Corrosion and Materials Degradation

8 pages, 2136 KiB

Open AccessArticle

Comparative Assessment of Aromatic Iron Corrosion Inhibitors with Electrochemical Methods

by Jessica Roscher, Dan Liu, Xuan Xie and Rudolf Holze

Corros. Mater. Degrad. 2024, 5(4), 593-600; https://doi.org/10.3390/cmd5040027 - 25 Nov 2024

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Molecular aromatic corrosion inhibitors are frequently applied to slow down the corrosion of iron, its alloys and numerous other metallic materials. This case study with three representative aromatic inhibitors and a pure iron electrode aims at the verification of the reported conclusions regarding [...] Read more.

Molecular aromatic corrosion inhibitors are frequently applied to slow down the corrosion of iron, its alloys and numerous other metallic materials. This case study with three representative aromatic inhibitors and a pure iron electrode aims at the verification of the reported conclusions regarding these inhibitors and at the verification and comparison of electrochemical corrosion assessment methods with attention to differences between iron alloys (steels) and pure iron possibly related to the presence/absence of alloying elements and non-iron impurities. Full article

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21 pages, 7270 KiB

Open AccessArticle

Application of Resistometric Sensors for Real-Time Corrosion Monitoring of Coated Materials

by Kateryna Popova, Maria Fátima Montemor and Tomáš Prošek

Corros. Mater. Degrad. 2024, 5(4), 573-592; https://doi.org/10.3390/cmd5040026 - 19 Nov 2024

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Abstract

Highly sensitive resistometric sensors were applied for the real-time corrosion monitoring of carbon steel protected with a polyolefin coating with and without an inhibitor under static and dynamic atmospheric and immersion conditions. The results were compared with conventional electrochemical impedance spectroscopy (EIS) data. [...] Read more.

Highly sensitive resistometric sensors were applied for the real-time corrosion monitoring of carbon steel protected with a polyolefin coating with and without an inhibitor under static and dynamic atmospheric and immersion conditions. The results were compared with conventional electrochemical impedance spectroscopy (EIS) data. An increase in the coating thickness from 20 µm to 50 µm and an addition of 1wt.% tannic acid significantly improved the coating corrosion stability. Based on the real-time corrosion data, the drying stage of atmospheric exposure in a chloride-rich environment was found to be the most critical. The highest corrosion rate was detected at 50% relative humidity when the electrolyte corrosiveness in coating defects reached the maximum. Resistometric sensors have the potential to become an interesting alternative for evaluating coating performance and degradation mechanisms in both laboratory and industrial applications. Full article

(This article belongs to the Special Issue Advances in Corrosion Protection by Coatings)

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12 pages, 7110 KiB

Open AccessArticle

Effect of Heat Treatment on Microstructure and Aqueous Corrosion Properties of AlCoCrNiFe High Entropy Alloy

by Soheil Saedi, Ahmed Korra, Hatim Raji and Hamdy Ibrahim

Corros. Mater. Degrad. 2024, 5(4), 561-572; https://doi.org/10.3390/cmd5040025 - 7 Nov 2024

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Abstract

This study examines the effects of heat treatment on corrosion behavior of equiatomic AlCoCrNiFe high-entropy alloy within a solution treatment temperature range of 800–1100 °C. Experimental observations on phase formation were compared with thermodynamic predictions. The microstructure, mechanical properties, and aqueous corrosion behavior [...] Read more.

This study examines the effects of heat treatment on corrosion behavior of equiatomic AlCoCrNiFe high-entropy alloy within a solution treatment temperature range of 800–1100 °C. Experimental observations on phase formation were compared with thermodynamic predictions. The microstructure, mechanical properties, and aqueous corrosion behavior of the as-deposited alloy were analyzed and contrasted with heat-treated samples. The results showed a decline in the corrosion resistance of the AlCoCrNiFe after heat treatment, which was attributed to chemical segregation and Cr depletion in the microstructure matrix. Additionally, post-corrosion analysis revealed a reduced volume fraction of protective oxides in the heat-treated samples. Full article

