Analysis of EIS characteristics of CO2 corrosion of well tube steels with corrosion scales

The electrochemical impedance spectroscopy (EIS) was used to study the characteristics of CO₂ corrosion of N80 and 4Cr steels with corrosion scales. The results indicated that CO₂ corrosion scale on tube steel could prevent the rate of mass transfer remarkably, corrosion rate was controlled by ions diffusion in corrosion scale, which led to finite length diffusion impedance occurred in electrochemical impedance spectra. Additionally, pitting of N80 steel could lead to additional capacitive reactance in impedance spectrum. The ion diffusion coefficient in corrosion scale and porosity of corrosion scale could be calculated by Warburg impedance coefficient, the results shown that the value of H⁺ diffusion coefficient in N80 and 4Cr corrosion scale is (3.46 and 1.76) × 10⁻¹⁰ m² s⁻¹, respectively. The protective ability of 4Cr corrosion scale was better than that of N80 corrosion scale.     

Investigation of the inhibitive effect of triphenyltin 2-thiophene carboxylate on corrosion of steel in 2 M H3PO4 solutions

A new organic compound was synthesised and tested as corrosion inhibitor of steel in phosphoric acid medium using gravimetric, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements. Results obtained show that the inhibitor studied is a good cathodic inhibitor. EIS results show that the change in the impedance parameters (R_T and C_dl) with concentration of triphenyltin 2-thiophene carboxylate (TTC) is indicative of the adsorption of molecules leading to the formation of a protective layer on the surface of steel. The effect of the temperature on the steel corrosion in 2 M H₃PO₄ and with addition of various concentrations of TTC in the range of temperature 298-348 K was studied. The associated apparent activation corrosion energy has been determined.     

Corrosion behaviour of AISI 304 stainless steel with Cu coatings in H2SO4

The work addresses the influence of cementation and electrodeposition of copper coatings on the corrosion resistance of AISI 304 stainless steel immersed in 30 wt.% H₂SO₄ at temperatures of 25 and 50 °C. Corrosion process was evaluated by gravimetric tests, DC measurements and electrochemical impedance spectroscopy (EIS). The specimen surfaces were analysed by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The corrosion performance of AISI 304 stainless steel in sulphuric acid solution was greatly improved by copper coatings. The amount of copper deposited by the cementation process was sufficient to protect the stainless steel of corrosion. A greater amount of copper obtained by electrodeposition treatments does not supply further improvement in the corrosion behaviour. The improved corrosion resistance is related to copper dissolution at the initial stages of immersion tests and the presence of Cu²⁺ in the solution, which makes the medium more oxidizing, increasing the stability of the passive layer. In addition, the presence of copper at the surface reduces the overpotential of cathodic reaction, enabling the transition from an active region to the passive one.     

CO_2活化温度对N-C复合碳气凝胶结构及电化学性能的影响

采用CO2活化工艺对氮掺杂碳气凝胶(N-CA)的结构进行重整,并系统研究了活化温度对活化氮掺杂碳气凝胶(N-ACA)孔结构及电化学性能的影响。利用N2吸附数据、X-光电子能谱(XPS)和元素分析对样品的结构及元素组成进行表征。结果表明,随活化温度的升高,N-ACA的比表面积逐渐增大,其含有的氮原子分数逐渐减少,吡咯氮含量明显增加。利用循环伏安(CV)、电化学阻抗谱(EIS)等测试技术评价了碳气凝胶样品在6mol·L-1 KOH电解液中的电化学性能,结果发现,合理的孔结构与较高的吡咯氮含量是影响电容器比容量的关键因素。在5mV·s-1扫描速率下测试950-N-ACA电极的比电容值高达267.4F·g-1,经1000次充放电后比电容损失值在1.5%以内。     

Development of electroless Ni-Zn-P/nano-TiO2 composite coatings and their properties

Ni-Zn-P-TiO₂ composite coatings were successfully obtained on low carbon steel by electroless plating technique. Deposits were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis (EDS) studies. The hardness and microstructure of as plated and heat treated Ni-Zn-P and Ni-Zn-P-TiO₂ composite coatings were analyzed. The change in microstructure and higher hardness was noticed for heat treated composite. The corrosion resistance behavior of as plated and heat treated Ni-Zn-P and Ni-Zn-P-TiO₂ coatings was investigated by anodic polarization, Tafel plots and electrochemical impedance spectroscopic (EIS) studies in 3.5 wt% NaCl solution. The composite coating exhibited enhanced corrosion resistance property over Ni-Zn-P coating.     

