The adsorption and corrosion inhibition of some cationic gemini surfactants on carbon steel surface in hydrochloric acid

The adsorption and corrosion inhibition of the gemini surfactants 1,2-ethane bis(dimethyl alkyl (C_nH_2n+1) ammonium bromide) (designated as n−2−n, n=10, 12 and 16) on the steel surface in 1 M hydrochloride acid were studied using the weight loss method. It was found that the adsorption of the gemini surfactants on the steel surface is the main reason to cause the steel corrosion inhibition in hydrochloride acid, and the inhibition efficiency increases with the increase of surfactant concentration and reaches the maximum value near the CMC. A possible adsorption model of gemini surfactant onto the metal surface was also discussed.     

Adsorption and Corrosion Inhibition Behavior of Polyethylene Glycol and Surfactants Additives on Mild Steel in H2SO4

The adsorption and corrosion inhibition behaviors of polyethylene glycol (PEG) alone and in the presence of surfactants sodium dodecyl benzene sulfonate and cetyltrimethyl ammonium bromide on mild steel in 0.1 M H₂SO₄ in temperature range of 30-60 °C was investigated using weight loss method, solvent analysis of iron ions, scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), atomic force microscopy (AFM) and determination of kinetic/thermodynamic parameters. The inhibition efficiency (IE) of PEG increased with increasing concentration showing a maximum IE of 86.91% at 30 °C at 25 ppm but decreased with increasing temperature. Inhibiting action of PEG is synergistically enhanced on addition of small amount of surfactants. Surface morphology of the corroded mild steel specimen as evaluated by SEM, EDAX and AFM confirmed the existence of an adsorbed protective film on the mild steel surface. The calculated thermodynamic/kinetic parameters reveal that adsorption process is spontaneous and obey Langmuir adsorption isotherm.     

On the corrosion inhibition of low carbon steel in concentrated sulphuric acid solutions. Part I: Chemical and electrochemical (AC and DC) studies

The influence of the concentration of adenine (AD), as a safe inhibitor, on the corrosion of low carbon steel (LCS) in aerated 4.0 M H₂SO₄ solutions was studied. The investigations involved weight loss, potentiodynamic polarization, impedance and electrochemical frequency modulation (EFM) methods. Variations of open-circuit potential (OCP) as a function of time till steady-state potentials were also studied. Measurements were conducted under the influence of various experimental conditions complemented with ex situ EDX examinations of the electrode surface. By using EFM measurements, corrosion current density was determined without prior knowledge of Tafel slopes. Results obtained revealed that together with iodide ion, AD is an effective corrosion inhibitor for LCS corrosion in H₂SO₄ solutions. Synergism between iodide ion and AD was proposed. Potentiodynamic polarization studies showed that AD alone and the mixture of AD and iodide ions act as mixed-type inhibitors for the corrosion of LCS in 4.0 M H₂SO₄ solution. The inhibition mechanism involves the electrostatic adsorption of protonated AD molecules on the LCS surface charged with a negative layer of chemisorbed I⁻ ions. An adherent layer of inhibitor is postulated to account for the protective effect. EDX examinations of the electrode surface confirmed the existence of such adherent layer on the electrode surface. The inhibition efficiency increases with increase in the concentration of AD and immersion time. The potential of zero charge (PZC) of the LCS electrode was determined in 4.0 M H₂SO₄ solutions in the absence and presence of 0.001 M KI, and the mechanism of adsorption was discussed. The results obtained from chemical and electrochemical measurements were in good agreement.     

Inhibition of Mild Steel Corrosion Using l-Histidine and Synergistic Surfactants Additives

The corrosion inhibition behavior of nitrogen-containing amino acid l-Histidine (LHS) on mild steel in 0.1 M H₂SO₄ solution in the temperature range of 30-60 °C was studied by weight loss measurements, and potentiodynamic polarization measurements. The effect of the addition of very small concentration of surfactants, sodium dodecyl sulfate (SDS), and cetyltrimethyl ammonium bromide (CTAB), respectively on the corrosion inhibition behavior of LHS was also studied. The surface morphology of the corroded steel samples was evaluated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). LHS significantly reduces the corrosion rates of mild steel, with the maximum inhibition efficiency (IE) being 71.09% at 30 °C in the presence of 500 ppm of LHS. The IE of LHS is synergistically increased in the presence of SDS and CTAB. The SEM and AFM photographs show a clearly different surface morphology in the presence of additives. LHS alone and in combination with surfactants obeys Langmuir adsorption isotherm from the fit of the experimental data of all concentration and temperature studied. The calculated thermodynamic parameters for adsorption reveal strong interaction between the inhibitors and the mild steel surface, and suggest physical adsorption. The results obtained by potentiodynamic polarization measurements are consistent with the results of the weight loss measurement. LHS acts more anodic than cathodic inhibitor.     

