significant. The static strength of the joint are affected by both kinds of corrosions and the corrosion resistance of the joint to salt environment is smaller. [ABSTRACT FROM AUTHOR]

There is a scarcity of available literature studies on the inhibition of aqueous corrosion using graphene and graphene oxide (GO) due to their poor aqueous solubility. The abundance of oxygen-containing functional groups on the surface of GO offers promising aspects for its chemical modification. Accordingly, we herein report the application of bis(2-aminoethyl)amine-modified graphene oxide (B2AA-GO) as a corrosion inhibitor for carbon steel in industrial oil-well acidizing conditions. B2AA was used to modify the graphene oxide (GO) chemically and characterized using FTIR, SEM, and TEM. The corrosion evaluations were undertaken in 15% HCl using weight loss, electrochemical impedance spectroscopy, and potentiodynamic polarization techniques supported by a thorough surface analysis using water contact angle measurements, FTIR, and atomic force microscopy. It observed that the B2AA-GO acted by adsorption on the metal surface and exhibited a mixed type of nature with cathodic prevalence. The results showed that the chemically modified GO exhibits excellent inhibition behavior showing 90.27% corrosion inhibition efficiency up to 65 °C. Furthermore, iodide ions were introduced to improve the inhibition efficiency of the GO via synergistic action and inhibition efficiency of 96.77% was obtained at 65 °C. The obtained results show that the chemically modified GO is a promising corrosion inhibitor in the acidizing environment. [ABSTRACT FROM AUTHOR]

It has recently been synthesized a Schiff base (E)-2-hydroxy-5-(2-benzylidene) aminobenzoic acid and characterized by FTIR, UV–vis and 1H NMR analysis. The electrochemical behaviour of mild steel in 1.0 M HCl solutions in the absence and presence of Hha has been investigated by electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy. The inhibition efficiency was found to increase with rise in concentration of synthesized molecule. Scanning electron microscopy observations of mild steel surface confirmed the existence of such an adsorbed film. Contact angle on the metal surface was also measured. Computational analyses of (E)2-hydroxy-5-((2-hydroxybenzylidene) amino benzoic acid were done at B3LYP/6-31G(d) level in gas phase. Sensitivity of this compound towards Fe2+ and Fe3+ ions were determined. Interaction mechanism was proposed. [ABSTRACT FROM AUTHOR]

We report the synthesis and corrosion inhibition performance of two imidazole‐based materials, 1,1′‐(4‐methyl‐1,3‐phenylene)bis(3‐(3‐(1H‐imidazol‐1‐yl)propyl)urea) (PIP) and 1,1′‐(hexane‐1,6‐diyl)bis(3‐(3‐(1 H‐imidazol‐1‐yl)propyl)urea) (HIP) dimers, in 1.0 M HCl. Electrochemical assessments indicated that the synthesized dimers facilitated the formation of a protective layer at the metal‐electrolyte interface and, as a result, blocked the active corrosion sites. At a concentration of 100 ppm, PIP behaved as a potential mixed‐type anticorrosive material with an overall efficiency of 99%. Density functional theory calculations showed that the aromaticity existing in the PIP backbone plays a major role in facilitating the corrosion‐inhibition role. [ABSTRACT FROM AUTHOR]

Endocarp and pericarp extracts of Cereus fricii cactus were used to inhibit carbon steel corrosion in HCl and NaCl solutions by gravimetric assays. Extracts were mechanically obtained, concentrations were fixed and characterized by phytochemical testing and FTIR analysis, and the nature of inhibition was determined by calculation of Gibbs Free Energy. It was established that the extracts have the presence of tannins, saponins, and antioxidant compounds, which was corroborated by the FTIR analysis, showing peaks of absorbance corresponding to groups OH and COOH, with the endocarp extract presenting the highest proportion. Endocarp extracts with 5% concentration showed better performance in inhibiting corrosion than extracts obtained from epicarp, with percentages of 97.71 when inhibiting HCl and 73.91% with NaCl. The presence of tannins, saponins, and antioxidant compounds inextracts of the endocarp and epicarp favour inhibition of metal corrosion. [ABSTRACT FROM AUTHOR]

