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In the geological repository of radioactive nuclear waste, anaerobic corrosion can generate hydrogen, and may conservatively lead to the production of hydrogen-air layer. The accumulated hydrogen may cause a hazardous flame propagation resulting from any potential ignition sources. This study numerically investigates the processes of ignition and flame propagation in the layered mixture. Simple geometry was chosen to represent the geological repository, and reactive flow simulations were performed with different ignition power, energy, and locations. The simulation results revealed the effects of power and energy of ignition source, which were also analyzed theoretically. The mechanism of layered flame propagation was suggested, which includes three stages: propagation into the hydrogen area, downward propagation due to the product gas, and horizontal propagation along the top wall. To investigate the effect of the ignition source location, simulations with eight different positions were performed, and the boundary of hazardous ignition area was identified. The simulation results were also explained through scaling analysis. This study evaluates the potential risk of the accumulated hydrogen in geological repository, and illustrates the layered flame propagation in related ignition scenarios.

Increasing groundwater temperatures caused by global warming, subsurface infrastructure, or heat storage projects may interfere with groundwater remediation techniques using zero-valent iron (ZVI) technology by accelerating anaerobic corrosion. The corrosion behavior of three ZVIs widely used in permeable reactive barriers (PRBs), Peerless cast iron (PL), Gotthart-Maier cast iron (GM), and an ISPAT iron sponge (IS), was investigated at temperatures between 25 and 70 °C in half-open batch reactors by measuring the volume of hydrogen gas generated. Initially, the corrosion rates of all tested ZVIs increased with temperature; at temperatures ≤40 °C, a material-specific steady state is reached, and at temperatures >40 °C, passivation causes a decrease in long-term corrosion rates. The observed corrosion behavior was therefore assumed to be superimposed by accelerating and inhibiting effects, caused by surface precipitates where the fitting of measured corrosion rates by a modeling approach, using the corroded amount of Fe0 to account for passivating minerals, yields intrinsic activation energies (Ea, ZVI) of 81, 90, and 107 kJ mol-1 for IS, GM, and PL, respectively. An increase in H2 production might not be directly transferable to an increase in general ZVI reactivity; however, the results suggest that an increase in chlorinated hydrocarbon degradation rates can be expected for ZVI-PRBs in the immediate vicinity of low-temperature underground thermal energy storages (UTESs) or in the impact areas of high-temperature UTES with temperatures of ≤40 °C.

In the Belgian supercontainer concept, a carbon steel overpack will surround high-level waste and spent fuel containers and be encased in a cementitious buffer material. A programme of research has...

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract] Developing innovative bioprocess strategies for carbon capture and utilization has been a major focus of research over the past decade as a way of creating a more resilient world. In this study, zero-valent iron (ZVI) was utilized to generate hydrogen, which was then utilized as an electron donor for CO2 reduction by either Clostridium aceticum or Clostridium carboxidivorans. For this bioprocess, an early acidic condition in the reactors facilitated more hydrogen production and thereby more acetic acid accumulation, in contrast to later acidification, elucidating the role of pH in ZVI-CO2 bioconversion. Acetic acid was produced as single end product of the process in both batch bottle studies with no pH control as well as in reactor studies with pH regulation. This is, to the best of our knowledge, the first report on selective pure CO2 bioconversion to acetic acid by clostridia, with ZVI. In order to minimize costs, scrap iron rather than pure ZVI can be used for scaling-up. By lowering the pH to 6.6 for C. aceticum, in reactor studies with 75 g/L ZVI, some ethanol production (125 mg/L) was also observed, besides acetic acid. In reactor studies, a maximum acetic acid concentration of about 2 g/L was obtained at ZVI concentrations of 50 and 75 g/L. Thus, ZVI dosage and medium pH have a major effect on the metabolites generated during CO2 utilization. This research was partly financed by the Spanish Ministry of Science and Innovation Through Project PID2020-117805RB-I00 and European FEDER funds. BB thanks Xunta de Galicia for funding her predoctoral fellowship (ED481A-2020/226) to undertake research at the BIOENGIN group. The BIOENGIN group also thanks Xunta de Galicia for financial support to Competitive Reference Research Groups (ED431C 2021/55). Funding for open access charge provided by Universidade da Coruña/CISUG Xunta de Galicia; ED481A-2020/226 Xunta de Galicia; ED431C 2021/55

