Search Results (17)

Molecular hydrogen (H₂) exhibits anti-inflammatory and antioxidant properties. However, its role in ultraviolet B (UVB)-induced skin carcinogenesis remains unclear. Male HR-1 hairless mice received continuous H₂ (2% hydrogen gas inhalation plus hydrogen-rich water (HRW)) or control treatment (normal air plus dehydrogenated water) during chronic dorsal UVB exposure (270 mJ/cm², three times per week, 20 weeks), followed by a 10-week observation period. This protocol was replicated independently. H₂ exposure consistently delayed the onset of papilloma and reduced cumulative tumor counts in both series, whereas prolonged survival and delayed squamous cell carcinoma (SCC) development each reached statistical significance in only one of the two experimental series. The cyclobutane pyrimidine dimer (CPD) levels remained unchanged, indicating no reduction in DNA photolesions. H₂ exposure decreased epidermal T-cell infiltration, dermal IL-6 levels, and nuclear phosphorylated STAT3 levels. ERK and JNK phosphorylation levels were decreased. H₂ preserved the GSH/GSSG ratio following acute UVB exposure and reduced nuclear Nrf2 accumulation during chronic exposure. Epidermal thickness and proliferation markers (Ki-67 and PCNA) were decreased. These findings suggest that continuous H₂ administration attenuates inflammation-associated early UVB carcinogenesis through modulation of the IL-6/STAT3 and ERK/JNK pathways, supporting its use as a chemopreventive approach. Full article

In recent years, significant increases in premature failures of rock bolts that are attributed to stress corrosion cracking (SCC) have been observed in underground reinforcement systems, which pose serious safety concerns for underground operations. A multitude of studies have focused on understanding the environmental factors, such as the composition of the corrosive medium, temperature, and humidity, in promoting the SCC of rock bolts, but the SCC failure mechanism associated with microstructural changes is still unclear due to the complexity of the underground environments. To understand its failure mechanism and develop effective mitigation strategies, this study evaluated different testing conditions, employing pin-loaded and bar-loaded coupon tests using representative specimens. The tests were conducted in an acidified sulfide solution. The failure characteristics and crack paths of the failed specimens were examined. It was observed that the steel with lower carbon content exhibited a reduced susceptibility to SCC. The subcritical cracks observed in the specimens were influenced by the microstructure of the material. SCC was observed not only on the original surface of rock bolts, which featured mill scale and decarburization, but also on freshly machined surfaces. Evidence for the occurrence of hydrogen-induced SCC was identified and discussed. The proposed testing methods and the obtained results contribute to a deeper understanding of SCC in rock bolts as well as promote the development of more durable materials for underground mining applications, ultimately enhancing the safety and reliability of rock bolt systems. Full article

Dry storage canisters of used nuclear fuels are fabricated using SUS 304L stainless steel. Chloride-induced stress corrosion cracking (CISCC) is one of the major failure modes of dry storage canisters. The cracked canisters can be repaired by friction stir welding (FSW), a low-heat input ‘solid-phase’ welding process. It is important to evaluate the ClSCC resistance of the friction stir welded material. Stress corrosion cracking (SCC) studies were carried out on mill-annealed base materials and friction stir welded 304L stainless U-bend specimens in 3.5% NaCl + 5 N H₂SO₄ solution at room temperature and boiling MgCl₂ solution at 155 °C. The engineering stress on the outer fiber of the FSW U-bend specimen was ~60% higher than that of the base metal (BM). In spite of the higher stress level of the FSW, both materials (FSW and BM) showed almost similar SCC failure times in the two different test solutions. The SCC occurred in the thermo-mechanically affected zone (TMAZ) of the FSW specimens in the 3.5% NaCl + 5 N H₂SO₄ solution at room temperature, while the stirred zone (SZ) was relatively crack-free. The failure occurred at the stirred zone when tested in the boiling MgCl₂ solution. Hydrogen reduction was the cathodic reaction in the boiling MgCl₂ solution, which promoted hydrogen-assisted cracking of the heavily deformed stirred zone. The emergence of the slip step followed by passive film rupture and dissolution of the slip step could be the SCC events in the 3.5% NaCl + 5 N H₂SO₄ solution at room temperature. However, the slip step height was not sufficient to cause passivity breakdown in the fine-grained SZ. Therefore, the SCC occurred in the partially recrystallized softer TMAZ. Overall, the friction-stirred 304L showed higher tolerance to ClSCC than the 304L base metal. Full article

