Editorial

3 pages, 184 KiB

Open AccessEditorial

Advances in Corrosion and Protection of Materials

by Renato Altobelli Antunes

Metals 2023, 13(6), 1059; https://doi.org/10.3390/met13061059 - 01 Jun 2023

Cited by 2 | Viewed by 1089

From an engineering standpoint, the corrosion of metallic materials is a challenging phenomenon, responsible for huge costs and serious failures [...] Full article

(This article belongs to the Special Issue Advances in Corrosion and Protection of Materials)

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22 pages, 6587 KiB

Open AccessArticle

Comparative Study of Protection Efficiency of C-Steel Using Polystyrene Clay Nanocomposite Coating Prepared from Commercial Indian Clay and Local Khulays Clay

by Nashwa A. Howyan, Layla A. Al Juhaiman, Waffa K. Mekhamer and Hissah H. Altilasi

Metals 2023, 13(5), 879; https://doi.org/10.3390/met13050879 - 02 May 2023

Cited by 3 | Viewed by 1377

Abstract

This work aimed to compare the coating protection efficiency of C-steel using two kinds of clay: a local Khulays clay (RC_Kh) from Saudi Arabia and a commercial clay (CC_In) from India. Clay-based polymer nanocomposites have a unique layered structure, [...] Read more.

This work aimed to compare the coating protection efficiency of C-steel using two kinds of clay: a local Khulays clay (RC_Kh) from Saudi Arabia and a commercial clay (CC_In) from India. Clay-based polymer nanocomposites have a unique layered structure, rich intercalation chemistry, and availability at low cost. They are promising reinforcements for polymers. The raw clay for both clay types was washed before being treated with NaCl to produce sodium clay (NaC). The cationic surfactant cetylpyridinium chloride (CPC) was then used to convert the NaC into the organoclay (OC) form. Polystyrene/organoclay nanocomposites (PCNs) were prepared by combining different concentrations of organoclay (1%, 3%, and 5% OC) in toluene solvent and polystyrene (PS) as the matrix. To ensure the success of the PCN modification process, the organoclay and PCN films were characterized using a variety of techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The shifts in the FT-IR spectra after the CPC treatment of NaC confirmed the presence of CPC in the organoclay samples and the presence of OC in the PCNs. The exfoliated structure was obtained from the XRD spectrum for low clay loading (1–3% PCN), while the intercalated structure was the dominant form for the 5% PCN. The XRD results were confirmed by TEM images. To calculate the coating efficiency of the PCNs, various electrochemical methods were used. The electrochemical measurements included electrochemical impedance spectroscopy (EIS), the electrochemical frequency modulation (EFM) method, and Tafel plots. The PCN with a concentration of 1 wt.% OC has a fully exfoliated structure and higher coating efficiency than the PCNs with partially exfoliated structures (3 wt.% and 5 wt.%). It was found from the Tafel plots that commercial Indian clay has better corrosion protection (81.4%) than local Khulays clay (60.2%). A comparison with other studies using current density values shows that our results are superior to those of many studies. Full article

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18 pages, 6863 KiB

Open AccessArticle

A Study of the Mechanisms and Kinetics of the Localized Corrosion Aggravation of Ductile Iron in a Harsh Water Quality Environment

by Bingqin Wang, Tao Liu, Kai Tao, Lingsheng Zhu, Chao Liu, Xingyue Yong and Xuequn Cheng

Metals 2022, 12(12), 2103; https://doi.org/10.3390/met12122103 - 07 Dec 2022

Cited by 5 | Viewed by 1706

Abstract

Ductile iron is a high-strength cast iron material. The spherical graphite obtained by inoculation treatment effectively improves the mechanical properties of cast iron, resulting in higher strength than carbon steel. However, severe corrosion may occur under specific circumstances, especially in thermal water pipelines. [...] Read more.

Ductile iron is a high-strength cast iron material. The spherical graphite obtained by inoculation treatment effectively improves the mechanical properties of cast iron, resulting in higher strength than carbon steel. However, severe corrosion may occur under specific circumstances, especially in thermal water pipelines. In this paper, the corrosion mechanisms at the main defective points of ductile iron were investigated using microscopic morphological characterization after accelerated tests combined with numerical simulations. The influence law of each environmental factor on the corrosion kinetics of ductile iron in a complex water quality environment was studied using dynamic potential polarization tests. The results showed that the main causative factors leading to the increased corrosion of ductile iron were the presence of tail-like gaps on its surface, and the crescent-shaped shrinkage and loosening organization around the graphite spheres. After mechanical treatment was applied to eliminate the obvious defects, the number of corrosion pits was reduced by 41.6%, and the depth of the pits was slowed down by 40% after five days. By comparison, after ten days, the number of pits was reduced by 51%, and the depth of the pits was slowed down by 50%. The dynamic potential polarization test results show that the dissolved oxygen concentration has the greatest influence on the corrosion of ductile iron in the simulated water environment; meanwhile, the water hardness can slow down the corrosion of ductile iron. The relative influence of each environmental factor is as follows: dissolved oxygen concentration > temperature > immersion time > water hardness > pH > Cl⁻. Full article

