Special Issue "Oxidation of Metals"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 January 2016)

Special Issue Editors

Guest Editor
Mr. Vineet V. Joshi

Applied Materials and Performance Group, Pacific Northwest National Laboratory, Richland, WA-99354, USA
Website | E-Mail
Interests: corrosion, oxidation of metals, thermal barrier coatings, light weight materials, nuclear materials, joining technologies, brazing, materials processing
Guest Editor
Dr. Alan Meier

Department of Metallurgical and Materials Engineering, Montana Tech of the University of Montana, 1300 West Park Street, ELC Room 212, Butte, MT 59701, USA
Website | E-Mail
Interests: material brazing and joining, surfaces and dissimilar material interfaces, physical and mechanical metallurgy, the processing and properties of cermets and MMC failure analysis, design of lightweight structures and components, mechanical testing and metal forming stress analysis

Special Issue Information

Dear Colleagues,

Currently, alloys are being rapidly developed. At the same time, environmental degradation, i.e., the corrosion of materials, is a major hindrance. The necessity of improving the efficiencies of propulsion systems, power generation units, gas separation units, and chemical plants has resulted in demand for materials that can withstand corrosion at high temperatures without drastically compromising strength. Also, the reductions in weight of automotive materials have resulted from the use of dissimilar materials and have therefore furthered the challenges of preventing corrosion. Over the years, several new alloys and systems have been developed to combat the most demanding of corrosive environments and rigorous research efforts are being made to understand the mechanism of corrosion or failure using advanced characterization tools.

This Special Issue concerning the environmental degradation of metals aims to present the latest research and trends that highlight advancements in corrosion resistant materials in different environments using advanced characterization and modeling tools.

Mr. Viineet V. Joshi
Dr. Alam Meier
Guest Editors

Manuscript Submission Information

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Keywords

  • oxidation
  • high temperature corrosion
  • galvanic corrosion
  • microstructure evolution
  • aqueous corrosion
  • in-situ investigations

Published Papers (15 papers)

