CO2-containing Solution Research Articles

Salinity effect on corrosion inhibition of 2-mercaptopyrimidine as an inhibitor in CO2-containing solution

In this work, the effects of Cl-, Ca2+, and Mg2+ on the corrosion inhibition performance of 2-mercaptopyrimidine (2-MP) were investigated. The analysis reveals a marked reduction in the inhibition efficiency of 2-MP, from 91.24 % to 76.29 %, as the NaCl content in the solution rises from 1 wt% to 20 wt%. UV–visible absorption spectroscopy and quartz crystal microbalance measurements indicate that the desorption of 2-MP worsens with an increasing content of corrosive ions. Molecular dynamics simulations reveal the inhibitor desorption mechanism. This work enhances understanding of ion effects on corrosion inhibition and film degradation in high salinity environments.

Electrochemical Study on the Macro-Cell Corrosion of Pipeline Steel Partially Covered by Different Kinds of Mineral Deposits.

This study presents the impact of mineral deposits (SiO2, Al2O3, and CaCO3) on the corrosion behavior of X65 pipeline steel in CO2-containing brine solution with low pH. The study investigates the initiation and propagation of under deposit corrosion (UDC) using a wire beam electrode (WBE) partially covered by different mineral deposit layers, in conjunction with electrochemical measurements and surface characterization. The results indicate that the corrosion behavior varies, depending on the characteristics of the deposit. During the test period, the Al2O3-covered steel acted as the main anode with more negative potential, while the bare steel acted as the cathode. The SiO2-covered steel acted as the cathode with more positive potential and a localized FeCO3 layer formed beneath the silica mineral. The CaCO3-covered steel initially acted as an anode with a more negative potential but transformed into the cathode at the end of the test. Additionally, shallow and small pits were observed beneath the deposits with the depth in the sequence Al2O3 > SiO2 > CaCO3.

Corrosion of steel in a CO2-containing solution droplet generated in wet gas pipelines studied by scanning Kelvin probe

A scanning Kelvin probe (SKP) was used to study corrosion of X52 pipeline steel under a CO2-containing solution droplet simulating the water condensate generated in interior of wet gas pipelines. The Volta potential measured by SKP was indicative of the feature of corrosion occurring under the droplet. Three potential zones were observed from the droplet center towards the transition and the side of the droplet, which were -0.1 V, -0.4 V and 0.1 V (Kelvin probe, kp), respectively, after 4 h of testing. The droplet side had the highest Volta potential, which was attributed to corrosion scale generation and precipitation due to a limited solution volume and achieved solubility limit of FeCO3 scale. The transition zone possessed the most negative Volta potential due to a higher corrosion activity than the droplet center with more supply and dissolution of CO2, while the droplet center had the thickest solution. The SKP measurements could estimate the volume evolution of the solution droplet with time at a relatively accurate scale. The solution droplet could maintain its topographic feature, i.e., a spherical cap shape, within 4 h of testing in this work. The increase in droplet concentration due to solution evaporation during testing affected the Volta potential, but slightly only.

Mercaptopropionic acid-modified oleic imidazoline as a highly efficient corrosion inhibitor for carbon steel in CO2-saturated formation water

Two imidazoline derivatives (OI and MOI) were synthesized as highly efficient inhibitors, and their inhibition performances and mechanisms in CO2-containing solution were studied using weight loss measurements, electrochemical tests, surface analysis and theoretical calculations. The results indicate that OI and MOI show excellent inhibition efficiency. Especially for MOI, its inhibition efficiency is as high as 95.58% at 20 ppm. Theoretical calculations confirm that both inhibitors successfully adsorb on metal surface via chemisorption. MOI shows a better inhibition performance than OI, because the sulfhydryl in MOI can be used as a powerful adsorption site, effectively improving the adsorption ability of MOI.

Rosin imidazoline as an eco-friendly corrosion inhibitor for the carbon steel in CO2-containing solution and its synergistic effect with thiourea

Rosin is known as an eco-friendly raw material from natural plants. The main component of rosin is abietic acid. Abietic acid has a carboxyl and a tricyclic phenanthrene skeleton in which conjugated double bonds are present. Conjugation structure will lead to local enrichment of electrons, thereby creating sites that can be used for adsorption. In this case, it is expected that a better performance could be obtained if an inhibitor is synthesized from rosin. In this work, rosin was used to synthesize an imidazoline derivative as a corrosion inhibitor, then the corrosion inhibition performance and synergistic effect with thiourea (TU) of rosin imidazoline (RI) for carbon steel in test solution were studied using weight loss measurement, electrochemical techniques and surface characterization. The results show that the inhibition efficiency of RI reaches 83.8% at 200 mg/L. A further increase in RI concentration does not effectively improve the inhibition performance since the critical micelle concentration of RI is present at around 200 mg/L. The molecular characteristics of RI was analyzed by quantum chemical calculations. It clearly shows that multiple adsorption sites exists in the RI molecular structure, hence RI could offer a good inhibition performance. With the compounding of 200 mg/L RI and 10 mg/L TU, the inhibition efficiency could increase as high as 89.8%, demonstrating a good synergistic effect between RI and TU. The corresponding synergistic mechanisms are also proposed.

