Investigation of adsorption and corrosion inhibition effect of 1,1’-thiocarbonyldiimidazole on mild steel in hydrochloric acid solution

The adsorption and inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion of mild steel (MS) in 0.5 M HCl solution was studied in both short and long immersion time (120 h) with the help of electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. For long-time tests, the hydrogen gas evolution (VH₂-t) and the change of open circuit potential with immersion time (E _ocp-t) were also utilized in addition to the former two techniques. The surface morphology of MS after its exposure to 0.5 M HCl solution with and without 1.0 × 10⁻² M TCDI was examined by scanning electron microscopy (SEM). It was demonstrated that the inhibition efficiency of studied inhibitor is concentration depended and increased with TCDI concentration. The higher value of inhibition efficiency was obtained after longer immersion time merely on the basis of strong increase of corrosion rate of mild steel in the blank solution. The high inhibition efficiency was discussed in terms of adsorption of inhibitor molecules and protective film formation on the mild steel surface which was substantiated by SEM micrographs. The adsorption of TCDI on MS was found to obey Langmuir adsorption isotherm.     

Long-term anticorrosion behaviour of polyaniline on mild Steel

Anticorrosion performances of polyaniline emeraldine base/epoxy resin (EB/ER) coating on mild steel in 3.5% NaCl solutions of various pH values were investigated by electrochemical impedance spectroscopy (EIS) for 150 days. In neutral solution (pH 6.1), EB/ER coating offered very efficient corrosion protection with respect to pure ER coating, especially when EB content was 5-10%. The impedance at 0.1 Hz of the coating increased in the first 1-40 immersion days and then remained constant above 10⁹ Ω·cm² until 150 days, which in combination with the observation of a Fe₂O₃/Fe₃O₄ passive film formed on steel confirmed that the protection of EB was mainly anodic. In acidic or basic solution (pH 1 or 13), EB/ER coating also performed much better than pure ER coating. However, these media weakened the corrosion resistance due to breakdown of the passive film or deterioration of the ER binder.     

Preparation of polyaniline–TiO2 composite and its comparative corrosion protection performance with polyaniline

Due to strict environmental regulations on the usage of chromate in the coating industries, search for effective inhibitive pigment in replacing those chromate pigments has become necessary. In recent years it has been shown that electrically conducting polymers such as polyaniline (PANI) incorporated coatings are able to protect steel due to their passivating ability similar to that of chromates. This work presents the comparative corrosion protection performance of the coatings containing polyaniline and polyaniline–TiO₂ composite (PTC) on steel in acrylic binder. The PANI and PTC were prepared by chemical oxidative method of aniline by ammonium persulfate. The polymers were characterized by FTIR, XRD and SEM. The corrosion protection performance of the coatings containing PANI and PTC on steel was evaluated by immersion test in 3% NaCl for 60 days and salt fog test for 35 days. The performance of the coatings in both the tests was investigated by open circuit potential measurements and EIS technique. It has been found that the open circuit potential values of PTC containing coating are more nobler by 50–200 mV in comparison to that of coatings with PANI. Besides, the resistance values of the coating containing PTC were more than 10⁷ Ω cm² in the 3% NaCl immersion test after 60 days and 10⁹ Ω cm² in the salt fog test of 35 days which were two orders high in comparison to that of PANI containing coatings. The better performance of PTC containing coatings may be due to uniform distribution of polyaniline which can form uniform passive film on the iron surface.     