Statistical optimization was used to optimize corrosion inhibition efficiency of Sapium ellipticum leaf extract as corrosion inhibitor of aluminum in acid medium. Response surface methodology was applied, and the effects of four independent variables; acid concentration, inhibitor concentration, temperature, time, and their expected responses were determined. Central composite design a statistical tool was used to generate a total of 16 individual experimental runs, which was previously design to study the effects of these variables during corrosion process. The uniqueness of the model was scrutinized with various criteria including coefficient of determination (R2 = 0.987), p value (< 0.0001), adequate precision (30.22) and coefficient of variation (5.30). The RSM is well fitted in the model which adequately predicted the optimum inhibition efficiency of 96.73% at optimum inhibitor concentration of 1.5g/L-1, acid concentration 1 M, temperature of 303 K and time of 6 hours. Also the electrochemical concept signifies that Sapium ellipticum acts as a mixed-kind inhibitor. The experimental data obtained is in conformity with other research works. [ABSTRACT FROM AUTHOR]

The results of laboratory studies concerning corrosion inhibitors that make it possible to decelerate the metal dissolution in heat-and-power equipment during its chemical cleaning are presented. The features of the decrease in the carbon steel corrosion rate using commonly known corrosion inhibitors, such as urotropin, captax, and thiourea, as well as an imported reagent based on alkylbenzene dimethylammonium chloride (hereinafter referred to as IK), are considered. An effect of the process temperature and the concentration of inhibitors exerted on their protective properties and the kinetics of metal corrosion is analyzed. In the first part of the paper, it is shown—based on the gravimetric method for corrosion testing—that the efficiency of captax, captax with neonol AF 9-12, thiourea (0.05 wt %), and reagent IK (0.2 wt %) at a temperature of 70–80°С for the protection of carbon steel from corrosion in a 5% solution of ammonium monocyrate amounts to 60–77%, which is higher than that with the use of urotropin. The high efficiency of inhibitors in the deceleration of steel corrosion in the 5% solution of ammonium monocyrate is caused by a strong inhibition of both electrode reactions of the metal. The results of corrosion tests using a polarization resistance technique are presented. Two parts of a decrease in the steel corrosion rate are clearly distinguished on the curves of an instantaneous corrosion rate. The decrease is caused by the formation of a protective film with the participation of an inhibitor and a subsequent stabilization of this film. The results of corrosion tests in the solutions of ammonium monocyrate with added inhibitors, such as captax, captax + AF 9-12, and reagent IK, that confirm the low instantaneous corrosion rate of carbon steel are discussed. These compositions could be used for chemical cleaning of heat-and-power equipment as well as for increasing its efficiency and reducing repair costs. [ABSTRACT FROM AUTHOR]

Herein, An examination into the corrosion inhibition of mild steel (MS) in 1.0 M HCl by the Chicoriumintybus extract as a green inhibitor had been achieved via chemical, electrochemical and morphological measurements. The effect of KI additives on corrosion inhibition efficiency was carried out using a weight loss method. The results reveal that the Chicoriumintybus extract inhibited the corrosion reaction by adsorption onto the metal/solution interface. Inhibition efficiency, increased with the Chicoriumintybus concentration and synergistically increased with the presence of KI. The addition of iodide ions to the Chicoriumintybus extract raises inhibition efficiency of 74 to 99%. Polarization data suggest that the Chicoriumintybus extract acts as a mixed inhibition-mechanism. This observation was further corroborated by the fit of experimental adsorption data to the Temkin isotherm. The results were confirmed by AFM, SEM images and ATR-IR for the surface morphology. [ABSTRACT FROM AUTHOR]

The corrosion inhibition performance of linoleic acid (LA) for 1018 carbon steel in 0.5 M H 2 SO 4 solution was evaluated by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and weight loss measurements. These tests were complemented by theoretical calculations using density functional theory (DFT). The inhibition efficiency increased with increasing the LA concentration but it decreased with an increase in the temperature. LA was found to be a mixed type inhibitor which is physically adsorbed on to carbon steel by following the Langmuir adsorption isotherm. Theoretical studies suggest that LA is a more effective inhibitor in acidic media than in neutral environments. Thus, in acidic media LA had the highest E HOMO value, the best chemical reactivity, the greatest tendency to transfer electrons and a greater facility of modifying its electronic configuration in presence of carbon steel specimens according to its chemical hardness value. Finally, the Tomasi Polarized Continuum Model to explain the LA adsorption on to the metal is provided. Image 1 • 1018 carbon steel was corroded in 0.5 M H 2 SO 4 solution. • Linoleic acid was added as inhibitor. • Inhibitor efficiency increased with inhibitor concentration but decreased with temperature. • Theoretical studies suggest that LA is a more effective inhibitor in acidic media than in neutral environments. • a model to explain the LA adsorption on to the metal is provided. [ABSTRACT FROM AUTHOR]