The CO2 removal of flue gas using hollow fiber membrane contactor: a comprehensive modeling and new perspectives

In this study, a novel hollow fiber membrane contactor (HFMC) under a non-wet condition was numerically explored by CFD techniques based on the finite element method to capture CO2 from the CH4/CO2 gas mixture. A new design, such as a shell and tube heat exchanger with baffles, was proposed. The MEA, DEA, and TEA, as different amines solutions, were selected as the liquid solvents. A CO2-containing gas mixture and amine solution were passed in the shell side and the tube side of the membrane contactor, respectively. The simulation findings indicated a good agreement with the reported experimental data demonstrating that such a model would evaluate the effects of different parameters during the HFMC system. Specifically, the results showed that the baffles' presence improved the separation efficiency due to the increased residence time on the shell side. The results also indicated that the MEA solution had the highest CO2 absorption. In the new design (shell and tube heat exchanger with baffles), the rising solvent inlet velocity, decreasing gas velocity, and counter-current flow pattern positively affected separation efficiency.

Corrosion Behavior and Characteristics of 3Cr Steel in Coexisting H2S- and CO2-Containing Solutions

The corrosion behavior and characteristics of 3Cr steel in coexisting H2S- and CO2-containing solution at temperature from 25 to 65 °C were investigated by potentiodynamic polarization sweep, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) with energy-dispersive x-ray (EDX). The EIS data fitted by ZsimpWin software were analyzed and discussed. The experimental results indicated that corrosion potential (Ecorr) became more negative and that corrosion current density (icorr) decreased as the Na2S·9H2O concentration (i.e., H2S/HS−) increased from 0 to 1.6%, with the obvious passivation characteristics occurring in anodic polarization branch curve in 1.6% Na2S·9H2O case. Warburg impedance characteristics of diffusion process in low-frequency region following a depressed capacitive semicircle in the intermediate frequency region were observed with the addition of certain Na2S·9H2O concentration or temperature, with the phase angle peaks for H2S-containing cases in the intermediate frequency region shifting to low-frequency direction and raising toward −90° significantly. Severe corrosion pits or cavities or river-liking platform could be observed after removing the corrosion products. The contents of S element in the “first deposition” black corrosion product layer were higher than those in the “second deposition” gray corrosion product crystals. All result displayed the inhibition effect with the addition of Na2S·9H2O. In addition, one four-stage corrosion model involving H2S and CO2 corrosion was proposed.

Adsorption and Corrosion Inhibitive Properties of Novel Surfactants in the Series of Fatty Acids Based on Palm Oil on Carbon Steel in CO2-containing Solution

Adsorption and Corrosion Inhibitive Properties of Novel Surfactants in the Series of Fatty Acids Based on Palm Oil on Carbon Steel in CO2-containing Solution

Effect of the carbon dioxide pressure on the electrochemical behavior of 3Cr low alloyed steel at high temperature

Electrochemical corrosion behavior of 3Cr steel in CO2-containing solution at a high temperature was investigated by various electrochemical measurements and analysis as well as thermodynamic calculations of ionic concentrations and equilibrium electrode potentials. A conceptual model was developed to illustrate the electrochemical corrosion mechanism of 3Cr steel in the CO2-containing sodium chloride solution. Comparing the corrosion potentials of 3Cr steel in the test solution under different CO2 pressures with the conceptual model, it is found that anodic reactions of the 3Cr steel contain a direct dissolution of Fe, and the formation of corrosion scales, FeCO3 and Cr(OH)3, by Fe+HCO3−=FeCO3+H++2e and Cr+3OH−=Cr(OH)3. With the CO2 pressure increasing, the corrosion potential has a positive shift. It indicates that the CO2 pressure has a greater effect on the cathodic reaction than that of anodic reaction. And the corrosion current has positive linear relationship with the increase of CO2 pressure. It is attributed to the concentration increasing of the reactants of the cathodic reaction. According to analysis of the electrochemical impedance spectroscopy, the scale forming reactions dominate the corrosion process when the CO2 pressure is lower than 0.6MPa and the dissolution of Fe, followed by the consecutive mechanism with adsorbed intermediate products, takes up the dominant part in the anodic process when the CO2 pressure exceeds 0.6MPa.

