Hydrogen gas bubble nucleation from corrosion of steel in compacted bentonite

<p>The reference concept for the deep geological disposal of spent fuel and high-level radioactive waste in Switzerland foresees carbon steel disposal canisters surrounded by compacted bentonite buffer material. In support of performance assessments, long-term in-situ corrosion experiments were conducted in Opalinus Clay at the Mont Terri Underground Research Laboratory (URL) in Switzerland, wherein carbon steel coupons were embedded in MX-80 bentonite. The preparation of the steel specimens and bentonite, the exposure in a sealed borehole in the URL, and the retrieval, dismantling and imaging of specimens were conducted under strictly anoxic conditions. Samples were removed for analysis after exposure durations of 372, 628, 1024, and 2008 days. A key finding was the development of visible reddish-brown corrosion fronts around the metal surfaces and along shrinkage cracks that extend up to approximately 0.5 cm into the bentonite. Iron that originated from the corroded surface was transported along the cracks and precipitated as Fe-hydroxides due to oxygen sorbed on bentonite.</p><p>The formation of shrinkage cracks is thought to result from a local desaturation of the bentonite near the steel surface. To test this hypothesis i.e., to test the likelihood of a separate gas phase forming in addition to hydrogen mass dissolved in liquid water, it is necessary to evaluate the fate of hydrogen in the bentonite adjacent to the steel surface. For this, a flow and transport numerical model of the steel coupon surface and surrounding bentonite was implemented for the simulation of hydrogen release with the simultaneous consumption of water at the steel surface. The effect of single- and (potentially) two-phase flow with the diffusive and advective transport of the hydrogen and water components in the gas and liquid phases were modelled in a fully coupled manner. The numerical simulations were performed probabilistically in a Monte Carlo framework to account for parametric uncertainty, comprising 1’000 perturbations of all flow and transport parameters used in the model for the bentonite.</p><p>Overall, the simulation results are consistent with the hypothesis of a link between cracks observed in the bentonite and a temporary formation of a gas phase that results in preferential pathways for the transport of iron corrosion products.  The probability of gas formation in the model lies between 89% and 94% at the steel-bentonite interface and decreases significantly at distance of 1 cm from the steel coupon. Peak gas saturation at the steel-bentonite interface ranges up to approximately 1% with a mean value of approximately 0.18%. In all simulations, any gas phase forming in the bentonite dissolves back into the liquid phase within 300 days.</p>

ANTI-CORROSION PERFORMANCE OF 2-ISONICOTINOYL-N-PHENYLHYDRAZINECARBOTHIOAMIDE FOR MILD STEEL HYDROCHLORIC ACID SOLUTION: INSIGHTS FROM EXPERIMENTAL MEASUREMENTS AND QUANTUM CHEMICAL CALCULATIONS

The corrosion inhibition performance of novel synthesized thiosemicarbazide derivative namely, 2-isonicotinoyl-N-phenylhydrazinecarbothioamide (IPC) on the mild steel coupon surface in 1[Formula: see text]M hydrochloric acid solution is investigated by weight loss measurements. The adsorption parameters of the IPC on the mild steel coupon surface have been evaluated and the surface morphology of the tested mild steel is studied by scanning electron microscope (SEM) technique. The results of this study demonstrate a significant inhibitor (IPC) for mild steel and showed the highest inhibitive efficiency of 96.3% at 5[Formula: see text]mM as optimum studied inhibitor concentration. The adsorption of IPC molecules on a mild steel coupon surface is obeyed completely by the model of Langmuir adsorption isotherms. SEM has been applied to analyse the layer of IPC molecules which formed on a mild steel coupon surface as a protective layer. The inhibition efficiency (IE) of IPC from weight loss techniques and SEM analysis was harmonic with each other. The Density Functional Theory (DFT) computations have been applied to evaluate the adsorption sites of the IPC molecules and the quantum chemical calculations correlation of IPC molecules with methodological results are discussed. The energy of the highest occupied molecular orbital (EHOMO) shows a significant tendency of the IPC molecules to donate pairs of electrons to the iron atoms on the surface of mild steel. The energy of the lowest unoccupied molecular orbital (ELUMO) for IPS molecules reveals a high tendency to accept electrons from iron atoms on the surface of mild steel.

