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Microstructure and Corrosion Behavior of Advanced Alloys

A topical collection in Materials (ISSN 1996-1944). This collection belongs to the section "Corrosion".

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Editor

Slovak University of Technology in Bratislava, Bratislava, Slovakia
Interests: metals; alloys; corrosion; high-temperature oxidation; solid state diffusion

Topical Collection Information

Dear Colleagues,

In many applications, metallic materials are exposed to high temperatures and oxidizing agents simultaneously. Due to a combination of chemical and thermal stresses, the constructional and functional materials are degraded and their useful properties are lost. These undesirable events are of a physicochemical nature and are commonly known as ‘corrosion’. Several internal and external factors influence the corrosion behavior of materials. Internal factors include the chemical composition, microstructure, and phase constitution of the materials. External factors that can significantly contribute to an increase in corrosion resistance include surface treatments and the use of various protective coatings. In this Topical Collection, original research papers and reviews focused on the complex relationships between the microstructure, phase constitution, and corrosion behavior of metallic materials will be presented. Furthermore, possibilities for increasing the corrosion resistance of metallic materials by means of surface modification and application of protective layers will be explored. Both high temperature and low temperature corrosion studies in aqueous and non-aqueous electrolytes are welcome as long as they investigate the electrochemical processes taking place at the material’s interfaces.

Dr. Marián Palcut
Collection Editor

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Keywords

  • light metals and alloys
  • ferrous and non-ferrous alloys
  • complex alloys
  • electrochemistry of corroding interfaces
  • local corrosion
  • corrosion-resistant coatings and their characterization
  • surface modification of advanced alloys

Published Papers (22 papers)

2023

Jump to: 2021, 2020

17 pages, 11749 KiB  
Article
Effects of the Mg Content on Microstructural and Corrosion Characteristics of Hot-Dip Al–Si–Mg Alloy-Coated Steel Sheets
by Kwang-Hyeok Jin and Min-Suk Oh
Materials 2023, 16(17), 5827; https://doi.org/10.3390/ma16175827 - 25 Aug 2023
Viewed by 810
Abstract
Hot-dip Al–Si alloy coatings with excellent resistance to corrosion and high-temperature oxidation have emerged as promising lightweight substitutes for conventional corrosion-resistant coatings. The introduction of Mg can be an effective strategy for enhancing the sacrificial protection capability of Al–Si coatings. In this study, [...] Read more.
Hot-dip Al–Si alloy coatings with excellent resistance to corrosion and high-temperature oxidation have emerged as promising lightweight substitutes for conventional corrosion-resistant coatings. The introduction of Mg can be an effective strategy for enhancing the sacrificial protection capability of Al–Si coatings. In this study, the effects of Mg addition on the morphology, electrochemical behavior, and mechanical properties of Al–Si coatings were investigated, along with the Mg-content optimization of the coating layer. Adding Mg promoted the formation of finely distributed eutectic intermetallic phases, such as Al/Mg2Si and the primary Mg2Si phase. Notably, the Mg2Si phase coarsened significantly when ≥15 wt.% of Mg was added. In addition, an Al3Mg2 intermetallic compound was observed in coating layers containing >20 wt.% of Mg, reducing the adhesion of the coating layers. Samples containing 5–10 wt.% of Mg exhibited excellent corrosion resistance (owing to a uniform distribution of the fine eutectic Al/Mg2Si phase and the formation of stable corrosion products), whereas those containing 20 wt.% of Mg exhibited unremarkable corrosion resistance (owing to the formation of an Al3Mg2 phase that is susceptible to intergranular corrosion). Full article
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2021