Effect of calcium ions on CO2 corrosion of 3Cr low-alloy steel

The effect of calcium ions on the corrosion behavior of 3Cr low-alloy steel in CO 2 containing sodium chloride solution was investigated by immersion test and electrochemical measurements. It is found that with the addition of Ca 2+ to CO 2-containing solution,the crazing level of the corrosion scale on the specimen is much slighter than that of the specimen immersed in solution without Ca 2+ . The pitting on the surface of the specimens immersed in the solution with Ca 2+ is relatively small and distributes uniformly all over the surface. The significant change in the anodic polarization curve is attributed to the deposition of the CaCO 3 . CaCO 3 deposits on the specimen surface and gives a protection to the metal substrate. And with the anodic proceeding,the concentration of H + in the solution increases. The CaCO 3 deposition dissolves in the low pH solution and the protection effect disappears.

Optimization of CO2 corrosion for API X70 steel on acetic acid contained environment

The corrosion behavior of X70 steel in a CO2-containing solution was evaluated by using linear polarization resistance. The corrosive media was a deoxygenated 3% NaCl solution, saturated with CO2 at different temperatures. The fluid flow over the steel surface was 2.5 m/s as a peripheral velocity of a rotating cylinder electrode (RCE). It is concluded that the specific micro-structure of X70 steel influences the corrosion behavior of the steel. The percentage contribution of different effective factors (acetic acid concentration, temperature and exposure time) has been discussed on corrosion rate of different samples.

Corrosion and Stress Corrosion Cracking Behavior of X70 Pipeline Steel in a CO2-Containing Solution

The electrochemical corrosion and stress corrosion cracking (SCC) behaviors of X70 pipeline steel in CO 2 -containing solution were studied by electrochemical measurements, slow strain rate tensile tests, and surface characterization. The results found that the electrochemical corrosion of X70 steel in aerated, alkaline solution is an activation-controlled process, and a stable passivity cannot develop on steel. Corrosion rate of the steel increases with the CO 2 partial pressure. The enhanced anodic dissolution due to the additional cathodic reaction in the presence of CO 2 , rather than the film-formation reaction, dominates the corrosion process. The mass-transfer step through FeCO 3 deposit is the rate-controlling step in corrosion of the steel. The susceptibility of steel to SCC and the fracture brittleness increase with the CO 2 partial pressure. The enhanced fracture brittleness is attributed to the evolution and penetration of hydrogen atoms into the steel, contributing to crack propagation. The formed deposit layer is not effective in reducing hydrogen permeation due to the loose, porous structure.

Evaluation of inhibition efficiency of an imidazoline derivative in CO 2-containing aqueous solution

The inhibition efficiency of an imidazoline derivative for API X65 steel in CO 2-saturated 5% NaCl solution has been studied by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. This imidazoline derivative acts as a mixed-type inhibitor, which suppresses both cathodic and anodic processes by its adsorption on the electrode surface according to Langmuir adsorption isotherm, together with a slight positive shift in corrosion potential ( E corr). The adsorbed inhibitor on the surface of electrode affects the kinetic processes of cathodic and anodic reactions and increases the reaction activation energy. Both potentiodynamic polarization and EIS measurements reveal that this imidazoline derivative inhibits the corrosion of API X65 steel in CO 2-saturated 5% NaCl solution and that the inhibition efficiency increases with increasing of the inhibitor concentration. The Nyquist plot of uninhibited electrode at E corr is characterized by a depressed semicircle from high to medium frequencies and an inductive loop at low frequencies while the inhibited ones emerge “degradation” phenomena with simple depressed capacitive loops. The semicircles representing the inhibitor film merge with the charge transfer loops. The inhibitor films form gradually and the inhibition efficiency increases with increase of immersion time.

Ionic Mechanism of the Carbon Dioxide Reception in the Japanese House Centipede, Thereuonema hilgendorfi

The carbon dioxide receptor in the temporal organ of the Japanese house centipede Thereuonema hilgendorfi shows spontaneous discharges in carbon dioxide-free air. These responses are decreased or totally suppressed accompanied by a hyperpolarizing receptor potential induced by carbon dioxide stimulation. In the present study the ionic basis of the CO2 reception has been examined by impulse analysis based upon a known linear relationship between receptor potential and impulse frequency. Even when the temporal organ was perfused with CO2-free distilled water, receptor cells showed spontaneous discharges, and these discharges were also decreased due to perfusion of CO2-containing solution. The spontaneous impulse frequency in the CO2-free solution increased with increasing Na and K concentration, and decreased with increasing Ca2 concentration. Other ions such as Mg2 , Li , choline and Cl− had little effect on the receptor cell discharges. In the CO2 containing perfusate, the effects of increasing Na or Ca2 concentration on the receptor cell discharges disappeared, whereas that of increasing K concentration remained. Response amplitudes to CO2 stimulation depended largely on Na and Ca2 concentration, but less on K concentration in the perfusate. These results suggest that Na ions are major current carriers for the generation of receptor potential in response to CO2 stimulation.