Study on corrosion properties of pipelines in simulated produced water saturated with supercritical CO2

This work aims at systematically investigating the corrosion properties of three pipeline steels in static simulated produced water (SPW) saturated with supercritical carbon dioxide using weight-loss tests. SEM, XRD and XPS were employed to study the chemical composition and structure of the corroded surface. The results showed that the corrosion rates of the tested steels significantly decreased with increasing the exposure temperature and time in static SPW saturated with SC-CO₂. The surface film on the corroded surface, which markedly influenced the CO₂ corrosion behavior of the samples, was mainly composed of (Fe, Ca)CO₃ and α-FeOOH. Inhomogeneous element distribution of carbon, oxygen, calcium and iron in the surface film was observed. (Fe, Ca)CO₃ formed at a lower temperature was more stable than that formed at elevated temperatures.     

1,3-Bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane as corrosion inhibitor for steel in 0.5 M H2SO4 solution

The effect of addition of 1,3-bis(3-hyroxymethyl-5-methyl-1-pyrazole) propane (M = 264 g). HMPP on steel corrosion in 0.5 M sulphuric acid is studied by weight-loss, electrochemical polarisation and electrochemical impedance spectroscopy (EIS) measurements at various temperatures. The results obtained showed that HMPP acts as a good corrosion inhibitor. The inhibition efficiency increases with the bipyrazole compound to attain 88%. It acts as a mixed-type inhibitor. Trends in the increase of charge-transfer resistance and decrease of capacitance values also show the adsorption of the molecule on the metal surface. The bipyrazole adsorbs on the steel surface according to the Langmuir isotherm adsorption model. Effect of temperature indicates that inhibition efficiency decreases with temperature between 25 and 85 °C.     

Surface Analysis of Inhibitor Film Formed by 4-Amino-N-(1,3-thiazol-2-yl) Benzene Sulfonamide on Carbon Steel Surface in Acidic Media

Inhibitive properties of the antibacterial sulfa drug sulfathiazole—IUPAC name being 4-amino-N-(1,3-thiazol-2-yl) benzene sulfonamide—on the corrosion of carbon steel in 1.0 M HCl solution were investigated using weight loss measurements, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Sulfathiazole is a good adsorption inhibitor, and the inhibition efficiency increases with increasing concentration. Adsorption is spontaneous and is best described by Temkin isotherm. XPS analysis showed, at this stage, that the main product of corrosion is a nonstoichiometric Fe³⁺ oxide/oxyhydroxide consisting of a mixture of Fe₂O₃, α, and γ-FeO(OH) and/or Fe(OH)₃, where α, γ-FeO(OH) is the main phase.     

Pd修饰Cu电极的电化学CO2还原

利用微分电化学质谱和电化学原位衰减全反射红外光谱技术探究了Cu和CuPd催化剂上CO₂和CO的电化学还原行为. 红外光谱观察到了生成甲醇、甲烷与乙烯的CH_x中间物种. 在CuPd电极CO₂还原过程中，红外光谱的CO吸附峰起始电位比Cu正移大约300 mV，说明CuPd能够有效促进CO₂还原；CO饱和溶液中，Cu和CuPd电极CO起始吸附电位基本相同；两电极上CO谱带出现的电位与CO₃^2-的谱带降低的电位基本相同，说明CO的吸附需要CO₃^2-的脱附. 利用电化学在线质谱发现在CuPd电极上CO还原产生CH₄和CH₃OH的起始电位比Cu电极正移约200 mV. 推测催化活性的提升可能是由于Pd的引入改变了Cu的d能带，且Pd吸附更多的H，从而促进CO₂还原，使CO能够与H结合并被深度还原.     

A novel electrodeposited Cu-Zn-Bi film with increased corrosion resistance in a 0.05 M K2SO4 solution

A single phase Cu-Zn-Bi film is fabricated on the steel wire by electrodeposition. Bi addition (∼1 wt.%) greatly increases the corrosion resistance of brass (Cu−36 wt.% Zn) film in a 0.05 M K₂SO₄ solution as shown by potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) experiments. It is proposed that the main reason for the improvement in the corrosion resistance by the Bi addition is that it greatly increased the crack resistance, which thus prevents crack-induced galvanic corrosion occurring between the brass film and the steel substrate.     