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Research

Open AccessArticle The Effect of the Si Content on the Morphology and Amount of Fe2SiO4 in Low Carbon Steels
Metals 2016, 6(4), 94; doi:10.3390/met6040094
Received: 3 March 2016 / Revised: 8 April 2016 / Accepted: 12 April 2016 / Published: 22 April 2016
Cited by 5 | PDF Full-text (3513 KB) | HTML Full-text | XML Full-text
Abstract
In order to study the effect of the Si content on the morphology, amount, and distribution of fayalite (Fe2SiO4), three low-carbon steels with different Si contents were selected, and reheating tests were conducted in an industrial furnace in a
[...] Read more.
In order to study the effect of the Si content on the morphology, amount, and distribution of fayalite (Fe2SiO4), three low-carbon steels with different Si contents were selected, and reheating tests were conducted in an industrial furnace in a hot strip plant. The results show that Si distributes in two forms—first, Fe2SiO4, in the innermost layer of the oxide scale, and, second, granular SiO2, dispersively distributed in the matrix near the scale. In addition, Fe2SiO4 appears in a net-like form in the innermost layer of the oxide scale close to the iron matrix when the Si content is 1.21 wt. %. However, no obvious net-like Fe2SiO4 is observed when the Si content is less than 0.25 wt. %. Moreover, the inhibition effect of the solid Fe2SiO4 on the oxidation reaction plays a more important role than the promotion effect of the liquid Fe2SiO4 during the entire oxidation reaction. Therefore, the total thickness of the scale decreases with the increase in Si content. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Microgalvanic Corrosion Behavior of Cu-Ag Active Braze Alloys Investigated with SKPFM
Metals 2016, 6(4), 91; doi:10.3390/met6040091
Received: 3 February 2016 / Revised: 21 March 2016 / Accepted: 6 April 2016 / Published: 19 April 2016
Cited by 1 | PDF Full-text (11081 KB) | HTML Full-text | XML Full-text
Abstract
The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy
[...] Read more.
The nature of microgalvanic couple driven corrosion of brazed joints was investigated. 316L stainless steel samples were joined using Cu-Ag-Ti and Cu-Ag-In-Ti braze alloys. Phase and elemental composition across each braze and parent metal interface was characterized and scanning Kelvin probe force microscopy (SKPFM) was used to map the Volta potential differences. Co-localization of SKPFM with Energy Dispersive Spectroscopy (EDS) measurements enabled spatially resolved correlation of potential differences with composition and subsequent galvanic corrosion behavior. Following exposure to the aggressive solution, corrosion damage morphology was characterized to determine the mode of attack and likely initiation areas. When exposed to 0.6 M NaCl, corrosion occurred at the braze-316L interface preceded by preferential dissolution of the Cu-rich phase within the braze alloy. Braze corrosion was driven by galvanic couples between the braze alloys and stainless steel as well as between different phases within the braze microstructure. Microgalvanic corrosion between phases of the braze alloys was investigated via SKPFM to determine how corrosion of the brazed joints developed. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Corrosion Resistance of the Superhydrophobic Mg(OH)2/Mg-Al Layered Double Hydroxide Coatings on Magnesium Alloys
Metals 2016, 6(4), 85; doi:10.3390/met6040085
Received: 18 January 2016 / Revised: 18 March 2016 / Accepted: 6 April 2016 / Published: 13 April 2016
Cited by 3 | PDF Full-text (5719 KB) | HTML Full-text | XML Full-text
Abstract
Coatings of the Mg(OH)2/Mg-Al layered double hydroxide (LDH) composite were formed by a combined co-precipitation method and hydrothermal process on the AZ31 alloy substrate in alkaline condition. Subsequently, a superhydrophobic surface was successfully constructed to modify the composite coatings on the
[...] Read more.
Coatings of the Mg(OH)2/Mg-Al layered double hydroxide (LDH) composite were formed by a combined co-precipitation method and hydrothermal process on the AZ31 alloy substrate in alkaline condition. Subsequently, a superhydrophobic surface was successfully constructed to modify the composite coatings on the AZ31 alloy substrate using stearic acid. The characteristics of the composite coatings were investigated by means of X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electronic microscope (SEM) and contact angle (CA). The corrosion resistance of the coatings was assessed by potentiodynamic polarization, the electrochemical impedance spectrum (EIS), the test of hydrogen evolution and the immersion test. The results showed that the superhydrophobic coatings considerably improved the corrosion resistant performance of the LDH coatings on the AZ31 alloy substrate. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Open AccessFeature PaperArticle Electrochemical Surface Treatment of a β-titanium Alloy to Realize an Antibacterial Property and Bioactivity
Metals 2016, 6(4), 76; doi:10.3390/met6040076
