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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Vapor Space Corrosion Testing Simulating The Environment Of Hanford Double Shell Tanks

As part of an integrated program to better understand corrosion in the high level waste tanks, Hanford has been investigating corrosion at the liquid/air interface (LAI) and at higher areas in the tank vapor space. This current research evaluated localized corrosion in the vapor space over Hanford double shell tank simulants to assess the impact of ammonia and new minimum nitrite concentration limits, which are part of the broader corrosion chemistry limits. The findings from this study showed that the presence of ammonia gas (550 ppm) in the vapor space is sufficient to reduce corrosion over the short-term (i.e. four months) for a Hanford waste chemistry (SY102 High Nitrate). These findings are in agreement with previous studies at both Hanford and SRS which showed ammonia gas in the vapor space to be inhibitive. The presence of ammonia in electrochemical test solution, however, was insufficient to inhibit against pitting corrosion. The effect of the ammonia appears to be a function of the waste chemistry and may have more significant effects in waste with low nitrite concentrations. Since high levels of ammonia were found beneficial in previous studies, additional testing is recommended to assess the necessary minimum concentration for protection of carbon steel. The new minimum R value of 0.15 was found to be insufficient to prevent pitting corrosion in the vapor space. The pitting that occurred, however, did not progress over the four-month test. Pits appeared to stop growing, which would indicate that pitting might not progress through wall.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2014

Liquid-Air Interface Corrosion Testing Simulating The Environment Of Hanford Double Shell Tanks

Coupon tests on A537 carbon steel materials were conducted to evaluate the Liquid-Air Interface (LAI) corrosion susceptibility in a series of solutions designed to simulate conditions in the radioactive waste tanks located at the Hanford Nuclear Facility. The new stress corrosion cracking requirements and the impact of ammonia on LAI corrosion were the primary focus. The minimum R value (i.e., molar ratio of nitrite to nitrate) of 0.15 specified by the new stress corrosion cracking requirements was found to be insufficient to prevent pitting corrosion at the LAI. The pH of the test solutions was 10, which was actually less than the required pH 11 defined by the new requirements. These tests examined the effect of the variation of the pH due to hydroxide depletion at the liquid air interface. The pits from the current testing ranged from 0.001 to 0.008 inch in solutions with nitrate concentrations of 0.4 M and 2.0 M. The pitting and general attack that occurred progressed over the four-months. No significant pitting was observed, however, for a solution with a nitrate concentration of 4.5 M. The pitting depths observed in these partial immersion tests in unevaporated condensates ranged from 0.001 to 0.005 inch after 4 months. The deeper pits were in simulants with low R values. Simulants with R values of approximately 0.6 to 0.8 appeared to significantly reduce the degree of attack. Although, the ammonia did not completely eliminate attack at the LAI, the amount of corrosion in an extremely corrosive solution was significantly reduced. Only light general attack (< 1 mil) occurred on the coupon in the vicinity of the LAI. The concentration of ammonia (i.e., 50 ppm or 500 ppm) did not have a strong effect.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Corrosion Assessment of Candidate Materials for the SHINE Subcritical Assembly Vessel and Components FY15 Report

In the previous report of this series, a literature review was performed to assess the potential for substantial corrosion issues associated with the proposed SHINE process conditions to produce 99 Mo. Following the initial review, substantial laboratory corrosion testing was performed emphasizing immersion and vapor-phase exposure of candidate alloys in a wide variety of solution chemistries and temperatures representative of potential exposure conditions. Stress corrosion cracking was not identified in any of the exposures up to 10 days at 80°C and 10 additional days at 93°C. Mechanical properties and specimen fracture face features resulting from slow-strain rate tests further supported a lack of sensitivity of these alloys to stress corrosion cracking. Fluid velocity was found not to be an important variable (0 to ~3 m/s) in the corrosion of candidate alloys at room temperature and 50°C. Uranium in solution was not found to adversely influence potential erosion-corrosion. Potentially intense radiolysis conditions slightly accelerated the general corrosion of candidate alloys, but no materials were observed to exhibit an annualized rate above 10 μm/y.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Flow-Assisted Corrosion in Nuclear Power Plants