Jump to: 2023, 2020

14 pages, 1715 KiB  
Article
Influence of Degradation Product Thickness on the Elastic Stiffness of Porous Absorbable Scaffolds Made from an Bioabsorbable Zn–Mg Alloy
by Jannik Bühring, Maximilian Voshage, Johannes Henrich Schleifenbaum, Holger Jahr and Kai-Uwe Schröder
Materials 2021, 14(20), 6027; https://doi.org/10.3390/ma14206027 - 13 Oct 2021
Cited by 2 | Viewed by 1830
Abstract
For orthopaedic applications, additive manufactured (AM) porous scaffolds made of absorbable metals such as magnesium, zinc or iron are of particular interest. They do not only offer the potential to design and fabricate bio-mimetic or rather bone-equivalent mechanical properties, they also do not [...] Read more.
For orthopaedic applications, additive manufactured (AM) porous scaffolds made of absorbable metals such as magnesium, zinc or iron are of particular interest. They do not only offer the potential to design and fabricate bio-mimetic or rather bone-equivalent mechanical properties, they also do not need to be removed in further surgery. Located in a physiological environment, scaffolds made of absorbable metals show a decreasing Young’s modulus over time, due to product dissolution. For magnesium-based scaffolds during the first days an increase of the smeared Young’s modulus can be observed, which is mainly attributed to a forming substrate layer of degradation products on the strut surfaces. In this study, the influence of degradation products on the stiffness properties of metallic scaffolds is investigated. For this, analytical calculations and finite-element simulations are performed to study the influence of the substrate layer thickness and Young’s modulus for single struts and for a new scaffold geometry with adapted polar cubic face-centered unit cells with vertical struts (f2cc,z). The finite-element model is further validated by compression tests on AM scaffolds made from Zn1Mg (1 wt% Mg). The results show that even low thicknesses and Young’s moduli of the substrate layer significantly increases the smeared Young’s modulus under axial compression. Full article
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25 pages, 8244 KiB  
Review
Duplex Steels Used in Building Structures and Their Resistance to Chloride Corrosion
by Mariusz Maslak, Marek Stankiewicz and Benedykt Slazak
Materials 2021, 14(19), 5666; https://doi.org/10.3390/ma14195666 - 29 Sep 2021
Cited by 8 | Viewed by 2491
Abstract
Welded structures made of duplex steels are used in building applications due to their resistance to local corrosion attack initiated by chlorides. In this paper, the material and technological factors determining the corrosion resistance are discussed in detail. Furthermore, recommendations are formulated that [...] Read more.
Welded structures made of duplex steels are used in building applications due to their resistance to local corrosion attack initiated by chlorides. In this paper, the material and technological factors determining the corrosion resistance are discussed in detail. Furthermore, recommendations are formulated that allow, in the opinion of the authors, to obtain a maximum corrosion resistance for welded joints. The practical aspects of corrosion resistance testing are also discussed, based on the results of qualification tests. This work is of a review character. The conclusions and practical recommendations are intended for contractors and investors of various types of structures made of the duplex steel. The recommendations concern the selection and use of duplex steels, including the issues of metallurgy, welding techniques, and corrosion protection. Full article
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28 pages, 9540 KiB  
Review
Aqueous Corrosion of Aluminum-Transition Metal Alloys Composed of Structurally Complex Phases: A Review
by Libor Ďuriška, Ivona Černičková, Pavol Priputen and Marián Palcut
Materials 2021, 14(18), 5418; https://doi.org/10.3390/ma14185418 - 19 Sep 2021
Cited by 11 | Viewed by 2630
Abstract
Complex metallic alloys (CMAs) are materials composed of structurally complex intermetallic phases (SCIPs). The SCIPs consist of large unit cells containing hundreds or even thousands of atoms. Well-defined atomic clusters are found in their structure, typically of icosahedral point group symmetry. In SCIPs, [...] Read more.
Complex metallic alloys (CMAs) are materials composed of structurally complex intermetallic phases (SCIPs). The SCIPs consist of large unit cells containing hundreds or even thousands of atoms. Well-defined atomic clusters are found in their structure, typically of icosahedral point group symmetry. In SCIPs, a long-range order is observed. Aluminum-based CMAs contain approximately 70 at.% Al. In this paper, the corrosion behavior of bulk Al-based CMAs is reviewed. The Al–TM alloys (TM = transition metal) have been sorted according to their chemical composition. The alloys tend to passivate because of high Al concentration. The Al–Cr alloys, for example, can form protective passive layers of considerable thickness in different electrolytes. In halide-containing solutions, however, the alloys are prone to pitting corrosion. The electrochemical activity of aluminum-transition metal SCIPs is primarily determined by electrode potential of the alloying element(s). Galvanic microcells form between different SCIPs which may further accelerate the localized corrosion attack. The electrochemical nobility of individual SCIPs increases with increasing concentration of noble elements. The SCIPs with electrochemically active elements tend to dissolve in contact with nobler particles. The SCIPs with noble metals are prone to selective de-alloying (de–aluminification) and their electrochemical activity may change over time as a result of de-alloying. The metal composition of the SCIPs has a primary influence on their corrosion properties. The structural complexity is secondary and becomes important when phases with similar chemical composition, but different crystal structure, come into close physical contact. Full article
