Imidazoline-based Inhibitor Research Articles

Imidazoline As a Volatile Corrosion Inhibitor for Mitigation of Top- and Bottom-of-the-Line CO2 Corrosion in Carbon Steel Pipelines.

A fatty acid imidazoline-based inhibitor was synthesized via a facile solvent-free synthesis method between tall oil fatty acid (TOFA) and diethylenetriamine (DETA) under atmospheric conditions with a short reaction time. The as-synthesized imidazoline (S-Imd) acted as an effective inhibitor for reducing or preventing corrosion of carbon steel pipelines at both bottom of the line (BOL) and top of the line (TOL) positions under simulated conditions of a gas pipeline in a CO2-saturated environment. The inhibition efficacy was examined by both weight loss and electrochemical measurements, such as the electrochemical impedance spectrum (EIS), potentiodynamic polarization (PDP), and linear polarization resistance (LPR). The results revealed that the S-Imd, 2-(8-heptadecenyl)-2-imidazoline-1-ethanamin, at 300 ppm exhibited a superior inhibition efficiency of up to 91.6 and 89.9% for BOL and TOL corrosion tests, respectively. The surface morphology of the carbon steel test specimens was also examined using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), and contact angle analysis. It was found that the as-synthesized S-Imd acted as a mixed-type inhibitor that exhibited a decreased surface roughness and oxide layer on carbon steel surfaces. However, the water contact angle was found to increase, implying enhanced hydrophobicity of the surface. Adsorption of the imidazoline molecules on carbon steel surfaces followed the Langmuir adsorption isotherm. The present work provides very promising results in the synthesis and utilization of the studied imidazoline as a volatile corrosion inhibitor (VCI), especially for carbon steel pipelines in petroleum industries.

Effect of akyl chain length, flow, and temperature on the corrosion inhibition of carbon steel in a simulated acidizing environment by an imidazoline-based inhibitor

An imidazoline, 2-heptadecyl-1-[2-(octadecanoylamino)ethyl]-2- imidazoline (QSI) with -C17H35 as the tail chain length was synthesized, characterized, and studied as corrosion inhibitor for low carbon steel in 15% HCl solution under static and hydrodynamic conditions. Influence of addition of KI, temperature, and chain length of pendant hydrocarbon on inhibition efficiency (η) was also examined. It is found that, QSI exhibits a mixed type behavior but fairly inhibited the corrosion of low carbon steel in the studied medium. The maximum concentration studied (400 mg/L) afforded η of <50%. Addition of KI to QSI synergistically enhanced the corrosion inhibition performance of QSI, upgrading the η to approximately 90%. Increase in the system temperature increases the η of both QSI and QSI + KI. From the variation of η with temperature and the calculated corrosion kinetic parameters, chemical adsorption is proposed as the adsorption mechanism of the additives. QSI performs better under hydrodynamic condition than static condition. However, the corrosion resistance of the metal decreases at rotation speed higher than 1000 rpm. Inhibition efficiency of imidazoline decreases as the length of the hydrocarbon pendant chain increases. Imidazoline compounds with -C13H27 and -C15H31 as the length of the pendant group hydrocarbon perform better than QSI with -C17H35.

Corrosion inhibition of mild steel by the hydrolysate of an imidazoline-based inhibitor in CO2-saturated solution.

The synthesized imidazoline phosphate quaternary ammonium salt has low stability, which is spontaneously and rapidly hydrolyzed to the long-chain fatty acid amide (LFA). The hydrolysate (LFA) has been found to be an efficient inhibitor for Q235 steel against CO2 corrosion, which yields a maximum value above 90% at a concentration of 1000 mg L−1. The LFA inhibitor acts as an anodic type inhibitor and its inhibition mechanism is a “negative catalysis effect”. The heteroatoms in the acyl, amine and phosphate groups in the LFA molecule are the active centers to bond with Fe atoms to form a chemisorbed film on the steel surface.