The flow-assisted corrosion, or flow-accelerated corrosion (FAC) is one of the major piping degradation mechanisms in aging nuclear power plants and it has been identified as a research area under the Light Water Reactor Sustainability program at Idaho National Laboratory (INL). While every nuclear power plant in US has a dedicated flow-assisted corrosion management program, there are several areas where the management of flow assisted corrosion can be improved. One of such areas is on-line corrosion monitoring which can significantly reduce maintenance inspections and contribute to improvement of economic efficiency of nuclear power plants. The proliferation of low cost sensor modalities such as strain fiber optics sensors and noninvasive concentration sensors, allowed development of on-line nonintrusive monitoring techniques, which can complement or replace existing evaluation techniques. The report presents a literature review of the current state-of-the-art in flow-assisted corrosion monitoring, and a research framework to study on-line monitoring techniques. The report addresses the problem on on-line monitoring of flow-assisted corrosion in nuclear power plants.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Corrosion Evaluation for Tank 241-AP-106 Re-purposing

Tank AP-106 will be an integral part of the Direct Feed Low Activity Waste (DF-LAW) activity. This tank is an underground, carbon steel, double shell tank (DST). Before it can be utilized, the Cs-137 concentration levels in the waste must be reduced significantly. The AP-106 re-purposing process will manage normal waste tank additions procedures such that waste acceptance criteria objectives for Cs-137 removal are achieved. As this process was being developed, concerns regarding tank integrity during and after the process to Tank AP-106 and associated tanks (i.e., AP-102, AN-101, and AP-108) were addressed. The degradation mechanisms identified include: general and pitting corrosion, caustic stress corrosion cracking, galvanic corrosion, and microbiologically induced corrosion (MIC). Recommendations were provided to minimize the exposure of the tank to corrosive conditions (see Section 6.0). These recommendations included chemistry adjustments at defined steps in the process that will maintain the waste in compliance with the corrosion control program. Additionally, sampling and inspection (see Sections 6.0 and 7.0, respectively) recommendations that will assess the final condition of the tank environment and the tank were presented. The greatest risk for this process involves the handling of large quantities of Columbia River water (i.e., greater than 450,000 gallons) within the AP-106, associated tanks and supporting infrastructure (i.e., transfer line piping). As long as this water is blended into the supernate in a timely fashion, and the waste is adjusted appropriately with corrosion inhibitors, the final condition is expected to be within compliance. Recommendations were also made to address process interruptions that could result in exposure of the tank walls to aggressive conditions.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Sensing and arresting metal corrosion in molten chloride salts at 800 degrees Celsius

Originally this was planned as a 5 task, 3 year project, starting in May 2019. Task 1 Detecting oxidants and metal corrosion in molten chloride salt at 800°C. Task 2 Effectiveness of Zr getter using head gas sensors of inlet and outlet gases. Task 3 Cathodic protection of metal in molten salt at reducing potential. Task 4 Find reduction potential of metals in molten chloride salts & quantum modeling. Task 5 Develop corrosion test sections integrated into molten salt flow loop. After Q4, the project was scaled back and the reorganized SOPO was reduced to 3 tasks to be completed at the end of Q7 on 01/05/2021. The 3 SOPO tasks are: Task 1 Sense oxidants and the metal corrosion in molten Na-K-Mg-Cl salt at 800°C. Task 3 Cathodically protect H230 alloy in molten Na-K-Mg-Cl salt at 800C by making H230 alloy the cathode of a power supply with a chromium-rich-metal as the anode. Task 4 Find the reduction potential of Cr metal in molten Na-K-Mg-Cl salt at 800°C. The total timeline was reduced from 12 to 7 quarters with the end date being, January 5, 2021. This amounted to task 1,3 and 4 being done in Q5,6 and 7 of an extended year 1, ending on January 5, 2021. Task 1, 3 and 4 were completed. For task1) the increase of oxidants in molten salt is detected by two things: i) a positive shift of the electrode potential for a Haynes 230 alloy (H230) metal coupon versus a silver/silver-chloride reference electrode (SSE) and ii) an increase in the corrosion rate of a H230 electrode at 800C. For task 3) applying a cathodic potential (negative overpotential) to a H230 electrode versus SSE arrested the corrosion of the cathodically protected H230 compared to an unprotected “spectator H230 electrode” in the same molten chloride salt. Lastly, for task 4) the reduction potential of chrome and chrome rich, and nickel metal electrodes were measured. The most valuable outcome of this work is that a power supply can arrest metal corrosion for metal in molten chloride salt when the power supply applies a cathodic potential to bare metal, like H230, in molten chloride salts, like ternary Mg-K-Na-chloride salt. H230 is a high strength metal for containing molten chloride salt and ternary Mg-K-Na-chloride salt is used as heat transfer fluids in concentrating solar power plants. When to use cathodic protection for protecting metal in molten chloride salts? Two scenarios are envisioned: 1) for protecting high-valued components, like solar collectors and heat exchangers and 2) for protecting the bare surface in holidays (point defects) of corrosion inhibitors that are to intended to cover the entire surface of metal.