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12 pages, 2036 KiB

Open AccessArticle

Effect of Immersion Time in Chloride Solution on the Properties of Structural Rebar Embedded in Alkali-Activated Slag Concrete

by Willian Aperador, Jorge Bautista-Ruiz and Jorge Sánchez-Molina

Metals 2022, 12(11), 1952; https://doi.org/10.3390/met12111952 - 15 Nov 2022

Cited by 4 | Viewed by 1389

Abstract

The electrochemical impedance spectroscopy (EIS) technique is widely used in the study of the corrosion of metallic materials. This method also allows for the electrical characterization at the ceramic–metal interface in contact with an aqueous solution composed of chloride ions. EIS makes it [...] Read more.

The electrochemical impedance spectroscopy (EIS) technique is widely used in the study of the corrosion of metallic materials. This method also allows for the electrical characterization at the ceramic–metal interface in contact with an aqueous solution composed of chloride ions. EIS makes it possible to discriminate the contribution of the phenomena that occur in the interface to determine the porosity of the cementitious material. The porosity determines the degree of corrosion of the metallic material and the diffusion processes on the electrode surface. In this study, the degradation of a type of non-Portland cement obtained from blast furnace steel slag and activated alkali was evaluated. This type of cement is of great interest because it avoids the emission of CO₂ during its manufacture. Estimating the porosity determined the degree of deterioration suffered by the steel embedded in the concrete as a function of the evaluation time. The hydrated samples were also characterized by ²⁹Si magic angle spinning nuclear magnetic resonance (MAS-NMR) to determine the structure of the formed calcium silicate hydrate (C-S-H) gel. This mixture formed a C-S-H gel, constituted mainly of silicon in the middle groups, in chains in the disilicates. The effect of the slag was remarkable in improving the other evaluated characteristics, i.e., in the porous matrix, the concrete was found to significantly reduce the current passing through as a function of time, showing a reduction in porosity and an increase in impedance because of the generated pozzolanic reaction. Full article

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25 pages, 8807 KiB

Open AccessEditor’s ChoiceArticle

Biofilm Development on Carbon Steel by Iron Reducing Bacterium Shewanella putrefaciens and Their Role in Corrosion

by Sachie Welikala, Saad Al-Saadi, Will P. Gates, Christopher Panter and R. K. Singh Raman

Metals 2022, 12(6), 1005; https://doi.org/10.3390/met12061005 - 12 Jun 2022

Cited by 4 | Viewed by 2075

Abstract

Microscopic, electrochemical and surface characterization techniques were used to investigate the effects of iron reducing bacteria (IRB) biofilm on carbon steel corrosion for 72 and 168 h under batch conditions. The organic nutrient availability for the bacteria was varied to evaluate biofilms formed [...] Read more.

Microscopic, electrochemical and surface characterization techniques were used to investigate the effects of iron reducing bacteria (IRB) biofilm on carbon steel corrosion for 72 and 168 h under batch conditions. The organic nutrient availability for the bacteria was varied to evaluate biofilms formed under nutritionally rich, as compared to nutritionally deficient, conditions. Focused ion beam-scanning electron microscopy (FIB-SEM) was used to investigate the effect of subsurface biofilm structures on the corrosion characteristics of carbon steel. Hydrated biofilms produced by IRB were observed under environmental scanning electron microscope (ESEM) with minimal surface preparation, and the elemental composition of the biofilms was investigated using energy dispersive spectroscopy (EDX). Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to provide information on the organic and inorganic chemical makeup of the biofilms. Electrochemical techniques employed for assessing corrosion, by open circuit potential, linear polarization and potentiodynamic polarization tests indicated no significant difference in the corrosion resistance for carbon steel in IRB-inoculated, compared to the abiotic solutions of common Postgate C after 72 and 168 h. However, the steel was found to be more susceptible to corrosion when the yeast extract was removed from the biotic environment for the 168 h test. In the absence of yeast nutrient, it is postulated that IRB received energy by transforming the protective film of Fe³⁺ into more soluble Fe²⁺ products. Full article