Localized CO2 corrosion of carbon steel with different microstructures in brine solutions with an imidazoline-based inhibitor

CO2 corrosion behavior of carbon steel with different microstructures (H steel: coarse laminar pearlite; T steel: globular and shot rod shaped pearlite) was analyzed in 3 wt.% NaCl solution at 60 °C with imidazoline-based inhibitor by electrochemical and weight loss methods. Electrochemical measurements showed that, compared to H steel, the inhibitor film adsorbed on T steel had a higher pitting corrosion resistance and the inhibition efficiency for T steel was larger at each concentration of inhibitor. Weight loss results exhibited that both steels suffered general corrosion in absence of inhibitor; however, localized corrosion was observed on the samples with insufficient concentration of inhibitor. H steel suffered more severe localized corrosion than T steel, it was related to that H steel had a higher density of dislocations in the pearlite area and the larger driving force for galvanic corrosion. The localized corrosion on H steel mainly distributed on the laminar pearlite area.

Lucky Switcheroo: Dramatic Potency and Selectivity Improvement of Imidazoline Inhibitors of Human Carbonic Anhydrase VII.

A substantial improvement of potency and selectivity of imidazoline-based inhibitors of hCA VII (a promising target for the treatment of seizures and neuropathic pain) was achieved by simply switching the position of the benzenesulfonamide moiety from N1 (as in the earlier reported series) to C2. Selectivity indices vs the off-target isoforms (hCA I, I, I and IV) greater than 100 were reached, which is exceedingly rare for hCA VII inhibitors. The drastic profile improvement of the new series has been rationalized by an additional hydrogen bonding with the nonconserved Q69 residue in the active site of hCA VII (absent in the other three isoforms studied), which also results in a favorable accommodation of the inhibitor's lipophilic periphery in the nearby hydrophobic pocket. The robustness of the docking simulations was tested and confirmed by molecular dynamics simulations.

Assembly of succinic acid and isoxazolidine motifs in a single entity to mitigate CO2 corrosion of mild steel in saline media

Inhibition of CO2 corrosion of mild steel in 0.5M NaCl under atmospheric pressure at 40°C as well as high pressure (10bar) at 120°C by 2-[2-methyl-4(or 5)-alkylisoxazolidin-5(or 4)-yl)methyl]succinic acids, a new class of molecules having inhibitive motifs of succinic acid, isoxazolidine and hydrophobic alkyl chain assembled in a single entity, has been examined by gravimetric and electrochemical methods. Inhibitor molecule containing CH3(CH2)8 outperformed its counterpart with a shorter hydrophobe CH3(CH2)4 and two other commercial imidazoline-based inhibitors. The effectiveness of these new inhibitors was also evaluated by electrochemical impedance spectroscopy. The inhibition efficiency by EIS was found to be 75%, 91% and 98% in the presence of 1, 5 and 20ppm, respectively, at 40°C. The potentiodynamic polarization studies indicated that the new inhibitors act as anodic inhibitors. The adsorption of the synthesized inhibitors follows Temkin adsorption isotherm model with favorable high values of –ΔG°ads and −ΔH°ads pointing the inhibitors adsorbed on the metal surface by chemisorption process. The XPS study confirmed the adsorption of the inhibitors on the metal surface.

Inhibition of the corrosion of X70 and Q235 steel in CO2-saturated brine by imidazoline-based inhibitor

Potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss methods were used to study the inhibition of the corrosion of X70 and Q235 steels in CO2-saturated 3wt% NaCl solution with various concentrations of imidazoline-based inhibitor. The inhibition efficiencies for X70 and Q235 reached 97.8% and 98.6%, respectively, with sufficient concentration of inhibitor. The results indicated that, the inhibition efficiencies for X70 and Q235 were dramatically different with low concentration of inhibitor. Compared with X70, Q235 exhibited higher inhibition efficiency and stronger adsorption ability because of the larger amount and more homogeneous distribution of carbides. The adsorption of the inhibitor on the metal surface consisted of a mix of physisorption and chemisorption and was observed to follow the Langmuir adsorption isotherm.

