Effect of acetic acid on CO2 corrosion of carbon steel in NaCl solution

Potentiodynamic sweep and electrochemical impedance spectroscopy measurements were applied to investigate the effects of both temperature and acetic acid (HAc) on the anodic and cathodic reactions in CO₂ corrosion of P110 steel in 3.5% NaCl solution. The temperatures were controlled at 30 and 60 °C. The concentrations of HAc were controlled at 0, 1000, 3000 and 5000 ppm. In this work, the corrosion parameters of polarization curves, such as corrosion potential (E_corr), corrosion current density (i_corr), and anodic and cathodic branch slopes (b_a and b_c), are presented and discussed in detail. In addition, the equivalent circuit models and ZsimpWin software were utilized to discuss the Nyquist plots. The plots showed that the E_corr values shifted in the positive direction as the HAc concentration increased. The i_corr values increased with the increase in HAc concentration, indicating that HAc could accelerate the corrosion. The impedance spectra measured at 30 and 60 °C have different time constants and characterization. The coverage fraction θ and the thickness L of corrosion film are two most important controlled variables that influence and control the CO₂ corrosion mechanisms. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

Several silica‐based solutions with 50 g/l of SiO₂ were prepared from sodium silicate solutions and silica sol; the silicate conversion coatings were obtained by immersing hot‐dip galvanized steel sheets in these solutions. These solutions were characterized using high‐resolution transmission electron microscopy and ²⁹Si nuclear magnetic resonance; the morphology of the coatings was observed by SEM and atomic force microscopy while the corrosion resistance was evaluated by electrochemical measurements as well as neutral salt spray tests. The results show that the coatings obtained from the single silica sol solution had poor adhesion and the coating obtained from the sodium silicate solution with low SiO₂/Na₂O molar ratio was uneven. By adding the silica sol to the silicate solution with low molar ratio, uniform coatings with better protection property were obtained. According to the results of ²⁹Si nuclear magnetic resonance spectra, the effects of the distribution of silicate anions with various polymerization degrees in the silica‐based solutions on the microstructure and corrosion resistance of the silicate coatings are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

A facile method for fabrication of superhydrophobic coating on aluminum alloy

A superhydrophobic coating applied in corrosion protection was successfully fabricated on the surface of aluminum alloy by chemical etching and surface modification. The water contact angle on the surface was measured to be 161.2° ± 1.7° with sliding angle smaller than 8°, and the superhydrophobic coating showed a long service life. The surface structure and composition were then characterized by means of SEM and XPS. The electrochemical measurements showed that the superhydrophobic coating significantly improved the corrosion resistance of aluminum alloy. The superhydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it was found that only about 6% of the water surface is in contact with the metal substrate and 94% is in contact with the air cushion. Copyright © 2011 John Wiley & Sons, Ltd.     

Corrosion inhibition of AISI 1020 steel based on tungstate anion and amoxicillin as corrosion inhibitors in 0.05 mol l−1 NaCl solution or inserted into cellulose acetate films

Sodium tungstate and amoxicillin were used separately or combined in a solution containing 0.05 mol l^?1 NaCl or inserted into cellulose acetate films as a corrosion inhibition method for American Iron and Steel Institute (AISI) 1020 steel. The electrochemical behavior of AISI 1020 steel was characterized using open‐circuit potential, anodic polarization and electrochemistry impedance spectroscopy. The inhibitor effect of tungstate anions was proved, and its combination with amoxicillin was considered inferior when tungstate was used alone. This behavior was attributed to weaker adsorption of amoxicillin when compared with the adsorption of tungstate anion both deposited on the alloy and into the cellulose acetate film on the steel. Copyright © 2014 John Wiley & Sons, Ltd.     