The materials corrosion test (MaCoTe) is a long‐term, multinational in situ corrosion experiment setup at the Grimsel Test Site, Switzerland. The experiment has been operating since 2014 with a focus on the corrosion behaviour of container materials for the disposal of high‐level waste and spent nuclear fuel under conditions representing a granitic deep geological repository. The experiment consists of eight modules containing metal coupons and bentonite. Two of the modules, each with a different bentonite density, have been retrieved after 394 days of exposure and have been analysed using a range of techniques aimed at studying the corrosion behaviour of the metals and the mineralogical evolution of the bentonite. Weight loss measurements show that carbon steel had a relatively low average corrosion rate (~2 µm year−1). Much lower average corrosion rates were measured for the various types of copper (0.13–0.32 µm year−1). No detectable corrosion was measured on stainless steel coupons. To date, no significant differences were observed in the corrosion behaviour and rate of the test metals in bentonite with different dry densities.

Some three hundred mainly steel shipwrecks from both World Wars lie buried at shallow depths along the Belgian North Sea coast. They were examined recently to estimate corrosion rates over periods ...

Perchloroethene (PCE) is a hazardous and persistent groundwater pollutant. Both treatment with nanoscaled zero-valent iron (nZVI) and biological degradation by bacteria have downsides. Distribution of nZVI underground is difficult and a high percentage of injected nZVI is consumed by anaerobic corrosion, forming H2 rather than being available for PCE dechlorination. On the other hand, microbial PCE degradation can suffer from the absence of H2. This can cause the accumulation of the hazardous metabolites cis-1,2-dichloroethene (DCE) or vinylchloride (VC). The combination of chemical and biological PCE degradation is a promising approach to overcome the disadvantages of each method alone. In this lysimeter study, artificial aquifers were created to test the influence of nZVI on anaerobic microbial PCE dechlorination by a commercially available culture containing Dehalococcoides spp. under field-like conditions. The effect of the combined treatment was investigated with molasses as an additional electron source and after cessation of molasses addition. The combination of nZVI and the Dehalococcoides spp. containing culture led to a PCE discharge in the lysimeter outflow that was 4.7 times smaller than that with nZVI and 1.6 times smaller than with bacterial treatment. Moreover, fully dechlorinated end-products showed an 11-fold increase compared to nZVI and a 4.2-fold increase compared to the microbial culture. The addition of nZVI to the microbial culture also decreased the accumulation of hazardous metabolites by 1.7 (cis-DCE) and 1.2 fold (VC). The stimulatory effect of nZVI on microbial degradation was most obvious after the addition of molasses was stopped.

When using cathodic protection of steel in sea water, hydrogen can be accumulated on the cathode surface and penetrate deep into the metal. This rather dangerous phenomenon of hydrogen corrosion can lead to hydrogen embrittlement, i.e., to destruction of the metal. We present the results of studying the impact of the temperature and external tensile stresses on the hydrogenation of cathodically protected steel in calm and mobile Baltic sea water. Dependence of the inhibitory hydrogenation on the temperature and applied load under the action of benzenesulfapyridine chloride as an inhibitor was analyzed. An MIP-102 machine (wire samples) and special equipment (half-ring and plate lamellar samples) were used to provide smooth control of the applied load set by the deflection and controlled by dynamometers (lamellar samples were tested under constant deformation). When studying the effect of temperature on steel hydrogenation, the working cell was thermostatically controlled. The wire and plate samples were polarized for 96 h, and half-ring samples for 1 h. The potential was measured with respect to the silver chloride reference electrode. The layered distribution of absorbed hydrogen in the metal was determined using anodic dissolution. It is shown that external tensile stresses increase the hydrogen content in the surface layers of steel. Hydrogen absorbed by a metal changes the potential of the steel surface (the more absorbed hydrogen, the stronger change). It is also shown that hydrogen is absorbed by the metal more actively in moving seawater than in calm water, and an increase in the load contributes to an increase in hydrogen content in the metal both in calm and mobile seawater. However, the load did not affect the hydrogen absorption with the inhibitor present, thus providing reduction of the hydrogen content in the metal under loading.