14 SOLAR ENERGY↗
DOE OSTI2025

Impact of Irradiation on Corrosion Performance of Hybrid Organic/Inorganic Coatings on Austenitic Stainless Steel

The effects of gamma radiation on the performance of two corrosion-resistant coatings applied to stainless-steel 304L (SS304L) surfaces are presented. Specifically, the ability of the coatings to mitigate corrosion of SS304L surfaces as a function of the dose received (0–1300 Mrad) and dose rate (176 compared to 1054 rad/s) is evaluated using electrochemical methods, spectroscopy, and microscopy. Coating A, an organic/inorganic hybrid coating consisting of a two-part silica ceramic component and a polymer linker was evaluated in comparison to Coating B, which utilized Coating A as a topcoat for a commercial, off-the-shelf, Zn-rich primer. Post irradiation, Coating A demonstrated some corrosion protection following exposure to low levels of gamma radiation, but coating degradation occurred with an increased exposure dose and resulted in isolated regions of corrosion initiation. For Coating B, greater corrosion resistance was observed compared to Coating A due to the sacrificial nature of the Zn at elevated doses of gamma radiation. No effect of the dose rate (for the single dose examined) was observed for either coating. It is proposed for Coating B that as the polymer coating thermally degrades above 250 °C (bond scission of the polymer occurs), the remaining Zinc layer adhered to the SS304L post-irradiation enables enhanced corrosion resistance as compared to Coating A, which displays solely polymer degradation. The results presented herein establish an understanding of coating behavior with radiation exposure, specifically the relationship between corrosion coating performance and radiation dose, and can inform ageing and lifetime management for various applications.

degradation↗
DOE OSTI2015

The long-term corrosion performance of Alloy 22 in heated brine solutions

Long-term corrosion experiments have been performed on Alloy 22 (UNS N06022), in a series of heated brines formulated to represent evaporatively concentrated ground water, to evaluate the long-term corrosion performance of the material. These solutions included 0.5 M NaCl, in addition to two simulated concentrated ground water solutions. Under conditions where Alloy 22 was anticipated to be passive, the corrosion rate was found to be vanishingly small (i.e., below the resolution of the weight-loss technique used to quantify corrosion in this study). However, under low pH conditions where Alloy 22 was anticipated to be active, or more specifically, where the chromium oxide passive film was not thermodynamically stable, the corrosion rate was appreciable. Furthermore, under such conditions the corrosion rate was observed to be a strong function of temperature, with an activation energy of 72.9±1.8 kJ/mol. Time of Flight-Secondary Ion Mass Spectroscopy analysis of the oxide layer revealed that, while sulfur was present within the oxide for all test conditions, no accumulation was observed at or near the metal/oxide interface. Furthermore, these observations confirm that inhibition of passive film formation via sulfur accumulation does not occur during the corrosion of Alloy 22.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Microstructural, Corrosion and Mechanical Characterization of Friction-Stir Welded Joints Between Aluminum and Magnesium Alloys

Friction Stir Welding (FSW) of Aluminum-Magnesium (Al-Mg) alloys has garnered increasing attention due to its wide-ranging applications in the automotive and aerospace industries. The microstructural, corrosion, and mechanical properties of FSW Al-Mg welds under selected conditions are critical factors that must be well-investigated to ensure their durability and performance. In this study, electrochemical tests, including Open Circuit Potential (OCP), Linear Polarization Resistance (LPR), Potentiodynamic Polarization Scan (PD), and Electrochemical Impedance Spectroscopy (EIS), have been used to analyze the corrosion resistance of these welds, along with weight loss measurements through cyclic corrosion testing (CCT) and surface evolution via SEM over an 8-week period. Mechanical properties are evaluated through microindentation, nanoindentation, fatigue, and lap-shear tests. The results of the electrochemical tests reveal that the corrosion properties of the center weld zone differ from those of the two base alloys. Indentation tests indicate that the weld zone behaves differently from the base alloys. Surprisingly, the lap shear strength did not decrease significantly even after 8 weeks of cyclic corrosion testing, indicating that the joint prevented any ingress of the electrolyte. Fatigue testing showed that applying an adhesive between the Al and Mg joint improved the fatigue life to some extent, although the corrosion resistance reduced due to the discontinuous bonding of the adhesive layer. Overall, these findings highlight the importance of investigating the corrosion and mechanical properties of FSW Al-Mg welds and provide valuable insights for future modeling works.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Laser Nitriding of the Newly Developed Ti-20Nb-13Zr at.% Biomaterial Alloy to Enhance Its Mechanical and Corrosion Properties in Simulated Body Fluid

