Editorial

2 pages, 161 KiB

Open AccessEditorial

Special Issue: Recent Advances in Corrosion Science

by Jacek Ryl

Materials 2020, 13(8), 1927; https://doi.org/10.3390/ma13081927 - 19 Apr 2020

Cited by 3 | Viewed by 1863

The International Union of Pure and Applied Chemistry (IUPAC) and European Federation of Corrosion (EFC) define corrosion as an irreversible interfacial reaction of a material with its environment which results in its consumption or dissolution, often resulting in effects detrimental to the usage [...] Read more.

The International Union of Pure and Applied Chemistry (IUPAC) and European Federation of Corrosion (EFC) define corrosion as an irreversible interfacial reaction of a material with its environment which results in its consumption or dissolution, often resulting in effects detrimental to the usage of the material considered [...] Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

Research

Jump to: Editorial, Review

16 pages, 4121 KiB

Open AccessFeature PaperArticle

High-Temperature Oxidation of Heavy Boron-Doped Diamond Electrodes: Microstructural and Electrochemical Performance Modification

by Jacek Ryl, Mateusz Cieslik, Artur Zielinski, Mateusz Ficek, Bartlomiej Dec, Kazimierz Darowicki and Robert Bogdanowicz

Materials 2020, 13(4), 964; https://doi.org/10.3390/ma13040964 - 21 Feb 2020

Cited by 17 | Viewed by 2808

Abstract

In this work, we reveal in detail the effects of high-temperature treatment in air at 600 °C on the microstructure as well as the physico-chemical and electrochemical properties of boron-doped diamond (BDD) electrodes. The thermal treatment of freshly grown BDD electrodes was applied, [...] Read more.

In this work, we reveal in detail the effects of high-temperature treatment in air at 600 °C on the microstructure as well as the physico-chemical and electrochemical properties of boron-doped diamond (BDD) electrodes. The thermal treatment of freshly grown BDD electrodes was applied, resulting in permanent structural modifications of surface depending on the exposure time. High temperature affects material corrosion, inducing crystal defects. The oxidized BDD surfaces were studied by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM), revealing a significant decrease in the electrode activity and local heterogeneity of areas owing to various standard rate constants. This effect was correlated with a resultant increase of surface resistance heterogeneity by scanning spreading resistance microscopy (SSRM). The X-ray photoelectron spectroscopy (XPS) confirmed the rate and heterogeneity of the oxidation process, revealing hydroxyl species to be dominant on the electrode surface. Morphological tests using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that prolonged durations of high-temperature treatment lead not only to surface oxidation but also to irreversible structural defects in the form of etch pits. Our results show that even subsequent electrode rehydrogenation in plasma is not sufficient to reverse this surface oxidation in terms of electrochemical and physico-chemical properties, and the nature of high-temperature corrosion of BDD electrodes should be considered irreversible. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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17 pages, 4174 KiB

Open AccessArticle

Ni/cerium Molybdenum Oxide Hydrate Microflakes Composite Coatings Electrodeposited from Choline Chloride: Ethylene Glycol Deep Eutectic Solvent

by Juliusz Winiarski, Anna Niciejewska, Jacek Ryl, Kazimierz Darowicki, Sylwia Baśladyńska, Katarzyna Winiarska and Bogdan Szczygieł

Materials 2020, 13(4), 924; https://doi.org/10.3390/ma13040924 - 19 Feb 2020

Cited by 13 | Viewed by 2512

Abstract

Cerium molybdenum oxide hydrate microflakes are codeposited with nickel from a deep eutectic solvent-based bath. During seven days of exposure in 0.05 M NaCl solution, the corrosion resistance of composite coating (Ni/CeMoOxide) is slightly reduced, due to the existence of some microcracks caused [...] Read more.