Long-term expression of c-H-ras stimulates Na-H and Na(+)-dependent Cl-HCO3 exchange in NIH-3T3 fibroblasts.

In a study of intracellular pH (pHi) regulation, we compared c-H-ras-transformed fibroblasts (FT9s) with parental NIH 3T3 cells. Cells were grown on a coverslip and placed in a flow-through cuvette; pHi was monitored using a fluorescent dye. Whether cells were in a CO2-free or CO2-containing solution, steady-state pHi was approximately 0.5 higher in FT9s than in 3T3s. Rates of pHi recovery from acid loads in the presence of CO2 indicate that total net acid extrusion (Jtotal) was far greater in FT9s than 3T3s in the pHi range 6.3-7.4. In both FT9s and 3T3s, pHi recovery was blocked by removing Na+. In FT9s, most of Jtotal was blocked by ethyl isopropyl amiloride (EIPA) and was probably due to Na-H exchange. A smaller component was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) and required Cl- and was probably due to Na(+)-dependent Cl-HCO3 exchange. In 3T3s, the DIDS-sensitive and Cl(-)-dependent components of Jtotal were very small. The dominant acid-extruder in 3T3s appears to be a Na-H exchanger insensitive to 50 microM EIPA. We determined the flux-pHi relationships for both the Na-H and Na(+)-dependent Cl-HCO3 exchangers in both FT9s and 3T3s. p21ras alkaline shifts the pHi profile of each transporter by approximately 0.7, without affecting the Vmax. These shifts in the flux-pHi relationships provide a mechanism for the large increase in steady-state pHi produced by long-term expression of p21ras.

Simultaneous measurement of intracellular and extracellular carbonic anhydrase activity in intact muscle fibres.

The presence and properties of membrane-bound carbonic anhydrases have been difficult to establish with conventional enzymological and immunohistochemical techniques. We have therefore studied carbonic anhydrase (CA) activity in single intact crayfish muscle fibres by superfusing them alternately with a 4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid (HEPES)-buffered and a 5% CO2/HCO3(-)-buffered solution (pH of both solutions 7.4) while recording the intracellular pH (pHi) and extracellular surface pH (pHs) with H(+)-selective microelectrodes. In order to prevent regulation of pHi, Na+ ions were replaced with N-methyl-D-glucamine. Application of the CO2-containing solution produced a fast fall in pHi coupled with a marked (0.5-0.8 pH units) transient increase in pHs. Submicromolar concentrations of acetazolamide (AA) and benzolamide (BA) immediately blocked the pHs transients. A concentration of 8 x 10(-8) M (both compounds) reduced the response by 50%. A more prolonged application of BA and AA at concentrations of 10(-7) M and higher slowed the CO2-induced fall in pHi, which attained a rate corresponding to uncatalysed intracellular CO2 hydration at an AA concentration of 10(-4) M. The effect of BA and AA on the pHi changes developed with a time constant of 25 +/- 4 min and 7.6 +/- 1.5 min respectively, indicating that BA is less permeant than AA. CNO- ions (5 x 10(-4) M) had little effect on the CO2-induced pHs and pHi changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Pitting Corrosion of Carbon Steel in CO2-Containing NaCl Brine

Abstract Studies of the susceptibility of carbon steel (line pipe steel) to pitting were performed at room temperature in deaerated, NaCl-saturated CO2-containing solution simulating natural brine....

Intracellular pH transients in rat diaphragm muscle measured with DMO.

Changes of the intracellular pH of rat diaphragm muscle were monitored at 30-min intervals with the weak acid DMO (5,5-dimethyl-2,4-oxazolidinedione). Transferring the muscle from a CO2-containing to a CO2-free solution caused intracellular pH (pHi) to rise by an average of 0.18 during the first 30 min and then to level off at a slightly lower value over the next 60-90 min. Transferring the muscle from a CO2-free to a CO2-containing solution caused pHi to fall by 0.18 during the first 30 min and then to recover by 0.05 over the next 90 min. Subsequent return to the CO2-free solution caused pHi to overshoot the control value by 0.10. Both the recovery and the overshoot can be accounted for by an acid-extruding pump. Intracellular acid loading with 118 mM DMO similarly caused pHi to fall initially, to recover slowly during the acid loading, and then to overshoot the control pHi on removal of the acid load. In the absence of HCO3-/CO2, acid extrusion was reduced by about a fifth. SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid) had no effect. The absence of either Na+ or Cl- from HCO3-/CO2- free solution reduced acid extrusion by about a half.