碳钢表面防腐超疏水TiO_2/PDMS涂层的制备及性能

针对碳钢腐蚀电位相对更负、更容易发生腐蚀的特点,在Q235钢表面制备超疏水TiO_2/PDMS涂层以提高其耐蚀性能。采用表面活性剂分散纳米TiO_2并进行改性,然后与PDMS混合,用溶胶凝胶法在Q235钢表面制备有聚二甲基硅氧烷(PDMS)过渡层的TiO_2/PDMS超疏水涂层。借助扫描电镜(SEM)、接触角测量仪、红外光谱(FT-IR)及X射线衍射仪(XRD)表征其表面涂层的表面形貌、化学成分及疏水性能,用电化学试验和浸泡试验测试其防腐性。结果表明:TiO_2/PDMS涂层表面具有独特的微纳结构,与水的接触角达到154.3°;其腐蚀电位由碳钢的-0.77 mV正移至超疏水涂层的-0.24 mV,腐蚀电流密度则下降两个数量级,即从5.02×10~(-6)A·cm~(-2)下降至3.95×10~(-8)A·cm~(-2);超疏水涂层的交流阻抗值高于碳钢基底3个数量级。经过7 d的3.5wt.%NaCl溶液浸泡,超疏水涂层并未发生失重。制备的TiO_2/PDMS超疏水涂层具有超疏水效果和良好的长期耐腐蚀性。     

Effect of Si nanoparticles on the corrosion protection performance of organic coating on carbon steel in chloride environment

This work examines the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy coating over carbon steel by Electrochemical Impedance Spectroscopy (EIS) and Transmission Electron Microscopy. The EIS was performed in a 0.1 M NaCl solution after a wet/dry cyclic corrosion and continuous immersion test. The addition of Si nanoparticles increased the film resistance (R_f) and the charge transfer resistance (R_ct) of the coated steel. The surface analysis showed that uniform and fine Si-Fe complex oxides layers were formed acting as barrier layers that enhanced the corrosion protection of the coated steel in the wet/dry cyclic corrosion test. The results of the EIS of the coated steel with Si nanoparticles suggested that Si nanoparticles play a beneficial role in enhancing the corrosion resistance of organic coated steel.     

Corrosion behavior of mild steel in the presence of scale inhibitor in sulfuric acid solution

Surfactants such as non-ionic polyethylene glycol tert-octylphenyl ether (Triton X-114) have been studied as efficient corrosion inhibitors in acid medium. In this study inhibition performance of Triton X-114 has been evaluated as corrosion inhibitor for mild steel in 0.5 mol l⁻¹ H₂SO₄. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and linear polarization (LPR) techniques has been applied to determine the electrochemical behaviour of Triton X-114. The maximum efficiency of Triton X-114 was found as 96% at the concentration 5.0 × 10⁻⁵ mol l⁻¹. The adsorption isotherm of inhibitor on the mild steel surface was found to be in a good agreement with the Langmuir and the standard free energy value (ΔG _ads^°) was calculated as −50.1 kJ mol⁻¹, which shows that adsorption of Triton X-114 on the mild steel surface improves the inhibition characteristics in 0.5 M H₂SO₄.     

Effect of extracellular polymeric substances isolated from Vibrio natriegens on corrosion of carbon steel in seawater

Extracellular polymeric substances (EPS) are isolated from marine Vibrio natriegens (V. natriegens) by a cation exchange resin method. The influences of EPS concentration and corrosion time on the corrosion of carbon steel in seawater are investigated. The results demonstrate that EPS are capable of forming a protective film on the surface of carbon steel in seawater, which retards the diffusion of dissolved oxygen and inhibits the reduction of oxygen on the cathode. In addition, the efficiency of corrosion inhibition increases with an increase in the amount of added EPS during the initial state (the first 3 days); however, excess EPS (exceeding 300?mg?L^?1) in seawater significantly accelerates the corrosion of carbon steel over the long term (10 days) due to the binding power of EPS with Fe ions.     

The Rhodanine inhibition effect on the corrosion of a mild steel in acid along the exposure time

The corrosion performance of a mild steel (MS) exposed to a 0.5 M HCl solution with various concentrations of Rhodanine (Rh) was studied by means of anodic and cathodic voltammetric curves, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. Rh makes the corrosion of MS in HCl solution decelerate with the exposure time so as to reach a protective value of more than 99% in 168 h. The adsorption of Rh molecules on the MS obeys Langmiur adsorption isotherm. Thermodynamic parameters, adsorption equilibrium constant (K _ads), and standard free energy of adsorption (ΔG _ads ^o ) were calculated and discussed. The high inhibition efficiency was discussed in terms of blockading the metal surface by the Rh molecules strongly adsorbing witch their active centers and thus forming a sufficiently effective protective film.      