Received: 18 February 2016 / Revised: 20 March 2016 / Accepted: 24 March 2016 / Published: 28 March 2016
Cited by 3 | PDF Full-text (3622 KB) | HTML Full-text | XML Full-text
Abstract
In this study, micro-arc oxidation (MAO) was performed on a β-type titanium alloy, namely, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), to improve not only its antibacterial property but also bioactivity in body fluids. The surface oxide layer formed on TNTZ by MAO treatment in a mixture
[...] Read more.
In this study, micro-arc oxidation (MAO) was performed on a β-type titanium alloy, namely, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), to improve not only its antibacterial property but also bioactivity in body fluids. The surface oxide layer formed on TNTZ by MAO treatment in a mixture of calcium glycerophosphate, calcium acetate, and silver nitrate was characterized using surface analyses. The resulting porous oxide layer was mainly composed of titanium oxide, and it also contained calcium, phosphorus, and a small amount of silver, all of which were incorporated from the electrolyte during the treatment. The MAO-treated TNTZ showed a strong inhibition effect on anaerobic Gram-negative bacteria when the electrolyte contained more than 0.5 mM silver ions. The formation of calcium phosphate on the surface of the specimens after immersion in Hanks’ solution was evaluated to determine the bioactivity of TNTZ with sufficient antibacterial property. As a result, thick calcium phosphate layers formed on the TNTZ specimen that underwent MAO treatment, whereas no precipitate was observed on TNTZ without treatment. Thus, the MAO treatment of titanium-based alloys is confirmed to be effective in realizing both antibacterial and bioactive properties. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Preparation of Property-Controlled Bi-Based Solder Powders by a Ball-Milling Process
Metals 2016, 6(4), 74; doi:10.3390/met6040074
Received: 28 January 2016 / Revised: 23 February 2016 / Accepted: 4 March 2016 / Published: 25 March 2016
Cited by 4 | PDF Full-text (2899 KB) | HTML Full-text | XML Full-text
Abstract
Three kinds of Bi-based solder powders with different chemical compositions of binary Bi–Sn, ternary Bi–Sn–In, and quaternary Bi–Sn–In–Ga were prepared using a gas atomization process and subsequently ball-milled for smaller-size fabrication. In particular, only the quaternary Bi–Sn–In–Ga solder powders were severely broken to
[...] Read more.
Three kinds of Bi-based solder powders with different chemical compositions of binary Bi–Sn, ternary Bi–Sn–In, and quaternary Bi–Sn–In–Ga were prepared using a gas atomization process and subsequently ball-milled for smaller-size fabrication. In particular, only the quaternary Bi–Sn–In–Ga solder powders were severely broken to the size of less than 10 μm in a polyhedral shape due to the presence of the constitutional element, the degree of overall oxidation, and the formation of solid solution, which had affected the fractured extent of the Ga-containing solder powders. Furthermore, a melting point also decreased by the addition of In and/or Ga into the binary Bi–Sn solder system, resulting in a melting point of 60.3 °C for the Bi–Sn–In–Ga solder powders. Thus, it was possible that fractured Bi–Sn–In–Ga solder powders were appropriate for the adhesion of more compact solder bump arrays, enabling reflowing at the low temperature of 110 °C on a flexible polyethylene terephthalate (PET) substrate. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Corrosion and Discharge Behaviors of Mg-Al-Zn and Mg-Al-Zn-In Alloys as Anode Materials
Metals 2016, 6(3), 65; doi:10.3390/met6030065
Received: 29 January 2016 / Revised: 16 February 2016 / Accepted: 4 March 2016 / Published: 17 March 2016
Cited by 5 | PDF Full-text (5792 KB) | HTML Full-text | XML Full-text
Abstract
The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%)In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS) analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their
[...] Read more.
The Mg-6%Al-3%Zn and Mg-6%Al-3%Zn-(1%, 1.5%, 2%)In alloys were prepared by melting and casting. Their microstructures were investigated via metallographic and energy-dispersive X-ray spectroscopy (EDS) analysis. Moreover, hydrogen evolution and electrochemical tests were carried out in 3.5 wt% NaCl solution aiming at identifying their corrosion mechanisms and discharge behaviors. The results suggested that indium exerts an improvement on both the corrosion rate and the discharge activity of Mg-Al-Zn alloy via the effects of grain refining, β-Mg17Al12 precipitation, dissolving-reprecipitation, and self-peeling. The Mg-6%Al-3%Zn-1.5%In alloy with the highest corrosion rate at free corrosion potential did not perform desirable discharge activity indicating that the barrier effect caused by the β-Mg17Al12 phase would have been enhanced under the conditions of anodic polarization. The Mg-6%Al-3%Zn-1.0%In alloy with a relative low corrosion rate and a high discharge activity is a promising anode material for both cathodic protection and chemical power source applications. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Open AccessArticle The Early Morphological Development of the Near Surface Region of Pickled Grade 91 Tubing Exposed to Steam and Its Long Term Implications
