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Corros. Mater. Degrad., Volume 3, Issue 4 (December 2022) – 10 articles

Cover Story (view full-size image): Corrosion management is moving into a new era due to recent developments. Using CT in characterisation gives insight into structures in paints where electrolyte transport occurs, as well as information on sites where localised corrosion takes place. A second area of development is in high-throughput (HT) approaches that can be adapted to probe corrosive environments as well as turned to HT assessment of potential inhibitors in controlled environments (e.g., wire beam electrode). The third area is machine learning; success in pharmaceutical discovery is being applied to inhibitor discovery. In the convergence of these areas, artificial intelligence can be combined with specific information about local environments and large databases to assess and predict new compounds that outperform current inhibitors and reduce risk to the environment and us. View this paper
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17 pages, 4078 KiB  
Article
Influence of Exposure Conditions and Particulate Deposition on Anodized Aluminum Corrosion
by Isabel Rute Fontinha and Elsa Eustáquio
Corros. Mater. Degrad. 2022, 3(4), 770-786; https://doi.org/10.3390/cmd3040040 - 12 Dec 2022
Viewed by 1959
Abstract
Anodizing is commonly used for corrosion protection of aluminum and its alloys in the construction industry. The anodic aluminum oxide (AAO) coating has a high ability to prevent the development of extensive pitting corrosion in aluminum substrates, particularly in marine sites, as was [...] Read more.
Anodizing is commonly used for corrosion protection of aluminum and its alloys in the construction industry. The anodic aluminum oxide (AAO) coating has a high ability to prevent the development of extensive pitting corrosion in aluminum substrates, particularly in marine sites, as was observed during a 10-year atmospheric corrosion study carried out in several marine and industrial sites. However, this study also evidenced that this coating can be highly affected by the deposition of particulate material in industrial polluted environments, sometimes in unexpected ways. This study presents information on the atmospheric corrosion of anodized aluminum exposed at two different chemical industrial complexes: a fertilizer production plant and a pulp and paper mill. Visual assessment of surface changes, pitting depth and mass variation with exposure were determined to quantify the degradation suffered. Additionally, SEM/EDS analyses were carried out on the exposed surfaces. Based on the results obtained, the role played by the deposition of airborne particles present in the two environments with respect to the type and level of damage observed is discussed. Deposits of roasted pyrite ash and phosphates or of wood chips and lime particles enhanced pitting corrosion or caused dissolution of the AAO coating. Full article
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11 pages, 3685 KiB  
Review
Electrochemical Impedance Spectroscropy Study on the Behavior of Reinforced Concrete Elements under Loading
by Belén Díaz, X. Ramón Nóvoa and Carmen Pérez
Corros. Mater. Degrad. 2022, 3(4), 759-769; https://doi.org/10.3390/cmd3040039 - 01 Dec 2022
Viewed by 1994
Abstract
Concrete is a material of porous nature that, when humidified, becomes an ionic conductor whose apparent conductivity depends on the ionic load (typically based on OH, Ca2+, Na+, and K+) and the amount of available [...] Read more.
Concrete is a material of porous nature that, when humidified, becomes an ionic conductor whose apparent conductivity depends on the ionic load (typically based on OH, Ca2+, Na+, and K+) and the amount of available free water. Under conditions of partial pore-saturation, the amount of free water can be modulated by an external load, which leads to observable changes in electrical properties such as conductivity and capacitance. Moreover, metallic reinforcements, either as bars or fibers, represent an additional parallel conduction path but of an electronic nature in this case. The free water develops a double-layer capacitance structure at the metallic interfaces, with associated charge-transfer resistance, representing an additional contribution to the capacitive behavior that can be modulated with an external load. The dependence that the electrical and/or ionic conducting properties of concrete and reinforced concrete elements have on the available free water makes them suitable for transductors in various sensing and self-sensing applications discussed in the text. Full article
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65 pages, 15719 KiB  
Review
A Critical Review of Radiolysis Issues in Water-Cooled Fission and Fusion Reactors: Part II, Prediction of Corrosion Damage in Operating Reactors
by Digby D. Macdonald and George R. Engelhardt
Corros. Mater. Degrad. 2022, 3(4), 694-758; https://doi.org/10.3390/cmd3040038 - 30 Nov 2022
Cited by 2 | Viewed by 2104
Abstract
The radiolysis of water is a significant cause of corrosion damage in the primary heat transport systems (PHTSs) of water-cooled, fission nuclear power reactors (BWRs, PWRs, and CANDUs) and is projected to be a significant factor in the evolution of corrosion damage in [...] Read more.