Despite the widespread application of Ti alloy in the biomedical field, surface treatments are typically applied to improve its resistance to corrosion and wear. A newly developed biomedical Ti-20Nb-13Zr at.% alloy (TNZ) was laser-treated in nitrogen environment to improve its surface characteristics with corrosion protection performance. Surface modification of the alloy by laser was performed through a Nd:YAG laser. The structural and surface morphological alterations in the laser nitrided layer were investigated by XRD and a FE-SEM. The mechanical properties have been evaluated using nanoindentation for laser nitride and as-received samples. The corrosion protection behavior was estimated using electrochemical corrosion analysis in a physiological medium (SBF). The obtained results revealed the production of a dense and compact film of TiN fine grains (micro-/nanosize) with 9.1 µm below the surface. The mechanical assessment results indicated an improvement in the modulus of elasticity, hardness, and resistance of the formed TiN layer to plastic deformation. The electrochemical analysis exhibited that the surface protection performance of the laser nitrided TNZ substrates in the SBF could be considerably enhanced compared to that of the as-received alloy due to the presence of fine grains in the TiN layer resulting from laser nitriding. Furthermore, the untreated and treated Ti-20Nb-13Zr alloy exhibited higher corrosion resistance than the CpTi and Ti6Al4V commercial alloys. The improvements in the surface hardness and corrosion properties of Ti alloy in a simulated body obtained using laser nitriding make this approach a suitable candidate for enhancing the properties of biomaterials.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Influence of Laser Nitriding on the Surface and Corrosion Properties of Ti-20Nb-13Zr Alloy in Artificial Saliva for Dental Applications

Ti alloys have been used for dentistry due to their lower density and improved compatibility. However, the resistance to corrosion and surface hardness of Ti alloys need to be improved to avoid the formation of debris, which affects the long-term biocompatibility. In the present work, the surface characteristics and corrosion protection in artificial saliva produced by laser nitriding of a new biomedical Ti-20Nb-13Zr at.% alloy have been investigated for dental applications. The laser nitrided and untreated alloy surfaces were examined using XRD, FE-SEM, x-ray photon spectroscopy, Vickers microhardness measurements, atomic force microscopy, scratch measurements, Raman spectroscopy, and surface energy measurements. The susceptibility of the laser nitrided TNZ alloy to corrosion in an artificial saliva medium was investigated by electrochemical corrosion tests, which were performed by utilizing open circuit potential monitoring, electrochemical frequency modulation, and electrochemical impedance spectroscopic methods. The findings revealed that a TiN layer formed on the alloy surface after nitriding. The surface hardness of the treated alloy was 2.4 times that of the as-received samples. Moreover, the results showed improved friction coefficient and hydrophilic surface characteristics. The corrosion analysis revealed that the compact and dense TiN layer produced during laser nitriding improved the corrosion resistance of the Ti-20Nb-13Zr sample in artificial saliva medium.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Mechanical Properties and Corrosion Behavior of AA5754-AA6061 Dissimilar Aluminum Alloys Welded by Cold Metal Transfer

The trend of using lightweight materials in the automotive industry brings along the necessity of dissimilar welding of aluminum alloys such as AA5754 and AA6061. Hybrid structures in automobiles are subjected not only to mechanical forces but also corrosive effects of the environment. In this study, cold metal transfer welding, which is suitable for welding thin sheets and dissimilar materials, was applied to join AA5754 to AA6061. It was aimed to investigate the effect of weld heat input on mechanical properties and corrosion rate measured by the Tafel extrapolation method in 3.5 wt.% NaCl solution at room temperature. The tensile strength of AA5754-AA6061 joints tended to reduce with increasing heat input. Corrosion test results showed that the increased heat input decreased the corrosion resistance and caused intergranular corrosion besides pitting corrosion.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Performance of 700 Series Stellite Alloys in Various Media