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14 pages, 6372 KiB

Open AccessArticle

Oxidation Behavior of Intermetallic Phase and Its Contribution to the Oxidation Resistance in Fe-Cr-Zr Ferritic Alloy

by Shenghu Chen and Lijian Rong

Metals 2022, 12(5), 827; https://doi.org/10.3390/met12050827 - 11 May 2022

Cited by 1 | Viewed by 1346

Abstract

Oxidation resistance of the ferritic Fe-Cr-W-Zr alloy with dispersed Fe₂Zr phase were investigated in stagnant air and in static oxygen-saturated liquid Pb-Bi eutectic separately considering the service environment in the advanced generation IV nuclear reactors. A duplex structure including an outer [...] Read more.

Oxidation resistance of the ferritic Fe-Cr-W-Zr alloy with dispersed Fe₂Zr phase were investigated in stagnant air and in static oxygen-saturated liquid Pb-Bi eutectic separately considering the service environment in the advanced generation IV nuclear reactors. A duplex structure including an outer Fe₂O₃ layer and an inner (Fe,Cr,Zr)₂O₃ layer is developed after oxidation in air, while a three-layered structure consisting of outer magnetite layer, inner Fe-Cr spinel layer, and internal oxidation zone is formed after oxidation in liquid Pb-Bi eutectic. The dispersed Fe₂Zr phase shows delayed oxidation with respect to the α-Fe in air and in liquid Pb-Bi eutectic, which significantly affects the oxidation behaviors of the alloy. After oxidation in air at 923 K, the incorporated Fe₂Zr phase in the scale would obstruct the diffusion of metal/oxygen across the scale, resulting in the nonuniform oxidation behavior. After oxidation in static oxygen-saturated liquid Pb-Bi eutectic at 823 K, a reduction in the Fe supply to the magnetite/Fe-Cr spinel interface is present adjacent to the Fe₂Zr phase, which might lead to the creation of cavities in the outer magnetite layer with prolonged oxidation time. Full article

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16 pages, 10323 KiB

Open AccessArticle

Corrosion Mechanism of L360 Pipeline Steel Coated with S8 in CO₂-Cl⁻ System at Different pH Values

by Fan Wang, Jinling Li, Chengtun Qu, Tao Yu, Yan Li, Shidong Zhu, Bo Yang and Frank Cheng

Metals 2021, 11(12), 1975; https://doi.org/10.3390/met11121975 - 08 Dec 2021

Cited by 2 | Viewed by 2215

Abstract

The corrosion behavior of L360 pipeline steel coated with or without elemental sulfur (S8) in CO₂–Cl⁻ medium at different pH was studied. An autoclave was used to simulate the working conditions for forming the corrosion scale, and an electrochemical workstation [...] Read more.

The corrosion behavior of L360 pipeline steel coated with or without elemental sulfur (S8) in CO₂–Cl⁻ medium at different pH was studied. An autoclave was used to simulate the working conditions for forming the corrosion scale, and an electrochemical workstation with a three-electrode cell was used to analyze the electrochemical characterization of the corrosion scale. A wire beam electrode was used to determine the potential and current distribution, and scanning electron microscopy and X-ray diffraction were used to characterize the morphology and composition of the corrosion scale. The results showed that the deposition of S8 on the surface of the electrodes caused serious localized corrosion, especially under acidic conditions. The morphology and localized corrosion intensity index further proved that the deposition of S8 significantly promoted corrosion, especially pitting corrosion. Finally, a novel corrosion mechanism of L360 pipeline steel coated with S8 in a CO₂-Cl⁻ environment under acidic conditions was proposed, and we then modeled the theoretical mechanisms that explained the experimental results. Full article

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17 pages, 59923 KiB

Open AccessEditor’s ChoiceArticle

Influence of Anodization on the Fatigue and Corrosion-Fatigue Behaviors of the AZ31B Magnesium Alloy

by Leandro Antonio de Oliveira, Silvano Leal dos Santos, Vinicius Antonio de Oliveira and Renato Altobelli Antunes

Metals 2021, 11(10), 1573; https://doi.org/10.3390/met11101573 - 01 Oct 2021

Cited by 9 | Viewed by 1911

Abstract

The aim of the present work was to investigate the effect of anodization on the fatigue and corrosion-fatigue behavior of the AZ31B magnesium alloy. Samples were anodized in constant current density mode at 20 mA cm⁻² for 5 min at room temperature, [...] Read more.