This study investigated the mechanism by which fucoxanthin acts as a novel ferroptosis inducer to inhibit tongue cancer. The MTT assay was used to detect the inhibitory effects of fucoxanthin on SCC−25 human tongue squamous carcinoma cells. The levels of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and total iron were measured. Reverse transcription–quantitative polymerase chain reaction (RT−qPCR) and Western blotting were used to assess glutathione peroxidase 4 (GPX4), nuclear factor erythroid 2−related factor 2 (Nrf2), Keap1, solute carrier family 7 member 11 (SLC7A11), transferrin receptor protein 1 (TFR1), p53, and heme oxygenase 1 (HO−1) expression. Molecular docking was performed to validate interactions. Compared with the control group, the activity of fucoxanthin−treated SCC−25 cells significantly decreased in a dose− and time−dependent manner. The levels of MMP, GSH, and SOD significantly decreased in fucoxanthin−treated SCC−25 cells; the levels of ROS, MDA, and total iron significantly increased. mRNA and protein expression levels of Keap1, GPX4, Nrf2, and HO−1 in fucoxanthin−treated cells were significantly decreased, whereas levels of TFR1 and p53 were significantly increased, in a concentration−dependent manner. Molecular docking analysis revealed that binding free energies of fucoxanthin with p53, SLC7A11, GPX4, Nrf2, Keap1, HO−1, and TFR1 were below −5 kcal/mol, primarily based on active site hydrogen bonding. Our findings suggest that fucoxanthin can induce ferroptosis in SCC−25 cells, highlighting its potential as a treatment for tongue cancer. Full article

The natural product Kochiae Fructus (KF) is the ripe fruit of Kochia scoparia (L.) Schrad and is renowned for its anti-inflammatory, anticancer, anti-fungal, and anti-pruritic effects. This study examined the anticancer effect of components of KF to assess its potential as an adjuvant for cancer treatment. Network-based pharmacological and docking analyses of KF found associations with oral squamous cell carcinoma. The molecular docking of oleanolic acid (OA) with LC3 and SQSTM1 had high binding scores, and hydrogen binding with amino acids of the receptors suggests that OA is involved in autophagy, rather than the apoptosis pathway. For experimental validation, we exposed SCC-15 squamous carcinoma cells derived from a human tongue lesion to KF extract (KFE), OA, and cisplatin. The KFE caused SCC-15 cell death, and induced an accumulation of the autophagy marker proteins LC3 and p62/SQSTM1. The novelty of this study lies in the discovery that the change in autophagy protein levels can be related to the regulatory death of SCC-15 cells. These findings suggest that KF is a promising candidate for future studies to provide insight into the role of autophagy in cancer cells and advance our understanding of cancer prevention and treatment. Full article

