Ceforanide: a new and efficient corrosion inhibitor for mild steel in HCl solution

The corrosion inhibition properties of ceforanide for mild steel in HCl solution were analyzed by electrochemical impedance spectroscopy, potentiodynamic polarization, and gravimetric methods. The increase in inhibitor concentration and immersion time showed a positive effect on inhibition efficiency. The experimental data showed a frequency distribution and therefore a modeling element with frequency dispersion behavior and a constant phase element have been used. In aqueous acid solution, mild steel reacts by evolution of hydrogen. Visual observations showed that the hydrogen evolution decreased (i.e., corrosion inhibition effect increased) with increasing concentration of ceforanide. Potentiodynamic polarization study revealed that ceforanide acted as a mixed type of inhibitor. The results obtained from different methods are in good agreement. The adsorption behavior of ceforanide is experimentally investigated by contact angle measurement on metal surface. The contact angle of metal surface to the acid solution increased with inhibitor concentration; thereby confirming the increased hydrophobic nature of metal surface to the acid solution having inhibitors.     

Indole‐3‐acetic acid and N‐acetyltryptophan corrosion inhibition effects on mild steel in 1 M hydrochloric acid solution

Corrosion inhibition of indole‐3‐acetic acid and N‐acetyl tryptophan on carbon steel was investigated using polarization and electrochemical impedance spectroscopy (EIS). Polarization results revealed that corrosion inhibitors could reduce the rate of cathodic and anodic reactions on metal surface. EIS analysis showed inhibition efficiency of indoles increases by increasing the inhibitor concentration. The maximum inhibition efficiency was 97% and 80% in solutions containing 10 mM indole‐3‐acetic acid and 10 mM N‐acetyl tryptophan, respectively. The adsorption of inhibitors was found to follow Langmuir isotherm. Adsorption and film formation of inhibitors on the metal substrate were confirmed by calculating thermodynamic adsorption parameter (ΔG⁰_ads) and characterization of exposed metals' surface through contact angle measurements. Copyright © 2014 John Wiley & Sons, Ltd.     

5-苯基-1H-四氮唑对铜片缓蚀性能的研究

通过金相显微镜和接触角测试研究了5-苯基-1H-四氮唑在硫-乙醇体系中对铜的缓蚀性能。结果显示,缓蚀剂可以在铜片表面形成疏水性保护膜,有效抑制了铜片的腐蚀。电化学测试表明,当缓蚀剂浓度为70 mg/L时缓蚀效率达到87%,对铜电极有明显的缓蚀作用。通过量子化学密度泛函理论研究了缓蚀剂分子结构与缓蚀性能的关系,分析了缓蚀剂分子的活性位点。通过分子动力学模拟研究了缓蚀剂分子在Cu的(111)表面的吸附行为。     

噻二唑衍生物对银的缓蚀性能研究

本文研究了主要成分为5-甲基-2-戊基二硫代-1,3,4-噻二唑的复配型缓蚀剂TSJ-T6,在浓度为5.0×10-5g/g的H2S中对银的缓蚀性能。通过增重实验、接触角分析、电化学极化曲线测试以及分子动力学模拟研究了该缓蚀剂的缓蚀效率及缓蚀机理。增重实验结果证明,缓蚀剂TSJ-T6对银片在H2S中的腐蚀具有良好的缓蚀效果,缓蚀剂浓度为2.5×10-5g/g时,缓蚀效率高达94.51%。接触角分析结果表明,该缓蚀剂分子在银片和腐蚀液的界面形成了一层疏水保护膜。极化曲线结果表明,缓蚀剂TSJ-T6的存在降低了阴、阳极的塔菲尔斜率,为混合型缓蚀剂;同时,该缓蚀剂的存在显著降低了腐蚀电流密度,表明该缓蚀剂对银片在H2S中的腐蚀有良好的缓蚀效果。分子动力学模拟表明,缓蚀剂分子通过噻二唑环和链上的硫、氮原子吸附在银表面,烷基链则以一定角度指向溶液。     