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15 pages, 5028 KiB  
Article
The Effect of Sn Addition on Zn-Al-Mg Alloy; Part I: Microstructure and Phase Composition
by Peter Gogola, Zuzana Gabalcová, Martin Kusý and Henrich Suchánek
Materials 2021, 14(18), 5404; https://doi.org/10.3390/ma14185404 - 18 Sep 2021
Cited by 12 | Viewed by 2106
Abstract
In this study, the addition of Sn on the microstructure of Zn 1.6 wt.% Al 1.6 wt.% Mg alloy was studied. Currently, the addition of Sn into Zn-Al-Mg based systems has not been investigated in detail. Both as-cast and annealed states were investigated. [...] Read more.
In this study, the addition of Sn on the microstructure of Zn 1.6 wt.% Al 1.6 wt.% Mg alloy was studied. Currently, the addition of Sn into Zn-Al-Mg based systems has not been investigated in detail. Both as-cast and annealed states were investigated. Phase transformation temperatures and phase composition was investigated via DSC, SEM and XRD techniques. The main phases identified in the studied alloys were η(Zn) and α(Al) solid solutions as well as Mg2Zn11, MgZn2 and Mg2Sn intermetallic phases. Addition of Sn enabled the formation of Mg2Sn phase at the expense of MgxZny phases, while the overall volume content of intermetallic phases is decreasing. Annealing did not change the phase composition in a significant way, but higher Sn content allowed more effective spheroidization and agglomeration of individual phase particles. Full article
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16 pages, 10570 KiB  
Article
The Effect of Sn Addition on Zn-Al-Mg Alloy; Part II: Corrosion Behaviour
by Zuzana Gabalcová, Peter Gogola, Martin Kusý and Henrich Suchánek
Materials 2021, 14(18), 5290; https://doi.org/10.3390/ma14185290 - 14 Sep 2021
Cited by 8 | Viewed by 1930
Abstract
Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure [...] Read more.
Corrosion behaviour of Sn (0.0, 0.5, 1.0, 2.0 and 3.0 wt.%)-doped Zn 1.6 wt.% Al 1.6 wt.% Mg alloys exposed to salt spray testing was investigated. Intergranular corrosion was observed for all alloys in both as-cast and annealed states. However, due to microstructure spheroidisation in the annealed samples, potential intergranular corrosion paths are significantly reduced. Samples with 0.5 wt.% of Sn showed the best corrosion properties. The main corrosion products identified by XRD analysis for all samples were simonkolleite and hydrozincite. Occasionally, ZnO and AlO were identified in limited amounts. Full article
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19 pages, 3764 KiB  
Article
Effect of Grain Size on the Corrosion Behavior of Fe-3wt.%Si-1wt.%Al Electrical Steels in Pure Water Saturated with CO2
by Gaetano Palumbo, Dawid Dunikowski, Roma Wirecka, Tomasz Mazur, Urszula Lelek-Borkowska, Kinga Wawer and Jacek Banaś
Materials 2021, 14(17), 5084; https://doi.org/10.3390/ma14175084 - 05 Sep 2021
Cited by 8 | Viewed by 2800
Abstract
The corrosion behavior of two silicon steels with the same chemical composition but different grains sizes (i.e., average grain area of 115.6 and 4265.9 µm2) was investigated by metallographic microscope, gravimetric, electrochemical and surface analysis techniques. The gravimetric and electrochemical results [...] Read more.
The corrosion behavior of two silicon steels with the same chemical composition but different grains sizes (i.e., average grain area of 115.6 and 4265.9 µm2) was investigated by metallographic microscope, gravimetric, electrochemical and surface analysis techniques. The gravimetric and electrochemical results showed that the corrosion rate increased with decreasing the grain size. The scanning electron microscopy/energy dispersive x-ray spectroscopy and X-ray photoelectron spectroscopyanalyses revealed formation of a more homogeneous and compact corrosion product layer on the coarse-grained steel compared to fine-grained material. The Volta potential analysis, carried out on both steels, revealed formation of micro-galvanic sites at the grain boundaries and triple junctions. The results indicated that the decrease in corrosion resistance in the fine-grained steel could be attributed to the higher density of grain boundaries (e.g., a higher number of active sites and defects) brought by the refinement. The higher density of active sites at grain boundaries promote the metal dissolution of the and decreased the stability of the corrosion product layerformed on the metal surface. Full article
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17 pages, 3539 KiB  
Article
Corrosion Prediction of Weathered Galvanised Structures Using Machine Learning Techniques
by Marta Terrados-Cristos, Francisco Ortega-Fernández, Guillermo Alonso-Iglesias, Marina Díaz-Piloneta and Ana Fernández-Iglesias