The radiolysis of water is a significant cause of corrosion damage in the primary heat transport systems (PHTSs) of water-cooled, fission nuclear power reactors (BWRs, PWRs, and CANDUs) and is projected to be a significant factor in the evolution of corrosion damage in future fusion reactors (e.g., the ITER that is currently under development). In Part I of this two-part series, we reviewed the proposed mechanisms for the radiolysis of water and demonstrate that radiolysis leads to the formation of a myriad of oxidizing and reducing species. In this Part II, we review the role that the radiolysis species play in establishing the electrochemical corrosion potential (ECP) and the development of corrosion damage due to intergranular stress corrosion cracking (IGSCC) in reactor PHTSs. We demonstrate, that the radiolytic oxidizing radiolysis products, such as O₂, H₂O₂, HO₂⁻, and OH, when in molar excess over reducing species (H₂, H, and O₂²⁻), some of which (H₂) are preferentially stripped from the coolant upon boiling in a BWR PHTS, for example, renders the coolant in many BWRs oxidizing, thereby shifting the ECP in the positive direction to a value that is more positive than the critical potential (E_crit = −0.23 V_she at 288 °C) for IGSCC in sensitized austenitic stainless steel (e.g., Type 304 SS). This has led to many IGSCC incidents in operating BWRs over the past five decades that has exacted a great cost on the plant operators and electricity consumers, alike. In the case of PWRs, the primary circuits are pressurized with hydrogen to give a hydrogen concentration of 10 to 50 cm³/kgH₂O (0.89 to 4.46 ppm), such that no sustained boiling occurs, and the hydrogen suppresses the radiolysis of water, thereby inhibiting the formation of oxidizing radiolysis products from water. Thus, the ECP is dominated by the hydrogen electrode reaction (HER), although important deviations from the HER equilibrium potential may occur, particularly at low [H₂]. In any event, the ECP is displaced to approximately −0.85 V_she, which is below the critical potential for IGSCC in sensitized stainless steels but is also more negative than the critical potential for the hydrogen-induced cracking (HIC) of mill-annealed Alloy 600. This has led to extensive cracking of steam generator tubing and other components (e.g., control rod drive tubes, pressurizer components) in PWRs that has also exacted a high cost on operators and power consumers. Although the ITER has yet to operate, the proposed chemistry protocol for the coolant places it close to a BWR operating on Normal Water Chemistry (NWC) without boiling or, if hydrogen is added to the IBED-PHTS, close to a BWR on Hydrogen Water Chemistry (HWC). In the current ITER technology, the concentration of H₂ in the IBED-PHTS is specified to be 80 ppb, which is the concentration that will be experienced in both the Plasma Flux Area (PFA) and in the Out of Plasma Flux Area (OPFA). That corresponds to 0.90 cc(STP) H₂/KgH₂O, compared with 20–50 cc(STP) H₂/KgH₂O employed in a PWR primary coolant circuit and 5.5 to 22 cc(STP) H₂/KgH₂O in a BWR on hydrogen water chemistry (HWC). We predict that a hydrogen concentration of 80 ppb is sufficient to reduce the ECP in the OPFA to a level (−0.324 V_she) that is sufficient to suppress the crack growth rate (CGR) below the practical, maximum level of 10⁻⁹ cm/s (0.315 mm/a) at which SCC is considered not to be a problem in a coolant circuit but, in the PFA, the ECP is predicted to be 0.380 V_she, which gives a calculated standard CGR of 2.7 × 10⁻⁶ cm/s. This is more than three orders in magnitude greater that the desired maximum value of 10⁻⁹ cm/s. We recommend that the HWC issue in ITER be revisited to develop a protocol that is effective in suppressing both the ECP and the CGR in the PFA to levels that permit the operation of the IBED-PHTS in accordance with the experience gained in fission reactor technology. Full article

This work evaluates the impact of different organic acids on the corrosion sensitivity and stress-corrosion cracking (SCC) of NiCrMoV steam turbine steel. For all organic acids, potentiodynamic measurements shows linear relationships between corrosion rate and hydrogen proton concentration between pH 2.4 and 3.9. For solutions with the same pH, i.e., similar conductivity, the corrosion rate differs depending on the type of organic acid. The anodic dissolution in formic acid is the highest, followed by acetic, propanoic and nonanoic acid. The acid dissociation reaction is identified as the rate determining step in the corrosion process. Nonanoic acid, alternatively, clearly acts as a corrosion inhibitor. In situ four-point constant-extension tests in formic acid, acetic acid and nonanoic acid, at a pH value of 3.4 were performed to evaluate their impact on the SSC sensitivity. The general degradation followed the trend of the corrosion rate, although the synergetic effect of corrosion and stress resulted in a higher degradation depth. Though nonanoic acid induced little visible corrosion, still stress-corrosion cracks were still detected. It was shown that solutions of different organic acids with the same pH do not have the same influence on stress-induced degradation. Full article