The aim of the present work was to investigate the effect of anodization on the fatigue and corrosion-fatigue behavior of the AZ31B magnesium alloy. Samples were anodized in constant current density mode at 20 mA cm⁻² for 5 min at room temperature, in an environmentally friendly electrolyte consisting of a mixture of sodium hydroxide and sodium silicate. Fatigue tests were conducted in air and in phosphate buffer solution (PBS) at room temperature in the tension-tension mode, at a frequency of 5 Hz and stress ratio of 0.1. S-N curves were obtained for polished and anodized samples. Fracture surface morphology was examined by optical stereo-microscopy and scanning electron microscopy. Results indicated that the fatigue limit was reduced approximately 60% at 10⁶ cycles for the anodized specimens, either for the fatigue tests conducted in air or PBS solution. Anodization had a remarkable effect on the fatigue behavior of the AZ31B alloy. The effect of the corrosive environment, in turn, was not significant. Full article

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13 pages, 85030 KiB

Open AccessArticle

Corrosion Behavior of Copper Bearing Steels and the Derived In-Situ Coating

by Na Li, Ling Yan, Shaodong Wang, Changshun Wang, Hongmei Zhang, Fangfang Ai and Zhengyi Jiang

Metals 2021, 11(9), 1462; https://doi.org/10.3390/met11091462 - 15 Sep 2021

Cited by 3 | Viewed by 2783

Abstract

Using a period immersion wet/dry cyclic corrosion test, in-situ copper-coated steels prepared by corroding copper-bearing steels were investigated in this study. The steel with a higher copper content (>3%) has a higher initial corrosion rate due to its obvious two-phase microstructure. The corrosion [...] Read more.

Using a period immersion wet/dry cyclic corrosion test, in-situ copper-coated steels prepared by corroding copper-bearing steels were investigated in this study. The steel with a higher copper content (>3%) has a higher initial corrosion rate due to its obvious two-phase microstructure. The corrosion rates of all copper bearing steels tend to be stable after a certain time of corrosion. A copper-rich layer is formed between the matrix and the rust layer, which is due to the diffusion of copper from the rust layer to the metal surface. The copper’s stability under this corrosion condition led to the formation of a thin copper-rich film, which was uncovered after removing the rust by choosing appropriate descaling reagents. The copper coating was generated from the matrix itself during the corrosion process at 25 °C, which provided a new approach for producing in-situ composite materials without any bonding defect. It is found that the corrosion rate, corrosion time, and copper content in steel all affect the formation of copper-rich layer. In addition to the noble copper surface, the electrochemical corrosion test results show that the corrosion resistance of copper-coated steel has been significantly improved. Full article

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15 pages, 3220 KiB

Open AccessArticle

The Effect of Immersion Corrosion Time on Electrochemical Corrosion Behavior and the Corrosion Mechanism of EH47 Ship Steel in Seawater

by Hongmei Zhang, Ling Yan, Yangyang Zhu, Fangfang Ai, Hongnan Li, Yan Li and Zhengyi Jiang

Metals 2021, 11(8), 1317; https://doi.org/10.3390/met11081317 - 20 Aug 2021

Cited by 17 | Viewed by 3637

Abstract

In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and [...] Read more.

In this paper, electrochemical corrosion tests and full immersion corrosion experiments were conducted in seawater at room temperature to investigate the electrochemical corrosion behavior and the corrosion mechanism of high-strength EH47. The polarization curve, EIS (electrochemical impedance spectroscopy), SEM (scanning electron microscope), and EDS analyses were employed to analyze the results of the electrochemical corrosion process. The electrochemical corrosion experiments showed that the open circuit potential of EH47 decreases and then increases with an increase in total immersion time, with the minimum value obtained at 28 days. With an increase in immersion time, the corrosion current density (I_corr) of EH47 steel first decreases and then increases, with the minimum at about 28 days. This 28-day sample also showed the maximum capacitance arc radius, the maximum impedance and the minimum corrosion rate. In the seawater immersion test in the laboratory, the corrosion mechanism of EH47 steel in the initial stage of corrosion is mainly pitting corrosion, accompanied by a small amount of crevice corrosion with increased corrosion time. The corrosion products of EH47 steel after immersion in seawater for 30 days are mainly composed of FeOOH, Fe₃O₄ and Fe₂O₃. Full article

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15 pages, 5032 KiB

Open AccessArticle

Structural Characterization, Global and Local Electrochemical Activity of Electroless Ni–P-Multiwalled Carbon Nanotube Composite Coatings on Pipeline Steel

by Mara Cristina Lopes de Oliveira, Olandir Vercino Correa, Rejane Maria Pereira da Silva, Nelson Batista de Lima, Jefferson Thadeu Dias de Oliveira, Leandro Antônio de Oliveira and Renato Altobelli Antunes

Metals 2021, 11(6), 982; https://doi.org/10.3390/met11060982 - 20 Jun 2021

Cited by 9 | Viewed by 1959

Abstract

In this work, composite Ni–P-multiwalled carbon nanotube films were produced by electroless deposition. The main goal was to investigate the influence of multiwalled carbon nanotube loading on the local electrochemical behavior of the composite films, as probed by scanning electrochemical microscopy (SECM). The [...] Read more.