Materials 2021, 14(14), 3906; https://doi.org/10.3390/ma14143906 - 13 Jul 2021
Cited by 7 | Viewed by 2880
Abstract
Galvanised steel atmospheric corrosion is a complex multifactorial phenomenon that globally affects many structures, equipment, and sectors. Moreover, the International Organization of Standardization (ISO) standards require specific pollutant depositions values for any atmosphere classification or corrosion loss prediction result. The aim of this [...] Read more.
Galvanised steel atmospheric corrosion is a complex multifactorial phenomenon that globally affects many structures, equipment, and sectors. Moreover, the International Organization of Standardization (ISO) standards require specific pollutant depositions values for any atmosphere classification or corrosion loss prediction result. The aim of this research is to develop predictive models to estimate corrosion loss based on easily worldwide available parameters. Experimental data from internationally validated studies were used for the data mining process, basing their characterisation on seven globally accessible qualitative and quantitative variables. Self-Organising Maps including both supervised and unsupervised layers were used to predict first-year corrosion loss, its corrosivity categories, and an uncertainty range. Additionally, a formula optimised with Newton’s method has been proposed for extrapolating these results to long-term results. The predictions obtained were compared with real values using Euclidean distances to know its similarity degree, offering high prediction performance. Specifically, evaluation results showed an average saving of up to 16% in coatings using these predictions. Therefore, using the proposed models reduces the uncertainty of the final structures state by predicting their material loss, avoiding initial over-dimensioning of structures, and meeting the principles of efficiency and sustainability, thus reducing costs. Full article
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24 pages, 12968 KiB  
Article
Effect of Sub-Zero Treatments and Tempering on Corrosion Behaviour of Vanadis 6 Tool Steel
by Peter Jurči, Aneta Bartkowska, Mária Hudáková, Mária Dománková, Mária Čaplovičová and Dariusz Bartkowski
Materials 2021, 14(13), 3759; https://doi.org/10.3390/ma14133759 - 05 Jul 2021
Cited by 9 | Viewed by 2303
Abstract
Sub-zero treatment of Vanadis 6 steel resulted in a considerable reduction of retained austenite amount, refinement of martensite, enhancement of population density of carbides, and modification of precipitation behaviour. Tempering of sub-zero-treated steel led to a decrease in population density of carbides, to [...] Read more.
Sub-zero treatment of Vanadis 6 steel resulted in a considerable reduction of retained austenite amount, refinement of martensite, enhancement of population density of carbides, and modification of precipitation behaviour. Tempering of sub-zero-treated steel led to a decrease in population density of carbides, to a further reduction of retained austenite, and to precipitation of M3C carbides, while M7C3 carbides precipitated only in the case of conventionally quenched steel. Complementary effects of these microstructural variations resulted in more noble behaviour of sub-zero-treated steel compared to the conventionally room-quenched one, and to clear inhibition of the corrosion rate at the same time. Full article
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13 pages, 8114 KiB  
Article
Intergranular Corrosion and Microstructural Evolution in a Newly Designed Al-6Mg Alloy
by Kweon-Hoon Choi, Bong-Hwan Kim, Da-Bin Lee, Seung-Yoon Yang, Nam-Seok Kim, Seong-Ho Ha, Young-Ok Yoon, Hyun-Kyu Lim and Shae-Kwang Kim
Materials 2021, 14(12), 3314; https://doi.org/10.3390/ma14123314 - 15 Jun 2021
Cited by 4 | Viewed by 2174
Abstract
In this work, the microstructure and corrosion behavior of a novel Al-6Mg alloy were investigated. The alloy was prepared by casting from pure Al and Mg+Al2Ca master alloy. The ingots were homogenized at 420 °C for 8 h, hot-extruded and cold-rolled [...] Read more.
In this work, the microstructure and corrosion behavior of a novel Al-6Mg alloy were investigated. The alloy was prepared by casting from pure Al and Mg+Al2Ca master alloy. The ingots were homogenized at 420 °C for 8 h, hot-extruded and cold-rolled with 20% reduction (CR20 alloy) and 50% reduction (CR50 alloy). The CR50 alloy exhibited a higher value of intergranular misorientation due to a higher cold rolling reduction ratio. The average grain sizes were 19 ± 7 μm and 17 ± 9 μm for the CR20 and CR50 alloys, respectively. An intergranular corrosion (IGC) behavior was investigated after sensitization by a nitric acid mass-loss test (ASTM G67). The mass losses of both the CR20 and CR50 alloys were similar at early periods of sensitization, however, the CR20 alloy became more susceptible to IGC as the sensitization time increased. Grain size and β phase precipitation were two critical factors influencing the IGC behavior of this alloy system. Full article
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15 pages, 14440 KiB  
Article
Effect of Cr on Aqueous and Atmospheric Corrosion of Automotive Carbon Steel
by Sang-won Cho, Sang-Jin Ko, Jin-Seok Yoo, Yun-Ha Yoo, Yon-Kyun Song and Jung-Gu Kim
Materials 2021, 14(9), 2444; https://doi.org/10.3390/ma14092444 - 08 May 2021
Cited by 5 | Viewed by 2463
Abstract
