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Corros. Mater. Degrad., Volume 4, Issue 2 (June 2023) – 6 articles

Cover Story (view full-size image): This paper explores the roles of empiricism and determinism in science and concludes that the intellectual exercise that we call “science” is best described as the transition from empiricism (i.e., observation) to determinism. This transition (i.e., “science”) is accomplished by formulating theories to explain the observations and models that are based on those theories to predict new phenomena. All models must possess a theoretical basis, but not all theories need to predict phenomena. The structure of a deterministic model is reviewed, and it is emphasized that all models must contain an input, a model engine, and an output, together with a feedback loop that permits the continual updating of the model parameters and a means of assessing predictions against new observations. View this paper
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14 pages, 4634 KiB  
Article
Investigation on the Effect of a Chromium-Free Sealing Treatment for the Corrosion Resistance of AA2198-T851 after Tartaric Sulphuric Anodizing (TSA)
by Fernanda Martins Queiroz, Aline de Fátima Santos Bugarin, Victor Hugo Ayusso, Maysa Terada and Isolda Costa
Corros. Mater. Degrad. 2023, 4(2), 331-344; https://doi.org/10.3390/cmd4020017 - 12 Jun 2023
Cited by 1 | Viewed by 1179
Abstract
The AA 2198-T851 is a third-generation Al-Li alloy developed for use in the aircraft industry. Al-Li alloys are susceptible to localized corrosion due to their complex microstructure resulting from the used thermomechanical treatment. In order to prevent localized corrosion, these alloys are usually [...] Read more.
The AA 2198-T851 is a third-generation Al-Li alloy developed for use in the aircraft industry. Al-Li alloys are susceptible to localized corrosion due to their complex microstructure resulting from the used thermomechanical treatment. In order to prevent localized corrosion, these alloys are usually protected by anodizing in order to avoid a corrosive environment. Subsequently, for anodizing, a sealing treatment is usually performed for parts. Some sealing treatments use hexavalent-chromium-ion-containing solutions. In this investigation, a chromium-free sealing treatment in a solution with cerium ions has been carried out, and the effect on the corrosion resistance of the AA2198-T851 alloy was investigated. Hydrothermally sealed or unsealed samples were also tested for corrosion resistance for comparison reasons. The corrosion resistance of the anodized aluminum alloy, either hydrothermally sealed or in a cerium-ion-containing solution, was evaluated in a sodium chloride solution by electrochemical impedance spectroscopy as a function of immersion time. The samples sealed in a cerium-containing solution increased their corrosion resistance when compared to the hydrothermally sealed. The effectiveness of the sealing process with cerium that was observed in the electrochemical tests indicated that after the corrosive attack of the barrier layer, there was a “sealing” process of the sample surface. Full article
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14 pages, 9519 KiB  
Article
Complete Desensitization of Aluminum–Magnesium Alloys via Boron Addition
by Ramasis Goswami, Alex Moser, Ronald L. Holtz, Syed B. Qadri and Andrew Geltmacher
Corros. Mater. Degrad. 2023, 4(2), 317-330; https://doi.org/10.3390/cmd4020016 - 06 Jun 2023
Viewed by 1214
Abstract
We address here an important issue related to sensitization effects in Al5083 by mitigating the grain boundary precipitation of the beta phase and demonstrate that the addition of a small amount of boron to Al5083 impedes the precipitation of the beta phase, Al [...] Read more.
We address here an important issue related to sensitization effects in Al5083 by mitigating the grain boundary precipitation of the beta phase and demonstrate that the addition of a small amount of boron to Al5083 impedes the precipitation of the beta phase, Al3Mg2, also known as the Samson phase. In Al–Mg alloys, the precipitation of Al3Mg2 usually occurs at grain boundaries in the temperature range of 50 to 200 °C from a supersaturated solid solution of Al–Mg and makes these alloys susceptible to intergranular corrosion and stress corrosion cracking. Upon boron addition, we show, using transmission electron microscopy, that a diboride phase, AlMgB2, forms at grain boundaries instead of the beta phase upon extended annealing at 150 °C. This diboride phase does not dissolve in saltwater, suggesting it is less anodic relative to the matrix. To quantify and compare the dissolution characteristics, we carried out nitric acid mass loss test for Al5083 samples containing 3 wt.% boron treated at 190 h at 150 °C, and fully sensitized Al5083 samples containing 0.0 wt.% boron. We estimate the mass loss to be 4 mg/cm2 for boron containing samples as compared to the mass loss of 45 mg/cm2 for samples without boron, indicating that the addition of boron is highly effective in suppressing the susceptibility to intergranular corrosion in Al5000 series alloys. This provides a potential route to minimize the longstanding problem of ship structure sensitization. Full article
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33 pages, 6580 KiB  
Review
Polymer-Based Coating for Steel Protection, Highlighting Metal–Organic Framework as Functional Actives: A Review
by Sarah Bill Ulaeto, Rajimol Puthenpurackal Ravi, Inime Ime Udoh, Gincy Marina Mathew and Thazhavilai Ponnu Devaraj Rajan
Corros. Mater. Degrad. 2023, 4(2), 284-316; https://doi.org/10.3390/cmd4020015 - 29 Apr 2023
Cited by 8 | Viewed by 5681
Abstract
Polymer-based coatings are a long-established category of protective coatings for metals and alloys regarding corrosion inhibition. The polymer films can degrade, and when coated on metallic substrates, the degradation facilitates moisture and oxygen penetration, reducing the polymer film’s adhesion to the metallic substrate [...] Read more.