Effectiveness of pretreatment method to hinder rebar corrosion in concrete

Abstract

This paper aims to evaluate the ability of phosphate pretreatments applied on steel rebars to hinder the corrosion reinforcements using synthetic pore electrolyte and mortar contaminated by chloride ions. The electrochemical behaviour of the pretreated substrate was assessed by corrosion potential, polarisation resistance and electrochemical impedance spectroscopy measurements. The results have demonstrated that the treatment of the rebar by immersion in the Na₃PO₄ (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which increases the resistance to corrosion initiation up to 0·3M Cl^– instead of 0·1M Cl^– without treatment. The pretreatment also provides enhancement of corrosion protection of the steel rebar in mortar. The evolution of the impedance spectra in function of chloride concentration is in a fairly good agreement with the results obtained from R_P measurements.     

Corrosion of hot-rolled 430 stainless steel in HCl-based solution

The mixtures of hydrochloric acid and hydrogen peroxide were employed as the environmental friendly pickling solution for 430 hot-rolled stainless steel in this study. Increase of HCl concentration accelerates the corrosion rate of base metal, however aggravates the intergranular attack in sole hydrochloric acid solution. Addition of oxidant (H₂O₂) boosts the corrosion potential of stainless steel significantly resulting in the change of electrode action. At high oxidant content (0.6?mol?l^?1 H₂O₂), a corrosion product film accumulates onto the surface and the corrosion is then governed by the mass-transport at the film/stainless steel interface. The random dissolving of metal ions because of the film leads to brightening of stainless steel surface and the local corrosion is suppressed.     

Corrosion protection of steel reinforcement by a pretreatment in phosphate solutions: assessment of passivity by electrochemical techniques

Abstract

The aim of this work is to study the protection of steel reinforcement against corrosion by pretreatment in phosphate (Na₃PO₄) solution. The work has been carried out using electrochemical techniques, i.e. corrosion potential E _corr, polarisation resistance R _P and electrochemical impedance spectroscopy (EIS) measurements. The results have been validated by a gravimetric method. It has been stressed that R _P measurements, determined by DC techniques, include the charge transfer resistance R _t plus the resistance associated with the redox process R _ox, both determined by EIS. Also the results have demonstrated that the treatment of the rebar by immersion in the Na₃PO₄ (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which is able to resist longer the action of chlorides to initiate corrosion. However, the resistance of the passive layer against chloride depends on the duration of the treatment by immersion of the rebar within the phosphate solution.     

The role of different surface damages in corrosion process in alkaline sour media

By applying different electrochemical methodologies to 1018 carbon steel/different electrolytic media interfaces, surfaces with generalised and blistered damages, commonly present in the oil refinery catalytic plants, were obtained. Afterwards, a freshly polished carbon steel surface as well as the damaged surfaces were characterised by electrochemical impedance spectroscopy and scanning electronic microscopy (SEM). The SEM results reveal that the damaged surfaces present films with different physical properties.In spite of the surface modification, the corrosion mechanism of these interfaces in a medium simulating catalytic plants condensates of the refineries in Mexico (0.1 M (NH₄)₂S, 0.4 mM NaCN (10 ppm CN⁻), pH=8.8) turned out to be the same. It was also found that the corrosion process presents the following steps: charge transfer resistance of steel oxidation in the metal/corrosion product film interface and the diffusion processes of Fe²⁺ and H^o ions through the corrosion product film. It was demonstrated that when there was no damage on the surface (freshly polished surface), a homogeneous film was formed instantaneously upon introducing carbon steel into the sour media. The corrosion process in this film occurs in three stages. On the surface with generalised corrosion the three stages are favoured, particularly that of atomic hydrogen process (inducing blistering). Meanwhile, the blistered surface presents a higher charge resistance of steel oxidation and the Fe²⁺ and atomic hydrogen diffusions through the corrosion products are slower than those presented on the other surface states.     