This study investigated the effect of Cr alloying element on the corrosion properties of automotive carbon steel (0.1C, 0.5Si, 2.5Mn, Fe Bal., composition given in wt.%) in aqueous and atmospheric conditions using electrochemical measurement and cyclic corrosion tests. Three steels with 0, 0.3, [...] Read more.
This study investigated the effect of Cr alloying element on the corrosion properties of automotive carbon steel (0.1C, 0.5Si, 2.5Mn, Fe Bal., composition given in wt.%) in aqueous and atmospheric conditions using electrochemical measurement and cyclic corrosion tests. Three steels with 0, 0.3, and 0.5 wt.% Cr were studied by electrochemical impedance spectroscopy. Polarization resistance (Rp) of 0.3 Cr and 0.5 Cr steels was higher than that of 0 Cr steel, and the Rp also increased as the Cr content increased. Therefore, Cr increases the corrosion resistance of automotive carbon steel immersed in a chloride ion (Cl)-containing aqueous solution. In the cyclic corrosion test results, Cl was concentrated at the metal/rust interface in all of the steels regardless of Cr content. The Cl was uniformly concentrated and distributed on the 0 Cr steel, but locally and non-uniformly concentrated on the Cr-added steels. The inner rust layer consisted of β-FeOOH containing Cl and Cr-goethite, while the outer rust layer was composed of amorphous iron oxyhydroxide mixed with various types of rust. FeCl2 and CrCl3 are formed from the Cl nest developed in the early stage, and the pitting at CrCl3-formed regions are locally accelerated because Cr is strongly hydrolyzed to a very low pH. Full article
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15 pages, 4797 KiB  
Article
Microstructure, Micro-Mechanical and Tribocorrosion Behavior of Oxygen Hardened Ti–13Nb–13Zr Alloy
by Alicja Łukaszczyk, Sławomir Zimowski, Wojciech Pawlak, Beata Dubiel and Tomasz Moskalewicz
Materials 2021, 14(8), 2088; https://doi.org/10.3390/ma14082088 - 20 Apr 2021
Cited by 2 | Viewed by 2224
Abstract
In the present work, an oxygen hardening of near-β phase Ti–13Nb–13Zr alloy in plasma glow discharge at 700–1000 °C was studied. The influence of the surface treatment on the alloy microstructure, tribological and micromechanical properties, and corrosion resistance is presented. A strong influence [...] Read more.
In the present work, an oxygen hardening of near-β phase Ti–13Nb–13Zr alloy in plasma glow discharge at 700–1000 °C was studied. The influence of the surface treatment on the alloy microstructure, tribological and micromechanical properties, and corrosion resistance is presented. A strong influence of the treatment on the hardened zone thickness, refinement of the α’ laths and grain size of the bulk alloy were found. The outer hardened zone contained mainly an oxygen-rich Ti α’ (O) solid solution. The microhardness and elastic modulus of the hardened zone decreased with increasing hardening temperature. The hardened zone thickness, size of the α’ laths, and grain size of the bulk alloy increased with increasing treatment temperature. The wear resistance of the alloy oxygen-hardened at 1000 °C was about two hundred times, and at 700 °C, even five hundred times greater than that of the base alloy. Oxygen hardening also slightly improved the corrosion resistance. Tribocorrosion tests revealed that the alloy hardened at 700 °C was wear-resistant in a corrosive environment, and when the friction process was completed, the passive film was quickly restored. The results show that glow discharge plasma oxidation is a simple and effective method to enhance the micromechanical and tribological performance of the Ti–13Nb–13Zr alloy. Full article
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14 pages, 39229 KiB  
Article
Corrosion Behavior of Cold-Formed AA5754 Alloy Sheets
by Anna Dobkowska, Agata Sotniczuk, Piotr Bazarnik, Jarosław Mizera and Halina Garbacz
Materials 2021, 14(2), 394; https://doi.org/10.3390/ma14020394 - 14 Jan 2021
Cited by 3 | Viewed by 2195
Abstract
In this work, the influence of bending an AA5457 alloy sheet and the resulting microstructural changes on its corrosion behavior was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to perform detailed microstructural analyses of the alloy in its [...] Read more.
In this work, the influence of bending an AA5457 alloy sheet and the resulting microstructural changes on its corrosion behavior was investigated. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to perform detailed microstructural analyses of the alloy in its original form and after bending. After immersion in naturally-aged NaCl under open-circuit conditions (0.5 M, adjusted to 3 by HCl), post-corrosion observations were made, and electrochemical polarization measurements were performed to investigate the corrosion mechanisms occurring on both surfaces. The results showed that the corrosion of AA5457 is a complex process that mainly involves trenching around coarse Si-rich particles, crystallographically-grown large pits, and the formation of multiple tiny pits around Si-rich nanoparticles. The experimental data showed that bending AA5457 changed the shape and distribution of Si-rich coarse particles, cumulated a higher dislocation density in the material, especially around Si-rich nanoparticles, and all of these factors caused that corrosion behavior of the AA5754 in the bending area was lowered. Full article
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2020