Cerium molybdenum oxide hydrate microflakes are codeposited with nickel from a deep eutectic solvent-based bath. During seven days of exposure in 0.05 M NaCl solution, the corrosion resistance of composite coating (Ni/CeMoOxide) is slightly reduced, due to the existence of some microcracks caused by large microflakes. Multielemental analysis of the solution, in which coatings are exposed and the qualitative changes in the surface chemistry (XPS) show selective etching molybdenum from microflakes. The amount of various molybdenum species within the surface of coating nearly completely disappear, due to the corrosion process. Significant amounts of Ce³⁺ compounds are removed, however the corrosion process is less selective towards the cerium, and the overall cerium chemistry remains unchanged. Initially, blank Ni coatings are covered by NiO and Ni(OH)₂ in an atomic ratio of 1:2. After exposure, the amount of Ni(OH)₂ increases in relation to NiO (ratio 1:3). For the composite coating, the atomic ratios of both forms of nickel vary from 1:0.8 to 1:1.3. Despite achieving lower corrosion resistance of the composite coating, the applied concept of using micro-flakes, whose skeleton is a system of Ce(III) species and active form are molybdate ions, may be interesting for applications in materials with potential self-healing properties. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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15 pages, 6607 KiB

Open AccessArticle

PDC Glass/Ceramic Coatings Applied to Differently Pretreated AISI441 Stainless Steel Substrates

by Milan Parchovianský, Ivana Parchovianská, Peter Švančárek, Günter Motz and Dušan Galusek

Materials 2020, 13(3), 629; https://doi.org/10.3390/ma13030629 - 31 Jan 2020

Cited by 13 | Viewed by 3437

Abstract

In this work, the influence of different cleaning procedures on adhesion of composite coatings containing passive ceramic and commercial glasses was investigated. Two compositions (C2c, D2-PP) of double-layer polymer-derived ceramic (PDC) coating systems, composed from bond coat and a top coat, were developed. [...] Read more.

In this work, the influence of different cleaning procedures on adhesion of composite coatings containing passive ceramic and commercial glasses was investigated. Two compositions (C2c, D2-PP) of double-layer polymer-derived ceramic (PDC) coating systems, composed from bond coat and a top coat, were developed. In order to obtain adherent coatings, stainless steel substrates were cleaned by four different cleaning procedures. The coatings were then deposited onto the steel substrate via spray coating. Pretreatment by subsequent ultrasonic cleaning in acetone, ethanol and deionised water (procedure U) was found to be the most effective, and the resultant C2c and D2-PP coatings, pyrolysed at 850 °C, indicated strong adhesion without delamination or cracks, propagating at the interface steel/bond coat. In the substrate treated by sandblasting and chemical etching, small cracks in the bond coat were observed under the same pyrolysis conditions. After oxidation tests, all coatings, except for those subjected to the U-treated substrates, showed significant cracking in the bond coat. The D2-PP coatings were denser than C2c, indicating better protection of the substrate. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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16 pages, 5154 KiB

Open AccessArticle

Influence of Alloyed Ga on the Microstructure and Corrosion Properties of As-Cast Mg–5Sn Alloys

by Jing Ren, Enyu Guo, Xuejian Wang, Huijun Kang, Zongning Chen and Tongmin Wang

Materials 2019, 12(22), 3686; https://doi.org/10.3390/ma12223686 - 08 Nov 2019

Cited by 10 | Viewed by 1946

Abstract

In this paper, the microstructures and corrosion behaviors of as-cast Mg–5Sn–xGa alloys with varying Ga content (x = 0, 0.5, 1, 2, 3 wt %) were investigated. The results indicated that Ga could not only adequately refine the grain structure [...] Read more.

In this paper, the microstructures and corrosion behaviors of as-cast Mg–5Sn–xGa alloys with varying Ga content (x = 0, 0.5, 1, 2, 3 wt %) were investigated. The results indicated that Ga could not only adequately refine the grain structure of the alloys, but could also improve the corrosion resistance. The microstructures of all alloys exhibited typical dendritic morphology. No Ga-rich secondary phases were detected when 0.5 wt % Ga was added, while only the morphology of Mg₂Sn phase was changed. However, when the addition rate of Ga exceeded 0.5 wt %, an Mg₅Ga₂ intermetallic compound started to form from the interdendritic region. The volume fraction of Mg₅Ga₂ monotonically increased with the increasing Ga addition level. Although Mg₅Ga₂ phase was cathode phase, its pitting sensitivity was weaker than Mg₂Sn. In addition, the standard potential of Ga (−0.55 V) was lower than that of Sn (−0.14 V), which relieved the driving force of the secondary phases for the micro-galvanic corrosion. An optimized composition of 3 wt % Ga was concluded based on the immersion tests and polarization measurements, which recorded the best corrosion resistance. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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20 pages, 4493 KiB