Synergistic effect of activated carbon from disposed plastics and polybenzoxazine composite coating on corrosion inhibition

The fabrication of activated carbon dispersed polybenzoxazine (BXP) composite through a single step melt condensation technique is reported. Employing green strategy, activated carbon (AC) was obtained from various types of worn-out plastics such as computer keyboard, sponge, electrical switches, and automobile tyres. Structural features of all the polymeric composites were explored using Fourier transform infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscope (FESEM) with Energy Dispersive X-ray Analysis (EDAX). Thermal stability and hardness of the composites was analyzed by recording thermogravimetric analysis (TGA) and Rockwell hardness measurements. The results of thermal studies revealed that AC–BXP composites show higher thermal stability (301.98°C) than BXP (220.71°C). Rockwell hardness study (RHN) for ACWCKB@BXP is 71 whereas pristine BXP showed only 20. The corrosion protection ability of coated steel was examined through potentiodynamic polarization and electrochemical impedance spectroscopy analysis. From the Tafel plot, more shift in E_corr value (from −0.6286 to −0.5065 V) towards positive side confirms its corrosion protection ability. Furthermore, the I_corr, the corrosion rate and the corrosion protection efficiency of the ACWTYR@BXP composite are 0.83 × 10⁻⁶ A/cm², 0.0098 mm/year, and 99.54%, respectively, which inhibit the rate of corrosion to a greater extent in 3.5% NaCl solution. The current study applies principles of green chemistry like minimum number of synthesis steps, non-usage of solvents and simply adoptable coating procedure.     

Effect of temperature on CO2 corrosion of carbon steel

This work investigates the effect of temperature on the corrosion product layer of carbon steel exposed to a CO₂‐containing solution. The measurement techniques, such as scanning electron microscopy with energy dispersive spectrometry, X‐ray diffraction, and X‐ray photoelectron spectroscopy, were used to systematically characterize the morphology and composition of the corrosion product layer. The corrosion rates were calculated by weight loss method. The corrosion mechanisms as a function of temperature are studied and discussed. The results showed that temperature is an important factor in the corrosion rate of carbon steel. Copyright © 2009 John Wiley & Sons, Ltd.     

A zirconia-polyester glycol coating on differently pretreated AISI 316L stainless steel: corrosion behavior in chloride solution

The effect of zirconia and zirconia-polyester glycol hybrid coatings on the corrosion resistance of mechanically polished or anodized AISI 316 stainless steel (316L), was studied by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.1 M NaCl and scanning electron microscope and atomic force microscopy examinations. The deposition of zirconia coatings was achieved by the sol–gel technique by immersing the samples in either the inorganic polymer or the organic–inorganic polymer mixture. From potentiodynamic and impedance measurements, the grade of protection is reduced with the exposure time to the electrolyte, which is mainly associated with lost of film adhesion and, consequently, detachment from the metal substrate. However, the uncoated anodized sample revealed an unexpected corrosion behavior; the anodic film formed during anodizing readily increased the corrosion resistance of the 316L stainless steel in 0.1 M NaCl, revealing a considerable reduction in the corrosion current density and an increase in the pitting potential.     

Characteristics of CO2 corrosion scale formed on P110 steel in simulant solution with saturated CO2

The SEM, X‐ray diffraction (XRD), and XPS were employed to systematically characterize the component and microstructure of the corrosion scale formed on P110 steel exposed to carbon dioxide (CO₂) environment. A loose and porous microstructure in corrosion scale was observed under turbulent flow condition for 120 h at 100 °C with a carbon dioxide partial pressure of 4 MPa in which the principal component was iron carbonate (FeCO₃), whereas at 160 °C the corrosion scale was composed mainly of FeCO₃ and a little amount of FeO(OH). In addition, complex carbonate (Mg,Fe)CO₃ was produced because some Fe positions in FeCO₃ lattice were substituted by Mg. It showed that a double‐layer structure of corrosion scale was observed at 160 °C compared with the result at 100 °C. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of anodic oxidation on corrosion properties of Al coating by arc spraying in seawater