Surface morphological and impedance spectroscopic studies on the interaction of polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) with mild steel in acid solutions

The inhibition of mild steel corrosion in aerated acid mixture of 0.5 N H₂SO₄ and 0.5 N HCl solution was investigated using potentiodynamic polarization studies, linear polarization studies, electrochemical impedance spectroscopy, adsorption, and surface morphological studies. The effect of inhibitor concentration on corrosion rate, degree of surface coverage, adsorption kinetics, and surface morphology is investigated. The inhibition efficiency increased markedly with increase in additive concentration. The presence of PEG and PVP decreases the double-layer capacitance and increases the charge-transfer resistance. The inhibitor molecules first adsorb on the metal surface following a Langmuir adsorption isotherm. Both PEG and PVP offer good inhibition properties for mild steel and act as mixed-type inhibitors. Surface analysis by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that PVP offers better protection than PEG.     

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ?M ?H₂SO₄ solution was studied. For this aim, the change of open circuit potential with exposure time (E_ocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (E_HOMO, E_LUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ?at concentrations from 0.01 ?mM to 1 ?mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (K_ads) and the standard free energy of adsorption were ΔG_ads 1.298 x 10³ ?M^?1 and -27.71 ?kJ/mol in the case of 0.5 ?M ?H₂SO₄ solution containing 1.0 ?mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (E_pzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.     

Role of novel oxazocine derivative as corrosion inhibitor for 304 stainless steel in acidic chloride pickling solutions

Inhibition of 304 stainless steel corrosion in acidic chloride pickling (1.0 M HCl) solutions by newly synthesized oxazocine derivative 4 as a corrosion inhibitor have been studied using weight loss, potentiodynamic polarization, and atomic absorption spectroscopy investigations. Potentiodynamic polarization curves show that the inhibitor behaves as a mixed-type. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The inhibition mechanism of the investigated inhibitor was discussed in terms of its adsorption on the metal surface. The relationship between the molecular structure and the inhibition efficiency was elucidated by quantum chemical calculations.     

Impedance spectroscopic study of corrosion inhibition of Al-Pure by organic Schiff base in hydrochloric acid

A new corrosion inhibitor namely o-Chloroaniline-N-benzylidene (o-CANB) has been synthesized and its inhibitive performance toward the corrosion of Al-Pure in 1.0 M hydrochloric acid has been investigated. Corrosion inhibition was studied by chemical method (weight loss) and electrochemical techniques including polarization method and electrochemical impedance spectroscopy (EIS). The present study has shown that this inhibitor is good in acidic media and the inhibition efficiency up to >99% in 1.0 M HCl. Polarization measurement revealed that the investigated inhibitor is a mixed type with a predominant action on cathode. Impedance measurement showed that the charge transfer resistance (R_ct) increased and double layer capacitance (C_dl) decreased with an increase in the inhibitor's concentration. Obtained results about inhibition efficiency from weight loss, polarization study and EIS are in good agreement with each other. The adsorption of the inhibitor on the metal surface in the acid solution was found to obey Langmuir's adsorption isotherm.     

Corrosion inhibition and adsorption behavior of methionine on mild steel in sulfuric acid and synergistic effect of iodide ion

The corrosion inhibition of mild steel in sulfuric acid by methionine (MTI) was investigated using electrochemical techniques. The effect of KI additives on corrosion inhibition efficiency was also studied. The results reveal that MTI inhibited the corrosion reaction by adsorption onto the metal/solution interface. Inhibition efficiency increased with MTI concentration and synergistically increased in the presence of KI, with an optimum [KI]/[MTI] ratio of 5/5, due to stabilization of adsorbed MTI cations as revealed by AFM surface morphological images. Potentiodynamic polarization data suggest that the compound functioned via a mixed-inhibition mechanism. This observation was further corroborated by the fit of the experimental adsorption data to the Temkin and Langmuir isotherms. The inhibition mechanism has been discussed vis-à-vis the presence of both nitrogen and sulfur atoms in the MTI molecule.     