Pipelines have been installed and operated around the globe to transport oil and gas for decades. They are considered to be an effective, economic and safe means of transportation. The major concern in their operation is corrosion. Among the different forms of corrosion, stress corrosion cracking (SCC), which is caused by stresses induced by internal fluid flow or other external forces during the pipeline’s operation, in combined action with the presence of a corrosive medium, can lead to pipeline failure. In this paper, an extensive review of different factors affecting SCC of pipeline steels in various environmental conditions is carried out to understand their impact. Several factors such as temperature, presence of oxidizers (O₂, CO_2, H₂S, etc.), composition and concentration of medium, pH, applied stress, and microstructure of the metal/alloy have been established to affect the SCC of pipeline steels. SCC susceptibility of a steel at a particular temperature strongly depends on the type and composition of the corrosive medium and microstructure. It was observed that pipeline steels with water quenched and quenched and tempered heat treatments, such as those that consist of acicular ferrite or bainitic ferrite grains, are more susceptible to SCC irrespective of solution type and composition. Applied stress, stress concentration and fluctuating stress facilitates SCC initiation and propagation. In general, the mechanisms for crack initiation and propagation in near-neutral solutions are anodic dissolution and hydrogen embrittlement. Full article

Hydrogen plays various roles in metals or at metal–environment interfaces. Well known effects on metals are hydrogen embrittlement, hydrogen enhanced local plasticity, hydrogen enhanced strain-induced vacancy, hydrogen accelerated oxidation, hydrogen-induced creep, and their synergy. In this study, the potential roles of hydrogen in materials degradation are demonstrated and studied by two different tests. One is the high temperature oxidation of Ni-based alloy in various environments with hydrogen penetration, and the other is the effects of neutron flux/fluence on the oxidation kinetics and SCC of 316L and 316LN stainless steels, regarding a possible role of transmuted H from N. The results emphasize that the hydrogen either permeated into metals from surrounding environments, such as high temperature water or gaseous hydrogen, or generated in metals by nuclei transmutation, such as hydrogen transmuted from N atoms in metals, which can promote metal oxidation through multiple mechanisms. Apparently, the oxidation/corrosion phenomenon is a synergy of sub-mechanisms. For instance, dissolved hydrogen (DH) is usually believed to slow down the corrosion process for lowering the open circuit potential (OCP). However, H also facilitates the transport of the cations in oxide, thereby accelerating the corrosion process. In this bi-mechanism system, two different, contradictory mechanisms work and exist simultaneously. Therefore, whether the metallic materials are benefited or degraded by the H during its oxidation process depends on which sub-mechanism is dominant. Namely, hydrogen can play the role an oxidant in the metal and metal/oxide interface to pre-oxidize metal elements, such as Cr, Ni, and Fe, and possibly promote inward oxygen diffusion and the oxidation rate at the interface. Moreover, hydrogen may play a role as a reductant in oxides where existing oxides can be reduced. Then, the protective capability of oxides will be decreased to result in corrosion acceleration at the metal–oxide interface. These phenomena were observed in Ni-based alloy and possibly austenitic stainless steel containing N such as 316LN SS. This work demonstrates a part of the role of hydrogen on oxidation, and more extensive and systematic work is needed to delineate the role of hydrogen on oxidation with and without irradiation. Full article