A comparison study in terms of inhibition performance between oil palm empty fruit bunch (OPEFB) extract and OPEFB powder against mild steel corrosion in 1 M hydrochloric acid was evaluated using weight loss technique and adsorption isotherms. OPEFB extract and powder were prepared at various concentrations of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (v/v) and dosages of 0.2, 0.4, 0.6, 0.8, and 1.0 g, respectively. The results showed that OPEFB extract achieved higher inhibition efficiency (IE) at high concentration and short immersion time compared to OPEFB powder. Despite having lower IE, OPEFB powder seemed to have better behavior; 6.6% IE increment at longer immersion time, gradual release of active compounds and stronger adsorption capacity. Fourier transform infrared (FTIR) and energy‐dispersive X‐ray studies confirmed the presence of active compounds in OPEFB extract and powder that is responsible for inhibition. Thermodynamic study revealed that both OPEFB extract and powder obeyed Langmuir isotherm and worked through physical adsorption. Overall, OPEFB powder is concluded to have better performance as corrosion inhibitor compared with OPEFB extract. [ABSTRACT FROM AUTHOR]

The method of reflective ellipsometry has been used to study the adsorption of the IFKhAN-92 inhibitor that is a triazole derivative on 12Kh18N10T nickel–chromium steel from dilute solutions of HCl and H2SO4 (t = 20 ± 2°C). It is shown that the adsorption process of this inhibitor is satisfactorily described by Temkin isotherm; its parameters are calculated. The values of free energy of adsorption of the inhibitor determined on the basis of this isotherm are ≈55 kJ/mol, which allows one to conclude about the chemisorption nature of the interaction of triazole molecules and the metal surface. An increase in the adsorption of the IFKhAN-92 inhibitor on chromium–nickel steel in H2SO4 solution with the addition of rhodanide-anions has been noted. [ABSTRACT FROM AUTHOR]

The anticorrosive potential of Ficus hispida leaf extract (FHLE) as a corrosion inhibitor in 1 M HCl was investigated using weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Stigmasterol as the major constituent of F. hispida was confirmed by Gas Chromatography–Mass Spectrometry (GC–MS). Inhibition efficiency of 90% was achieved with 250 ppm of FHLE at 308 K. Temperature studies revealed an increase in inhibition efficiency with decrease in temperature and activation energies increased in the presence of the extract. Cathodic and anodic polarization curves revealed that FHLE acts as mixed type inhibitor, but cathodic effect was more pronounced. Impedance diagrams showed that increasing FHLE concentration, increased charge transfer resistance and decreased double layer capacitance. The adsorption of FHLE on mild steel surface obeyed Langmuir adsorption isotherm. The morphology of the surface was examined by scanning electron microscopy (SEM) and the surface composition was evaluated using energy-dispersive X-ray (EDX) spectroscopy to verify the presence of inhibitor on the mild steel surface. The adsorbed film on the mild steel surface containing the FHLE inhibitor was also characterized by diffuse reflectance Fourier transform infrared spectroscopy (DRFT-IR) and X-ray diffraction (XRD) studies. [ABSTRACT FROM AUTHOR]