A layer of Al coatings was prepared on the S355 steel by arc spraying, which was conducted by anodic oxidation treatment; the morphologies, chemical element compositions and phases of Al coating, and anodic oxide layer were analyzed with field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and X‐ray diffraction (XRD), respectively. The corrosion protections of Al coating before and after anodic oxidation were discussed with a seawater immersion test; the corrosion resistance mechanisms of Al coating and anodic oxide layer in the seawater were also investigated. The results show that the thickness of Al coating is about 300 µm by arc spraying, the sample surfaces become loose after seawater immersion corrosion and Cl^? and O^2? penetrate into the substrate from the cracks, destroying the binding properties of coating–substrate, and the coating fails. After anodic oxidation, the oxide layer is formed in the surface of Al coating with the thickness of about 30 µm; the corrosion products are mainly composed of Al(OH)₃, which barraged the holes caused by seawater corrosion. The corrosion cracks are formed during the corrosion, while the number and depth of cracks decrease obviously after anodic oxidation treatment. The corrosion of Al coating becomes the local corrosion after anodic oxidation treatment, and the grains are smaller, which are easily nucleated to form a new corrosion resistance layer. Copyright © 2015 John Wiley & Sons, Ltd.     

Enhanced corrosion protection performance with MWCNT dispersed epoxy coating prepared under supercritical CO2 assistance

The corrosion protection performance of epoxy coatings could be enhanced by incorporation of nanofillers such as MWCNT. However, a homogeneous dispersion of MWCNT in epoxy polymer is still a teasing challenge. Herein, we report an environmentally benign single‐step supercritical CO₂ processing method to improve the dispersion of MWCNT in epoxy matrix in order to achieve an effective anticorrosive coating. The executed approach provides a cluster‐free uniform distribution of MWCNT in epoxy matrix as characterized with UV‐visible spectroscopy, Fourier transforms infrared spectroscopy, X‐ray diffraction, and surface analysis. The anticorrosive characteristics of MWCNT/epoxy coating were studied in NaCl as well as in photodegraded dye medium through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. We observed the remarkable corrosion of model metal substrate in photodegraded dye medium besides NaCl medium. In both mediums, the protection efficacy of MWCNT/epoxy coating was deduced from the stable impedance arcs in Nyquist plot and increased impedance modulus. The electrochemical impedance spectra were best fitted with equivalent circuits showing the higher values of pore resistance. Also, the MWCNT/epoxy coating exhibited a positive shift of corrosion potential and possessed a lower corrosion rate as compared with neat epoxy coating. More direct evidence of the excellent barrier properties for MWCNT/epoxy coating was visualized in SEM images. The obtained results implied that the superior dispersion of MWCNT into epoxy matrix significantly reduces the porosity of coating and inhibits the permeability of corrosive ions. We expect supercritical CO₂ assisted dispersion method can offer an efficient, cost‐effective, and industrially viable route to develop high performance protective coatings for varied commercialized applications.     

Corrosion protection of carbon steel using a combination of Zr conversion coating and subsequent zinc-rich silicate coating with a flake ZnAl alloy

To improve the corrosion protection properties of zinc-rich silicate coatings on steel, zirconium pretreatment loaded with (3-aminopropyl)triethoxysilane (APTES) 0.025 % (v/v) and the partial replacement of spherical zinc by flake ZnAl alloy were investigated. DC polarization and electrochemical impedance spectroscopy (EIS) show that the zirconium pre-treated layer containing APTES improves the corrosion protection of the bare steel. Zinc-rich silicate coatings containing flake ZnAl with and without pretreatment were evaluated by EIS, salt spray test and pull-off test. Pretreatment with a zirconium conversion layer reduces corrosion products and adhesion loss (from 16.53% to 12.54%) while the performance of corrosion protection significantly increased from 2003 Ω.cm² to 2640 Ω.cm² in comparison with the non-pretreated samples. The results show that flake ZnAl pigment (5 wt%) significantly improves corrosion resistance and prolongs the duration of cathodic protection of zinc-rich silicate coatings.     