Structural, optical and electrochemical properties of TiO2 thin films grown by APCVD method

Atmospheric pressure chemical vapor deposition (APCVD) of TiO₂ thin films has been achieved onto glass and onto ITO-coated glass substrates, from the reaction of TiCl₄ with ethyl acetate (EtOAc). The effect of the synthesis temperature on the optical, structural and electrochemical properties was studied through spectral transmittance, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) measurements. It was established that the TiO₂ films deposited onto glass substrate, at temperatures greater than 400 °C grown with rutile type tetragonal structure, whereas the TiO₂ films deposited onto ITO-coated glass substrate grown with anatase type structure. EIS was applied as suitable method to determine the charge transfer resistance in the electrolyte/TiO₂ interface, typically found in dye-sensitized solar cells.     

Electrochemical, theoretical and XPS studies of 2-mercapto-1-methylimidazole adsorption on carbon steel in 1 M HClO4

The inhibition of the corrosion of carbon steel in 1 M HClO₄ by 2-mercapto-1-methylimidazole (MMI) has been investigated in relation to the concentration of the inhibitor as well as the temperature using weight loss and electrochemical measurements. The effect of the temperature on the corrosion behaviour with addition of different concentrations of MMI was studied in the temperature range 30-60 °C. Polarization curves reveal that MMI is a mixed type inhibitor. The inhibition efficiency of MMI is temperature independent but increases with the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R_t, and double-layer capacitance, C_dl) were indicative of adsorption of MMI on the metal surface, leading to the formation of a protective film. Adsorption of MMI on the carbon steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined. The X-ray photoelectron spectroscopy (XPS) of the carbon steel indicated that MMI is chemically adsorbed on the steel surface. Moreover, the electronic properties such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) energy levels and molecular orbital densities were calculated.     

Inhibition of steel corrosion in 2 M H3PO4 by artemisia oil

Artemisia oil (Ar) is extracted from artemisia herba alba collected in Ain es-sefra-Algeria, and tested as corrosion inhibitor of steel in 2 M H₃PO₄ using weight loss measurements, electrochemical polarisation and EIS methods. The naturally oil reduces the corrosion rate. The inhibition efficiency was found to increase with oil content to attain 79% at 6 g/l. Ar acts as a cathodic inhibitor. The effect of temperature on the corrosion behaviour of steel indicates that inhibition efficiency of the natural substance decreases with the rise of temperature. The adsorption isotherm of natural product on the steel has been determined.     

Corrosion behaviour of galvanized steel and electroplating steel in aqueous solution: AC impedance study and XPS

The efficiency of a new triazole derivative, namely, 2-{(2-hydroxyethyl)[(4-methyl-1H-1,2,3-benzotriazol-1-yl)methyl]amino}ethanol (TTA) has been studied for corrosion inhibition of galvanized steel and electroplating steel in aqueous solution. Corrosion inhibition was studied using electrochemical impedance spectroscopy (EIS). These studies have shown that TTA was a very good inhibitor. Data obtained from EIS show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The corrosion behaviour of galvanized steel and electroplating steel in aqueous solution was also investigated in the presence of 4-methyl-1H-benzotriazole (TTA unsubstituted) by EIS. These studies have shown that the ability of the molecule to adsorb on the steel surface was dependent on the group in triazole ring substituent. X-ray photoelectron spectroscopy surface analysis with TTA shows that it chemisorbed on surface of galvanized steel and electroplating steel.     

Investigation of the characteristics and corrosion resistance of Al2O3/TiN coatings

Al₂O₃ /TiN double and Al₂O₃/Cr/TiN triple coatings were produced on stainless steel substrates using plasma-detonation techniques. Investigation of the microstructure and characteristics of the coatings after the preparation was performed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES). The corrosion resistance of the coatings was studied in several electrolytic solutions (0.5 M H₂SO₄, 1 M HCl, 0.75 M NaCl) using electrochemical techniques (open circuit potential, cyclovoltammetry and potentiodynamic polarization). The obtained results showed, in most of the cases, an improvement of the corrosion resistance, except in NaCl solutions. The effect of the controlled thickness of TiN and Cr layers as well as the additional treatment with a high-current electron beam was also investigated. Nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM) were applied for the characterization of the samples before and after the corrosion experiments.     