The corrosion performance of 700 series Stellite alloys including Stellite 706, Stellite 712 and Stellite 720, which are high-carbon high-molybdenum Stellite alloys, in various media such as Green Death solution, 3.5 wt.% NaCl solution and morpholine solution with pH 9.5, is studied using electrochemical and immersion methods. The obtained polarization curves are analyzed along with the corroded surfaces examined using SEM/EDS to investigate the corrosion mechanisms of these alloys. The experimental results reveal that the 700 series Stellite alloys possess excellent corrosion resistance in the tested media, even in the severe corrosive condition—Green Death solution at 60 °C where no noticeable pitting is found on the surfaces of the alloys. It is shown that the corrosion resistance of these Stellite alloys depends strongly on the behavior of the passivation film formed on the alloy surfaces. Additional Mo content in these alloys benefits the stabilization of the passivation film thus enhances the corrosion resistance of the alloys. Both carbon and molybdenum contents affect the passivation film formation and stabilization.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Chloride-Induced Stress Corrosion Cracking Characteristics of the Used Nuclear Fuel Canister Material

The used nuclear fuel (UNF) dry storage systems are located in the coastal and lake/river-side regions, the service time of which is 60 years and more. One type of dry storage systems is composite of a thin-walled austenitic stainless steel (SS) welded canister and a concrete overpack. The air flows through the canister surface and brings away the decay heat. Meanwhile, the air brings the salt species into the canister and make them deposit on the surface. The salt deposit will be deliquescent when absorbing the moisture air, being corrosive to the surface. NRC and other programs claimed that chloride induced stress corrosion cracking (CISCC) would lead to the canister failure, being one of the major technical gaps for extended dry storage systems. CISCC is induced by the combined influence of the aggressive environment (chloride ions in our case) and tensile stresses (residual stresses in our case) on the susceptible materials (the austenitic SS in our case). Chrome (Cr), as one of the chemical compositions of SSs, plays an important role in the corrosion resistance. It can form a chrome-rich inner barrier oxide layer to prevent the SS from corrosion. However, chloride ions can easily break down the barrier and accelerate dissolution of the underlying metal, the phenomena of which is pitting corrosion. Pitting is the precursor to CISCC as which provides the combination of a local aggressive solution chemistry and a stress concentrating feature. Accordingly, CISCC invariably originates from the pits, and cracks that have nucleated on pit walls can grow around the pit and coalesce to form a complete through-crack. Significant tensile residual stresses, caused by the welding process, exist throughout the thickness of the canister wall. Enos and Bryan found that large residual stresses were in the full-scale mockup container simulating a canister, which supports the SCC propagation. It is therefore interesting to achieve a good knowledge about the effect of welding on the durability of SSs, especially in the corrosive environment. In order to understand the fundamental of the cracking behaviors, it's vital to elucidate the microstructure and microchemistry of cracking. This study focused on observing the CISCC characteristics of the UNF canister material exposed to the humid environment with salt deposit. Extensive micro-characteristics have been achieved by the techniques include focused ion beam/ scanning electron microscope (FIB/SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and optical profiler. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Corrosion property of Alloy 625 in Molten FLiNaK salt according to the Tellurium Concentrations

For this work, the corrosion properties of Alloy 625 have been studied in molten FLiNaK salt for 48 h at 700 °C as a function of tellurium (Te) concentrations using immersion tests and electrochemical methods. Under specific Te concentrations, we found that Te-induced corrosion can be suppressed and help protect the alloy against corrosion. The sample after the immersion test containing 0.1 wt.% Te (0.1 wt.% Te sample) had the lowest corrosion depth and mass loss, coupled with the highest charge transfer resistance, obtained using electrochemical impedance spectroscopy (EIS). On the other hand, the alloy with Te content above 0.1 wt.% exhibited severe corrosion penetration and lower charge transfer resistance in FLiNaK. Based on thermodynamical and electrochemical analyses, a corrosion mechanism of Alloy 625 in the molten salt containing Te was theorized involving the formation of stable corrosion products such as Ni/Fe rich layer depleted in Cr, nickel telluride, and chromium oxide.