Open AccessArticle

Corrosion Inhibition Mechanism and Efficiency Differentiation of Dihydroxybenzene Isomers Towards Aluminum Alloy 5754 in Alkaline Media

by Jacek Ryl, Mateusz Brodowski, Marcin Kowalski, Wiktoria Lipinska, Pawel Niedzialkowski and Joanna Wysocka

Materials 2019, 12(19), 3067; https://doi.org/10.3390/ma12193067 - 20 Sep 2019

Cited by 31 | Viewed by 4325

Abstract

The selection of efficient corrosion inhibitors requires detailed knowledge regarding the interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. The position of functional groups between different isomers is often overlooked, but is no less important, [...] Read more.

The selection of efficient corrosion inhibitors requires detailed knowledge regarding the interaction mechanism, which depends on the type and amount of functional groups within the inhibitor molecule. The position of functional groups between different isomers is often overlooked, but is no less important, since factors like steric hinderance may significantly affect the adsorption mechanism. In this study, we have presented how different dihydroxybenzene isomers interact with aluminum alloy 5754 surface, reducing its corrosion rate in bicarbonate buffer (pH = 11). We show that the highest inhibition efficiency among tested compounds belongs to catechol at 10 mM concentration, although the differences were moderate. Utilization of novel impedance approach to adsorption isotherm determination made it possible to confirm that while resorcinol chemisorbs on aluminum surface, catechol and quinol follows the ligand exchange model of adsorption. Unlike catechol and quinol, the protection mechanism of resorcinol is bound to interaction with insoluble aluminum corrosion products layer and was only found efficient at concentration of 100 mM (98.7%). The aforementioned studies were confirmed with Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses. There is a significant increase in the corrosion resistance offered by catechol at 10 mM after 24 h exposure in electrolyte: from 63 to 98%, with only negligible changes in inhibitor efficiency observed for resorcinol at the same time. However, in the case of resorcinol a change in electrolyte color was observed. We have revealed that the differentiating factor is the keto-enol tautomerism. The Nuclear Magnetic Resonance (NMR) studies of resorcinol indicate the keto form in structure in presence of NaOH, while the chemical structure of catechol does not change significantly in alkaline environment. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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13 pages, 4490 KiB

Open AccessArticle

Effect of Pre-Corrosion Pits on Residual Fatigue Life for 42CrMo Steel

by Dezheng Liu, Yan Li, Xiangdong Xie and Jing Zhao

Materials 2019, 12(13), 2130; https://doi.org/10.3390/ma12132130 - 02 Jul 2019

Cited by 8 | Viewed by 2413

Abstract

The effect of pre-corrosion pits on residual fatigue life for the 42CrMo steel (American grade: AISI 4140) is investigated using the accelerated pre-corrosion specimen in the saline environment. Different pre-corroded times are used for the specimens, and fatigue tests with different loads are [...] Read more.

The effect of pre-corrosion pits on residual fatigue life for the 42CrMo steel (American grade: AISI 4140) is investigated using the accelerated pre-corrosion specimen in the saline environment. Different pre-corroded times are used for the specimens, and fatigue tests with different loads are then carried out on specimens. The pre-corrosion fatigue life is studied, and the fatigue fracture surfaces are examined by a surface profiler and a scanning electron microscope (SEM) to identify the crack nucleation sites and to determine the size and geometry of corrosion pits. Moreover, the stress intensity factor varying with corrosion pits in different size parameters is analyzed based on finite element (FE) software ABAQUS to derive the regression formula of the stress intensity factor. Subsequently, by integrating the regression formula with the Paris formula, the residual fatigue life is predicted and compared with experimental results, and the relationship of the stress intensity factor, pit depth, and residual fatigue life are given under different corrosion degrees. The fatigue life predicted by the coupled formula agrees well with experiment results. It is observed from the SEM images that higher stress amplitude and longer pre-corroded time can significantly decrease the residual fatigue life of the steel. Additionally, the research work has brought about the discovery that the rate of crack extension accelerates when the crack length increases. The research in this paper also demonstrates that the corrosion pit size can be used as a damage index to assess the residual fatigue life. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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21 pages, 10477 KiB