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50 pages, 7632 KiB

Open AccessReview

Aromatic Metal Corrosion Inhibitors

by Jessica Roscher, Dan Liu, Xuan Xie and Rudolf Holze

Corros. Mater. Degrad. 2024, 5(4), 513-560; https://doi.org/10.3390/cmd5040024 - 31 Oct 2024

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Abstract

Molecular inhibitors added to the corrosive medium attacking metallic materials are a well-established way of combating corrosion. The inhibitive action proceeds via adsorption of the inhibitor on the surface to be protected. Aromatic building blocks in the inhibitor play a major role in [...] Read more.

Molecular inhibitors added to the corrosive medium attacking metallic materials are a well-established way of combating corrosion. The inhibitive action proceeds via adsorption of the inhibitor on the surface to be protected. Aromatic building blocks in the inhibitor play a major role in its protective action, and further details like substituents, heteroatoms, and molecular geometry contribute. An overview focused on aromatic inhibitors is provided, aiming at the identification of particularly promising inhibitors and their mode of action. Directions for further research and development are pointed out in the conclusion. Full article

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23 pages, 1880 KiB

Open AccessArticle

Correlation Between the Anticorrosive Performance of Protective Coatings Under Neutral Salt Spray Testing and Outdoor Atmospheric and Immersion Exposure

by Matthias J. Schmid

Corros. Mater. Degrad. 2024, 5(4), 490-512; https://doi.org/10.3390/cmd5040023 - 30 Oct 2024

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Abstract

Anticorrosive organic coatings are usually tested with accelerated weathering methods to assess their anticorrosive performance. The results of lab testing often do not correlate well with results from field testing, which resembles the conditions of actual use more closely. We tested the correlation [...] Read more.

Anticorrosive organic coatings are usually tested with accelerated weathering methods to assess their anticorrosive performance. The results of lab testing often do not correlate well with results from field testing, which resembles the conditions of actual use more closely. We tested the correlation of the neutral salt spray test (NSS, ISO 9227) and tests for mechanical properties and a 5-year field exposure in four different locations in the atmospheric zone, splash zone and immersion zone using 19 organic coatings for hydraulic steelwork. No correlation was found between the anticorrosive performance under outdoor exposure and the mechanical properties of a coating. The NSS test showed a positive correlation with the results in the field in 6 of 12 cases. For the fresh water testing location in Trier, the correlation proved to be very good. The biggest difference between lab and field testing was observed for zinc-primer-free coatings, which passed in the lab testing and failed in the outdoor testing. This study shows that the NSS test correlates with outdoor exposure only in some cases on a statistically significant level, but the results of NSS testing can be useful in approval testing for protective coating systems using predefined pass/fail criteria. Full article

(This article belongs to the Special Issue Advances in Corrosion Protection by Coatings)

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14 pages, 3898 KiB

Open AccessArticle

Degradation of Concrete Cement Stone Under the Influence of Aspergillus niger Fungi

by Viktoriya S. Konovalova, Varvara E. Rumyantseva, Konstantin B. Strokin, Aleksey A. Galtsev, Denis G. Novikov and Pavel V. Monastyrev

Corros. Mater. Degrad. 2024, 5(4), 476-489; https://doi.org/10.3390/cmd5040022 - 28 Oct 2024

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Abstract

The concepts of physical and chemical transformations occurring in cement concrete under conditions of microbiological deterioration can be used to control the processes of the destruction of cement concretes in order to ensure the required durability and to predict the service life of [...] Read more.