Metals 2016, 6(3), 62; doi:10.3390/met6030062
Received: 29 January 2016 / Revised: 26 February 2016 / Accepted: 8 March 2016 / Published: 14 March 2016
Cited by 1 | PDF Full-text (4265 KB) | HTML Full-text | XML Full-text
Abstract
To improve intra-laboratory consistency and experimental repeatability during high temperature oxidation testing, metallic coupons undergo a standardised surface preparation. It is stipulated in international testing standards that grinding of a coupons surface acceptably replicates surface conditions encountered in industrial settings whilst ensuring that
[...] Read more.
To improve intra-laboratory consistency and experimental repeatability during high temperature oxidation testing, metallic coupons undergo a standardised surface preparation. It is stipulated in international testing standards that grinding of a coupons surface acceptably replicates surface conditions encountered in industrial settings whilst ensuring that each coupons surface is chemically and topographically homogenised [1,2]. Grade 91 steel tubing exposed in the laboratory to flowing steam at 650 °C and 1 bar for up to 3000 h has been compared with Grade 91 tubing exposed in a commercially operated boiler system at elevated pressures at temperatures in the range of 500 to 650 °C for 91 kh. It has been found that a pre-existing surface structure dissimilar from that of the bulk alloy and that of a ground surface, is present on the inside surface of the tubing. The presence of pre-existing surface features in commercially exposed material has implications on the long term morphological development of the oxidation region and may account for some of the discrepancies between observations made in laboratory and service exposures. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Surface and Microstructural Failures of PET-Coated ECCS Plates by Salmon-Polymer Interaction
Metals 2016, 6(3), 59; doi:10.3390/met6030059
Received: 17 January 2016 / Revised: 27 February 2016 / Accepted: 29 February 2016 / Published: 11 March 2016
PDF Full-text (3306 KB) | HTML Full-text | XML Full-text
Abstract
The new types of knowledge-intensive, multilayer containers consist of steel plates protected against corrosion by nanometric electrolytic chromium (Cr0) and chromium oxide (Cr2O3) layers chemically bonded to polyethylene terephthalate (PET) polymer coating to preserve food. It was
[...] Read more.
The new types of knowledge-intensive, multilayer containers consist of steel plates protected against corrosion by nanometric electrolytic chromium (Cr0) and chromium oxide (Cr2O3) layers chemically bonded to polyethylene terephthalate (PET) polymer coating to preserve food. It was observed that after emptying the cans, the salmon adhered to the polymer coating, changing its color, and that this adhesion increased with longer storage times. This work was aimed at determining the product-container interactions and their characterization by X-ray diffraction (XRD), confocal Raman and micro-Raman imaging and scanning electron microscopy (SEM) analysis. The zones of adhesion showed surface changes, variations in crystallinity and microstructural degradation of the PET coating. In addition, localized damages altering the functional properties of the multilayer system were observed as microcracking in the chromium layers that protect the steel. The degradation undergone was evaluated and characterized at a surface and microstructural level to establish the failure mechanisms, which were mainly associated with the activity of the adhered muscle and its biochemical components. Finally, a recommendation is done to preserve the useful life and functionality of cans for the preservation and efficient use of resources with an impact on recycling and environmental conservancy. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Composition Distribution and Electrochemical Behavior of an Ni2Al3 Coating on Q235 Steel
Metals 2016, 6(3), 58; doi:10.3390/met6030058
Received: 13 November 2015 / Revised: 1 March 2016 / Accepted: 8 March 2016 / Published: 11 March 2016
Cited by 2 | PDF Full-text (1542 KB) | HTML Full-text | XML Full-text
Abstract
An Ni2Al3 coating was prepared via the electrodeposition of nickel followed by pack aluminization. Polarization curve and electrochemical impedance spectroscopy were performed to study the room temperature corrosion behavior of the coating in a 3.5 wt. % NaCl solution. The
[...] Read more.