Jump to: 2023, 2021

12 pages, 11235 KiB  
Article
Effect of Phase Transformation on Stress Corrosion Behavior of Additively Manufactured Austenitic Stainless Steel Produced by Directed Energy Deposition
by Tomer Ron, Ohad Dolev, Avi Leon, Amnon Shirizly and Eli Aghion
Materials 2021, 14(1), 55; https://doi.org/10.3390/ma14010055 - 24 Dec 2020
Cited by 16 | Viewed by 2720
Abstract
The present study aims to evaluate the stress corrosion behavior of additively manufactured austenitic stainless steel produced by the wire arc additive manufacturing (WAAM) process. This was examined in comparison with its counterpart, wrought alloy, by electrochemical analysis in terms of potentiodynamic polarization [...] Read more.
The present study aims to evaluate the stress corrosion behavior of additively manufactured austenitic stainless steel produced by the wire arc additive manufacturing (WAAM) process. This was examined in comparison with its counterpart, wrought alloy, by electrochemical analysis in terms of potentiodynamic polarization and impedance spectroscopy and by slow strain rate testing (SSRT) in a corrosive environment. The microstructure assessment was performed using optical and scanning electron microscopy along with X-ray diffraction analysis. The obtained results indicated that in spite of the inherent differences in microstructure and mechanical properties between the additively manufactured austenitic stainless steel and its counterpart wrought alloy, their electrochemical performance and stress corrosion susceptibility were similar. The corrosion attack in the additively manufactured alloy was mainly concentrated at the interface between the austenitic matrix and the secondary ferritic phase. In the case of the counterpart wrought alloy with a single austenitic phase, the corrosion attack was manifested by uniform pitting evenly scattered at the external surface. Both alloys showed ductile failure in the form of “cap and cone” fractures in post-SSRT experiments in corrosive environment. Full article
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10 pages, 6000 KiB  
Article
Effect of Natural Aging on the Stress Corrosion Cracking Behavior of A201-T7 Aluminum Alloy
by Mien-Chung Chen, Ming-Che Wen, Yang-Chun Chiu, Tse-An Pan, Yu-Chih Tzeng and Sheng-Long Lee
Materials 2020, 13(24), 5631; https://doi.org/10.3390/ma13245631 - 10 Dec 2020
Cited by 6 | Viewed by 2002
Abstract
The effect of natural aging on the stress corrosion cracking (SCC) of A201-T7 alloy was investigated by the slow strain rate testing (SSRT), transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), conductivity, and polarization testing. The results indicated that [...] Read more.
The effect of natural aging on the stress corrosion cracking (SCC) of A201-T7 alloy was investigated by the slow strain rate testing (SSRT), transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), conductivity, and polarization testing. The results indicated that natural aging could significantly improve the resistance of the alloys to SCC. The ductility loss rate of the unaged alloy was 28%, while the rates for the 24 h and 96 h aged alloys were both 5%. The conductivity of the as-quenched alloy was 30.54 (%IACS), and the conductivity of the 24 h and 96 h aged alloys were decreased to 28.85 and 28.65. After T7 tempering, the conductivity of the unaged, 24 h, and 96 h aged alloys were increased to 32.54 (%IACS), 32.52 and 32.45. Besides, the enthalpy change of the 24 h and 96 h aged alloys increased by 36% and 37% compared to the unaged alloy. The clustering of the solute atoms would evidently be enhanced with the increasing time of natural aging. Natural aging after quenching is essential to improve the alloy’s resistance to SCC. It might be due to the prevention of the formation of the precipitation free zone (PFZ) after T7 tempering. Full article
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24 pages, 8535 KiB  
Article
Effect of CO2 Partial Pressure on the Corrosion Inhibition of N80 Carbon Steel by Gum Arabic in a CO2-Water Saline Environment for Shale Oil and Gas Industry
by Gaetano Palumbo, Kamila Kollbek, Roma Wirecka, Andrzej Bernasik and Marcin Górny
Materials 2020, 13(19), 4245; https://doi.org/10.3390/ma13194245 - 23 Sep 2020
Cited by 15 | Viewed by 3419
Abstract
The effect of CO2 partial pressure on the corrosion inhibition efficiency of gum arabic (GA) on the N80 carbon steel pipeline in a CO2-water saline environment was studied by using gravimetric and electrochemical measurements at different CO2 partial pressures [...] Read more.
The effect of CO2 partial pressure on the corrosion inhibition efficiency of gum arabic (GA) on the N80 carbon steel pipeline in a CO2-water saline environment was studied by using gravimetric and electrochemical measurements at different CO2 partial pressures (e.g., PCO2 = 1, 20 and 40 bar) and temperatures (e.g., 25 and 60 °C). The results showed that the inhibitor efficiency increased with an increase in inhibitor concentration and CO2 partial pressure. The corrosion inhibition efficiency was found to be 84.53% and 75.41% after 24 and 168 h of immersion at PCO2 = 40 bar, respectively. The surface was further evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), grazing incidence X-ray diffraction (GIXRD), and X-ray photoelectron spectroscopy (XPS) measurements. The SEM-EDS and GIXRD measurements reveal that the surface of the metal was found to be strongly affected by the presence of the inhibitor and CO2 partial pressure. In the presence of GA, the protective layer on the metal surface becomes more compact with increasing the CO2 partial pressure. The XPS measurements provided direct evidence of the adsorption of GA molecules on the carbon steel surface and corroborated the gravimetric results. Full article