Corrosion Investigation of Mild Steel in Aqueous Hydrochloric Acid Environment Using N-(Naphthalen-1-yl)-1-(4-Pyridinyl)Methanimine Complemented with Antibacterial Studies

The inhibitive performance of N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine Schiff base on mild steel corrosion in one molar hydrochloric acid environment was investigated by utilizing weight loss techniques. N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine has significant inhibitive performance on the mild steel corrosion in the corrosive medium. The effect of immersion time (1-24 h) and temperature (303 to 333 K) on the behavior of mild steel corrosion in the absence and presence of the N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine have also been investigated. The adsorption of N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine molecules on the surface of mild steel follows Langmuir adsorption isotherm. The surface morphology of the mild steel coupon was investigated by scanning electron microscopy. The antibacterial efficiencies of N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine for gram-negative bacteria, namely Escherichia coli, and gram-positive bacteria, namely Staphylococcus aureus was studied. The antibacterial activity findings exhibited that the N-(naphthalen-1-yl)-1-(4-pyridinyl)methanimine has significant antibacterial efficiencies against tested microorganisms.

Performance Assessment of Ship Hull Metal in Seawater Media

This research was undertaken to determine the effects of corrosion on material performance using mild steel and Aluminum as selected material in seawater media. The result from the experiment showed higher corrosion rate in uncoated mild steel coupon as higher corrosion rate ranges from 0.0494 mmpy, 0.0565 mmpy, and 0.0656 mmpy was evident, while a reduction in corrosion rate from 0.0369mmpy, 0.0432 mmpy and 0.0452mmpy was observed in the fourth week, fifth week and sixth week. Corrosion rate for coated mild steel ranges from 0.0396 mmpy in the first week and reduces to 0.0333 mmpy and continually reduces to 0.0206 mmpy in the sixth week. From the hardness testing device using MITECH 320, uncoated Mild steel metal specimen gave an average Brinell hardness reading of 112 before immersion and 105 after immersion to seawater. Also, the tensile strength of the uncoated mild steel specimen deteriorated from 414 Mpa before immersion to 403Mpa after immersion to seawater media. Also, uncoated Aluminum specimen gave a brinell average reading of 163 before immersion and 152 after immersion to the seawater media. Likewise, the tensile strength result of the aluminum specimen gave 776M pa before immersion and 744 Mpa after immersion to the seawater media. The overall result from weight loss technique and metal hardness using MITECH 320 showed aluminum metal is more resistive to corrosion attack.

Effectiveness of a Novel Rechargeable Polycationic N-Halamine Antibacterial Coating on Listeria monocytogenes Survival in Food Processing Environments

ABSTRACT The goal of this research was to evaluate the efficacy of a novel rechargeable nonleaching polycationic N-halamine coating applied to stainless steel food contact surfaces to reduce Listeria monocytogenes contamination on ready-to-eat (RTE) foods. Four L. monocytogenes strains were inoculated onto the charged (C; chlorine activated) or noncharged (NC) N-halamine–coated steel coupon surfaces that were either intact or scratched. After inoculation, test surfaces were incubated at 2, 10, and 25°C for 0, 48, and 72 h. L. monocytogenes transfer from coated adulterated surfaces to RTE meat (beef sausages and roast beef) was also tested at 2°C. L. monocytogenes on both intact-C and scratched-C surfaces was significantly reduced at all temperatures; however, in the presence of organic material, these coatings were more effective for reducing L. monocytogenes at 2 and 10°C than at 25°C (P < 0.05). In contrast, on NC intact and scratched surfaces, reduction at 25°C increased (P < 0.05), decreasing the difference in L. monocytogenes levels between charged and noncharged intact and scratched surfaces at this temperature. Overall, greater L. monocytogenes reduction was achieved on intact-C and scratched-C (4.1 ± 0.19 log CFU/cm2) than on intact-NC and scratched-NC (2.3 ± 0.19 log CFU/cm2) surfaces at all temperatures (P < 0.05). The combination of surface condition and chlorine with coupons exposed for 2 h at 2°C in the presence of an organic load (50% meat purge) did not significantly affect the bactericidal efficacy of the N-halamine coating. Regarding transfer to RTE meat, an overall 3.7-log reduction in L. monocytogenes was observed in sausages and roast beef. These findings suggest that a novel rechargeable N-halamine coating on stainless steel surfaces can inactivate L. monocytogenes. HIGHLIGHTS