• The inhibition of S235JR steel in HCl by poly(2-ethyl-2-oxazoline)(PO) is studied. • Myristyltrimethylammonium bromide (MTAB) and KI effect on PO is examined. • PO average inhibition efficiency (η) is 80 % at 1000 mg/L. • The additives synergistically enhanced the performance of PO. • PO + MTAB + KI can offer ∼ 99 % inhibition and corrosion rate of 0.09 mm/y after 72 h. Organic compounds that exhibit little or no toxicity, have high solubility properties, and are affordable are highly sought after as metal corrosion inhibitors. The key to formulating an effective and economically viable corrosion inhibitor is the identification of compounds with strong synergistic effects. The synergistic inhibition of S235JR carbon steel in 1 M HCl by poly(2-ethyl-2-oxazoline) (PO), KI, and myristyl trimethylammonium bromide (MTAB) is studied. The durability of the PO + KI + MTAB blend is examined for up to 72 h. Results reveal an average inhibition efficiency (η) of 80 % for PO at 1000 mg/L. Adding 5 mg/L KI or MTAB to 1000 mg/L PO raised η to 97 % or 94 % from EIS measurements. PO(1000 mg/L) + KI(5 mg/L) + MTAB(5 mg/L) produced ∼ 99 % inhibition and kept the corrosion rate at 0.09 mm/y for up to 72 h. Spectroscopic and computational studies reveal PO interacted with the steel surface making use of the carbonyl functional group. The DFT calculations and MD simulations confirm the favorable tendency of the PO molecule to adsorb on the metal surface and the synergistic adsorption with KI and MTAB. Furthermore, SEM and AFM results confirm the high inhibitive performance of the blend. PO + KI + MTAB blend is highly recommended for long-term acid pickling of a metal surface and acid cleaning of plants. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effectiveness of Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione), for mitigating the deterioration of mild steel (MS) in 1 M HCl by using an expired drug. • Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) studies were performed to measure the -efficiency and to explain the adsorption isotherm. • To analyze thermodynamic and kinetic parameters at higher temperatures. • Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), atomic force microscopy (AFM) techniques and contact angle measurements (CA). The research undertaken highlights the effectiveness of pharmaceutical drug Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione) (PB) as inhibitor to mitigate corrosion of mild steel (MS) in 1 M HCl. Corrosion studies were done by electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in the absence and presence of the Phenobarbitone (PB) drug. Kinetic parameters were calculated by studying the corrosion rate at different temperatures. Results were fitted into suitable adsorption isotherm and from the adsorption data thermodynamic parameters were computed and discussed in detail. Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), and atomic force microscopy (AFM) techniques. The nature of the protective layer formed over the metal was studied by measuring the contact angle (CA), which demonstrated the formation of the adsorbed inhibitor layer. Inhibition efficiency increased with increase in concentration of inhibitor and with increase in temperature. For the addition of 0.04 gL-1, the maximum corrosion inhibition efficiency of 78.3 % was achieved at 313 K. Inhibitor acted as a mixed inhibitor with more control over the anodic reaction. Increase in efficiency with increase in temperature suggested the possibility of chemical adsorption. Inhibitor obeyed Langmuir adsorption isotherm, supporting chemical adsorption. Surface morphology clearly demonstrated the formation of barrier film on the surface of metal which prevented further dissolution of metal thereby decreasing the corrosion rate. [ABSTRACT FROM AUTHOR]

This study investigated synergistic effect of temperature, solution velocity, and sulphuric acid concentration on corrosion behaviour of carbon steel using response surface methodology. Electrochemical and surface characterisation techniques were employed. A statistically significant mathematical model was obtained, correlating corrosion rate to the environmental parameters. Temperature affected anodic reactions, while solution velocity influenced cathodic reactions. Acid concentration profoundly influenced corrosion mechanisms by altering deposition, dissolution, and properties of FeSO 4 surface layer. The lowest corrosion rate was 0.546 mm/year at 35 ° C , 98.5 wt%, 0 rpm, and the highest was 368.223 mm/year under 70 ° C , 49 wt% and 500 rpm. • Corrosion behaviour of carbon steel using response surface methodology was studied. • Synergistic effect of temperature, solution velocity, and acid concentration was investigated. • A statistically significant mathematical model for corrosion rate was obtained. • Temperature affected anodic reactions, while solution velocity influenced cathodic reactions. • Acid concentration influenced corrosion mechanisms by altering FeSO 4 surface layer. [ABSTRACT FROM AUTHOR]