硫酸溶液中聚天冬氨酸对碳钢的吸附缓蚀性能

应用电化学极化曲线和交流阻抗研究聚天冬氨酸(PASP)对碳钢的缓蚀性能,讨论了PASP浓度和温度对缓蚀效果的影响.结果表明:PASP是一种以抑制阳极为主的缓蚀剂.在实验温度范围内,PASP在0.5mol/L硫酸溶液中对碳钢的缓蚀效率随着温度升高而降低,并以10℃时的缓蚀效果最好.在给定温度下,缓蚀率均随PASP浓度的增加而迅速增加,但当PASP质量浓度达到2.5g/L时,缓蚀率的增加趋于平缓,10℃下,缓蚀率的最高值可达80.33%(PASP 6.0g/L),PASP在碳钢表面的吸附基本服从Freund lich吸附等温式,PASP的加入增大了碳钢的腐蚀反应表观活化能.     

Self‐assembly of stearic acid on aluminium: the importance of oxide surface chemistry

The influence of ambient atmospheric exposure on the chemistry of the magnetron‐sputtered aluminium surface has been characterized as hydroxyl incorporation to the oxide surface and concurrent adsorption of airborne carbonaceous contamination. Here, the consequence of these changes in oxide surface chemistry upon the adsorption of stearic acid from solution is investigated. Water contact angle and polarization modulation infrared refection–absorption spectroscopy (PM‐IRRAS) reveal a strong dependence of stearic acid monolayer order upon ambient exposure time prior to assembly. It is proposed that hydroxyl formation in the ambient atmosphere increases the stearic acid adsorption density and thus the self‐assembled monolayer (SAM) order, whereas airborne carbonaceous material blocks these adsorption sites and introduces disorder in the monolayers through a decrease in adsorption density. Monolayer adsorption has been correlated with the aluminium oxide surface chemistry. It is proposed that this phenomenon represents an explanation for the irreproducible results often reported for assembly on metal oxide substrates. Furthermore, it indicates that in this broad class of material surfaces assembly can be used as a means of estimating the reactivity of surfaces with respect to organic overlayers such as paints and adhesives. Removal of adsorbed carbonaceous material from the aluminium surface using an oxygen plasma resulted in a significantly increased order of the stearic acid monolayer, as assessed by water contact angle. This observation is rationalized as the removal of carbonaceous material blocking surface adsorption sites by the plasma, but retention of the underlying hydroxyl functionality. This is predicted to have important implications in the preparation of aluminium for painting and adhesive bonding. Copyright © 2004 John Wiley & Sons, Ltd.     

Inhibition of steel corrosion by calcium benzoate adsorption in nitrate solutions: theoretical and experimental approaches

The inhibitive effects of calcium benzoate on steel corrosion were studied in sodium nitrate solutions at room temperature. Corrosion parameters of the steel/nitrate and steel/benzoate + nitrate interfaces were obtained from polarization curves. Adsorption parameters of benzoate on steel in sodium nitrate solutions were determined through changes in the degree of surface coverage by the inhibitor, as a function of concentration, time, and adsorption potential. The most likely adsorption configuration of benzoate on iron was envisaged with the help of semiempirical calculations such as extended Hückel calculations. A two-dimensional flat configuration was involving at least two metal atoms, one interacting with the phenolic group and the other with the carboxylate moiety. The effect of chloride on the corrosion inhibition of benzoate was analyzed by exposing the metal to different chloride solution concentrations, from which corrosion parameters were calculated and compared with those in nitrate solutions.     

Effect of Avogadro natural oil on the corrosion inhibition of mild steel in hydrochloric acid solution

The inhibition action of Avogadro natural oil on corrosion of mild steel in one molar hydrochloric acid solution was investigated by gravimetric and potentiodynamic polarization techniques. The surface morphology of as-corroded samples was assessed with high resolution scanning transmission electron microscopy equipped with energy dispersive spectroscopy (HR-STEM/EDS). From the results, the presence of Avogadro natural oil in the metal–acidic interface decreased the corrosion rate with all the exposure times. The inhibition efficiency (%IE) increases with the concentration of the inhibitor considered. Results obtained from gravimetric measurements indicate that the natural oil exhibited higher efficiencies of 93.26 % after 384 h of exposure time and 98.26 % recorded in the potentiodynamic polarization method, both at 4.5 g/v inhibitor addition. Equally, results from the linear polarization indicated higher potential value with an increase in the polarization resistance (R _p) and lower current density for the inhibited samples than the uninhibited mild steel sample. The inhibitive effect of this oil was explained in view of adsorption on the metal surface. The adsorption process follows the Langmuir adsorption isotherm.     