Synergistic influence of iodide ions on the inhibition of corrosion of C-steel in sulphuric acid by some aliphatic amines

The synergistic influence caused by iodide ions on the inhibition of corrosion of C-steel in 1 M H₂SO₄ in the presence of some aliphatic amines has been studied using weight loss, potentiodynamic polarization, linear polarization and a.c. impedance techniques. Aliphatic amines used inhibit the corrosion of C-steel and the inhibition efficiency increases by increasing the concentration of the additives and also by addition of iodide ions. The adsorption of these compounds is found to obey Frumkin’s adsorption isotherm. The increase in surface coverage in the presence of iodide ions indicates that iodide ions enhance the adsorption of these aliphatic amines on the metal surface. Defines and evaluates synergism parameter (S_θ). Values of the parameter which are more than unity indicate the fact that the enhanced inhibition efficiency in the presence of iodide ions is only due to synergism and there is a definite contribution from the inhibitors molecules, which are adsorbed by coulombic interaction on the metal surface, where iodide ions are already adsorbed and thus reduces the corrosion rate.     

Influence of iodide ions on corrosion of dual‐phase steel in sulfuric acid solution

Potassium iodide was studied for its corrosion inhibition property on the corrosion of dual‐phase steel in 0.5 M sulfuric acid at 25°C by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy was used to characterize the steel surface. The inhibition efficiency increases with the concentration of iodide ions. The thermodynamic parameters K_ads and ΔG⁰_ads are calculated and discussed. The probable inhibitive mechanism is proposed from the viewpoint of adsorption theory.     

The influence of SDS and CTAB surfactants on the surface morphology and surface topography of electroless Ni–P deposits

The effect of surfactants sodium dodecyl sulphate (SDS) and cetyltrimethyl ammonium bromide (CTAB) on the surface roughness, surface morphology and surface topography of electroless nickel (EN)–phosphorus surface protective coating obtained from an alkaline bath is presented in this paper. In this study the influence of surfactant concentrations on the surface roughness of coated samples were investigated. It was observed that the surface roughness, surface morphology and surface topography of Ni–P coating were clearly influenced by the addition of surfactants SDS and CTAB. EN deposits with addition of surfactant SDS and CTAB at a concentration of 0.6 g/l produce a smooth surface and the average roughness (R_a) value is 1.715 μm for SDS and 1.607 μm for CTAB which is less than the R_a value of EN deposit without surfactant addition (1.885 μm). The mean average roughness (R_a) value with addition of surfactant is 1.796 μm.EN deposit with addition of surfactants consists of a significant fraction of particles of nickel. In the presence of SDS, fine nickel particles have dispersed uniformly on the substrate surface resulting in smoother surface finish of the deposited layers. In the presence of CTAB, at lower concentrations (upto 0.6 g/l) coalescence of nickel particles have been deposited on the substrate surface and at the higher concentration (above 0.6 g/l) uniformly improved surface finish of the deposited layer is resulted. The complete experimental details, results obtained and their analysis are presented in this paper.     

Electrochemical characterization of sintered magnetite electrode in LiOH solution

In relation to the mitigation of flow assisted corrosion (FAC) occurring at the carbon steel materials at power plants, magnetite powder was sintered into pellets and used to construct electrodes for electrochemical property measurements in LiOH solutions at ambient conditions. Measurements indicated adsorption of hydroxide ions on the magnetite surface. Slow cathodic scanning removed the adsorbed OH⁻ and returned the electrode surface to its original state. It is proposed that the cause of cyclic voltammetric (CV) peaks is the reduction of H₂O involving the conduction band edge (E_C) and valence band edge (E_V) of the magnetite. Negative polarization by the CV produced hydrogen atoms and injected them into the magnetite body; these were oxidized when the sweep was reversed and then dissipated at the magnetite surface by contact with OH⁻ ions. Results support the interaction of magnetite energy levels with adsorbed species, rather than the dissolution of magnetite.     