Hong, Minsung↗
DOE OSTI2020

Multiscale Investigation of the Mechanisms Controlling the Corrosion of Borosilicate Glasses in Hyper-Alkaline Media

The overarching goal of the present multiscale investigation is to unearth the kinetics and mechanisms of corrosion of borosilicate glasses in hyper-alkaline (pH = 13) environments as a function of their chemical composition. Accordingly, a series of 3- to 6-component borosilicate glasses have been designed starting from Na 2 O–B 2 O 3 –SiO 2 ternary, wherein the compositional complexity has been added in a systematic tiered approach, finally resulting in the composition of the well-known international simple glass (ISG). Tetramethylammonium hydroxide (TMAH), one of the most widely used alkaline etchant in the glass and electronics industry, has been used as the corrosion media. A series of state-of-the-art characterization techniques including magic angle spinning nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectroscopy, elastic recoil detection analysis, and high-resolution transmission electron microscopy have been employed to unearth the compositional dependence of glass corrosion in hyper-alkaline environments. The glass compositions underwent congruent corrosion in the forward rate regime, whereas the controlling mechanism of corrosion in the residual rate regime depends on the presence/absence of Ca in the surrounding environment and can be explained on the basis of the dissolution–reprecipitation model. The dependence of corrosion kinetics and the chemistry of alteration products (in the residual rate regime) on the glass composition have been discussed. Here, the results presented in this contribution will ultimately supplement the scientific literature attempting to understand the fundamental science governing the aqueous corrosion of silicate-based glass chemistries and add to the growing database required to develop non-empirical predictive models for designing glasses with controlled dissolution rates.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Amine Structure Governs Corrosion Rates of Copper Catalysts in Electrochemical Reactive Capture of CO 2

Reactive capture of CO 2 (RCC) offers an integrated approach that combines CO 2 capture with its direct electrochemical conversion, eliminating the need for CO 2 release from the capture agent. By avoiding the pH, pressure, and temperature swings required for the release step, RCC has the potential to reduce both energy consumption and capital costs compared to the conventional sequential process of CO 2 capture, release, concentration, and conversion. Amines, widely used in industrial CO 2 capture, face challenges in RCC systems due to their incompatibility with transition metal catalysts as well as their tendency to promote electrode corrosion and parasitic hydrogen evolution. Identifying suitable combinations of amines and catalysts is therefore critical to enabling integrated CO 2 capture and conversion. Here, this work systematically investigates the performance of four primary and four secondary amines for RCC on polycrystalline Cu catalysts. Among the eight tested amines, only dimethylamine showed no measurable Cu corrosion near the open circuit potential. In contrast, ammonia, methylamine, ethylamine, monoethanolamine, diethylamine, diethanolamine, and piperazine all induced Cu corrosion. Corrosion rates correlate with the pK a and steric hindrance of the amines, highlighting key parameters for catalyst–amine codesign. Grand canonical DFT calculations indicate a correlation between the adsorption strength of protonated amines, their pK a , and the extent of Cu corrosion, suggesting that both the surface binding of protonated amines and the lability of their protons play critical roles in corrosion acceleration near open circuit potentials. These finding suggest that amines with high pK a values and weak binding of their protonated forms to Cu surfaces are preferred, as they offer better corrosion resistance.

Choi, Jounghwan [Univ. of California, Los Angeles,↗
DOE OSTI2020

Corrosion interactions between stainless steel and lead vanado-iodoapatite nuclear waste form part I

This study explores the corrosion interactions between a metallic canister material, stainless steel (SS) 316, and an I-bearing ceramic waste form, lead vanado-iodoapatite (I-APT, Pb 9.85 (VO 4 ) 6 I 1.7 ), in a chloride solution. Crevice corrosion of the SS in close proximity to the I-APT resulted in the development of an aggressive environment at the interface of the two materials, which was acidic and enriched in Cl – anions. I-APT also corroded in the crevice region, primarily through ion-exchange between the I – ions from the I-APT matrix and anions from the environment. The enrichment of Cl – anions within the occluded crevice space as the result of SS crevice corrosion enhanced the corrosion of I-APT. The release of iodine from this apatite waste form could be accelerated owing to this mechanism. This is evidenced by a depletion of iodine from the I-APT matrix and a large amount of Cl-bearing precipitates on the surfaces of both SS and I-APT. On the other hand, the corrosion of I-APT leads to the precipitation of a V- and Pb-rich layer, which inhibits the localized corrosion of SS to an extent. This study advances the understanding of the near-field corrosion interactions between metallic canisters and ceramic waste forms.

36 MATERIALS SCIENCE↗