In this work, composite Ni–P-multiwalled carbon nanotube films were produced by electroless deposition. The main goal was to investigate the influence of multiwalled carbon nanotube loading on the local electrochemical behavior of the composite films, as probed by scanning electrochemical microscopy (SECM). The coatings were also characterized with respect to their crystalline structure, surface, and cross-section morphologies. Adhesion strength was examined by scratch tests. The global electrochemical behavior was evaluated by potentiodynamic polarization. The local electrochemical activity was investigated by probing the Fe²⁺ oxidation in the surface generation/tip collection mode of the SECM. The results revealed that multiwalled carbon nanotubes increased the adhesion strength and reduced the electrochemical activity on the surface of the coated samples. Full article

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14 pages, 3404 KiB

Open AccessFeature PaperArticle

Comparison of Corrosion Resistance of the AA2524-T3 and the AA2024-T3

by Fernanda Martins Queiroz, Maysa Terada, Aline F. Santos Bugarin, Hercílio Gomes de Melo and Isolda Costa

Metals 2021, 11(6), 980; https://doi.org/10.3390/met11060980 - 19 Jun 2021

Cited by 6 | Viewed by 2271

Abstract

The 2XXX Al alloys are characterized by their superior mechanical properties resulting from alloying elements and precipitation hardening treatments. The AA2524-T3 alloy was developed to replace the AA2024-T3 alloy in the aerospace industry. However, both alloys present many intermetallic particles (IMCs) in their [...] Read more.

The 2XXX Al alloys are characterized by their superior mechanical properties resulting from alloying elements and precipitation hardening treatments. The AA2524-T3 alloy was developed to replace the AA2024-T3 alloy in the aerospace industry. However, both alloys present many intermetallic particles (IMCs) in their microstructure, and this is the main reason for their high susceptibility to localized corrosion (such as pitting and stress corrosion cracking). Despite the similarities between these alloys (e.g., chemical composition and type of intermetallics) the literature comparing their properties is scarce and focuses mainly on their mechanical properties, not their corrosion resistances. In this investigation, the corrosion resistance of the AA2524-T3 alloy was compared to the AA2024-T3 alloy. The microstructure of both alloys was analyzed by Scanning Electron Microscopy before and after immersion in the test electrolyte, and the number and area fraction of intermetallics of each alloy was determined. The corrosion resistance of both alloys was monitored as a function of exposure time by electrochemical impedance spectroscopy and the results were fitted using electrical equivalent circuits. The AA2524-T3 alloy presented not only higher impedance values but also less corroded areas than the AA2024-T3 alloy. Full article

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14 pages, 4903 KiB

Open AccessArticle

Effect of Molybdenum Content on the Corrosion and Microstructure of Low-Ni, Co-Free Maraging Steels

by Asiful H. Seikh, Hossam Halfa and Mahmoud S. Soliman

Metals 2021, 11(6), 852; https://doi.org/10.3390/met11060852 - 21 May 2021

Cited by 5 | Viewed by 2572

Abstract

Molybdenum (Mo) is an important alloying element in maraging steels. In this study, we altered the Mo concentration during the production of four cobalt-free maraging steels using an electroslag refining process. The microstructure of the four forged maraging steels was evaluated to examine [...] Read more.

Molybdenum (Mo) is an important alloying element in maraging steels. In this study, we altered the Mo concentration during the production of four cobalt-free maraging steels using an electroslag refining process. The microstructure of the four forged maraging steels was evaluated to examine phase contents by optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. Additionally, we assessed the corrosion resistance of the newly developed alloys in 3.5% NaCl solution and 1 M H₂SO4 solution through potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Furthermore, we performed SEM and energy-dispersive spectroscopy (EDS) analysis after corrosion to assess changes in microstructure and Raman spectroscopy to identify the presence of phases on the electrode surface. The microstructural analysis shows that the formation of retained austenite increases with increasing Mo concentrations. It is found from corrosion study that increasing Mo concentration up to 4.6% increased the corrosion resistance of the steel. However, further increase in Mo concentration reduces the corrosion resistance. Full article

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