Anaerobic corrosion at the metal/bentonite interface determines the performance of bentonite-based high-level radioactive waste (HLRW) barriers. Both magnetite and Fe-silicate formation were previo...

The structure, the static tensile properties, the impact toughness, and the fracture mechanisms of the 12GSB pipe steel specimens cut from the defect regions in a pipeline 530 mm in diameter are studied. Hydrogen corrosion is found to affect the anomalous character of the temperature dependences of the impact toughness and the fraction of ductile component in a fracture surface. Sulfur is shown to substantially influence the ductile crack propagation energy in the transverse direction and to weakly influence this energy along the rolling direction. The development of hydrogen corrosion in the pipeline is found to be accompanied by a significant increase in the reduced fraction of intergranular fracture (15.8–35%) in brittle fracture surfaces, and this fraction in the separation plane reaches 50.5%. The relation between the impact toughness of the transverse specimens and the fraction of ductile component in a fracture surface has an anomalous character: this relation has two linear segments, the fracture energies in which differ by an order of magnitude. The segment with a low fracture energy (4.4–16.1 J/cm2) characterizes the action of the sear component of separation in the rolling plane, and the segment with a high fracture energy (38–246 J/cm2), the action of a ductile mode I fracture mechanism. The impact toughness anisotropy coefficient is found to be high, Ka = 2.31.

The Belgian reactor 1 fuel cladding is made of aluminium. If disposed of in a geological disposal repository, aluminium could come into contact with ordinary Portland cement and is going to corrode to form hydrogen gas and aluminium hydroxide. In this study, the long‐term corrosion was evaluated by electrochemical impedance spectroscopy on metal embedded in cement paste immersed in saturated calcium hydroxide solution under anaerobic conditions. Mass transfer effects were investigated by embedding aluminium in cement paste with two different porosities. LiNO3 was also added to the systems to study its corrosion inhibiting effect. After high initial values, the corrosion rate rapidly declined to reach a steady state after a few days. After ~100 days, the corrosion rate was the lowest when cement paste possessing a low porosity with the addition of LiNO3 was used and the highest when cement paste with high porosity without LiNO3 was used. Finally, scanning electron microscopy–energy X‐ray dispersive spectroscopy revealed that the corrosion product layer was thicker than expected by electrochemical impedance spectroscopy measurements, while it is only composed of aluminium and oxygen. Aluminium was found to diffuse into the cement paste close to this corrosion product layer.

Carbon steel is a potential canister material for the disposal of high-level radioactive waste in deep geological repositories in clays and clay rocks. Bentonite is considered as a potential backfill material for those multi-barrier systems. To predict the long-term performance and for safety assessment the knowledge of canister corrosion behavior is important. The corrosion products formed and mineralogically altered bentonite at the canister/bentonite interface can potentially provide an additional barrier against radionuclide migration. In-situ corrosion experiments were performed at the Mont Terri underground research laboratory. Coupons of carbon steel were embedded in Volclay MX-80 bentonite with controlled densities, installed in a borehole under simulated repository and anaerobic conditions and exposed to natural Opalinus clay porewater for a period up to 5.5 years (Smart et al., 2017). In the present study, the bentonite layer at the canister/bentonite interface was characterized by complementary microscopic and spectroscopic techniques (XPS, SEM-EDX, µXANES) under anoxic conditions. The interface revealed reddish-brown staining up to 2 mm depth into the bentonite in the zone adjacent to the steel in all three obtained samples. The XPS analysis revealed formation of sulfides at the interface consisting of iron and other trace metals present in the steel. The SEM-EDX analyses of the interface (embedded cross-cut with steel removed) showed different degrees of calcium enrichment in the bentonite adjacent to the metal for various samples. The µXRF analysis performed on the bentonite at the interface showed a scarce or distinct calcium-enriched rim up to 100 µm into the bentonite and iron-enriched rim depending on the sample (one sample in Fig. 1), while µXANES analysis revealed formation of iron silicate compounds in the reacted reddish-brown zone. The iron appears to displace calcium from the interlayer sites in montmorillonite. The calcium then precipitates at the interface as calcite. The extent of this process seems to be strongly related to the bentonite density. The steel coupon was removed prior to embedding, with the location marked as resin in Fig. 1. A line scan from the edge towards the bulk bentonite did not indicate any systematic gradient in the Fe2+/3+ ratio. The formation of mixed Fe2+/3+ silicate compounds appears to be heterogeneous. This work contributes to an increasing understanding of steel corrosion mechanisms in clay, which can improve the robustness of canister lifetime predictions.