A novel Schiff base-based cationic gemini surfactants: Synthesis and effect on corrosion inhibition of carbon steel in hydrochloric acid solution

The corrosion inhibition characteristics of the synthesized cationic gemini surfactants, namely bis(p-(N,N,N-decyldimethylammonium bromide)benzylidene thiourea (10-S-10), bis(p-(N,N,N-dodecyldimethylammonium bromide)benzylidene thiourea (12-S-12) and bis(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene thiourea (14-S-14) on the carbon steel corrosion in 1 M hydrochloric acid have been investigated at 25 °C by weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiencies obtained from all methods employed are in good agreement with each other. The obtained results show that compound 14-S-14 is the best inhibitor with an efficiency of 97.75% at 5 × 10⁻³ M additive concentration. Generally, the inhibition efficiency increased with increase of the inhibitor concentration. Changes in impedance parameters (charge transfer resistance, R_ct, and double-layer capacitance, C_dl) were indicative of adsorption of 14-S-14 on the metal surface, leading to the formation of a protective film. The potentiodynamic polarization measurements indicated that the inhibitors are of mixed type. The adsorption of the inhibitors on the carbon steel surface in the acid solution was found to obey Langmuir’s adsorption isotherm. The free energy of adsorption processes were calculated and discussed. The surface parameters of each synthesized surfactant were calculated from its surface tension including the critical micelle concentration (CMC), maximum surface excess (Γ_max) and the minimum surface area (A_min). The free energies of micellization (ΔG^o_mic) were calculated. The surface morphology of carbon steel sample was investigated by scanning electron microscopy (SEM).     

The effect of molybdate anion on the ion-selectivity of hydrous ferric oxide films in chloride solutions

The ion-selective property of hydrous ferric oxide precipitate films has been investigated by measuring membrane potentials which arise across precipitate membranes of hydrous ferric oxide with and without adsorbed MoO₄^2? ions and of ferric molybdate in solutions of NaCl, KCl, MgCl₂, CaCl₂, BaCl₂, AlCl₃, and FeCl₃. The hydrous ferric oxide membrane was only permeable to Cl^? ions in chloride solutions, whereas the membrane with adsorbed MoO₄^2? ions was permeable to cations in NaCl and KCl solutions, and to both Cl^? and cations in the presence of multivalent cations. The ferric molybdate membrane was permeable to Cl^? and cations in NaCl and KCl solutions, and only to Cl^? ions in the presence of multivalent cations. It is suggested that in chloride solutions, the corrosion of iron covered with a precipitate film of hydrous ferric oxide is accelerated by enrichment of Cl^? ions under the film, which may decrease the local pH and introduce a positive diffusion potential in the film. The adsorption of MoO₄^2? ions on the oxide changes the ion-selectivity of the precipitate film from the anion-selective to the cation-selective in solutions of NaCl and KCl. This cation-selectivity of the film may inhibit the corrosion of iron, because of H⁺ ions diffusing out of the film. The inhibitive effect of MoO₄^2? ions would be reduced in the presence of multivalent cations.     

在NaCl溶液中CTAB、SDS和钨酸钠对印刷电路板缓蚀作用研究

采用电化学阻抗和极化曲线法,研究了在NaCl溶液中,钨酸钠、十六烷基三甲基溴化铵(CTAB)及十二烷基硫酸钠(SDS)的单一配方以及其复配对印刷电路板的缓蚀作用.结果表明:CTAB、SDS和钨酸钠各自的单一配方对印刷电路板(PCB)均具有一定的缓蚀作用,其中CTAB浓度为1.0×10-4mol/L,SDS浓度为5.0×10-3mol/L及350 me,/L钨酸钠表现出最佳的缓蚀效率;SDS和钨酸钠属于阳极型缓蚀剂,CTAB为混合型缓蚀剂;当二者复配使用时,浓度为250 ms/L钨酸钠和1.0 x 10-4moL/L CTAB以及300 mg/L钨酸钠和5.0×10-3～moL/L SDS的复配缓蚀剂的缓蚀效果最佳,复配缓蚀剂具有协同效应,并且对印刷电路板的缝隙腐蚀有一定的抑制作用.     