Open AccessArticle

Non-Isothermal Oxidation Behaviors and Mechanisms of Ti-Al Intermetallic Compounds

by Peixuan Ouyang, Guangbao Mi, Peijie Li, Liangju He, Jingxia Cao and Xu Huang

Materials 2019, 12(13), 2114; https://doi.org/10.3390/ma12132114 - 30 Jun 2019

Cited by 11 | Viewed by 2400

Abstract

Non-isothermal oxidation is one of the important issues for the safe application of Ti-Al alloys, so this study aimed to illustrate the non-isothermal oxidation behaviors and the corresponding mechanisms of a TiAl-based alloy in comparison with a Ti₃Al-based alloy. The non-isothermal [...] Read more.

Non-isothermal oxidation is one of the important issues for the safe application of Ti-Al alloys, so this study aimed to illustrate the non-isothermal oxidation behaviors and the corresponding mechanisms of a TiAl-based alloy in comparison with a Ti₃Al-based alloy. The non-isothermal oxidation behaviors of Ti-46Al-2Cr-5Nb and Ti-24Al-15Nb-1.5Mo alloys in pure oxygen were comparatively investigated with a thermogravimetry-differential scanning calorimetry (TGA/DSC) simultaneous thermal analyzer heating from room temperature to 1450 °C with a heating rate of 40 °C/min. When the temperature rose above 1280 °C, the oxidation rate of the Ti-46Al-2Cr-5Nb alloy sharply increased and exceeded that of the Ti-24Al-15Nb-1.5Mo alloy owing to the occurrence of internal oxidation. When the temperature was higher than 1350 °C, the oxidation rate of the Ti-46Al-2Cr-5Nb alloy decreased obviously due to the generation of an oxygen-barrier β-Al₂TiO₅-rich layer by a chemical reaction between Al₂O₃ and TiO₂ in the oxide scale. Based on Wagner’s theory of internal oxidation, the reason for the occurrence of internal oxidation in the Ti-46Al-2Cr-5Nb alloy is the formation of the α phase in the subsurface, while no internal oxidation occurred in the Ti-24Al-15Nb-1.5Mo alloy due to the existence of the β phase in the subsurface with the enrichment of Nb and Mo. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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17 pages, 6735 KiB

Open AccessArticle

Relationship between Phase Occurrence, Chemical Composition, and Corrosion Behavior of as-Solidified Al–Pd–Co Alloys

by Marián Palcut, Libor Ďuriška, Ivona Černičková, Sandra Brunovská, Žaneta Gerhátová, Martin Sahul, Ľubomír Čaplovič and Jozef Janovec

Materials 2019, 12(10), 1661; https://doi.org/10.3390/ma12101661 - 22 May 2019

Cited by 3 | Viewed by 2547

Abstract

The microstructure, phase constitution, and corrosion performance of as-solidified Al₇₀Pd₂₅Co₅ and Al₇₄Pd₁₂Co₁₄ alloys (element concentrations in at.%) have been investigated in the present work. The alloys were prepared by arc-melting of Al, Pd, [...] Read more.

The microstructure, phase constitution, and corrosion performance of as-solidified Al₇₀Pd₂₅Co₅ and Al₇₄Pd₁₂Co₁₄ alloys (element concentrations in at.%) have been investigated in the present work. The alloys were prepared by arc-melting of Al, Pd, and Co lumps in argon. The Al₇₄Pd₁₂Co₁₄ alloy was composed of structurally complex ε_n phase, while the Al₇₀Pd₂₅Co₅ alloy was composed of ε_n and δ phases. The corrosion performance was studied by open circuit potential measurements and potentiodynamic polarization in aqueous NaCl solution (3.5 wt.%). Marked open circuit potential oscillations of the Al₇₀Pd₂₅Co₅ alloy have been observed, indicating individual breakdown and re-passivation events on the sample surface. A preferential corrosion attack of ε_n was found, while the binary δ phase (Al₃Pd₂) remained free of corrosion. A de-alloying of Al from ε_n and formation of intermittent interpenetrating channel networks occurred in both alloys. The corrosion behavior of ε_n is discussed in terms of its chemical composition and crystal structure. The corrosion activity of ε_n could be further exploited in preparation of porous Pd–Co networks with possible catalytic activity. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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20 pages, 10358 KiB