Polymer-based coatings are a long-established category of protective coatings for metals and alloys regarding corrosion inhibition. The polymer films can degrade, and when coated on metallic substrates, the degradation facilitates moisture and oxygen penetration, reducing the polymer film’s adhesion to the metallic substrate and exposing the substrate to extreme conditions capable of corrosion. For this reason, pigments, inhibitors, and other compatible blends are added to the polymer coating formulations to enhance adhesion and protection. To prevent the possible deterioration of inhibitor-spiked polymer coatings, inhibitors are encapsulated through diverse techniques to avoid leakage and to provide a controlled release in response to the corrosion trigger. This review discusses polymer-based coating performance in corrosion-causing environments to protect metals, focusing more on commercial steels, a readily available construction-relevant material used in extensive applications. It further beams a searchlight on advances made on polymer-based coatings that employ metal–organic frameworks (MOFs) as functional additives. MOFs possess a tailorable structure of metal ions and organic linkers and have a large loading capacity, which is crucial for corrosion inhibitor delivery. Results from reviewed works show that polymer-based coatings provide barrier protection against the ingress of corrosive species and offer the chance to add several functions to coatings, further enhancing their anti-corrosion properties. Full article
(This article belongs to the Special Issue Corrosion Barrier Coatings)
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10 pages, 1667 KiB  
Article
Utilizing Computational Modelling to Bridge the Gap between In Vivo and In Vitro Degradation Rates for Mg-xGd Implants
by Tamadur Al Baraghtheh, Alexander Hermann, Arman Shojaei, Regine Willumeit-Römer, Christian J. Cyron and Berit Zeller-Plumhoff
Corros. Mater. Degrad. 2023, 4(2), 274-283; https://doi.org/10.3390/cmd4020014 - 31 Mar 2023
Cited by 1 | Viewed by 2123
Abstract
Magnesium (Mg) and its alloys are promising materials for temporary bone implants due to their mechanical properties and biocompatibility. The most challenging aspect of Mg-based implants involves adapting the degradation rate to the human body, which requires extensive in vitro and in vivo [...] Read more.
Magnesium (Mg) and its alloys are promising materials for temporary bone implants due to their mechanical properties and biocompatibility. The most challenging aspect of Mg-based implants involves adapting the degradation rate to the human body, which requires extensive in vitro and in vivo testing. Given that in vivo tests are significantly more labour-intensive than in vitro and ethics prohibit direct experiments on animals or humans, attempts are commonly undertaken to infer conclusions on in vivo degradation behavior from in vitro experiments. However, there is a wide gap between these tests, and in vitro testing is often a poor predictor of in vivo outcomes. In the development of biodegradable Mg-based implants, considerable efforts are being made to reduce the overall time and cost of in vitro and in vivo testing. Finding a suitable alternative to predict the degradation of Mg alloys, however, remains challenging. We present computational modelling as a possible alternative to bridge the gap between in vitro and in vivo testing, thus reducing overall cost, duration and number of experiments. However, traditional modelling approaches for complex biodegradable systems are still rather time-consuming and require a clear definition of the relations between input parameters and the model result. In this study, Kriging surrogate models based on the peridynamic in vitro degradation model were developed to simulate the degradation behavior for two main alloys, Mg-5Gd and Mg-10Gd, for both in vitro and in vivo cases. Using Kriging surrogate models, the simulation parameters were calibrated to the volume loss data from in vitro and in vivo experiments. In vivo degradation of magnesium has one order of magnitude higher apparent diffusion coefficients than in vitro degradation, thus yielding the higher volume loss observed in vivo than in vitro. On the basis of the diffusivity of the Mg2+ ions modeled under in vitro degradation, Kriging surrogate models were able to simulate the in vivo degradation behavior of Mg-xGd with a ratio between 0.46 and 0.5, indicating that the surrogate-modelling approach is able to bridge the gap between in vitro and in vivo degradation rates for Mg-xGd implants. Full article
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62 pages, 12998 KiB  
Review
The Role of Determinism in the Prediction of Corrosion Damage
by Digby D. Macdonald
Corros. Mater. Degrad. 2023, 4(2), 212-273; https://doi.org/10.3390/cmd4020013 - 27 Mar 2023
Viewed by 1508
Abstract
This paper explores the roles of empiricism and determinism in science and concludes that the intellectual exercise that we call “science” is best described as the transition from empiricism (i.e., observation) to determinism, which is the philosophy that the future can be predicted [...] Read more.