The behavior of pre-corrosion effect on the performance of imidazoline-based inhibitor in 3 wt.% NaCl solution saturated with CO2

An imidazoline-based inhibitor was synthesized, characterized and tested as a corrosion inhibitor for low alloy steel in CO2-saturated 3wt.% NaCl solution at 60°C. The influence of pre-corrosion on inhibition efficiency of the inhibitor was evaluated. The results showed that the inhibitor had excellent inhibition effectiveness on freshly abraded samples, with an inhibition efficiency of 98.7% in the presence of 2.4390×10−5mol/l inhibitor. The adsorption of the inhibitor on the steel surface was found to obey Langmuir's adsorption isotherm and chemisorption. Pre-corrosion had a detrimental effect on the inhibitor performance, significant localized corrosion was observed on the pre-corroded samples with 1.2195×10−5mol/l inhibitor after 96h immersion. The differences in inhibition efficiency of the inhibitor for samples pre-corroded for different time were related to the different corrosion products and the increase of surface area after pre-corrosion.

Tests of Imidazoline-Based Corrosion Inhibitors for Low-Carbon Steel Tending to Absorb Hydrogen in Acidic Media

The protective action of imidazoline-based corrosion inhibitors for low-carbon steel tending to absorb hydrogen in acidic media is studied using impedance spectroscopy and breaking tests. It is shown that commercial inhibitors FLEK-IK 201 A and FLEK-IK 201 B reduce corrosion and the hydrogen-absorption rate, having an St3 steel-protection degree above 80%, and lower the strength-loss coefficient of steel-wire samples in acidic H2S-containing media to 1.3-4.3%.

A Review of CO2Corrosion Inhibition by Imidazoline-based Inhibitor

Carbon dioxide (CO2) corrosion is one of the most significant forms of attack in the oil and gas production and transportation systems. Corrosion inhibitors have been widely used in an effort to reduce the detrimental effect of the corrosion process. Different types of corrosion inhibitors have been applied for this purpose. The most frequent is the imidazoline-based inhibitors (IM), owing to their good adsorption characteristics and film-forming capability. Albeit their extensive use, their inhibition mechanism is not fully understood. This paper highlights the inhibition mechanism of IM and also the factors that contribute to its inhibition mechanism.

A New Approach for Predicting Inhibited Erosion-Corrosion in CO2-Saturated Oil/Brine Flow Condition

Summary Chemical inhibition is a common method for controlling erosion-corrosion in offshore mild steel pipelines, tubing and pipe fittings. This paper introduces a new approach for predicting inhibited erosion-corrosion in mild steel pipes, including the effects of flow and environmental conditions, sand production, and an oil phase. When sand is produced, sand particle impingement on piping surfaces can decrease the efficiency of corrosion protection systems, such as iron-carbonate scale formation or chemical inhibition, and can result in severe corrosion and even pitting. The need to be able to predict inhibitor performance under sand-production conditions is particularly acute when the wells are deep or offshore because of the difficulty in running coupon tests to evaluate the inhibitor efficiency at critical points throughout a system. The research reported in this paper is aimed at providing producers with information that will help them make decisions on the design of the well given advanced knowledge of the inhibition options and their predicted effectiveness under sand-production conditions. Inhibition mechanisms and the relation between inhibitor concentration and inhibitor coverage are described using adsorption isotherms. The Frumkin isotherm showed the best fit to experimental data for an imidazoline-based inhibitor used in sand-free conditions. Flow-loop tests indicated that sand particle erosion decreased the efficiency of the inhibitor. However, Frumkin isotherms modified to handle effects of erosivity, temperature, and oil phase were successfully fitted to erosion-corrosion data. Inhibitor adsorption isotherms, for both sand-free and sand-production conditions, were integrated into a mechanistic model for prediction of CO2 corrosion rates as a function of inhibitor concentration, and good results were obtained when compared with data. Results of this study show that the inhibitor adsorption isotherm, modified to handle effects of sand production, temperature, and oil phase, can be a valuable tool for predicting inhibited metal loss rates under sand-production conditions.