The radiolysis of water is a significant cause of corrosion damage in the primary heat transport systems (PHTSs) of water-cooled, fission nuclear power reactors (BWRs, PWRs, and CANDUs) and is projected to be a significant factor in the evolution of corrosion damage in future fusion reactors (e.g., the ITER that is currently under development). In Part I of this two-part series, we reviewed the proposed mechanisms for the radiolysis of water and demonstrate that radiolysis leads to the formation of a myriad of oxidizing and reducing species. In this Part II, we review the role that the radiolysis species play in establishing the electrochemical corrosion potential (ECP) and the development of corrosion damage due to intergranular stress corrosion cracking (IGSCC) in reactor PHTSs. We demonstrate, that the radiolytic oxidizing radiolysis products, such as O2, H2O2, HO2, and OH, when in molar excess over reducing species (H2, H, and O22−), some of which (H2) are preferentially stripped from the coolant upon boiling in a BWR PHTS, for example, renders the coolant in many BWRs oxidizing, thereby shifting the ECP in the positive direction to a value that is more positive than the critical potential (Ecrit = −0.23 Vshe at 288 °C) for IGSCC in sensitized austenitic stainless steel (e.g., Type 304 SS). This has led to many IGSCC incidents in operating BWRs over the past five decades that has exacted a great cost on the plant operators and electricity consumers, alike. In the case of PWRs, the primary circuits are pressurized with hydrogen to give a hydrogen concentration of 10 to 50 cm3/kgH2O (0.89 to 4.46 ppm), such that no sustained boiling occurs, and the hydrogen suppresses the radiolysis of water, thereby inhibiting the formation of oxidizing radiolysis products from water. Thus, the ECP is dominated by the hydrogen electrode reaction (HER), although important deviations from the HER equilibrium potential may occur, particularly at low [H2]. In any event, the ECP is displaced to approximately −0.85 Vshe, which is below the critical potential for IGSCC in sensitized stainless steels but is also more negative than the critical potential for the hydrogen-induced cracking (HIC) of mill-annealed Alloy 600. This has led to extensive cracking of steam generator tubing and other components (e.g., control rod drive tubes, pressurizer components) in PWRs that has also exacted a high cost on operators and power consumers. Although the ITER has yet to operate, the proposed chemistry protocol for the coolant places it close to a BWR operating on Normal Water Chemistry (NWC) without boiling or, if hydrogen is added to the IBED-PHTS, close to a BWR on Hydrogen Water Chemistry (HWC). In the current ITER technology, the concentration of H2 in the IBED-PHTS is specified to be 80 ppb, which is the concentration that will be experienced in both the Plasma Flux Area (PFA) and in the Out of Plasma Flux Area (OPFA). That corresponds to 0.90 cc(STP) H2/KgH2O, compared with 20–50 cc(STP) H2/KgH2O employed in a PWR primary coolant circuit and 5.5 to 22 cc(STP) H2/KgH2O in a BWR on hydrogen water chemistry (HWC). We predict that a hydrogen concentration of 80 ppb is sufficient to reduce the ECP in the OPFA to a level (−0.324 Vshe) that is sufficient to suppress the crack growth rate (CGR) below the practical, maximum level of 10−9 cm/s (0.315 mm/a) at which SCC is considered not to be a problem in a coolant circuit but, in the PFA, the ECP is predicted to be 0.380 Vshe, which gives a calculated standard CGR of 2.7 × 10−6 cm/s. This is more than three orders in magnitude greater that the desired maximum value of 10−9 cm/s. We recommend that the HWC issue in ITER be revisited to develop a protocol that is effective in suppressing both the ECP and the CGR in the PFA to levels that permit the operation of the IBED-PHTS in accordance with the experience gained in fission reactor technology. Full article
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22 pages, 2755 KiB  
Review
Corrosion Inhibition, Inhibitor Environments, and the Role of Machine Learning
by Anthony E. Hughes, David A. Winkler, James Carr, P. D. Lee, Y. S. Yang, Majid Laleh and Mike Y. Tan
Corros. Mater. Degrad. 2022, 3(4), 672-693; https://doi.org/10.3390/cmd3040037 - 29 Nov 2022
Cited by 5 | Viewed by 3203
Abstract
Machine learning (ML) is providing a new design paradigm for many areas of technology, including corrosion inhibition. However, ML models require relatively large and diverse training sets to be most effective. This paper provides an overview of developments in corrosion inhibitor research, focussing [...] Read more.