Electrochemical noise analysis of pitting corrosion of J55 steel in NaCl + NaHCO3 electrolytes

Electrochemical noise (EN) was used to study the pitting corrosion of J55 steel in NaCl/NaHCO₃ electrolytes. Below critical ratio for Cl^? to HCO^?, the corrosion rate increased with added NaCl, and conversely, decreased above that level. Also, the critical ratio was between 1 and 1.66. The PSD for potential and current noise were linear and rather gently sloped. J55 casing steel was quite sensitive to NaCl/NaHCO₃ electrolytes. Copyright © 2010 John Wiley & Sons, Ltd.     

Delamination of organic coating on carbon steel studied by scanning Kelvin probe force microscopy

Corrosion‐induced delamination of an epoxy coating on the AISI/SAE 1045 carbon steel was studied under a humid atmospheric condition (temperature of 25 °C, 1 standard atmospheric pressure, relative humidity of 90%) by the technique of scanning Kelvin probe force microscopy (SKPFM). Surface‐polished 1045 samples were first cold‐coated with the epoxy and then subject to the atmospheric corrosion under the specified condition. At predetermined time intervals, surface Volta potential differences of the samples were measured using the SKPFM over the dry surface of epoxy coating. The map of Volta potential differences demonstrated high contrasts among three characteristic zones: intact steel‐epoxy interface, delaminated interface, and interface with active corrosion, which was then linked to the actual corrosion potential of the steel (measured using a potentiostat with respect to a saturated calomel electrode) based on a rigorous calibration procedure. It was found that the SKPFM was able to provide direct and nondestructive detection of early active corrosion and coating delamination on steels at a submicroscopic resolution, which outperformed the conventional electrochemical techniques for the same purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

Synergistic corrosion inhibition effect of copolymer and an amphoteric surfactant on carbon steel in 3.5 NaCl solution: experimental and theoretical research

Journal of Solid State Electrochemistry - The copolymer poly (aniline-co-orthotoluidine) noted poly (ANI-co-OT) was chemically synthesized and characterized by FT-IR, UV–Vis, and XRD...     

Sebacic acid as corrosion inhibitor for hot-dip galvanized (HDG) steel in 0.1 M NaCl

The potential of sebacic acid as a corrosion inhibitor for hot-dip galvanized steel in 0.1 M NaCl solution has been investigated. Different concentrations of the organic acid have been tested in order to understand the inhibition mechanism of the compound. The electrochemical test revealed a competitive mechanism between the dissolution of the metal in the acidified solution and the inhibition provided by the dicarboxylic species. The formation of a whitish layer consisting of zinc carboxylates and corrosion products was proved by means of scanning electron microscopy (SEM) investigation combined with Fourier transform infrared (FT-IR) analysis. A bidentate bridging coordination between the Zn(II) and the carboxylic species is suggested.     

Electrochemical analysis of molybdate conversion coating on hot‐dip galvanized steel in various growth stages

The electrochemical behavior of molybdate conversion coatings in various growth stages was investigated by electrochemical impedance spectroscopy and equivalent circuits. The chemical composition and microstructure were characterized by SEM/energy dispersive spectroscopy, atomic force microscopy, and AES. Neutral salt spray tests complemented the information. The results indicated that the growth process of the molybdate conversion coating was accompanied by the growth of micro cracks, consisting of three stages: in the early and middle stages, the protective property of the coatings increased with increasing treatment time and then decreased when the cracks developed in the last stage. On the basis of the observation of the microstructure and the analysis of the electrochemical impedance spectra of the coatings in various stages, a simplified growth process model of the molybdate conversion coating on hot‐dip galvanized steel was created. Copyright © 2017 John Wiley & Sons, Ltd.     