An Ni2Al3 coating was prepared via the electrodeposition of nickel followed by pack aluminization. Polarization curve and electrochemical impedance spectroscopy were performed to study the room temperature corrosion behavior of the coating in a 3.5 wt. % NaCl solution. The long-term impedance of the coating was also investigated after immersion for 30 days. Results show that the Ni2Al3 coating possessed lower corrosion current density (Icorr) and higher polarization resistance (Rp) than the substrate in the solution. The Bode plots of the coating showed two time constants after the long-term immersion. Pitting corrosion was found on the coating surface. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Al-Co Alloys Prepared by Vacuum Arc Melting: Correlating Microstructure Evolution and Aqueous Corrosion Behavior with Co Content
Metals 2016, 6(3), 46; doi:10.3390/met6030046
Received: 18 January 2016 / Revised: 11 February 2016 / Accepted: 19 February 2016 / Published: 27 February 2016
Cited by 3 | PDF Full-text (6526 KB) | HTML Full-text | XML Full-text
Abstract
Hypereutectic Al-Co alloys of various Co contents (7–20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures
[...] Read more.
Hypereutectic Al-Co alloys of various Co contents (7–20 weight % (wt.%) Co) were prepared by vacuum arc melting, aiming at investigating the influence of the cobalt content on the microstructure and corrosion behavior. Quite uniform and directional microstructures were attained. The obtained microstructures depended on the Co content, ranging from fully eutectic growth (7 wt.% and 10 wt.% Co) to coarse primary Al9Co2 predominance (20 wt.% Co). Co dissolution in Al far exceeded the negligible equilibrium solubility of Co in Al; however, it was hardly uniform. By increasing the cobalt content, the fraction and coarseness of Al9Co2, the content of Co dissolved in the Al matrix, and the hardness and porosity of the alloy increased. All alloys exhibited similar corrosion behavior in 3.5 wt.% NaCl with high resistance to localized corrosion. Al-7 wt.% Co showed slightly superior corrosion resistance than the other compositions in terms of relatively low corrosion rate, relatively low passivation current density and scarcity of stress corrosion cracking indications. All Al-Co compositions demonstrated substantially higher resistance to localized corrosion than commercially pure Al produced by casting, cold rolling and arc melting. A corrosion mechanism was formulated. Surface films were identified. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Effect of Synthesizing Temperature on Microstructure and Electrochemical Property of the Hydrothermal Conversion Coating on Mg-2Zn-0.5Mn-Ca-Ce Alloy
Metals 2016, 6(3), 44; doi:10.3390/met6030044
Received: 14 January 2016 / Revised: 6 February 2016 / Accepted: 15 February 2016 / Published: 25 February 2016
Cited by 2 | PDF Full-text (3553 KB) | HTML Full-text | XML Full-text
Abstract
Mg(OH)2 conversion coatings were formed on an Mg-2Zn-0.5Mn-Ca-Ce alloy via hydrothermal method at three different synthesizing temperatures (160, 170 and 180 °C). The effect of synthesizing temperature on microstructure and electrochemical property of the coatings were systematically studied. With increasing synthesizing temperature,
[...] Read more.
Mg(OH)2 conversion coatings were formed on an Mg-2Zn-0.5Mn-Ca-Ce alloy via hydrothermal method at three different synthesizing temperatures (160, 170 and 180 °C). The effect of synthesizing temperature on microstructure and electrochemical property of the coatings were systematically studied. With increasing synthesizing temperature, the coating became thicker due to the faster reaction and deposition of Mg(OH)2 on the α-Mg phase and secondary phases of the substrate Mg alloy. Internal micro-cracks were also generated in the higher-temperature synthesized coatings due to the increased shrinking stress, but the cross-cutting micro-cracks were suppressed. Benefiting from the improved barrier effect against penetration of corrosive medium, the higher-temperature synthesized thicker coating presented significantly enhanced electrochemical property and anti-corrosion efficiency in Hanks’ solution. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Effect of Al Hot-Dipping on High-Temperature Corrosion of Carbon Steel in N2/0.1% H2S Gas
Metals 2016, 6(2), 38; doi:10.3390/met6020038
Received: 11 January 2016 / Revised: 3 February 2016 / Accepted: 5 February 2016 / Published: 17 February 2016
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Abstract
High-temperature corrosion of carbon steel in N2/0.1% H2S mixed gas at 600–800 °C for 50–100 h was studied after hot-dipping in the aluminum molten bath. Hot-dipping resulted in the formation of the Al topcoat and the Al-Fe alloy layer
[...] Read more.
High-temperature corrosion of carbon steel in N2/0.1% H2S mixed gas at 600–800 °C for 50–100 h was studied after hot-dipping in the aluminum molten bath. Hot-dipping resulted in the formation of the Al topcoat and the Al-Fe alloy layer firmly adhered on the substrate. The Al-Fe alloy layer consisted primarily of a wide, tongue-like Al5Fe2 layer and narrow Al3Fe layer. When corroded at 800 °C for 100 h, the Al topcoat partially oxidized to the protective but non-adherent α-Al2O3 layer, and the interdiffusion converted the Al-Fe alloy layer to an (Al13Fe4, AlFe3)-mixed layer. The interdiffusion also lowered the microhardness of the hot-dipped steel. The α-Al2O3 layer formed on the hot-dipped steel protected the carbon steel against corrosion. Without the Al hot-dipping, the carbon steel failed by forming a thick, fragile, and non-protective FeS scale. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Biodegradable Behaviors of Ultrafine-Grained ZE41A Magnesium Alloy in DMEM Solution