Machine learning (ML) is providing a new design paradigm for many areas of technology, including corrosion inhibition. However, ML models require relatively large and diverse training sets to be most effective. This paper provides an overview of developments in corrosion inhibitor research, focussing on how corrosion performance data can be incorporated into machine learning and how large sets of inhibitor performance data that are suitable for training robust ML models can be developed through various corrosion inhibition testing approaches, especially high-throughput performance testing. It examines different types of environments where corrosion by-products and electrolytes operate, with a view to understanding how conventional inhibitor testing methods may be better designed, chosen, and applied to obtain the most useful performance data for inhibitors. The authors explore the role of modern characterisation techniques in defining corrosion chemistry in occluded structures (e.g., lap joints) and examine how corrosion inhibition databases generated by these techniques can be exemplified by recent developments. Finally, the authors briefly discuss how the effects of specific structures, alloy microstructures, leaching structures, and kinetics in paint films may be incorporated into machine learning strategies. Full article
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11 pages, 3600 KiB  
Article
Abrasion and Cavitation Erosion Resistance of Multi-Layer Dip Coated Sol-Gel Coatings on AA2024-T3
by Manasa Hegde, Yvonne Kavanagh, Brendan Duffy and Edmond F. Tobin
Corros. Mater. Degrad. 2022, 3(4), 661-671; https://doi.org/10.3390/cmd3040036 - 22 Nov 2022
Cited by 4 | Viewed by 1678
Abstract
AA2024-T3 are widely used in various applications because of their exceptional physical properties. However, they are susceptible to corrosion and cavitation erosion in aggressive environments due to high concentration of copper. Sol-gel coatings in the field of corrosion prevention are emerging. Improved thickness [...] Read more.
AA2024-T3 are widely used in various applications because of their exceptional physical properties. However, they are susceptible to corrosion and cavitation erosion in aggressive environments due to high concentration of copper. Sol-gel coatings in the field of corrosion prevention are emerging. Improved thickness of coatings significantly improves the barrier effect of the coatings, thereby improving their operational-life in industrial applications. To date, a limited amount of work has been carried out in determining the effect of hybrid sol-gel coatings on abrasion and cavitation erosion of AA2024-T3. The present study investigates the effect of thickness of the coatings on morphology, corrosion, abrasion and cavitation erosion properties of the prepared hybrid sol-gel coatings deposited on AA2024-T3 surfaces. The hybrid sol-gels have been synthesized from 3-trimethoxysilylpropylmethacrylate (MAPTMS), and a zirconium complex prepared from the chelation of zirconium n-propoxide (ZPO), and methacrylic acid (MAAH). AA-2024 T3 were coated using single-dip, double-dip and triple-dip. Abrasion and cavitation erosion tests were performed according to the relevant standards. Structural damage caused by corrosion, abrasion and cavitation erosion was studied by Optical Microscope and Scanning Electron Microscope (SEM). Corrosion protection performance of the coatings was tested using Open Circuit Potential (OCP) and Potentiodynamic polarization (PDS). Results indicated that the multilayer coated samples improved the corrosion, cavitation erosion and abrasion resistance of AA2024-T3. Hence, the prepared silica-based coatings can be proposed as a potential choice for marine renewable energy applications. Full article
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15 pages, 11832 KiB  
Article
Degradation of Steel Wires in Bimetallic Aluminum–Steel Conductors Exposed to Severe Corrosion Conditions
by Alan Rondineau, Laurent Gaillet, Lamine Dieng and Sébastien Langlois
Corros. Mater. Degrad. 2022, 3(4), 646-660; https://doi.org/10.3390/cmd3040035 - 10 Nov 2022
Viewed by 1970
Abstract
High-voltage electrical cables are prone to saline corrosion, mostly in coastal environments. Steel wires are a crucial element in withstanding the mechanical solicitations of commonly used aluminum conductor steel reinforced (ACSR) cables. An experimental accelerated corrosion test was made, using salt spray tests [...] Read more.