Effects of Halides on the Corrosion of Mild Steel in Molten NaNO3-KNO3 Eutectic

Abstract

The effect of alkali halides on the corrosion behaviour of mild steel in, (Na,K)NO₃ eutectic has been studied at temperatures ranging from 300°–450°c. Steady-state potentials of the steel electrode vary with the concentration of Cl^?, Br^?, and I^? ions according to: E = a + b log C. Gravimetric; measurements show that the corrosion process of steel in the melt without and with halide ions, at concentrations ≤0·l M, is essentially the same, the weight gain being parabolic with time. At higher halide concentrations the corrosion rate is linear with time. The corrosion rate also increases with increase in temperature. Both potential and weight gain measurements show that aggressiveness increases in the order: Cl^?<Br^?<I^?. It is suggested that in this system two opposing forces compete on the steel surface. The oxide ions help in building or repairing a passivating film of Fe₃O₄, whilst the aggressive halide ions attack weak areas in the film and assist the corrosion process. The process which prevails depends on the relative concentrations of the two species.

In the case of fluoride, both the potential and weight gain of steel vary with time in an irregular manner, and no definite relation could be obtained. This has been attributed to the low solubility of fluoride in the melt and to the properties of the corrosion products, in that the film formed does not adhere to the metal surface.     

Galvanic Corrosion of a Carbon Steel-Stainless Steel Couple in Sulfide Solutions

The galvanic corrosion behavior of carbon steel-stainless steel couples with various cathode/anode area ratios was investigated in S ²⁻-containing solutions, which were in equilibrium with air, by electrochemical measurements, immersion test, and surface characterization. It is found that the galvanic corrosion effect on carbon steel anode increases with the cathode/anode area ratios, and decreases with the increasing concentration of S²⁻ in the solution. A layer of sulfide film is formed on carbon steel surface, which protects it from corrosion. When the cathode/anode area ratio is 1:1, the potentiodynamic polarization curve measurement and the weight-loss determination give the identical measurement of the galvanic corrosion effect. With the increase of the cathode/anode area ratio, the electrochemical method may not be accurate to determine the galvanic effect. The anodic dissolution current density of carbon steel cannot be approximated simply with the galvanic current density.     

聚左旋多巴-SiO_(2)复合材料在1 M HCl中的缓蚀作用EI北大核心CSCD

随着缓蚀剂的广泛应用,传统缓蚀剂对环境和生物的负面影响日益显现,开发高水溶性、健康无毒、绿色环保的高效缓蚀剂成为研究热点。基于纳米胶体SiO_(2)在水中良好的分散性、无毒等特性,通过左旋多巴(L-DOPA)在纳米胶体SiO_(2)表面接枝聚合,实现聚左旋多巴(Poly-(L-DOPA))在纳米胶体SiO_(2)上的负载,制备低细胞毒性、良好分散性的聚左旋多巴-SiO_(2)(Poly-(L-DOPA)-SiO_(2))缓蚀剂,并探究1 M HCl中Poly-(L-DOPA)-SiO_(2)对Q235碳钢的缓蚀作用。傅里叶红外光谱(FTIR)、紫外可见光吸收光谱(UV-vis)和X射线衍射(XRD)结果证实了Poly-(L-DOPA)-SiO_(2)的合成。电化学结果表明,缓蚀效率随Poly-(L-DOPA)-SiO_(2)浓度的增加而增加,当Poly-(L-DOPA)-SiO_(2)的浓度为500 mg/L时,缓蚀效率可以达到85.9%。添加Poly-(L-DOPA)-SiO_(2)使极化曲线的阴阳极斜率发生明显改变,说明阳极的金属氧化反应和阴极O_(2)/H+的还原反应和均被抑制,是一种混合型抑制剂。扫描电子显微镜(SEM)和激光共聚焦显微镜(CLSM)观察发现,Poly-(L-DOPA)-SiO_(2)可以在金属表面形成保护膜有效抑制酸性溶液对碳钢的腐蚀。该缓蚀剂以生物质L-DOPA为原料,纳米SiO_(2)为载体,是绿色高效缓蚀剂合成的新思想。     