Low-alloy reactor pressure vessel steels have a rather low susceptibility to stress corrosion cracking (SCC) in a boiling water reactor (BWR) environment if the high-temperature water contains no anionic impurities. Recent investigations revealed that under oxidizing BWR normal water chemistry (NWC) conditions extremely small amounts of chloride, can cause very high SCC growth rates in these materials. Therefore, the effect of continuous and temporary chloride additions on the crack initiation behaviour was explored by a series of constant extension rate tensile (CERT) and constant load tests in high-temperature water. In an NWC environment, containing ≥2 ppb of chloride, strain-induced corrosion cracking (SICC) initiation occurred briefly after the onset of plastic yielding and at much smaller strains than in high-purity water. On the other hand, under reducing hydrogen water chemistry conditions with up to 700 ppb chloride, no SICC was detected up to very high strains. CERT experiments, with moderate short-term chloride transients before and during the loading, showed that even serious mechanical loading transients, one day after returning to high-purity water, did not result in early SICC initiation. Full article

The effect of SRB and applied potential on the stress corrosion sensitivity of X80 pipeline steel was analyzed in high-pH soil simulated solution under different conditions using a slow strain rate tensile test, electrochemical test, and electronic microanalysis. The experimental results showed that X80 pipeline steel has a certain degree of SCC sensitivity in high-pH simulated solution, and the crack growth mode was trans-granular stress corrosion cracking. In a sterile environment, the SCC mechanism of X80 steel was a mixture mechanism of anode dissolution and hydrogen embrittlement at −850 mV potential, while X80 steel had the lowest SCC sensitivity due to the weak effect of AD and HE; after Sulfate Reducing Bacteria (SRB) were inoculated, the SCC mechanism of X80 steel was an AD–membrane rupture mechanism at −850 mV potential. The synergistic effect of Cl⁻ and SRB formed an oxygen concentration cell and an acidification microenvironment in the pitting corrosion pit, and this promoted the formation of pitting corrosion which induced crack nucleation, thus significantly improving the SCC sensitivity of X80 steel. The strong cathodic polarization promoted the local corrosion caused by SRB metabolism in the presence of bacteria, whereby the SCC sensitivity in the presence of bacteria was higher than that in sterile conditions under strong cathodic potential. Full article

An electron-donating−accepting (D−A) molecule, namely, 4-(1-(4-(9H-carbazol-9-yl)phenyl)-1H-1,2,3-triazol-4-yl)benzo[c][1,2,5]thiadiazole (BT-SCC) containing carbazole as the donor moiety and benzothiadiazole as the acceptor moiety is prepared. Single-crystal X-ray structure analysis elucidated the multiple intermolecular interactions, such as hydrogen bonds, CH…π, and π…π interplays. Interestingly, the aggregation-induced emission phenomenon is observed for BT-SCC featured with enhanced fluorescent quantum yield from diluted solution of CH₂Cl₂ (Φ = ca. 0.1) to CH₂Cl₂/hexane mixed solutions or solid states (Φ = ca. 0.8). Finally, aggregates of BT-SCC are obtained through precipitating from hot and saturated solutions or solvent-vapor methods and the aggregating morphologies could be easily controlled through different preparation methods. Fabulous cube-like micro-crystals and nanospherical structures are obtained, which is established by the synergistic effects of the multiple non-covalent interactions, endowing potential utility in the field of optoelectronic devices. Full article