Open AccessArticle

Effect of Hot Deformation Process Parameters on Microstructure and Corrosion Behavior of 35CrMoV Steel

by Qiumei Yang, Yajun Zhou, Zheng Li and Daheng Mao

Materials 2019, 12(9), 1455; https://doi.org/10.3390/ma12091455 - 06 May 2019

Cited by 16 | Viewed by 2764

Abstract

Hot deformation experiments of as-cast 35CrMoV steel, with strain rates of 0.01 s⁻¹ and 10 s⁻¹, deformation temperatures of 850, 950, and 1050 °C, and an extreme deformation reaching 50%, were carried out using a Gleeble-3810 thermal simulator. Electrochemical corrosion [...] Read more.

Hot deformation experiments of as-cast 35CrMoV steel, with strain rates of 0.01 s⁻¹ and 10 s⁻¹, deformation temperatures of 850, 950, and 1050 °C, and an extreme deformation reaching 50%, were carried out using a Gleeble-3810 thermal simulator. Electrochemical corrosion experiments were conducted on the deformed specimens. The microstructure was observed by optical microscope (OM), and the corrosion morphology and corrosion products of the specimens were investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), confocal laser scanning microscopy (CLSM), and X-ray diffraction (XRD) techniques. The results show that the grain size increased gradually with an increase in the deformation temperature at the same strain rate, whereas the corrosion resistance deteriorated. At the same deformation temperature, the grain size becomes smaller as the strain rate increases, which enhances the corrosion resistance. This is mainly attributed to the fine grains, which can form more grain boundaries, increase the grain boundary area, and accelerate the formation of the inner rust layer at the beginning of corrosion. Moreover, fine grains can also refine the rust particles and enhance the bonding strength between the inner rust layer and the matrix. The denseness and stability of the inner rust layer increases as the corrosion process progresses, thereby improving corrosion resistance. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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12 pages, 6072 KiB

Open AccessArticle

Microstructure Characterization and Corrosion Resistance of Zinc Coating Obtained on High-Strength Grade 10.9 Bolts Using a New Thermal Diffusion Process

by Henryk Kania and Jacek Sipa

Materials 2019, 12(9), 1400; https://doi.org/10.3390/ma12091400 - 29 Apr 2019

Cited by 24 | Viewed by 4124

Abstract

The article presents the results of research on the application of innovative thermal diffusion zinc coating technology with the recirculation of the reactive atmosphere to high-strength grade 10.9 bolts. The innovation of this method consists in the introduction of reactive atmosphere recirculation and [...] Read more.

The article presents the results of research on the application of innovative thermal diffusion zinc coating technology with the recirculation of the reactive atmosphere to high-strength grade 10.9 bolts. The innovation of this method consists in the introduction of reactive atmosphere recirculation and the application of coating powder mix which contains zinc powder and activator. Recirculation of the reactive atmosphere ensures its uniform composition, while the presence of an activator intensifies the process of saturating steel surface with zinc, which boosts the efficiency of active agents. Coatings were created at 440 °C and a heat soaking time of 30–240 min. Coating structure (SEM) was exposed, chemical composition in microsites (EDS) was defined, and coating phase structure (XRD) was identified. The kinetics of coating growth were defined. It was found that the increment of coating thickness was controlled by square root of soaking time. Coatings obtained using innovative thermal diffusion zinc coating technology had a two-layer structure. At the substrate, a compact layer of phase Γ₁ (Fe₁₁Zn₄₀) was created, which was covered with a layer of phase δ₁ (FeZn₁₀). The new method of thermal diffusion zinc coating will alow for the creation of coatings of very good corrosion resistance while maintaining strength properties of bolts defined as strength class 10.9. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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11 pages, 2680 KiB

Open AccessArticle

Experimental and Theoretical Studies on the Corrosion Inhibition of Carbon Steel by Two Indazole Derivatives in HCl Medium

by Shenying Xu, Shengtao Zhang, Lei Guo, Li Feng and Bochuan Tan

Materials 2019, 12(8), 1339; https://doi.org/10.3390/ma12081339 - 24 Apr 2019

Cited by 29 | Viewed by 3134

Abstract

In this work, two indazole derivatives, namely 5-aminoindazole (AIA) and 5-nitroindazole (NIA), were investigated as corrosion inhibitors for carbon steel in 1 M HCl solution by experimental and density functional theory (DFT) methods. The electrochemical results indicate that the inhibition ability follows the [...] Read more.