Since 2012, a long-term in situ corrosion experiment (IC-A) has been conducted in the Mont Terri Underground Research Laboratory in Switzerland. The aims of the project with international partners are to confirm the long-term anaerobic corrosion rate of carbon steel and copper in compacted bentonite under repository-relevant environmental conditions, to gather in situ corrosion data supporting canister lifetime predictions, to provide confirmation of the effect of the bentonite buffer on microbial activity and microbially influenced corrosion, and to study the effects of welding (steel) and deposition technique (copper) on the corrosion properties of these candidate materials for disposal canisters. To date, carbon steel and cold sprayed and electrodeposited copper coatings have been retrieved after different exposure periods up to 3 years and characterised to establish the composition of the corrosion product, the morphology of the corroded surface, and to measure the rate of corrosion. For carbon steel specimens, a complex corrosion product was identified, consisting predominantly of magnetite. Low average anaerobic corrosion rates were measured for carbon steel and a very modest amount of alteration was identified on copper. The density and the initial form of the bentonite had a small influence on the rate of corrosion, across all materials.

There have been many studies on TCE degradation by synthesized nanoscale zero-valent iron (nZVIB) and commercial nanoscale zero-valent iron (nZVIH), but the effect of anaerobic corrosion on the dechlorination pathways and speciation distribution of chlorine is still unclear. Compared with nZVIH, nZVIB has a faster degradation rate of TCE and formation rate of Cl−(aq) (kSA, TCE = 3.67 ± 0.85 × 10−4 & 2.17 ± 0.13 × 10−4 L·h−1·m−2 and kobs, Cl− = 0.344 ± 0.027 & 0.166 ± 0.010 μM·h−1 for nZVIB & nZVIH, respectively). Based on the characterization of XRD, XPS and TEM during the anaerobic corrosion, the corrosion of nZVIB was dramatic under the dissolution-reprecipitation mechanism; but that of nZVIH was moderate and inward by maintaining the core-shell structure and shaping slightly rough and lumpy surface. Due to the different corrosion products (FeOOH for nZVIB and Fe3O4/γ-Fe2O3 for nZVIH) and the catalysis of boron on the nZVIB surface, the preferential dechlorination pathway of TCE was not identical by hydrogenolysis (nZVIB) vs. reductive β-elimination (nZVIH). Meanwhile, the dechlorination pathway of nZVIH was similar to that of ZVI and the reductive pathway to acetylene bypassed the formation of more toxic VC. This study shows that the high reactivity of nZVIB results in rapid corrosion with the side effect of enhanced adsorption of VC while nZVIH has a stable core-shell structure and less sorbed chlorine, which provides a new sight to access the ecological risk of nZVI due to the overlooked effect of non-identical corrosion.

Gas production from low- and intermediate-level nuclear waste (LLW/ILW) is important to the safety of near surface and deep geological nuclear waste repositories through the release of gaseous radionuclides and pressurization that can ultimately affect the transport of radionuclides in groundwater. The main gases generated from LLW/ILW are H2 from anaerobic corrosion of steel and CH4 from organic (cellulose) wastes. Microbes mediate CH4 generation and also can consume H2 as an energy source such as for the reduction of sulfate. A 20-year Gas Generation Experiment at Olkiluoto, Finland has furthered the understanding that microbes play in mediating gas production from LLW. The processes involved in gas generation from the experiment have been elucidated by, interpretation of gas and chemical data, DNA pyrosequencing and biogeochemical modeling. Methanogenesis develops initially mainly by utilizing hydrogen formed by anaerobic corrosion. In contrast, generation of CH4 from cellulose develops more slowly as a consequence of the complexity of the preceding cellulose degradation, fermentation processes, competition with sulfate reduction processes, and inhibition effects related to high pH and aqueous sulfide. The maximum rate of CH4 production develops after 8 years, when concrete buffered high pH regions of the experiment are neutralized by cellulose degradation and fermentation.