Octa- and tetra-(benzo-15-crown-5)phthalocyanines in surfactant-containing solutions

The behavior of octa-(benzo-15-crown-5)phthalocyanine (H₂cr₈Pc), as well as cobalt octa- and tetra-(benzo-15-crown-5)phthalocyaninates (Cocr₈Pc and Cocr₄Pc), in aqueous solutions containing cationic or anionic surfactants, such as cetyl trimethylammonium bromide (CTAB), sodium carboxymethyl cellulose (Na-CMC), and sodium dodecyl sulfate (SDS), is studied using electronic spectroscopy. The presence of eight benzo-15-crown-5 ether fragments on the periphery of the phthalocyanine ring is shown to facilitate the dissolution of Pc in an aqueous environment. The interactions between CTAB and crown-containing Pc promotes the dissolution of H₂cr₈Pc; Cocr₈Pc; and, to a lesser degree, Cocr₄Pc, which is accompanied by the appearance of molecular aggregates, including heteronuclear cofacial dimers. The presence of a metal in the ring is not the necessary condition of the process. In microscopically heterogeneous medium, such as an aqueous SDS-containing solution, H₂cr₈Pc is present in monomeric form at SDS concentrations close to C _cr and in dimeric form at SDS content below C _cr. Under similar conditions (environment, surfactant), Cocr₄Pc can exist in monomeric form at SDS concentrations much high than C _cr. The effect of the size of cation on the form of the crown-containing Pc in an aqueous solution is illustrated by an example of H₂cr₈Pc. Na-CMC promotes the dissolution of Pc and enables one to produce K⁺/Mcr₈Pc-modified films from aqueous solutions.     

2—巯基苯并噻唑在铜表面的吸附状态

在pH值大于6时，2－巯基苯并噻唑（MBT）在银和铜表面具有相同的吸附状态；随溶液pH值降低，部分吸附的硫醇离子逐渐异构化为硫酮，破坏了MBT平面吸附层。在pH值高于3时，MBT在铜表面仍然以其分子平面平行于表面，起到阻挡侵蚀分子的作用，由此可知在弱碱性溶液中它对于铜有更的保护效果。     

The effect of chromate in the corrosion behavior of duplex stainless steel in LiBr solutions

The electrochemical behavior of duplex stainless steel (DSS) in LiBr media was investigated by anodic cyclic polarization curves and AC impedance measurements. The effect of bromide concentration and chromate presence in the solutions on the corrosion behavior of DSS was studied. It was found, by cyclic polarization curves analyses, that there was different pitting susceptibility of passive films formed on DSS depending on the chromate/bromide ratio: pitting corrosion susceptibility highly decreased from a chromate/bromide ratio lower than 0.01.The comparative investigations carried out in LiBr and LiBr + 0.032Li₂CrO₄ verify the assumption that the halide ions facilitate inhibitor adsorption. The addition of halides increased inhibition efficiency to a considerable extent. Passive film becomes more resistant when bromide concentration increases, although film thickness decreases.     

十六烷基三甲基溴化铵对镁合金腐蚀行为的影响

采用动电位极化和电化学阻抗等方法检测了十六烷基三甲基溴化铵(CTAB) 对AZ31镁合金在3.5% NaCl溶液中腐蚀行为影响的规律, 用扫描电镜观察表面腐蚀产物膜的形貌并分析其组成. 结果表明, 当NaCl溶液中加入2000~3500 mg/L CTAB时, 镁合金的腐蚀速率降低, 且CTAB浓度为3500 mg/L时, 镁合金的腐蚀速率最低. 这主要是因为CTAB在镁合金表面发生吸附, 使阳极溶解过程受阻, 同时, CTAB减少了腐蚀产物膜内的微观缺陷数量, 减少了腐蚀介质的渗入通道, 增大了电荷转移阻力, 从而使镁合金的耐蚀性得到改善.。     

Synergistic effect between cationic gemini surfactant and chloride ion for the corrosion inhibition of steel in sulphuric acid

Corrosion inhibition of cold rolled steel in 0.5 mol L⁻¹ sulphuric acid by a quaternary ammonium gemini surfactant, l,3-propane-bis(dimethyl dodecylammonium bromide) (designated as 12-3-12), in the absence and presence of chloride ions was investigated at different temperatures. The results revealed significant synergistic effect between gemini 12-3-12 and chloride ions for the corrosion protection of cold rolled steel in sulphuric acid, and that the novel composite inhibitor system containing cationic gemini surfactant and chloride ions was efficient and low-cost for steel corrosion inhibition in sulphuric acid medium, even when concentration of 12-3-12 was as low as 1 × 10⁻⁶ mol L⁻¹. By fitting the obtained experimental data with Langmuir adsorption model and Arrhenius equation, some thermodynamic and kinetic parameters such as adsorption free energy, the apparent activation energy, and the pre-exponential factor were estimated. The adsorption mechanism of the gemini surfactant onto steel surface in acid medium in the absence and presence of chloride ions was also discussed, respectively.     