In the realm of oil and natural gas, material durability is compromised by sand particle abrasion, corrosive media, and hydrogen-induced cracking. This study investigates the impact of PTFE on wear and corrosion resistance of Ni-P coatings in a CO 2 environment. Hydrogen barrier properties of the substrate, Ni-P, and PTFE are evaluated using the Devanathan-Stachursky cell. Results show that incorporating PTFE enhances the coating's wear and corrosion resistance, and hydrogen barrier performance compared to substrate and Ni-P alone. The coating effectively hinders corrosive media transmission. A comprehensive analysis of the Ni-P-PTFE corrosion mechanism is provided, along with a robust corrosion model. • Examined the influence of varied PTFE levels on morphology and wear traits of chemically deposited Ni-P coatings. PTFE's innate hydrophobicity reduces grain size. A minor PTFE addition enhances hardness via dispersion strengthening. Simultaneously, PTFE's self-lubrication reduces direct material-wear debris contact, bolstering wear resistance. • Examined PTFE's hydrogen barrier in the petroleum sector. PTFE notably fortified hydrogen resistance, curbing coating's hydrogen-induced cracking susceptibility. This, ascribed to enhanced coating integrity, curtails hydrogen ingress, thus minimizing cracking. • Conducted an extensive study on Ni-P-PTFE coating's corrosion resistance in CO2-saturation. PTFE improved surface integrity, functioning as a corrosion inhibitor via stable C-F bonds. The "maze effect" by PTFE and Ni-P thwarted corrosive media. • An in-depth analysis of the corrosion mechanism of Ni-P-PTFE in a saturated CO2 environment yielded a robust corrosion model, offering a thorough elucidation of the excellent CO2 saturation corrosion resistance of Ni-P-PTFE coatings. [ABSTRACT FROM AUTHOR]

• Methanolic Ustilago maydis extract was obtained. • It was used as corrosion inhibitor for 1018 carbon steel in 0.5 M H 2 SO 4. • Weight loss and electrochemical tests were carried out at 25, 40 and 60 °C. • Quantum chemical calculations using DFT technique were carried out. A study on the use of Ustilago maydis extract as a green corrosion inhibitor for 1018 carbon steel in 0.5 m H 2 SO 4 by using gravimetric, potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy electrochemical techniques at 25, 40 and 60 °C. Density functional theory (DFT) calculations were performed to know the relationship between inhibitor electronic properties and inhibition efficiency. Weight loss results indicated that Ustilago maydis was a good corrosion inhibitor with an efficiency that increased with its concentration but decreased with the temperature. However, the efficiency was around 60% because it was physically adsorbed on to the steel surface according to a Langmuir type of adsorption isotherm obtaining relatively low free energy values, which lied between −14.8 and −27 kJ/mol at 25 and 60 °C respectively. Activation energy decreased in presence of Ustilago maydis making corrosion process more difficult to occur. Potentiodynamic polarization curves showed a decrease in the corrosion current density in one order of magnitude and determined this extract as a cathodic type of corrosion inhibitor affecting. There was no evidence of a passive film, whereas the corrosion mechanism was controlled by the adsorption/desorption of some intermediate species and the double electrochemical layer resistance increased with the addition of the inhibitor. Gas chromatography showed that the main compounds found in this extract included D-Mannose, β-D-Glucopyranose,4-O-β-D-galactopyranosyl, Melibiose and Arabinose, whereas quantum chemical calculations by density functional theory analysis showed that Melibiose had the highest inhibition efficiency because it had the highest E HOMO value and lowest gap energy value, ∆ E. [Display omitted] [ABSTRACT FROM AUTHOR]

• The passive film properties of Ce-added AlCoCrFeNi 2.1 alloys are studied for the first time. • Ce addition is not conducive to corrosion resistance of the AlCoCrFeNi 2.1 alloy in H 2 SO 4 solution. • Ce increases the doping density and reduces the proportion of Cr oxides in the passive film. Eutectic high-entropy alloys (EHEAs), represented by AlCoCrFeNi2.1, are considered to be promising materials. However, the study of the corrosion behavior of EHEAs remains limited, which hinders further development. This study investigated the effect of Ce addition on the electrochemical behavior and passive film properties of AlCoCrFeNi 2.1 EHEAs in H 2 SO 4 solutions. The results show that the addition of Ce changed the properties of the passive film formed on the alloys, resulting in reduction in the proportion of Cr 2 O 3 , and thereby reduced the corrosion resistance. Moreover, a higher Ce content in the EHEAs was found to correspond to a more pronounced deterioration in corrosion resistance. Compared with the film formed at 0.2 V vs SCE , the film formed at 0.5 V vs SCE exhibited more optimal physicochemical properties, leading to a decrease in the passive current density. Notably, Ce was absent in the film formed at 0.2 V vs SCE , but present at 0.5 V vs SCE. [ABSTRACT FROM AUTHOR]