Since 2012, a long‐term in situ corrosion experiment (IC‐A) is being conducted in the Mont Terri Underground Research Laboratory in Switzerland to investigate the corrosion behaviour of candidate canister materials in conditions representative of the Swiss concept for the disposal of high‐level waste and spent nuclear fuel. To date, carbon steel and various types of copper coatings have been retrieved after different exposure periods of up to 3 years, and characterised to establish the composition of the corrosion product, the morphology of the corroded surface, the nature of the interaction between the metal and the surrounding bentonite, and the microbial populations in the bentonite and surrounding porewater. For carbon steel specimens, a complex corrosion product was identified, consisting predominantly of magnetite. Much less alteration on either the metal or the bentonite was observed in the case of copper samples. Low average anaerobic corrosion rates were measured for carbon steel and a very modest amount of alteration was identified on copper. The density and the initial form of the bentonite had a small influence on the rate of corrosion, across all materials. This paper summarises the results of the experimental programme obtained to date and discusses the relationship observed between exposure time and the evolution of the metal–bentonite interface for both carbon steel and copper.

Carbon steel is a potential canister material for the disposal of high-level radioactive waste in deep geological repositories in clays and clay rocks. Bentonite is considered as a potential backfill material for those multi-barrier systems. To predict the long-term performance and for safety assessment the knowledge of canister corrosion behavior is important. The formed corrosion products and mineralogically altered bentonite at the canister/bentonite interface can potentially provide an additional barrier against radionuclide migration. In-situ corrosion experiments were performed at the Mt. Terri underground research laboratory. Coupons of carbon steel were embedded in Volclay MX-80 bentonite with controlled densities, installed in a borehole under simulated repository and anaerobic conditions and exposed to natural Opalinus Clay porewater for a period up to 5.5 years. The bentonite layer at the canister/bentonite interface was characterized by complementary microscopic and spectroscopic techniques (XPS, SEM-EDX, XRD) under anoxic conditions. The interface revealed reddish-brown staining up to 2 mm depth into the bentonite in the zone adjacent to the steel. The SEM-EDX analyses of the interface (embedded crosscut with steel removed) showed calcium and iron enrichment in the bentonite adjacent to the metal. µXRF analysis performed on the bentonite at the interface showed calcium enriched rim up to 100 µm into the bentonite, while µXANES analysis revealed formation of iron silicate compounds in the reacted reddish-brown zone. The steel coupon was removed prior embedding. A line scan from the edge towards bulk bentonite did not indicate any systematic gradient in the Fe2+ / Fe3+ ratio. The formation of mixed Fe2+/3+ silicate compounds appears to be heterogeneous. This work contributes to an increased understanding of steel corrosion mechanisms in clay, which can improve the robustness of canister lifetime predictions. We acknowledge the German Federal Ministry of Education and Research (BMBF) and the Helmholtz association for the financial support. We thank the Mont Terri IC-A Partners and Swisstopo for providing the samples. We acknowledge the provision of the beamtime at the KIT Light Source, KARA, Germany.