Effect of temperature on the inhibition of the acid corrosion of steel by benzaldehyde thiosemicarbazone: Impedance measurements

An impedance study has been carried out of the corrosion of steel in sulphuric acid containing benzaldehyde thiosemicarbazone as an inhibitor, over the temperature range 25 – 60 °C. The impedance data indicate that the corrosion of steel is controlled by a charge transfer process at all the temperatures examined and in solutions containing various concentrations of the inhibitor. At a critical concentration of the inhibitor (5 × 10^-4 M) a high protection efficiency is maintained over the temperature range examined. This is thought to relate to a high surface coverage of a relatively compact adsorbed film, which resists desorption at elevated temperatures, unlike the behaviour evident at lower inhibitor concentrations.     

A new steel with good low‐temperature sulfuric acid dew point corrosion resistance

In this work, new steels (1#, 2#, and 3#) were developed for low‐temperature sulfuric acid dew point corrosion. The mass loss rate, macro‐ and micro‐morphologies and compositions of corrosion products of new steels in 10, 30, and 50% H₂SO₄ solutions at its corresponding dew points were investigated by immersion test, scanning electron microscopy (SEM) and energy‐dispersive spectrometry (EDS). The results indicated that mass loss rate of all the tested steels first strongly increased and then decreased as H₂SO₄ concentration increased, which reached maximum at 30%. Corrosion resistance of 2# steel is the best among all specimens due to its fine and homogeneous morphologies of corrosion products. The electrochemical corrosion properties of new steels in 10 and 30% H₂SO₄ solutions at its corresponding dew points were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The results demonstrated that corrosion resistance of 2# steel is the best among all the experimental samples due to its lowest corrosion current density and highest charge transfer resistance, which is consistent with the results obtained from immersion tests.     

Modeling and experimental calibration of the corrosion of RHA steel in immersion and salt-fog environments

ABSTRACT

An investigation into the general and pitting corrosion rates of rolled homogeneous armour (RHA) steel in immersion and salt-fog environments is presented. Although the mechanical properties of RHA steel have been studied, the corrosion effects on RHA steel have not been quantified. An immersion environment of 3.5% NaCl was used to induce corrosion for four immersion samples. A Q-fog corrosion tester was used to simulate a salt-fog/humidity/drying environment for four salt-fog samples. The different mechanisms of corrosion and their rates were quantified through mass loss, laser profilometry and scanning electron microscopy. The immersion samples show a linear rate of corrosion of 1.47?g/year (R²?=?0.994) throughout the entire testing period. The salt-fog samples had a significant mass gain for the first 500?h of corrosion, as the corrosion products are retained. Immersion samples showed no signs of pitting, while the salt-fog samples had sustained pit nucleation, growth, and coalescence.     

Influence of Zn injection on characteristics of oxide film on 304 stainless steel in borated and lithiated high temperature water

The oxide film on 304 stainless steel exposed to the hydrothermal environments at 573.15 K up to 20 days without/with 10 ppb Zn injection has been investigated ex situ by X-ray photoelectron spectroscopy (XPS). ZnFe₂O₄ and ZnCr₂O₄ were found to be formed in the oxide film at the initial stage of immersion by substitution reaction between Zn²⁺ and Fe²⁺, and ZnCr₂O₄ became dominant after long-term immersion. The calculations of potential-pH diagrams, solubilities and crystallographic features of spinels have been done to evaluate the oxide film structure and the inhibition mechanism caused by Zn injection.     

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).