The study examined the effectiveness of Berlinia grandiflora (BEG) and cashew (CEG) exudate gums in protecting mild steel from corrosion in 1 M HCl solution using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP). The corrosion products were analyzed using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDX), atomic force microscopy (AFM), Fourier Transformed Infrared spectroscopy (FTIR), and optical profilometry. Results indicate that the exudate gums are effective against the corrosion of mild steel in an HCl solution. The EIS results reveal that the charge transfer resistance of the metal in the acid solution increased from 82.2 Ω cm2 to 1074.0 Ω cm2 and 325.1 Ω cm2 in the presence of 1000 ppm BEG and CEG, respectively corresponding to inhibition efficiency (η) of 92% and 75% at 25 °C. The Gum's performance depends on immersion time and temperature. It improves with an increase in immersion time up to 48 h but thereafter slightly diminishes. The η of 1000 ppm of BEG and CEG after 48 h of immersion is 76% and 67%, respectively at 30 °C. With a temperature rise, η of BEG appreciates to 80% while that of CEG depreciates to 57% at 60 °C after 24 h of immersion. Both BEG and CEG retard the metal corrosion through an adsorptive mechanism whereby it blocks the active corrosion reaction sites on the surface. The adsorption was confirmed by SEM/EDX, AFM, UV–vis, and FTIR. BEG and CEG are promising and sustainable sources for metal corrosion inhibitor formulations. [Display omitted] • BEG and CEG were assessed as sustainable corrosion inhibitors for mild steel in acid medium. • BEG and CEG are effective in protecting mild steel. Inhibition efficiency increases with concentration. • BEG extract outperformed CEG under all testing conditions. • The exudate gums exhibited features peculiar with mixed-type inhibitors. • The inhibition performance of BEG increased with temperature while CEG decreased. [ABSTRACT FROM AUTHOR]

Aiming at the acid-etched freeze-thaw rock for geotechnical engineering in cold regions, chemical damage variables, freeze-thaw damage variables, and force damage variables were introduced to define the degree of degradation of rock materials, the law of damage evolution, the total damage variable of acid-corroded rock under the coupling action of freeze-thaw and confining pressure was deduced. The continuous damage mechanics theory was adopted to derive the damage evolution equation and constitutive model of acid-eroded rock under the coupling action of freeze-thaw and confining pressure. The theoretical derivation method was used to obtain the required model parameter expressions. Finally, the model’s rationality and accuracy were verified by the triaxial compression test data of frozen-thawed rocks. Comparing the test curve’s peak point with the peak point of the model theoretical curve, the results show that the two are in suitable agreement. The damage constitutive model can better reflect the stress-strain peak characteristics of rock during triaxial compression, verifying the rationality and reliability of the model and the method for determining the model parameters. The model extends the damage model of rock under the coupling action of freeze-thaw and confining pressure in the chemical environment and further reveals the damage mechanism and failure law of acid-corroded rock under the coupling action of freeze-thaw and confining pressure.

A component of Salvia hispanica, α-linolenic acid, has been evaluated as a green corrosion inhibitor for 1018 carbon steel in 0.5 M sulfuric acid using weight loss tests, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Theoretical calculations using Density Functional Theory (DFT) were used also. The results have shown that this compound is a good corrosion inhibitor, with an efficiency which increased with an increase in its concentration up to 600 ppm, but it decreased with a further increase in the concentration. α-linolenic acid formed protective corrosion products layer because it was chemically adsorbed onto the steel surface according to a Langmuir type of adsorption isotherms. Polarization curves have shown that α-linolenic acid is a good, mixed type of inhibitor with a predominant effect on the cathodic hydrogen evolution reactions. EIS measurements indicated a charge transfer-controlled corrosion process. DFT calculations indicated that α-linolenic acid was more efficient in an acidic environment than in a neutral one because has a high tendency to donate electrons and can be easily protonated. In addition to this, it had the highest EHUMO value, the best chemical reactivity, the greatest tendency to transfer electrons and a greater facility of modifying its electronic configuration in the presence of carbon steel specimens according to its chemical hardness value.