One of the causes of pipeline corrosion and a way to solve it are considered

The effect of low temperatures on abiotic and biotic nitrate (NO3−) reduction by zero-valent iron (ZVI) were examined at temperatures below 25 °C. The extent and rate of nitrate removal in batch ZVI reactors were determined in the presence and absence of microorganisms at 3.5, 10, 17, and 25 °C. Under anoxic conditions, NO3− reduction rates in both ZVI-only and ZVI-cell reactors declined as temperature decreased. In ZVI-only reactor, 62% and 17% of initial nitrate concentration were reduced in 6 days at 25 and 3.5 °C, respectively. The reduced nitrate was completely recovered as ammonium ions (NH4+) at both temperatures. The temperature-dependent abiotic reduction rates enabled us to calculate the activation energy (Ea) using the Arrhenius relationship, which was 50 kJ/mol. Nitrate in ZVI-cell reactors was completely removed within 1–2 days at 25 and 10 °C, and 67% of reduction was achieved at 3.5 °C. Only 18–25% of the reduced nitrate was recovered as NH4+ in the ZVI-cell reactors. Soluble iron concentrations (Fe2+ and Fe3+) in the ZVI reactors were also measured as the indicators of anaerobic corrosion. In the ZVI-cell reactors, soluble iron concentrations were 1.7 times higher than that in ZVI-only reactors at 25 °C, suggesting that the enhanced nitrate reduction in the ZVI-cell reactors may be partly due to increased redox activity (i.e., corrosion) on iron surfaces. Anaerobic corrosion of ZVI was also temperature-dependent as substantially lower concentrations of corrosion product were detected at lower incubation temperatures; however, microbially induced corrosion (MIC) of ZVI was much less impacted at lower temperatures than abiotic ZVI corrosion. This study demonstrated that ZVI-supported microbial denitrification is not only more sustainable at lower temperatures, but it becomes more dominant reaction for nitrate removal in microbial-ZVI systems at low temperatures.

This paper reports the results of research on the effect of hydrogen permeation and the absence of passive layers on the variations in the corrosive properties of aluminum alloys. The study demonstrated that such variations contribute to the deterioration of corrosive properties, which in turn contributes to shortening the reliability time associated with the operation of aluminum alloy structures. The analysis involved structural aluminum alloys: EN AW-1050A, EN AW-5754, and EN AW-6060. It was demonstrated that the absorption of hydrogen by the analyzed alloys led to the shift of the electrode potential to the negative side. The built hydrogen corrosion cells demonstrate in each case the formation of electromotive force (EMF) cells. The initial EMF value of the cell and its duration depends on the duration of hydrogenation. As a result of removing the passive layers, the electrode potential also changes to the negative side. Following the removal of the passive layer from one of the electrodes, the cells also generated a galvanic (metal) cell. The duration of such a cell is equivalent to the time of restoration of the passive layer. The formation of such hydrogen and metal galvanic cells changes the electrochemical properties of aluminum alloys, therefore deteriorates the corrosive properties of aluminum alloys.

Modified supermartensitic stainless steel surfaces were investigated as protective means against deterioration in Cl−- and H+-rich media. Nitrogen plasma immersion ion implantation at the 300–400 °C range produced top nitride-rich layers (with mainly γ′-Fe4N and e-Fe2-3N, but also with α′N, according to the treatment temperature) followed by underneath expanded martensite cases. The 400 °C nitrided sample presented the best performance in potentiodynamic polarization tests with NaCl electrolyte, featured by 4.3 times increase in the corrosion potential and the absence of pits, attributed to the thickest and continuous e-phase containing nitride-rich layer. The hydrogen embrittlement was assessed through cathodic hydrogenation tests. Both reference and 400 °C nitrided surfaces disclosed the phenomenon of intensified plastic flow under normal and tangential loadings. A decrease in hardness, elastic modulus and scratch resistance featured a ductile-to-brittle transition on the nitrided surface, possibly due to improved hydrogen trapping by nitride species with subsequent effects in plasticity. In summary, while the nitride layer played an advantageous role in protecting SMSS from chlorine attack, it was susceptible against the hydrogen corrosion.

One of the most common types of metal destruction in the oil and gas industry is hydrogen embrittlement. Hydrogen corrosion is a complex of negative effects of hydrogen on steel, leading to the destruction of metal structures. Hydrogen passes through a defect-free metal, without lingering in it. In the presence of defects, hydrogen is retained in the metal forming a brittle solid solution, metal stratification along the segregation streamer, blistering. Studies of the metal of a gas pipeline made of steel 09G2S are presented in the article. The sample was selected from the local zone of destruction in the condensate collector, the metal of the pipe had typical for hydrogen corrosion stratifications. The scope of the study was identification of the most dangerous part of hydrogen corrosion on the sample taken from the local zone of destruction. Studies on the chemical composition and mechanical properties of 09G2S steel were also carried out. Stress-related characteristics of the metal microstructure of the failed gas pipeline were obtained and the character of the destruction progress was revealed. The presence of sulfides cluster in the metal of studied pipe was determined applying metallographic method for determining nonmetallic inclusions.