Inhibition of CO2 Corrosion of X52 Steel by Imidazoline-Based Inhibitor in High Pressure CO2-Water Environment

The influence of imidazoline-based inhibitor on the formation, microstructure, and thickness of the corrosion product film that formed on X52 steel after exposure in an environment of high pressure CO2 containing formation water at high temperature was studied by using weight loss measurement, linear polarization resistance, scanning electron microscopy, energy dispersive x-ray, x-ray diffraction, and x-ray photoelectron spectroscopy. The results showed that the inhibitor significantly influenced the surface morphology and thickness of the corrosion product film. The severity of localized corrosion (pitting) increased with decreased inhibitor concentration. Inhibitor efficiency was observed to be strongly affected by the concentration of inhibitor and CO2 pressure. The corrosion product film was mainly composed of FeCO3.

Reprint of BMCL_19101

The pathogenesis of rheumatoid arthritis is mainly driven by NF-κB-mediated production of cytokines, such as TNF-α. We report herein that the orally available imidazoline-based NF-κB inhibitor, TCH-013, was found to significantly reduce TNF-α signaling and attenuate collagen antibody induced arthritis in BALB/c mice.

Inhibition of CO2 corrosion of carbon steel with 1% Cr

One of the most employed methods for CO2 corrosion control in oil and gas production and transportation industry is the use of carbon and low alloy steels in conjunction with corrosion inhibitors. The inhibitor performance can be influenced by the microstructure and chemical composition of the steel. In previous works, it was shown that 1% Cr addition to carbon steel decreased the protectiveness of a commercial imidazoline-based inhibitor. However, it was suspected that changing the flow rates may modify the inhibitor behaviour. In the present work, the performance of an imidazoline-based inhibitor was investigated on two carbon steels one with the other without 1% Cr, under different flow rates.Corrosion and corrosion inhibition experiments were carried out using a rotating cylinder electrode at different rotation speeds in a deoxygenated 5 wt.% NaCl CO2-saturated solution at 40 °C, pH 6 with and without inhibitor addition. Electrochemical measurements were taken during each experiment and sample surfaces were analyzed after each experiment. Inhibitor performance was found to be dependent on flow velocity and chemical composition of carbon steel.

Characterization and Prediction of Chemical Inhibition Performance for Erosion-Corrosion Conditions in Sweet Oil and Gas Production

The effects of sand erosion on inhibitor performance have been examined in a flow loop using an impinging jet test cell and different techniques such as long-term weight loss (WL), linear polarization resistance (LPR), potentiodynamic polarization (PDYN), 3-D profilometry, and electrochemical impedance spectroscopy (EIS). Inhibition mechanisms and the relation between inhibitor concentration and corrosion penetration rate are described by the Flory-Huggins, Frumkin, Temkin, and Langmuir adsorption isotherms. Flow loop tests indicated that sand particle erosion can decrease the efficiency of an imidazoline-based inhibitor by removing the inhibitor protective layer from the surface. Therefore, an increased concentration of inhibitor is needed during sand production to achieve the same effectiveness. It was shown that an inhibitor adsorption isotherm can be integrated into a mechanistic model for prediction of carbon dioxide (CO2) corrosion to predict CO2 corrosion rates as a function of inhibitor concentration. Also, the inhibitor adsorption isotherm has been modified as a function of erosivity to predict the effect of erosivity on corrosion inhibition. One novel approach is discussed for predicting the inhibited erosion-corrosion rate based on the modified inhibitor adsorption isotherms combined with mechanistic models for predicting CO2 corrosion rates and sand particle erosion rates.