Enhanced corrosion resistance of mild steel in normal sulfuric acid medium by 2,5-bis(n-thienyl)-1,3,4-thiadiazoles: Electrochemical, X-ray photoelectron spectroscopy and theoretical studies

The inhibitive action of some thiadiazole derivatives, namely 2,5-bis(2-thienyl)-1,3,4-thiadiazole (2-TTH) and 2,5-bis(3-thienyl)-1,3,4-thiadiazole (3-TTH) against the corrosion of mild steel in 0.5 M H₂SO₄ solution has been investigated using weight loss measurements, Tafel polarisation and electrochemical impedance spectroscopy (EIS) techniques. The experimental results obtained revealed that these compounds inhibited the steel corrosion in acid solution. The protection efficiency increased with increasing inhibitors concentration and the ability of the molecule to adsorb on the steel surface was dependent on the position of the sulphur atom on the thienyl substituent. Inhibition efficiency values obtained from various methods employed were in reasonable agreement. Potentiodynamic polarisation studies clearly showed that 2-TTH and 3-TTH acted as mixed inhibitors. Adsorption of these inhibitors on steel surface obeyed to Langmuir adsorption isotherm. X-ray photoelectron spectroscopy and the thermodynamic data of adsorption showed that inhibition of steel corrosion in normal sulphuric solution by n-TTH is due to the formation of a chemisorbed film on the steel surface. Molecular modelling was used to gain some insight, about structural and electronic effects in relation to the inhibiting efficiencies.     

Inhibition performance of 2-mercaptobenzothiazole derivatives in CO2 saturated solution and its adsorption behavior at Fe surface

Two 2-mercaptobenzothiazole derivatives, N,N′-bis-(2-thionobenzothiazolin-3-yl-methyl)-n-dodecylamine (BTBMDA) and N,N′-bis-(2-thionobenzothiazolin-3-yl-methyl)-n-octadecylamine (BTBMOA), were synthesized under microwave irradiation. Their inhibition performance for N80 steel in CO₂ saturated solution at 90 °C were tested by weight loss method and the surface analysis was performed by SEM. The adsorption behavior of two inhibitors at the Fe surface was studied by the molecular dynamics simulation method and the quantum chemistry calculations. Results showed that the two inhibitors could inhibit the corrosion of N80 steel in simulated solution significantly. There were two types of end configurations for two inhibitors at the Fe surface in the molecular dynamics simulation, and the two inhibitors adsorbed at the surface mainly through one of the two types.     

Synthesis and characterization of poly(N-methylpyrrole)/TiO2 composites on steel

Poly(N-methyl pyrrole) coating was successfully electrodeposited on steel substrates in mixed electrolytes of dodecyl benzene sulphonic acid (DBSA) with oxalic acid in the absence and the presence of TiO₂ nanoparticles (NPs). The morphology and compositions were characterized by Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray spectroscopy (EDX). X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to calculate the size of nanoparticles. Electrode/polymer/electrolyte system was studied by Electrochemical Impedance Spectroscopy (EIS). The FESEM micrographs suggest that the incorporation of TiO₂ nanoparticles affects the morphology of the film significantly and makes the TiO₂ to be loosely piled up with PMPy. The results of EIS showed that synthesized PMPy in the presence of TiO₂ NPs increases and decreases the R_po and C_c of the coating respectively. The increase of the area of synthesized PMPy in the presence of nanoparticles can increase its ability to interact with the ions liberated during the corrosion reaction of steel in NaCl solution.     

Rugged distal tips for CO2 laser medicine

Low-loss and rugged distal tips for CO₂ laser have been proposed and fabricated based on a commercially available stainless steel (St) pipe. A method of smoothening the inner surface of the St pipe with a rough inner surface is put forward. Fabrication parameters, transmission properties, and mechanical strength of the cyclic olefin polymer-coated silver hollow St distal tip are experimentally discussed.     

A new hydrothermal blackening technology for Fe3O4 coatings of carbon steel

This paper proposes a new blackening technology for growing magnetite (Fe₃O₄) coating on surface of carbon steel. Dense black coating composed of Fe₃O₄ ultrafine particles could be successfully prepared by hydrothermal treatment of the carbon steel substrate in the N₂H₄·H₂O-FeSO₄-NaOH solution at 150 °C. Electrochemical analysis, including Tafel and electrochemical impedance spectroscopy, indicated that the anodic dissolution reaction was effectively limited and the corrosion resistance increased by the Fe₃O₄ coating. The key factors and growth mechanism for the hydrothermal formation of the Fe₃O₄ coating are also discussed.