Recent studies suggest that the supplementation of powdered Fe° generates a positive effect on anaerobic fermentation processes but the exact relationship between metals with biological systems has not been fully elucidated. Experimental tests on dark fermentation (DF) were carried out at different Fe° concentrations. The anaerobic corrosion (AC) of Fe° and the production of H2 through DF of Organic Waste Market (OWM) were tested separately, and subsequently DF tests with Fe° at 1 g/L and 2 g/L were carried out. A macroscopic dynamic study was conducted, using Roels approach based on relaxation times (τR) to establish whether interactions between AC and DF phenomena exist. Experimental bioH2 production and Fe° AC were fit by Gompertz and saturative models, respectively to estimate τR. The results of the macro-analysis suggest that both phenomena are concurrent, with τR of the same order of magnitude, generating a positive symbiotic effect. The experimental tests of hydrogen production via DF in presence of 2 g/L of Fe° showed an increase of 46% compared with the control tests, of amount of gas and a greater H2/CO2 ratio. The results suggest an enhancement of key enzymes activity due to the action of iron increasing bioH2 production.

To determine the contributions of elastic strain energy to chemical driving force of uranium hydride growth, an elastic fields model was set up by a spherical hydride particle growing at sub-surface of parent metal, which was used to interpret strain energy influence on the evolution of microstructure and kinetics characteristics of the hydride precipitates. The results showed that strain energy during hydride expansile growth in the matrix is considerably different for the three U materials. When hydride grows, the order of the strain energy value is U-5.7%Nb > U > U-2.5%Nb(mass fraction), which indicated that the U-2.5%Nb alloy is the most susceptible to hydrogen corrosion, followed by U, while U-5.7%Nb is the most resistant to hydrogen corrosion basing on reaction activation theory. Agreement of calculated strain energy with experimental results of hydride growth kinetics showed that the model in this work is correct, in which the large strain energy from volume change during hydride growth plays an important role in determination of growth kinetics. In addition to strain energy calculation, the stress distribution associated with hydride precipitate was used to interpret the interaction between hydride pattern and stress. The study provides quantificational evidences to understand the association of strain energy and stress with hydride of metals, which will lead to novel process opportunities.

Speciation of carbon during the anoxic corrosion of steel is poorly known, whereas its knowledge would be of great importance in connection with assessments of the safe disposal of 14C-con...

In this work we have experimentally studied the impact of bentonite clay on the process of radiation-induced copper corrosion in anoxic water. The motivation for this is to further develop our unde ...

The characteristics of hydride formation on metallic U at the early stages were investigated for three differently treated samples. The first sample reacted in its as-received state, the second was thermally annealed and the third sample underwent cold work-hardening prior to reaction with deuterium. From the analysis, the vacuum heat-treated sample was found to be more resilient to hydriding at the nucleation and growth stage, exhibiting a reduced number of nucleation points when compared to the as-cast uranium. The work-hardened sample was observed to be more susceptible to H2 corrosion, displaying very dissimilar hydriding behaviour when compared to the other.

The hydrogenation and corrosion behaviour of La2Ni9 · CoSn0.2 alloy was analysed in respect of its use in Ni–MH batteries. It has been proved that the presence of tin in the alloy causes a decrease in hydrogen equilibrium pressure. In the electrochemical studies several techniques, such as chronopotentiometry, multi-potential steps, linear sweep voltammetry and the potentiokinetic polarization were applied to characterize the electrochemical properties of a La2Ni9CoSn0.2 powder composite electrode. During long cycling, powder particles undergo micro-cracking or other forms of surface development causing a progressive increase in the exchange current density of the H2O/H2 system, but, on the other hand, this increase favours corrosion processes such as the electrode material's oxidation. This is also reflected in the capacity loss values.