Metals 2016, 6(1), 3; doi:10.3390/met6010003
Received: 10 October 2015 / Revised: 6 December 2015 / Accepted: 17 December 2015 / Published: 23 December 2015
Cited by 2 | PDF Full-text (975 KB) | HTML Full-text | XML Full-text
Abstract
The main limitation to the clinical application of magnesium alloys is their too-fast degradation rate in the physiological environment. Bio-corrosion behaviors of the ZE41A magnesium alloy processed by multi-pass equal channel angular pressing (ECAP) were investigated in Dulbecco's Modified Eagle Medium (DMEM) solution,
[...] Read more.
The main limitation to the clinical application of magnesium alloys is their too-fast degradation rate in the physiological environment. Bio-corrosion behaviors of the ZE41A magnesium alloy processed by multi-pass equal channel angular pressing (ECAP) were investigated in Dulbecco's Modified Eagle Medium (DMEM) solution, in order to tailor the effect of grain ultrafining on the biodegradation rate of the alloy implant. Hydrogen evolution tests indicated that a large number of ECAP passes decreased the stable corrosion rate of the alloy after the initial incubation period. Potentiodynamic polarization curves showed that more ECAP passes made the corrosion potential nobler and the corrosion tendency lower. Corroded surfaces of the ECAPed alloy indicated a higher resistance toward localized corrosion due to the homogeneous redistribution of broken second phases on the ultrafine-grained Mg matrix. It suggests that grain ultrafining can decrease the biodegradable rate of the magnesium alloy-containing rare-earth elements and tailor the lifetime of the biodegradable material. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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Open AccessArticle Galvanic Corrosion between Alloy 690 and Magnetite in Alkaline Aqueous Solutions
Metals 2015, 5(4), 2372-2382; doi:10.3390/met5042372
Received: 15 October 2015 / Revised: 18 November 2015 / Accepted: 9 December 2015 / Published: 14 December 2015
Cited by 1 | PDF Full-text (650 KB) | HTML Full-text | XML Full-text
Abstract
The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple
[...] Read more.
The galvanic corrosion behavior of Alloy 690 coupled with magnetite has been investigated in an alkaline solution at 30 °C and 60 °C using a potentiodynamic polarization method and a zero resistance ammeter. The positive current values were recorded in the galvanic couple and the corrosion potential of Alloy 690 was relatively lower. These results indicate that Alloy 690 behaves as the anode of the pair. The galvanic coupling between Alloy 690 and magnetite increased the corrosion rate of Alloy 690. The temperature increase led to an increase in the extent of galvanic effect and a decrease in the stability of passive film. Galvanic effect between Alloy 690 and magnetite is proposed as an additional factor accelerating the corrosion rate of Alloy 690 steam generator tubing in secondary water. Full article
(This article belongs to the Special Issue Oxidation of Metals)
Open AccessArticle Beeswax-Colophony Blend: A Novel Green Organic Coating for Protection of Steel Drinking Water Storage Tanks
Metals 2015, 5(3), 1645-1664; doi:10.3390/met5031645
Received: 30 July 2015 / Revised: 7 September 2015 / Accepted: 9 September 2015 / Published: 15 September 2015
Cited by 1 | PDF Full-text (1749 KB) | HTML Full-text | XML Full-text
Abstract
Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking
[...] Read more.
Beeswax-colophony blend is mainly used as a sealant mixture for preservation applications. The beeswax itself, however, has had a long way in history taking part in conservation processes including mummification. In this research, this blend was used as a protective coating for drinking water distribution tanks. Initially, a layer with 400 μm thickness was applied on a sand blasted mild steel plate. The long-term electrochemical behavior of the coating was investigated by open circuit potential (OCP) and electrochemical microbiological characteristics of the coating, microbial and chemical examinations were performed on drinking water samples that had been in contact with the coating. Furthermore, its behavior in an up-flow anaerobic sludge blanket reactor (UASBR) in a wastewater treatment plant was investigated using the scanning electron microscopy (SEM) technique. Regarding the consistency of experimental results, it was concluded that this proposed recyclable blend could be considered as a novel green organic coating and also a good corrosion barrier even in aggressive environments. Full article
(This article belongs to the Special Issue Oxidation of Metals)
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