The review presented herein is regarding the stress corrosion cracking (SCC) phenomena of carbon steel pipelines affected by the corrosive electrolytes that comes from external (E) and internal (I) environments, as well as the susceptibility and tensile stress on the SCC. Some useful tools are presented including essential aspects for determining and describing the E-SCC and I-SCC in oil and gas pipelines. Therefore, this study aims to present a comprehensive and critical review of a brief experimental summary, and a comparison of physicochemical, mechanical, and electrochemical data affecting external and internal SCC in carbon steel pipelines exposed to corrosive media have been conducted. The SCC, hydrogen-induced cracking (HIC), hydrogen embrittlement, and sulfide stress cracking (SSC) are attributed to the pH, and to hydrogen becoming more corrosive by combining external and internal sources promoting cracking, such as sulfide compounds, acidic soils, acidic atmospheric compounds, hydrochloric acid, sulfuric acid, sodium hydroxide, organic acids (acetic acid, mainly), bacteria induced corrosion, cathodic polarization, among others. SCC growth is a reaction between the microstructural, chemical, and mechanical effects and it depends on the external and internal environmental sources promoting unpredictable cracks and fractures. In some cases, E-SCC could be initiated by hydrogen that comes from the over-voltage during the cathodic protection processes. I-SCC could be activated by over-operating pressure and temperature at flowing media during the production, gathering, storage and transportation of wet hydrocarbons through pipelines. The mechanical properties related to I-SCC were higher in comparison with those reviewed by E-SCC, suggesting that pipelines suffer more susceptibility to I-SCC. When a pipeline is designed, the internal fluid being transported (changes of environments) and the external environment concerning SCC should be considered. This review offers a good starting point for newcomers into the field, it is written as a tutorial, and covers a large number of basic standards in the area. Full article

To understand the effect of surface machining on the resistance of AISI 316L to SCC (stress–corrosion cracking) in marine environments, we tested nuts surface-machined by different methods in a seawater-spraying chamber. Two forms of cracks were observed: on the machined surface and underneath it. On the surface, cracks connected with the pitting sites were observed to propagate perpendicular to the hoop-stress direction, identifying them as stress–corrosion cracks. Under the surface, catastrophic transgranular cracks developed, likely driven by hydrogen embrittlement caused by the chloride-concentrating level of humidity in the testing environment. Under constant testing conditions, significantly different SCC resistance was observed depending on how the nuts had been machined. Statistical evaluation of the nut surface-crack density indicates that machining by a “form” tool yields a crack density one order of magnitude lower than machining by a “single-point” tool. Microstructural analysis of form-tool-machined nuts revealed a homogeneous deformed subsurface zone with nanosized grains, leading to enhanced surface hardness. Apparently, the reduced grain size and/or the associated mechanical hardening improve resistance to SCC. The nanograin subsurface zone was not observed on nuts machined by a single-point tool. Surface roughness measurements indicate that single-point-tool-machined nuts have a rougher surface than form-tool machined nuts. Apparently, surface roughness reduces SCC resistance by increasing the susceptibility to etch attack in Cl--rich solutions. The results of X-ray diffractometry and transmission electron microscopy diffractometry indicate that machining with either tool generates a small volume fraction (< 0.01) of strain-induced martensite. However, considering the small volume fraction and absence of martensite in regions of cracking, martensite is not primarily responsible for SCC in marine environments. Full article

The demand for pipeline steels has increased in the last several decades since they were able to provide an immune and economical way to carry oil and natural gas over long distances. There are two important damage modes in pipeline steels including stress corrosion cracking (SCC) and hydrogen induced cracking (HIC). The SCC cracks are those cracks which are induced due to the combined effects of a corrosive environment and sustained tensile stress. The present review article is an attempt to highlight important factors affecting the SCC in pipeline steels. Based on a literature survey, it is concluded that many factors, such as microstructure of steel, residual stresses, chemical composition of steel, applied load, alternating current (AC) current and texture, and grain boundary character affect the SCC crack initiation and propagation in pipeline steels. It is also found that crystallographic texture plays a key role in crack propagation. Grain boundaries associated with {111}∥rolling plane, {110}∥rolling plane, coincidence site lattice boundaries and low angle grain boundaries are recognized as crack resistant paths while grains with high angle grain boundaries provide easy path for the SCC intergranular crack propagation. Finally, the SCC resistance in pipeline steels is improved by modifying the microstructure of steel or controlling the texture and grain boundary character. Full article