The incidence of chromium-rich corrosion products on the efficiency of an imidazoline-based inhibitor used for CO 2 corrosion prevention

A study has been conducted to analyze the influence of 1% Cr additions, microstructure, and pre-corrosion on the performance of CO 2 corrosion inhibitors for C–Mn steels. Two carbon steels with two different microstructures were tested in a deoxygenated 5 wt.% NaCl solution, saturated with CO 2 at 40 °C, pH 6. An imidazoline-based inhibitor was added after different pre-corrosion periods. Its performance was studied by means of d.c. electrochemical measurements, SEM and EDS. The results demonstrated a detrimental effect of 1% Cr and pre-corrosion on the inhibitor efficiency. It was also proven that the impact of pre-corrosion depends on microstructure and chemical composition.

Templates for wax deposition?

Molecular dynamics simulations have been used to study the behaviour of a liquid mixture of octacosane and heptane between two planar hematite surfaces; one of the surfaces was coated by a monolayer of an imidazoline-based corrosion inhibitor (CI). It was found that the octacosane could be inserted into the CI monolayer when it was aligned with the alkyl tails of the CIs, but the rate for such an insertion was slow. Potential of mean force calculations confirmed that there is a free energy barrier to insertion of octacosane into the CI film, and identified a secondary minimum about 13 A from the surface as a metastable intermediate for insertion. A much more rapid process was adsorption of the octacosane onto the exposed hematite (1012) surface, forming multiple layers and with a packing that was reminiscent of the octacosane crystal structure but with an orientation that matched the topology of the haematite surface.

Inhibition Behavior of Two Imidazoline-Based Inhibitors with Different Hydrophilic Groups in Single Liquid Phase and Liquid/Particle Two-Phase Flow

Two kinds of imidazoline inhibitors with different hydrophilic groups, i.e. hydroxyethyl imidazoline (HEI-11) and aminoethyl imidazoline (AEI-11), were used for resisting CO, corrosion of N80 steel in single liquid phase and liquid/particle two-phase flow. Inhibition performance of these imidazoline inhibitors for CO, corrosion of N80 in 3% (omega) NaCl solution was investigated using polarization curve and electrochemical impedance spectroscopy under static and flow conditions. The results showed that the inhibition efficiency under both static and flow conditions increased according to the following: HEI-11>AEI-11. The inhibition performance of both inhibitors was severely degraded by single liquid phase and liquid/particle two-phase flow at 5 m . s(-1). Additionally, quantum chemical calculation was carried out to correlate the inhibition performance of both inhibitors with their chemical structures and to explain the inhibition mechanism. The theoretical calculation was in good agreement with experimental results.

The effect of pre-corrosion and steel microstructure on inhibitor performance in CO 2 corrosion

The importance of chemical composition and microstructure on CO 2 corrosion of carbon and low alloy steels has been widely recognized, still contradictory results can be found in the literature. The aim of this work is to assess the relationship between microstructure, surface condition and inhibitor efficiency in CO 2 corrosion. A C–Mn steel with two different microstructures was tested in a deoxygenated 5% wt. NaCl solution saturated with CO 2 at 40 °C, pH 6. A commercial imidazoline-based inhibitor was added after different pre-corrosion periods. The results obtained showed that pre-corrosion decreases the inhibitor efficiency, but that its impact is microstructure dependent.

EIS studies of a corrosion inhibitor behavior under multiphase flow conditions

EIS studies of an imidazoline-based inhibitor under multiphase flow conditions were conducted in a large diameter flow loop system. The Warburg diffusion parameter, b f =σω −1/2 was used to qualitatively analyze inhibitor films formed on the metal surface. Experimental results show that the inhibitor films become less porous with increase in exposure time and inhibitor concentration. Inhibition performance of the corrosion inhibitor is reduced in slug flow at high rate of turbulence and bubble impact. This study demonstrates that EIS is an effective technique to investigate the inhibition performance of corrosion inhibitors in turbulent flow conditions.