Corrosion and Materials Degradation

15 pages, 3481 KiB

Open AccessArticle

Forensic Investigation of Stainless Steel 316 Hydrogen-Membrane and Ammonia-Cracking Reactors Through Mechanical Testing

by Alexander Ilyushechkin, Veronica Gray, Riley Ingle, Lachlan Carter and Liezl Schoeman

Corros. Mater. Degrad. 2025, 6(2), 17; https://doi.org/10.3390/cmd6020017 - 13 May 2025

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Abstract

Knowledge of alloy behavior under industry-relevant conditions is critical to hydrogen production and processing, yet it is currently limited. To understand more about the impact of hydrogen damage on stainless steel 316 under realistic in-service conditions, we conducted a forensic investigation of two reactors exposed to various hydrogen-processing conditions. We examined samples of reactor walls exposed to hydrogen-containing atmospheres for >100 and ~1000 h at elevated temperatures during hydrogen separation and ammonia cracking. The samples were characterized by tensile testing, stretch–bend testing, and three-point bending. A loss in ductility and strength was observed for the reactor wall material compared with both untreated materials and materials annealed in neutral atmospheres at the same temperatures used during reactor operation. The three-point bend testing, which was conducted on inner and outer pipe-surface material extracted via electrical discharge machining, showed larger changes in the flexural modulus of exposed reactors but increases in the elastic limit. Microstructural observations revealed that hydrogen may play a role in stress relaxation, possibly promoting normalization at lower-than-expected temperatures. We also observed that materials exposed to ammonia undertake more damage from nitriding than from hydrogen. Full article

(This article belongs to the Special Issue Hydrogen Embrittlement of Modern Alloys in Advanced Applications)

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25 pages, 7619 KiB

Open AccessArticle

In Situ Surface-Enhanced Raman Spectroscopy Investigation of the Passive Films That Form on Alloy 600, Alloy 690, Unalloyed Cr and Ni, and Alloys of Ni-Cr and Ni-Cr-Fe in Pressurized Water Nuclear Reactor Primary Water

by Feng Wang and Thomas M. Devine

Corros. Mater. Degrad. 2025, 6(2), 16; https://doi.org/10.3390/cmd6020016 - 6 May 2025

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Abstract

Passive films that form on Alloy 600 and Alloy 690 during four hours in simulated Primary Water (PW) of Pressurized Water Nuclear Reactors (PWRs) at 320 °C were investigated by in situ surface-enhanced Raman spectroscopy (SERS). Similar tests conducted on unalloyed nickel, unalloyed chromium, and laboratory alloys of Ni-10Cr, Ni-20Cr, Ni-5Cr-8Fe, and Ni-10Cr-8Fe aided in assigning the peaks in the surface-enhanced Raman (SER) spectra of the passive films of Alloy 600 and Alloy 690. SERS indicates an inner layer (IL) of Cr₂O₃/CrOOH forms on both Alloy 600 and Alloy 690 and that Alloy 690’s IL was more protective against corrosion due to its greater resistance to ion transport. The outer layer (OL) of Alloy 600 consists of NiO and spinels, FeCr₂O₄—M(Cr,Fe)₂O₄. The OL of Alloy 690 contains no spinel. A comparison of SER spectra in 320 °C PWR PW to the spectra following cooling down to room temperature and after exposure to air indicates some differences between in situ films and ex situ films. Full article

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

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26 pages, 39179 KiB

Open AccessArticle

Corrosion Behavior of Fe-Ni Electrodeposited Coatings in Weak Ammonium Hydroxide Solution

by Joel Andrew Hudson and Henry E. Cardenas

Corros. Mater. Degrad. 2025, 6(2), 15; https://doi.org/10.3390/cmd6020015 - 17 Apr 2025

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Abstract

Iron and iron-nickel alloy electrodeposits synthesized from sulfate-based electroplating baths were applied to a mild carbon steel substrate. Coated specimens were immersed in an oxygen-saturated, weak ammonium hydroxide solution (pH 9.5–10.0), and their corrosion performance was evaluated using electrochemical techniques. Galvanic and general corrosion behaviors were analyzed to assess the sacrificial protection provided by Fe and Fe-Ni coatings relative to uncoated steel. The influence of anode-to-cathode (A/C) surface area ratios (1:1, 10:1, and 100:1) on the occurrence of plating-induced surface cracks was also examined. Surface morphology and elemental composition of the deposits were characterized. Results of the study indicated that increasing the Ni²⁺/Fe²⁺ molar ratio of the electroplating bath from 0 to 0.167 led to (1) reduced surface porosity and cracking, (2) decreased galvanic corrosion rates between the electrodeposit and substrate, and (3) a progressive increase in the temperature dependence of the general corrosion rate between 20 °C and 60 °C. The development of Fe and Fe-Ni alloy electrodeposits as protective coatings is of particular interest in water-tube power boiler applications, where production of corrosion products must be controlled. Further research is needed to develop coatings that perform predictably under elevated pressures and temperatures typical of operating boiler environments. Full article

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18 pages, 4570 KiB

Open AccessArticle

Validation of Water Radiolysis Models Against Experimental Data in Support of the Prediction of the Radiation-Induced Corrosion of Copper-Coated Used Fuel Containers

by Scott Briggs, Mehran Behazin and Fraser King

Corros. Mater. Degrad. 2025, 6(2), 14; https://doi.org/10.3390/cmd6020014 - 1 Apr 2025

Viewed by 285

Abstract

Copper has been proposed as a container material for the disposal of used nuclear fuel in a number of countries worldwide. The container materials will be subject to various corrosion processes in a deep geological repository, including radiation-induced corrosion (RIC) resulting from the γ-irradiation of the near-field environment. A comprehensive model is being developed to predict the extent of RIC by coupling a radiolysis model to the interfacial electrochemical reactions on the container surface. An important component of the overall model is a radiolysis model to predict the time-dependent concentration of oxidizing and reducing radiolysis products. As a first step in the model development, various radiolysis models have been validated against experimental measurements of the concentrations of dissolved and gaseous radiolysis products. Experimental data are available for pure H₂O- and Cl⁻-containing solutions, with and without a gas headspace. The results from these experiments have been compared with predictions from corresponding radiolysis models, including the effects of the partitioning of gaseous species (O₂ and H₂) at the gas–solution interface. Different reaction schemes for the Cl⁻ radiolysis models are also compared. The validated radiolysis model will then be coupled with interfacial reactions on the copper surface and additional processes related to the presence of bentonite clay in Steps 2 and 3 of the overall model, respectively. Full article

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

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Corros. Mater. Degrad., Volume 6, Issue 2 (June 2025) – 4 articles

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