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24 pages, 8625 KiB  
Article
Corrosion Susceptibility and Allergy Potential of Austenitic Stainless Steels
by Lucien Reclaru and Lavinia Cosmina Ardelean
Materials 2020, 13(18), 4187; https://doi.org/10.3390/ma13184187 - 21 Sep 2020
Cited by 7 | Viewed by 3325
Abstract
Although called stainless steels, austenitic steels are sensitive to localized corrosion, namely pitting, crevice, and intergranular form. Seventeen grades of steel were tested for localized corrosion. Steels were also tested in general corrosion and in galvanic couplings (steels–precious alloys) used in watchmaking applications. [...] Read more.
Although called stainless steels, austenitic steels are sensitive to localized corrosion, namely pitting, crevice, and intergranular form. Seventeen grades of steel were tested for localized corrosion. Steels were also tested in general corrosion and in galvanic couplings (steels–precious alloys) used in watchmaking applications. The evaluations have been carried out in accordance with the ASTM standards which specifically concern the forms of corrosion namely, general (B117-97, salt fog test), pitting (G48-11, FeCl3), crevice (F746-87) and intergranular (A262-15, Strauss chemical test and G108-94, Electrochemical potentiodynamic reactivation test). All tests revealed sensitivity to corrosion. We have noticed that the transverse face is clearly more sensitive than the longitudinal face, in the direction of rolling process. The same conclusion has been drawn from the tests of nickel release. It should be pointed out that, despite the fact that the grade of steel is in conformity with the classification standards, the behavior is very different from one manufacturer to another, due to parameters dependent on the production process, such as casting volume, alloying additions, and deoxidizing agents. The quantities of nickel released are related to the operations involved in the manufacturing process. Heat treatments reduce the quantities of nickel released. The surface state has little influence on the release. The hardening procedures increase the quantities of nickel released. The quantities of released nickel are influenced by the inclusionary state and the existence of the secondary phases in the steel structure. Another aspect is related to the strong dispersion of results concerning nickel release and corrosion behavior of raw materials. Full article
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21 pages, 11553 KiB  
Article
Microstructure and Corrosion of Cast Magnesium Alloy ZK60 in NaCl Solution
by Zhen Li, Zeyin Peng, Kai Qi, Hui Li, Yubing Qiu and Xingpeng Guo
Materials 2020, 13(17), 3833; https://doi.org/10.3390/ma13173833 - 30 Aug 2020
Cited by 14 | Viewed by 2926
Abstract
In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical [...] Read more.
In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical techniques. The alloy was found to be composed of α-Mg matrix, with large second-phase particles of MgZn2 deposited along grain boundaries and a Zr-rich region in the central area of the grains. The large second-phase particles and the Zr-rich regions were more stable than the Mg matrix, resulting in a strong micro-galvanic effect. A filiform corrosion was found. It originated from the second-phase particles in the grain boundary regions in the early corrosion period. The filaments gradually occupied most areas of the alloy surface, and the general corrosion rate decreased significantly. Corrosion pits were developed under filaments. The pit growth rate decreased over time; however, it was about eight times larger than the general corrosion rate. A schematic model is presented to illustrate the corrosion mechanism. Full article
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32 pages, 5825 KiB  
Review
Electrochemical Deposition of Ni, NiCo Alloy and NiCo–Ceramic Composite Coatings—A Critical Review
by Nyambura Samuel Mbugua, Min Kang, Yin Zhang, Ndumia Joseph Ndiithi, Gbenontin V. Bertrand and Liang Yao
Materials 2020, 13(16), 3475; https://doi.org/10.3390/ma13163475 - 06 Aug 2020
Cited by 40 | Viewed by 5299
Abstract
In recent years, alloy and alloy-ceramic coatings have gained a considerable attention owing to their favorable physicochemical and technological properties. In this review, we investigate Ni, NiCo alloy and NiCo–ceramic composite coatings prepared by electrodeposition. Electrodeposition is a versatile tool and cost-effective electrochemical [...] Read more.