This paper explores the roles of empiricism and determinism in science and concludes that the intellectual exercise that we call “science” is best described as the transition from empiricism (i.e., observation) to determinism, which is the philosophy that the future can be predicted from the past based on the natural laws that are condensations of all previous scientific knowledge. This transition (i.e., “science”) is accomplished by formulating theories to explain the observations and models that are based on those theories to predict new phenomena. Thus, models are the computational arms of theories, and all models must possess a theoretical basis, but not all theories need to predict. The structure of a deterministic model is reviewed, and it is emphasized that all models must contain an input, a model engine, and an output, together with a feedback loop that permits the continual updating of the model parameters and a means of assessing predictions against new observations. This latter feature facilitates the application of the “scientific method” of cyclical prediction/assessment that continues until the model can no longer account for new observations. At that point, the model (and possibly the theory, too) has been “falsified” and must be discarded and a new theory/model constructed. In this regard, it is important to stress that no amount of successful prediction can prove a theory/model to be “correct”, because theories and models are merely the figments of our imagination as developed through imperfect senses and imperfect intellect and, hence, are invariably wrong at some level of detail. Contrariwise, a single failure of a model to predict an observation invalidates (“falsifies”) the theory/model. The impediment to model building is complexity and its impact on model building is discussed. Thus, we employ instruments such as microscopes and telescopes to extend our senses to examining smaller and larger objects, respectively, just as we now employ computers to extend our intellects as reflected in our computational prowess. The process of model building is illustrated with reference to the deterministic Coupled Environment Fracture Model (CEFM) that has proven to be highly successful in predicting crack growth rate in metals and alloys in contact with high-temperature aqueous environments of the type that exist in water-cooled nuclear power reactor primary coolant circuits. Full article
(This article belongs to the Special Issue Mechanism and Predictive/Deterministic Aspects of Corrosion)
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16 pages, 3934 KiB  
Article
Corrosion Resistance and Biological Properties of Pure Magnesium Modified by PEO in Alkaline Phosphate Solutions
by Mónica Echeverry-Rendón, Luisa F. Berrio, Sara M. Robledo, Jorge A. Calderón, Juan G. Castaño and Felix Echeverría
Corros. Mater. Degrad. 2023, 4(2), 196-211; https://doi.org/10.3390/cmd4020012 - 23 Mar 2023
Cited by 2 | Viewed by 1888
Abstract
Magnesium (Mg) has been explored during the last few decades in the biomedical industry as a biodegradable implant. However, mechanical properties and corrosion resistance are still big concerns for clinical use. Therefore, this study proposes a suitable surface modification of the Mg by [...] Read more.
Magnesium (Mg) has been explored during the last few decades in the biomedical industry as a biodegradable implant. However, mechanical properties and corrosion resistance are still big concerns for clinical use. Therefore, this study proposes a suitable surface modification of the Mg by plasma electrolytic oxidation (PEO) to improve its corrosion resistance and biological performance. Mg samples were processed in a galvanostatic mode using an electrolytic solution of a phosphate compound supplemented with either potassium pyrophosphate or sodium-potassium tartrate. The obtained coatings were physiochemically characterized by SEM, XRD, EDS, and micro-Raman spectroscopy. The corrosion resistance of the coatings was studied using a hydrogen evolution setup and electrochemical tests. Finally, the biological performance of the material was evaluated by using an indirect test with osteoblasts. Obtained coatings showed a porous morphology with thicknesses ranging from 2 to 3 µm, which was closely dependent on the PEO solution. The corrosion resistance tests improved the degradation rate compared to the raw material. Additionally, an unreported active–passive corrosion behavior was evidence of a protective layer of corrosion products underneath the anodic coating. Indirect in vitro cytotoxicity assays indicated that the coatings improved the biocompatibility of the material. In conclusion, it was found that the produced coatings from this study not only lead to material protection but also improve the biological performance of the material and ensure cell survival, indicating that this could be a potential material used for bone implants. Full article
(This article belongs to the Special Issue Corrosion Barrier Coatings)
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