Inhibition effect of environmentally benign Karanj (Pongamia pinnata) seed extract on corrosion of mild steel in hydrochloric acid solution

The inhibition of the corrosion of mild steel in hydrochloric acid solution by the seed extract of Karanj (Pongamia pinnata) has been studied using weight loss, electrochemical impedance spectroscopy, potentiodynamic polarization, and linear polarization techniques. Inhibition was found to increase with increasing concentration of the extract. The effect of temperature, immersion time, and acid concentration on the corrosion behavior of mild steel in 1 M HCl with addition of extract was also studied. The adsorption of the extract on the mild steel surface obeyed the Langmuir adsorption isotherm. Values of inhibition efficiency calculated from weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy are in good agreement. Polarization curves showed that Karanj (P. pinnata) seed extract behaves as a mixed-type inhibitor in hydrochloric acid. The activation energy as well as other thermodynamic parameters for the inhibition process was calculated. The adsorbed film on mild steel surface containing Karanj (P. pinnata) seed extract inhibitor was also measured by Fourier transform infrared spectroscopy. The results obtained showed that the seed extract of Karanj (P. pinnata) could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric acid media.     

二硫代酰胺类化合物在盐酸中对碳钢的缓蚀性能(英文)

采用失重实验,动电位极化,交流阻抗,量子化学计算和拉曼光谱等方法研究了N,N′-二异丙氧基丙基二硫代二丙酰胺(DPDA)在1 mol.L-1盐酸溶液中对碳钢的缓蚀性能.失重实验结果表明,DPDA在盐酸溶液中能够有效地抑制碳钢的腐蚀,当缓蚀剂DPDA的浓度为1×10-3 mol.L-1时,其缓蚀效率达到90.2%.极化曲线表明DPDA为混合型缓蚀剂,单一的容抗弧变化表明碳钢电极表面的腐蚀过程主要由电荷转移步骤控制.由失重实验,动电位极化和电化学交流阻抗方法得到的DPDA缓蚀效率具有较好的相关性,均表现为缓蚀效率随着DPDA浓度的增大而增加.另外,DPDA在碳钢表面的吸附符合Langmuir吸附等温式.吸附过程的吉布斯自由能(ΔG0a0d0s)为-38.65 kJ.mol-1,这说明DPDA分子在碳钢表面形成共价键而发生了自发的化学吸附.拉曼光谱表明DPDA分子有效地吸附在碳钢表面,量子化学计算结果证明DPDA分子在碳钢表面的化学吸附活性中心集中在S原子上.     

Adsorption and inhibition performance of the novel cationic Gemini surfactant as a safe corrosion inhibitor for carbon steel in hydrochloric acid

The new synthesized cationic Gemini surfactant (CGS) was tested as a corrosion inhibitor for carbon steel (CS) in 1.0?M hydrochloric acid using weight loss, electrochemical spectroscopy and potentiodynamic polarization. The inhibition efficiency is increased by increasing the CGS concentration and is almost constant within the temperature range studied. The inhibition was explained by adsorption of the CGS molecule on the CS surface. A mixed-type inhibitor is suggested for the inhibitory effects of CGS as revealed by the potentiodynamic polarization technique. The changes in impedance parameters suggested that the adsorption of the inhibitor on the CGS surface led to the formation of protective films. The adsorption of the CGS on the surface of CS obeys Langmuir adsorption isotherm. Thermodynamic and kinetic parameters were calculated and discussed.     