The concepts of physical and chemical transformations occurring in cement concrete under conditions of microbiological deterioration can be used to control the processes of the destruction of cement concretes in order to ensure the required durability and to predict the service life of products. The study of changes in the structural and phase composition of cement stone made of Portland cement grade CEM I 42.5N in the process of fungal deterioration for 6 months when moistened, as well as a sample of a concrete wall exposed to fungal microorganisms for 20 years, was carried out. Diffractograms of the studied cement stone samples contain a large number of pronounced narrow peaks and indicate a highly crystalline structure of phases with the presence of an X-ray amorphous phase of calcium hydrosilicates and tobermorite gel in the cement stone. Changes in the structure of cement stone under the influence of fungi are confirmed by the data of a derivatographic analysis. A decrease in the content of calcium hydrosilicates and ettringite, as well as other crystalline phases in cement stone, leads to a decrease in compressive strength by about 15% over 6 months of fungal degradation. Similar changes after 20 years of exposure to microorganisms suggest deterioration in the strength characteristics of concrete. Full article

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26 pages, 4879 KiB

Open AccessArticle

Mechanistic Analysis of Anodic Oxidation of Gold in KOH (0.1 M) Solution Using the Point Defect Model

by Zahed Ghelichkhah, Digby D. Macdonald and Gregory S. Ferguson

Corros. Mater. Degrad. 2024, 5(4), 450-475; https://doi.org/10.3390/cmd5040021 - 9 Oct 2024

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Abstract

The potentiostatic, anodic formation of gold oxide at potentials of 0.55 to 0.80 V versus SHE in aqueous KOH (0.1 M) was studied using an impedance-based Point Defect Model (PDM). The film thickness and refractive indices at each formation potential were estimated using [...] Read more.

The potentiostatic, anodic formation of gold oxide at potentials of 0.55 to 0.80 V versus SHE in aqueous KOH (0.1 M) was studied using an impedance-based Point Defect Model (PDM). The film thickness and refractive indices at each formation potential were estimated using spectroscopic ellipsometry. The thickness of the oxide increases linearly with increasing applied voltage within this range. Mott-Schottky (MS) analysis showed that gold oxide formed in KOH (0.1 M) is an n-type semiconductor, and the dominant defect (

{A u}_{i}^{3 +}

) density is calculated to be in the order of 10²¹–10²² (1/cm³). The steady-state current density of the oxide formation was independent of voltage, also in agreement with an n-type oxide. Reasonable agreement between PDM predictions and experimental observations of dominant defect density, steady-state current density, and thickness, demonstrates the value of the PDM in this system. Full article

(This article belongs to the Special Issue Corrosion Mechanisms and Electrochemical Interfaces: In Honor of Prof. Digby Macdonald)

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11 pages, 2477 KiB

Open AccessArticle

Cyclic Loading of Metallic Glasses Prepared Using Cryogenic Treatments

by Nicolás Amigo

Corros. Mater. Degrad. 2024, 5(4), 439-449; https://doi.org/10.3390/cmd5040020 - 26 Sep 2024

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Abstract

This study investigates the degradation of mechanical properties in CuZr metallic glasses (MGs) under cyclic loading using molecular dynamics simulations. Both as-cast (AC) and cryogenically thermal-cycled (TC) samples with Cu₃₆Zr₆₄ and Cu₆₄Zr₃₆ compositions were analyzed. Results show [...] Read more.

This study investigates the degradation of mechanical properties in CuZr metallic glasses (MGs) under cyclic loading using molecular dynamics simulations. Both as-cast (AC) and cryogenically thermal-cycled (TC) samples with Cu₃₆Zr₆₄ and Cu₆₄Zr₃₆ compositions were analyzed. Results show that cyclic loading significantly degrades Young’s modulus, ultimate tensile stress, and toughness, with most pronounced reductions occurring in the initial cycles. TC samples exhibit improved ductility and stability compared to AC samples. In contrast, AC samples demonstrate greater initial strength but faster degradation. Cu-rich samples maintain higher strength but degrade similarly to Cu-poor samples. The AC Cu-rich sample experiences more localized deformation and delayed degradation, while TC and AC Cu-poor samples quickly reach a steady state. These findings highlight the influence of atomic composition and thermal treatments on the mechanical performance and degradation behavior of MGs. Full article

(This article belongs to the Special Issue Effects of Cryogenic Treatment on the Corrosion and Materials Degradation)

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Corros. Mater. Degrad., Volume 5, Issue 4 (December 2024) – 8 articles

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