A supercritical H2O/CO2 turbine is a key piece of equipment for the coal gasification in the supercritical water (CGSW) cycle to achieve conversion of heat into power. Compared with a traditional steam turbine, the working medium of an H2O/CO2 turbine has a relatively high CO2 concentration. In the initial condensation zone (ICZ), steam condenses into droplets on the turbine blades and the droplets combine with CO2 to form carbonic acid, which corrodes the turbine blades. In order to research the characteristics of acid corrosion in the ICZ of a H2O/CO2 turbine, the acid corrosion rate of the blades in the ICZ of the H2O/CO2 turbine was calculated and analyzed based on the three-dimensional CFD (3D CFD) method and a one-dimensional numerical model of CO2 corrosion. The results suggest that acid corrosion rates decrease stage by stage in the ICZ due to the reduction in temperature and pressure. Rotor blades in the first stage in the ICZ suffer the worst and form a corrosion zone at the trailing edge of the blade and on the pressure surface. The decline of efficiency caused by corrosion settles down to a relatively steady value of 0.6% for a 10 year service time. Moreover, the corrosion area for the last two stages shrinks with the service time due to the rearward movement of the ICZ.

The methanolic extract of Peumus boldus (P. boldus) has been studied as a potential green corrosion inhibitor for carbon steel in 0.5 M H2SO4 using gravimetric, potentiodynamic polarization and electrochemical impedance spectroscopy tests at 25, 40 and 60°C, and concentrations of 0, 0.1, 0.3, 0.5, 0.7 and 1.0 g/L. Results indicate that P. boldus is physically adsorbed onto the steel surface and acts as a mixed corrosion inhibitor of carbon steel corrosion. The data fitted best to the Temkin adsorption isotherm. The inhibition efficiency of P. boldus extracts was observed to increase with increasing its concentration but decreases on increasing the test temperature. The inhibitive effect is attributed to the presence of vitamin E, Limonene and eucalyptol in the extract.

The anticorrosion effect of 5-hydroxytryptophan (5-HTP) on mild steel (MS) was investigated by gravimetric and electrochemical techniques. Two different concentrations (1 M and 15%) of hydrochloric acid were used to simulate well-acidizing fluid. The results show that 10 × 10−5 M 5-HTP is 96.1% efficient in 1 M HCl and 78.1% efficient in 15% HCl at 30 °C. The efficiency decreases as the temperature increases, reaching 66.9% and 39.8% in 1 M and 15% HCl, respectively, at 90 °C. When 5-HTP is blended with potassium iodide and glutathione, the efficiency increases to above 88% and 78% in 1 M and 15% HCl, respectively, at 90 °C. Increasing the 5-HTP concentration decreases the double-layer capacitance and increases the charge-transfer resistance. 5-HTP behaves as a mixed‐type corrosion inhibitor with anodic predominance and is spontaneously adsorbed on the steel surface. Physisorption of 5-HTP is best described by the Langmuir adsorption model and is also exothermic with a resultant decrease in the entropy of the bulk solution. The results of SEM/EDAX, FTIR and UV–VIS studies support the hypothesis that a protective film of 5-HTP forms on MS facilitated by O, N and CC functionalities.

The influence of an aromatic hydrazide derivative, 2-(3,4,5-trimethoxybenzylidene) hydrazinecarbothioamide (TMBHC) as corrosion inhibitor on mild steel in 1 M hydrochloric acid was studied by Tafel polarization and electrochemical impedance spectroscopy (EIS) technique. The results showed that the inhibition efficiency (% IE) of TMBHC increased with increasing inhibitor concentrations and also with increase in temperatures. TMBHC acted as a mixed type of inhibitor and its adsorption on mild steel surface was found to follow Langmuir’s adsorption isotherm. The evaluation of thermodynamic and activation parameters indicated that the adsorption of TMBHC takes place through chemisorption. The formation of protective film was further confirmed by scanning electron microscopy (SEM).

Modazar drug was tested as corrosion inhibitor for carbon steel in 1 M HCl solution using chemical (weight loss and gasometric) and electrochemical (open {circdeg;}uit potential, potentiodynamic polarization, electrochemical frequency modulation and electrochemical impedance spectroscopy) techniques. The results showed that the inhibitory efficiency increased with the increase in drug concentration reaching a maximum value of 92.3% at 300 ppm while it decreases with increasing the temperature. Polarization curves showed that Modazar drug is a mixed type inhibitor but the cathode is more polarized than the anode. The drug was adsorbed physically on the C-steel surface obeying Langmuir adsorption isotherm. The morphology of the surface of the specimens was analyzed using atomic force microscopy, energy dispersion spectroscopy and scanning electron microscopy. The results obtained from chemical and electrochemical techniques are in good agreement.