Thermal analysis of corrosion products formed on carbon steel in ammonium chloride solution

The influence of different ions NO₃ ^? and SO₄ ^2? on the carbon steel corrosion in ammonium chloride was investigated using mass loss measurements and potentiodynamic polarization. Corrosion products were analyzed using X-ray photoelectron spectroscopy (XPS) and simultaneous thermal and differential scanning calorimetry (TG/DSC). XPS analysis shows that the main product of corrosion is a non-stoichiometric Fe³⁺ oxyhydroxide, consisting of a mixture of FeO(OH) and FeO(OH) containing inclusions of these anions, species such as Fe³⁺O(OH,Cl^?); Fe³⁺O(OH,SO₄ ^2?); and Fe³⁺O(OH,NO₃ ^?). TG/DSC confirms the decomposition of the rusty products formed by chemical corrosion, compounds like Fe³⁺ oxyhydroxides, with β-FeOOH as the major phase, crystal structure of which may contain Cl^?, NO₃ ^?, and SO₄ ^2?—e.g., akaganeite [Fe³⁺O(OH,A)].     

Structure,corrosion, and tribological properties of CrSiN coatings with various Si contents in 3.5% NaCl solution

The CrSiN coatings with different silicon contents were deposited on 304L stainless steel and single silicon substrates using medium frequency magnetron sputtering via adjusting the silicon target current. Microstructures, mechanical, corrosion, and tribological performances were systematically investigated by the corresponding equipment. The results showed that the CrSiN coatings were composed of 2 phases: the nanocrystalline CrN coordinated with adjacent Si₃N₄ to form a typical nanocrystalline amorphous structure. With the increase of silicon content, the hardness emerged a rising trend until 12.65 at.%, where the hardness reached its highest value at approximately 22 GPa. At the moment, the friction coefficient and wear rate were approximately 0.27 and 6.9 × 10⁻⁸ mm³/Nm, respectively, which were 18.75% and 61.67% lower than that of the CrN coating, respectively. This mainly attributed to the lubrication of tribochemical products of SiO₂ and Si(OH)₄. In addition, excellent toughness, high hardness, preferable adhesion, and good corrosion resistance also contributed to improve the tribological properties of CrSiN coating.     

Construction and corrosion behaviors of a bilayer superhydrophobic film on copper substrate

A novel bilayer superhydrophobic film was constructed on Cu substrate by a simple multi‐step process. First, (3‐mercaptopropyl) trimethoxysilane (MPTMS) molecules were self‐assembled onto the pre‐etched Cu surface via covalent bonding followed by hydrolysis and condensation, then 1H, 1H, 2H, 2H‐perfluorodecyltrichlorosilane (PFDTS) were grafted onto the resultant hydroxyl terminated surface via the Si‐O‐Si bonding. The so‐prepared sample was defined as Cu‐MPTMS‐PFDTS. The structure and morphology of the samples were characterized by means of contact angle measurement, X‐ray photoelectron spectroscopy and scanning electron microscopy. The corrosion behaviors of the films were evaluated by Tafel plot and electrochemical impedance spectroscopy on an electrochemical work station. The results indicated that the bilayer superhydrophobic film possessed better corrosion protection as compared with the control samples. The superiority of the corrosion protection was mainly ascribed to the following two aspects: the superhydrophobicity and polysiloxane micro‐structures of the Cu‐MPTMS‐PFDTS. Copyright © 2012 John Wiley & Sons, Ltd.     

Layer-by-layer stacked graphene nanocoatings by Marangoni self-assembly for corrosion protection of stainless steel

Graphene nanosheets are widely used in anti-corrosion polymeric coating as filler,owing to the excellent electrochemical inertness and barrier property.However,as the arrangement of graphene nanosheets is difficult to form a perfect layered structure,polymeric coating with graphene nanosheets usually needs micron-scale thickness to ensure the enhancement of corrosion protection.In this work,layer-by-layer stacked graphene nanocoatings were fabricated on stainless steel by self-assembly based on Marangoni effect.The anti-corrosion property of graphene coatings were studied through Tafel polarization curves,electrochemical impedance spectroscopy and accelerated corrosion test with extra applied voltage.The self corrosion current density of optimized three-layered graphene coated sample was one quarter of that of bare stainless steel.And the self corrosion potential of optimized sample is increased to-0.045 V.According to the results,graphene nanocoatings composed of layered nanosheets exhibits good anticorrosion property.Besides,the self-assembly method provide a promising approach to make layeredstructure coating for other researches about 2 D material nanosheets.