In recent years, alloy and alloy-ceramic coatings have gained a considerable attention owing to their favorable physicochemical and technological properties. In this review, we investigate Ni, NiCo alloy and NiCo–ceramic composite coatings prepared by electrodeposition. Electrodeposition is a versatile tool and cost-effective electrochemical method used to produce high quality metal coatings. Surface finish and tribological properties of the coatings can be further improved by the addition of suitable agents and control of deposition operating conditions. In this review, Ni, NiCo alloy and NiCo–ceramic composite coatings prepared by electrodeposition are reviewed by critically evaluating previous researches. The use of the coatings and their potential for future research and development are discussed. Full article
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17 pages, 8576 KiB  
Article
Oxidation of Al-Co Alloys at High Temperatures
by Patrik Šulhánek, Marián Drienovský, Ivona Černičková, Libor Ďuriška, Ramūnas Skaudžius, Žaneta Gerhátová and Marián Palcut
Materials 2020, 13(14), 3152; https://doi.org/10.3390/ma13143152 - 15 Jul 2020
Cited by 18 | Viewed by 3269
Abstract
In this work, the high temperature oxidation behavior of Al71Co29 and Al76Co24 alloys (concentration in at.%) is presented. The alloys were prepared by controlled arc-melting of Co and Al granules in high purity argon. The as-solidified alloys [...] Read more.
In this work, the high temperature oxidation behavior of Al71Co29 and Al76Co24 alloys (concentration in at.%) is presented. The alloys were prepared by controlled arc-melting of Co and Al granules in high purity argon. The as-solidified alloys were found to consist of several different phases, including structurally complex m-Al13Co4 and Z-Al3Co phases. The high temperature oxidation behavior of the alloys was studied by simultaneous thermal analysis in flowing synthetic air at 773–1173 K. A protective Al2O3 scale was formed on the sample surface. A parabolic rate law was observed. The rate constants of the alloys have been found between 1.63 × 10−14 and 8.83 × 10−12 g cm−4 s−1. The experimental activation energies of oxidation are 90 and 123 kJ mol−1 for the Al71Co29 and Al76Co24 alloys, respectively. The oxidation mechanism of the Al-Co alloys is discussed and implications towards practical applications of these alloys at high temperatures are provided. Full article
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9 pages, 4315 KiB  
Communication
Molar Ratio Effect of Sodium to Chloride Ions on the Electrochemical Corrosion of Alloy 600 and SA508 in HCl + NaOH Mixtures
by Do Haeng Hur, Jeoh Han and Jun Choi
Materials 2020, 13(8), 1970; https://doi.org/10.3390/ma13081970 - 23 Apr 2020
Cited by 3 | Viewed by 1869
Abstract
This study aims to investigate the molar ratio effect of sodium to chloride ions on the corrosion of an Alloy 600 steam generator tube and an SA508 tubesheet material. The corrosion behavior was evaluated in solutions with three different molar ratios of sodium [...] Read more.
This study aims to investigate the molar ratio effect of sodium to chloride ions on the corrosion of an Alloy 600 steam generator tube and an SA508 tubesheet material. The corrosion behavior was evaluated in solutions with three different molar ratios of sodium to chloride ions using a potentiodynamic polarization method. The corrosion potentials and corrosion rates of both the two materials were significantly decreased as the molar ratio increased from 0.1 to 10. Therefore, it is recommended that the molar ratio control to a value of 1 is beneficial only when the crevice chemistry has a low molar ratio with an acidic pH. The corrosion potentials and corrosion rates were little affected by the total sodium and chloride ion concentrations. SA508 acted as an anode and its corrosion rate was accelerated by galvanic coupling with Alloy 600. Full article
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10 pages, 7481 KiB  
Article
Effect of Mo Addition on the Chemical Corrosion Process of SiMo Cast Iron
by Marcin Stawarz and Paweł M. Nuckowski
Materials 2020, 13(7), 1745; https://doi.org/10.3390/ma13071745 - 09 Apr 2020
Cited by 10 | Viewed by 2172
Abstract
The study was carried out to evaluate five SiMo cast iron grades and their resistance to chemical corrosion at elevated temperature. Corrosion tests were carried out under conditions of an actual cyclic operation of a retort coal-fired boiler. The duration of the study [...] Read more.
The study was carried out to evaluate five SiMo cast iron grades and their resistance to chemical corrosion at elevated temperature. Corrosion tests were carried out under conditions of an actual cyclic operation of a retort coal-fired boiler. The duration of the study was 3840 h. The range of temperature changes during one cycle was in the range of 300–650 °C. Samples of SiMo cast iron with Si content at the level of 5% and variable Mo content in the range 0%–2.5% were used as the material for the study. The examined material was subjected to preliminary metallographic analysis using scanning microscopy and an Energy dispersive spectroscopy (EDS) system. The chemical composition was determined on the basis of a Leco spectrometer and a Leco carbon and sulfur analyzer. The examination of the oxide layer was carried out with the use of Scanning electron microscope (SEM), EDS, and X-ray diffraction (XRD) methods. It was discovered that, in the analyzed alloys, oxide layers consisting of Fe2O3, Fe3O4, SO2, and Fe2SiO4 were formed. The analyzed oxide layers were characterized by high adhesion to the substrate material, and their total thickness was about 20 μm. Full article
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