High-voltage electrical cables are prone to saline corrosion, mostly in coastal environments. Steel wires are a crucial element in withstanding the mechanical solicitations of commonly used aluminum conductor steel reinforced (ACSR) cables. An experimental accelerated corrosion test was made, using salt spray tests on greased and ungreased ACSR cables and individual galvanized steel wires. The corrosion mechanism occurring on the specimens was observed by optical microscopy for several durations of corrosion, to determine the evolution of the galvanic layer and steel substrate degradation. This study was completed by an SEM (Scanning Electron Microscopy) and Raman spectroscopy analysis to characterize the corrosion products occurring on the galvanized steel wires. An estimation of the evolution of the mean zinc thickness loss is also given, for each type of specimen. It is shown that the loss rate of the zinc layer is significantly reduced by the presence of aluminum layers around the steel wires and by the effect of the grease. Tensile tests were made on the exposed galvanized steel wires which led to fracture surface observations to assess the effect of corrosion on the evolution of mechanical properties. Full article
(This article belongs to the Special Issue Atmospheric Corrosion of Materials)
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18 pages, 6355 KiB  
Article
Protection of Reinforced Concrete Steel Exposed to a Marine Environment: A Preliminary Onsite Study of the Performance of a New Generation of Surface-Applied Corrosion Inhibitors
by Diana Martín and Engin Seyhan
Corros. Mater. Degrad. 2022, 3(4), 628-645; https://doi.org/10.3390/cmd3040034 - 31 Oct 2022
Viewed by 2462
Abstract
Reinforcement corrosion is the risk most frequently cited to justify concrete durability research, especially where it is induced by chlorides. Surface-applied corrosion inhibitors are widely used to mitigate the corrosion process both for carbonation and chlorides of steel reinforcement in concrete. They are [...] Read more.
Reinforcement corrosion is the risk most frequently cited to justify concrete durability research, especially where it is induced by chlorides. Surface-applied corrosion inhibitors are widely used to mitigate the corrosion process both for carbonation and chlorides of steel reinforcement in concrete. They are applied onto the surface of hardened concrete and penetrate towards steel reinforcement. This paper discusses the corrosion inhibition performance of a new generation of a dual-phase surface-applied corrosion inhibitor (DP-SACI), and its efficiency in corrosion induced by chlorides over 3% referred to cement mass, and also in pre- and post-cracked structures. This corrosion mitigation activity was evaluated onsite for almost four years, in a sea wall exposed to XS1 ambiance. The electrochemical techniques used were based on the determination of the electrical resistivity of concrete, the half-cell corrosion potential and the steel corrosion rate (from linear polarization resistance measurements). All of these electrochemical parameters provide accurate information for on-site structures about the efficiency over the time of surface-applied corrosion inhibitors. The effectiveness of the dual-phase surface-applied corrosion inhibitor proved to be up to 99%, even with ongoing corrosion and 0.3 mm cracks near the rebar. The use of DP-SACI provides a non-destructive repair method that inhibits the corrosion process and increases the service life of the element. Full article
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16 pages, 5784 KiB  
Article
Hybrid Polyurethane/Polypyrrole Composite Coatings on Passivated 316L SS for Surface Protective Action against Corrosion in Saline Medium
by Arumugam Madhan Kumar, Akeem Yusuf Adesina, Jothi Veeramani, Mohammad Mizanur Rahman and J. S. Nirmal Ram
Corros. Mater. Degrad. 2022, 3(4), 612-627; https://doi.org/10.3390/cmd3040033 - 31 Oct 2022
Cited by 5 | Viewed by 1530
Abstract
Hybrid treatments consisting of surface modification and subsequent protective coatings have gained extensive attention among corrosion mitigation approaches for a wide variety of structural metallic materials. This study aims to review the enhancement of the corrosion protection performance of polyurethane (PU) coatings on [...] Read more.