界面缓蚀剂的吸附稳定性

研究表明：在一定条件下,阳极脱附电位可作为评价缓蚀剂吸附稳定性的一个经验参数：缓蚀剂吸脱附诱导的电化学振荡是缓蚀体系的一种特殊失稳状态,即缓蚀剂吸附过程与电极反应中间吸附态产物耦合的结果;卤素离子的协同作用不仅可以提高某些有机缓蚀剂的吸附复盖度,而且可以增强其吸附稳定性;微分极化曲线是研究吸附稳定性的有效方法。     

酸性介质中羧甲基纤维素钠在低碳钢表面的吸附和缓蚀作用

The effect of sodiumcarboxymethyl cellulose (Na-CMC) on the corrosion behavior of mild steel in 1.0 mol·L-1 HCl solution has been investigated by using weight loss (WL) measurement, potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods. These results showed that the inhibition efficiency of Na-CMC increased with increasing the inhibitor concentration. Potentiodynamic polarization studies revealed that the Na-CMC was a mixed type inhibitor in 1.0 mol·L-1 HCl. The adsorption of the inhibitor on mild steel surface has been found to obey the Langmuir isotherm. The effect of temperature on the corrosion behavior of mild steel in 1.0 mol·L -1 HCl with addition of 0.04% of Na-CMC has been studied in the temperature range of 298-328 K. The associated apparent activation energy (E*a) of corrosion reaction has been determined. Scanning electron microscopy (SEM) has been applied to investigate the surface morphology of mild steel in the absence and presence of the inhibitor molecules.     

Inhibition of cold rolled steel corrosion by Tween-20 in sulfuric acid: weight loss, electrochemical and AFM approaches

The inhibiting action of a nonionic surfactant of Tween-20 on the corrosion of cold rolled steel (CRS) in 0.5-7.0 M sulfuric acid (H(2)SO(4)) was studied by weight loss and potentiodynamic polarization methods. Atomic force microscope (AFM) provided the surface conditions. The results show that inhibition efficiency increases with the inhibitor concentration, while it decreases with the sulfuric acid concentration. The adsorption of inhibitor on the cold rolled steel surface obeys the Langmuir adsorption isotherm equation. Effect of immersion time was studied and discussed. The effect of temperature on the corrosion behavior of cold rolled steel was also studied at four temperatures ranging from 30 to 60 degrees C, the thermodynamic parameters such as adsorption heat, adsorption free energy, and adsorption entropy were calculated. The results revealed that the adsorption was physisorption mechanism. A kinetic study of cold rolled steel in uninhibited and inhibited acid was also discussed. The kinetic parameters such as apparent activation energy, pre-exponential factor, rate constant, and reaction constant were calculated for the reactions of corrosion. The inhibition effect is satisfactorily explained by both thermodynamic and kinetic models. Polarization curves show that Tween-20 is a cathodic-type inhibitor in sulfuric acid. The results obtained from weight loss and potentiodynamic polarization are in good agreement, and the Tween-20 inhibition action could also be evidenced by surface AFM images.     

Adsorption Behavior and Inhibition Corrosion Effect of Sodium Carboxymethyl Cellulose on Mild Steel in Acidic Medium

The effect of sodium carboxymethyl cellulose (Na-CMC) on the corrosion behavior of mild steel in 1.0 mol·L-1 HCl solution has been investigated by using weight loss (WL) measurement, potentiodynamic polarization, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) methods. These results showed that the inhibition efficiency of Na-CMC increased with increasing the inhibitor concentration. Potentiodynamic polarization studies revealed that the Na-CMC was a mixed type inhibitor in 1.0 mol·L-1 HCl. The adsorption of the inhibitor on mild steel surface has been found to obey the Langmuir isotherm. The effect of temperature on the corrosion behavior of mild steel in 1.0 mol·L-1 HCl with addition of 0.04% of Na-CMC has been studied in the temperature range of 298-328 K. The associated apparent activation energy (E*a ) of corrosion reaction has been determined. Scanning electron microscopy (SEM) has been applied to investigate the surface morphology of mild steel in the absence and presence of the inhibitor molecules.