Inhibitory efficiency of oxalic N-phenylhydrazide-N′-phenylthiosemicarbazide on corrosion of carbon steel in 0·5M H2SO4

The inhibitory effect of an oxalic type organic compound oxalic N-phenylhydrazide-N′-phenylthiosemicarbazide on the corrosion of carbon steel in 0·5M H₂SO₄ aqueous solution was investigated by different experimental methods; gravimetry, voltammetry and electrochemical impedance spectroscopy. The surface state of the electrode after immersion of the steel coupons in corrosion test solutions, in absence and in presence of the inhibitor was characterised by scanning electron microscopy. The potentiodynamic polarisation measurements showed that the presence of the inhibitor in 0·5M H₂SO₄ decreased both cathodic and anodic processes. The action of this inhibitor is therefore of a mixed type. The electrochemical impedance measurements showed the adsorption of the inhibitor. The inhibitory efficiency reaches a value of 95% at an inhibitor concentration of 10^?3M.     

表面活性剂对镁合金浸锌的影响

研究了阳离子型表面活性剂(十六烷基三甲基溴化铵)、阴离子型表面活性剂(十二烷基苯磺酸钠)以及非离子型表面活性剂(聚乙二醇)对镁合金浸锌液的稳定性、浸锌层表面形貌和耐腐蚀性能的影响。结果表明:随着表面活性剂加入,浸锌液稳定性明显改善;表面活性剂对浸锌层的表面形貌和耐蚀性影响较大,添加阴离子表面活性剂的浸锌层细小致密,耐蚀性能良好。     

Effects of surfactants on electrodeposition of nickel-carbon nanotubes composite coatings

The influences of surfactants sodium dodecylsulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB) on electrodeposition of Ni-carbon nanotubes (CNTs) composite coatings were studied, with a 0.6 g/L addition for SDS or CTAB in Watts bath. The results showed that SDS in the bath slightly decreased but CTAB increased the co-deposited CNTs content in the coatings. The coatings deposited with SDS or CTAB became coarser in low CNTs concentration baths. While as CNTs concentration in the bath increased, the coatings deposited with either SDS or CTAB became more homogeneous. XRD analysis showed that both SDS and CTAB decreased the grain sizes of deposited coatings. The surfactants also affected the preferred orientations of the deposited grains: (220) plane was the preferred orientation in coatings without surfactant, while the preferred orientations for coatings formed in solutions with SDS or CTAB were (200) plane and (111) plane respectively. The addition of SDS in depositing bath increased hardness of the composite coatings and improved adherence of the coating to the matrix. Corrosion resistance of the composite coatings was also slightly improved. However, CTAB was detrimental to both mechanical property and corrosion resistance of the composite coatings. The affecting mechanism of surfactants on the coating properties was discussed.     

Effect of molybdate ions as corrosion inhibitors of iron in neutral aqueous solutions

Abstract

The effect of molybdate ions on the corrosion of Fe in neutral solutions was investigated by electrochemical measurements (dc polarisation and impedance spectroscopy) together with gravimetric determinations. Studies were conducted in solutions containing sodium hydrogen/sodium sulphate salts with molybdate concentrations ranging between 10^?4 and 10^?2M at pH 8 and 9. Mass loss measurements indicated that about 10^?3M of molybdate was necessary in order to inhibit completely the corrosion of Fe at room temperature. The potentiodynamic polarisation and electrochemical impedance studies gave indications about the mechanism of action of the MoO^2?₄ ion. They also showed that the inhibiting effect of the oxyanion is increased in the presence of dissolved oxygen. Spontaneous passivation of the corroding Fe electrode could happen only in the presence of dissolved oxygen at concentrations greater than 10^?4M. However, passivity was also obtained under potentiodynamic polarisation conditions in deaerated solutions. The effect of the oxygen was attributed to displacement of the corrosion potential into the region of selfpassivation of the steel. Finally, the results indicated that the corrosion inhibition of Fe in neutral solutions by molybdate ions was largely insensitive to pH over the range from 8 to 9.