In this work, two indazole derivatives, namely 5-aminoindazole (AIA) and 5-nitroindazole (NIA), were investigated as corrosion inhibitors for carbon steel in 1 M HCl solution by experimental and density functional theory (DFT) methods. The electrochemical results indicate that the inhibition ability follows the order of AIA > NIA, which is due to the stronger electron-donating effect of –NH₂ of the AIA group than the –NO₂ group of NIA. Besides, the frontier orbital theory shows that the AIA exhibits higher reaction activity than NIA, and a more negative adsorption energy for AIA was also obtained, which is consistent with the analysis of the electrochemical measurements. We draw the conclusion that the electron-donating effect makes it easier for AIA to donate electrons to iron atoms to form a stronger protective layer than NIA. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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20 pages, 6012 KiB

Open AccessArticle

The Influence of Microstructure on the Passive Layer Chemistry and Corrosion Resistance for Some Titanium-Based Alloys

by Nader El-Bagoury, Sameh I. Ahmed, Ola Ahmed Abu Ali, Shimaa El-Hadad, Ahmed M. Fallatah, G. A. M. Mersal, Mohamed M. Ibrahim, Joanna Wysocka, Jacek Ryl, Rabah Boukherroub and Mohammed A. Amin

Materials 2019, 12(8), 1233; https://doi.org/10.3390/ma12081233 - 15 Apr 2019

Cited by 19 | Viewed by 3815

Abstract

The effect of microstructure and chemistry on the kinetics of passive layer growth and passivity breakdown of some Ti-based alloys, namely Ti-6Al-4V, Ti-6Al-7Nb and TC21 alloys, was studied. The rate of pitting corrosion was evaluated using cyclic polarization measurements. Chronoamperometry was applied to [...] Read more.

The effect of microstructure and chemistry on the kinetics of passive layer growth and passivity breakdown of some Ti-based alloys, namely Ti-6Al-4V, Ti-6Al-7Nb and TC21 alloys, was studied. The rate of pitting corrosion was evaluated using cyclic polarization measurements. Chronoamperometry was applied to assess the passive layer growth kinetics and breakdown. Microstructure influence on the uniform corrosion rate of these alloys was also investigated employing dynamic electrochemical impedance spectroscopy (DEIS). Corrosion studies were performed in 0.9% NaCl solution at 37 °C, and the obtained results were compared with ultrapure Ti (99.99%). The different phases of the microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Chemical composition and chemistry of the corroded surfaces were studied using X-ray photoelectron spectroscopy (XPS) analysis. For all studied alloys, the microstructure consisted of α matrix, which was strengthened by β phase. The highest and the lowest values of the β phase’s volume fraction were recorded for TC21 and Ti-Al-Nb alloys, respectively. The susceptibility of the investigated alloys toward pitting corrosion was enhanced following the sequence: Ti-6Al-7Nb < Ti-6Al-4V << TC21. Ti-6Al-7Nb alloy recorded the lowest pitting corrosion resistance (R_pit) among studied alloys, approaching that of pure Ti. The obvious changes in the microstructure of these alloys, together with XPS findings, were adopted to interpret the pronounced variation in the corrosion behavior of these materials. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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17 pages, 10165 KiB

Open AccessArticle

Corrosion Characteristics of Copper-Added Austempered Gray Cast Iron (AGCI)

by Asiful H. Seikh, Amit Sarkar, Jitendra Kumar Singh, Sohail M. A. Khan Mohammed, Nabeel Alharthi and Manojit Ghosh

Materials 2019, 12(3), 503; https://doi.org/10.3390/ma12030503 - 06 Feb 2019

Cited by 9 | Viewed by 4311

Abstract

The aim of this investigation was to assess the corrosion behavior of gray cast iron (GCI) alloyed with copper. Alloyed GCI specimens were austempered isothermally at varying temperatures. After austenitizing at 927 °C, the samples were austempered at different temperatures ranging from 260 [...] Read more.