Hybrid treatments consisting of surface modification and subsequent protective coatings have gained extensive attention among corrosion mitigation approaches for a wide variety of structural metallic materials. This study aims to review the enhancement of the corrosion protection performance of polyurethane (PU) coatings on 316L stainless steel (SS) specimens. This was achieved via a two-step strategic treatment, primarily by electrochemical passivation and subsequent deposition of PU composite coatings with the different feed ratio of synthesized polypyrrole (PPy) nanoparticles. The effect of different applied voltage on the surface features and the corrosion behavior of the passivated SS surfaces was systematically investigated using surface characterization techniques and a potentiodynamic polarization test in a NaCl solution. Surface morphological images revealed the porous structure on the passivated surface. It is inferred from the topographical surface results that homogeneous surface roughness was achieved with the applied voltage of 5 V. Infra-red spectroscopic results validate the formation of PU/PPy composite coatings and the intermolecular chemical interaction between the PU and PPy moieties. Furthermore, corrosion measurements corroborate the improved corrosion resistance of PU/30PPy coatings with higher values of charge transfer resistance, Rct (1.0869 × 107 Ω cm2), and film resistance, Rf (2.258 × 105 Ω cm2), with the lowest values of corrosion, icorr (4.7 × 10−3 µA cm−2) compared to that of the PU/Bare specimen. In conclusion, it is confirmed that the passivated surface enhances the corrosion resistance performance of PU coated SS, and this performance is further increased with the incorporation of PPy particles. Full article
(This article belongs to the Special Issue Corrosion Barrier Coatings)
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14 pages, 3842 KiB  
Article
Statistical Treatments of Chloride Threshold and Corrosion Propagation Rate
by Carmen Andrade and David Izquierdo
Corros. Mater. Degrad. 2022, 3(4), 598-611; https://doi.org/10.3390/cmd3040032 - 31 Oct 2022
Cited by 7 | Viewed by 1531
Abstract
The variability found in real structures is a function of the “intrinsic” variability of the material itself, of its aging with time and of the external climatic conditions, and, therefore, it is normal that the chloride threshold and the corrosion rates could vary [...] Read more.
The variability found in real structures is a function of the “intrinsic” variability of the material itself, of its aging with time and of the external climatic conditions, and, therefore, it is normal that the chloride threshold and the corrosion rates could vary spatially in the same structure or temporarily as the concrete ages. In present communication, some statistical distributions of chloride threshold are discussed, as well as the variability of the corrosion rate in real exposure conditions. In all both cases, the values found in laboratory specimens are in the same range than those found in real structures. The chloride threshold can vary from 0.2% to around 3% by weight of cement depending on the corrosion potential, which, in turn, depends on the particular condition of the steel bar in each structure. The corrosion rates show to be below 0.1 µA/cm2 when the steel is passive and values above 1 µA/cm2 are seldom found in real structures. The high variability when considering all choices may impact in a prediction of residual life of several decades of difference which aims into the need for the assessment of a specialized engineering judgement in function of the quality of the concrete and the exposure class. Full article
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32 pages, 21874 KiB  
Review
Mg Corrosion—Recent Progress
by Andrej Atrens, Xingrui Chen and Zhiming Shi
Corros. Mater. Degrad. 2022, 3(4), 566-597; https://doi.org/10.3390/cmd3040031 - 29 Sep 2022
Cited by 12 | Viewed by 2405
Abstract
Recent progress is reviewed. Recent developments include: (i) accumulation of evidence that electrochemical measurements of the Mg corrosion rate often do not agree with the steady state Mg corrosion rate as measured by weight loss; (ii) low Fe tolerance limits are caused by [...] Read more.
Recent progress is reviewed. Recent developments include: (i) accumulation of evidence that electrochemical measurements of the Mg corrosion rate often do not agree with the steady state Mg corrosion rate as measured by weight loss; (ii) low Fe tolerance limits are caused by heat treatment of nominally high-purity Mg and the presence of Si, (iii) the intrinsic Mg corrosion rate is 0.3 mm/y in a chloride solution as measured by weight loss, (iv) there are many Mg alloys with corrosion rates between 0.3 and 1.0 mm/y, (v) there are few Mg alloys with corrosion rates less than 0.3 mm/y, (vi) experimental evidence contradicts the enhanced catalytic activity mechanism of Mg corrosion, (vii) experiments support the uni-positive Mg+ mechanism, (viii) new compelling experimental evidence supporting the uni-positive Mg+ corrosion mechanism has been provided by electrochemical impedance spectroscopy (EIS), and (ix) the uni-positive Mg+ corrosion mechanism provides new insights for understanding the performance of Mg-air batteries and for the development of better Mg anodes. Full article
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