The aim of this investigation was to assess the corrosion behavior of gray cast iron (GCI) alloyed with copper. Alloyed GCI specimens were austempered isothermally at varying temperatures. After austenitizing at 927 °C, the samples were austempered at different temperatures ranging from 260 to 385 °C with an interval of 25 °C for 60 minutes. As a result, these samples developed an ausferrite matrix with different percentages of austenite. The resulting microstructures were evaluated and characterized by optical microscope (OM), scanning electron microscope (SEM), and X-ray diffraction (XRD). The corrosion characteristics were determined using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) of these samples. These tests were carried out in a medium of 0.5 M H₂SO₄ and 3.5% NaCl solution. It was observed from the potentiodynamic polarization results that with increasing austempering temperature, the corrosion rate decreased. All results of the EIS were in accordance with a constant phase element (CPE) model. It was found that with an increase in austempering temperature, the polarization resistance (R_p) increased. The austenite content was also found to influence the corrosion behavior of the austempered gray cast iron (AGCI). Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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15 pages, 5037 KiB

Open AccessArticle

Mannich Base as Corrosion Inhibitors for N80 Steel in a CO₂ Saturated Solution Containing 3 wt % NaCl

by Mingjin Tang, Jianbo Li, Zhida Li, Luoping Fu, Bo Zeng and Jie Lv

Materials 2019, 12(3), 449; https://doi.org/10.3390/ma12030449 - 01 Feb 2019

Cited by 32 | Viewed by 3175

Abstract

In this paper, a corrosion inhibitor containing nitrogen atoms and a conjugated π bond was synthesised, and its final product synthesised by the optimal conditions of the orthogonal test results is named multi-mannich base (MBT). The corrosion inhibition effect on the N80 steel [...] Read more.

In this paper, a corrosion inhibitor containing nitrogen atoms and a conjugated π bond was synthesised, and its final product synthesised by the optimal conditions of the orthogonal test results is named multi-mannich base (MBT). The corrosion inhibition effect on the N80 steel sheet of the corrosion inhibitor was evaluated in a CO₂ saturated solution containing 3 wt % NaCl; the corrosion rate was 0.0446 mm/a and the corrosion inhibition rate was 90.4%. Through electrochemical and adsorption theory study, MBT is a mixed corrosion inhibitor that mainly shows cathode suppression capacity. The adsorption of MBT on the surface of the steel sheet follows the Langmuir adsorption isotherm; it can be spontaneously adsorbed on the surface of the N80 steel sheet, which has a good corrosion inhibition effect. The surface of the N80 steel sheet was microscopically characterised by atomic force microscope (AFM). It can be seen from the results that the N80 steel sheet with MBT added is significantly different from the blank control group; the surface of the steel sheet is relatively smooth, indicating that MBT forms an effective protective film on the surface of N80 steel, which inhibits the steel sheet. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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47 pages, 16725 KiB

Open AccessReview

Application of Electrochemical Atomic Force Microscopy (EC-AFM) in the Corrosion Study of Metallic Materials

by Hanbing Chen, Zhenbo Qin, Meifeng He, Yichun Liu and Zhong Wu

Materials 2020, 13(3), 668; https://doi.org/10.3390/ma13030668 - 03 Feb 2020

Cited by 28 | Viewed by 7317

Abstract

Electrochemical atomic force microscopy (EC-AFM), a branch of a scanning probe microscopy (SPM), can image substrate topography with high resolution. Since its inception, it was extended to a wide range of research areas through continuous improvement. The presence of an electrolytic cell and [...] Read more.

Electrochemical atomic force microscopy (EC-AFM), a branch of a scanning probe microscopy (SPM), can image substrate topography with high resolution. Since its inception, it was extended to a wide range of research areas through continuous improvement. The presence of an electrolytic cell and a potentiostat makes it possible to observe the topographical changes of the sample surface in real time. EC-AFM is used in in situ corrosion research because the samples are not required to be electrically conductive. It is widely used in passive film properties, surface dissolution, early-stage corrosion initiation, inhibitor efficiency, and many other branches of corrosion science. This review provides the research progress of EC-AFM and summarizes the extensive applications and investigations using EC-AFM in corrosion science. Full article

(This article belongs to the Special Issue Recent Advances in Corrosion Science)

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