Benzylidene as Efficient Corrosion Inhibition of Mild Steel in Acidic Solution

A New benzylidene derivative namely benzylidene-5-phenyl-1,3,4-thiadiazol-2-amine (BPTA), was successfully synthesized and characterized using Fourier Transform Infrared Spectroscopy, Nuclear Magnetic Resonance and elemental analysis (CHN) techniques. The inhibition efficiency of BPTA on mild steel corrosion in 1.0 N HCl was tested at various temperatures. The methodological work was achieved by gravimetric method complemented with morphological investigation. The concentrations of inhibitor were 0.1, 0.2, 0.3, 0.4 and 0.5 mM at the temperatures 303, 313, 323 and 333 K. The BPTA, molecules as become superior corrosion inhibitor with 92% inhibition efficiency of mild steel coupon in the acidic environment. The inhibition efficiency increased with increasing concentrations of BPTA and the excellent efficiency was performed with the 0.5 mM concentration and followed with 0.4 mM. In acidic environment, the 0.5 and 0.4 mM gave the optimum performance with weight loss technique and scanning electron microscopy analysis. On the other hand, the inhibition efficiency decreased with the increase of temperature. Results of BPTA indicated mixed type inhibitor and the adsorption on the mild steels surface obeys the Langmuir adsorption isotherm. It was found that the BPTA performance depend on the concentration and the solution temperature. Quantum chemical calculations have been done to correlate the electronic characteristics of BPTA with the corrosive inhibitive impact. Experimental and theoretical results are in good agreement.

Experimental and Theoretical Approach to the Corrosion Inhibition of Mild Steel in HCl Solution by a Newly Coumarin

New coumarin namely 2-(3-(7-methylcoumarin)acetamido)benzoic acid (MAB) was successfully synthesized by reaction of ethyl 2-(7-methylcoumarin)acetate with anthranilic acid. The chemical structure of MAB was confirmed by FT-IR, NMR spectroscopies and Elemental Analysis. The inhibition performance of MAB was investigated using the weight loss method. The results illustrate the strong adsorption of MAB molecules on the mild steel coupon surface and this adsorption follows the Langmuir adsorption isotherm. DFT calculations were performed to show the relationship between the MAP molecular structure and inhibition performance.

Biocorrosion Inhibitory Potential of Aqueous Extract of Phyllanthus amarus against Acid Producing Bacteria

Biocorrosion is a form of corrosion of metallic and concrete materials mediated by microorganisms. Acid producing bacteria are major culprits in the corrosion of materials in the environment. This study focused on the inhibition of biocorrosion by acid producing bacteria using aqueous extract of Phyllanthus amarus (PAAE). Acid producing bacteria were isolated from produced water samples collected from oilfields located in Niger Delta, Nigeria. Multiple fermentation tube technique was adopted for the isolation of the acid producing bacteria using phenol red dextrose broth as culture broth medium. The gravimetric analysis was performed with different concentrations of the plant extract incorporated in universal culture bottles containing broth, sample and carbon steel coupon. The setup was incubated at 20ºC, 30ºC and 40ºC for 7 days and for 14 days. The least corrosion rate (CR) at 20ºC, 30ºC and 40ºC for the 7 days test were 1.446mp/y (80mg/ml PAAE); 27.558mp/y (5 mg/mlLeu+20 mg/ml PAAE) and 5.134 mp/y (80 mg/ml PAAE) with corresponding inhibition efficiency (IE) of 81.92, 87.750 and 80.91 respectively. For the 14 days, the CR values at 20ºC, 30ºC and 40ºC were: 3.192mp/y (5mg/mlLeu+20mg/ml PAAE); 1.458 mp/y (5 mg/mlLeu + 20 mg/ml PAAE) and 117.345mp/y (5 mg/mlLeu + 20 mg/ml PAAE) with corresponding IE of 86.09, 83.87 and 98.89 respectively. The results obtained show that the extract could be considered as a good inhibitor for the biocorrosion of carbon steel mediated by acid producing bacteria.

Environmental Evidence for and Genomic Insight into the Preference of Iron-Oxidizing Bacteria for More-Corrosion-Resistant Stainless Steel at Higher Salinities

ABSTRACTIron-oxidizing bacteria (FeOB) are some of the initial colonizing organisms during microbially influenced corrosion of steel infrastructure. To better understand the abiotic conditions under which FeOB colonize steel, an environmental study was conducted to determine the effects of salinity, temperature, dissolved oxygen levels, and steel type on FeOB colonization. Stainless steel (304 and 316 [i.e., 304SS and 316SS]) was used to determine the potential susceptibility of these specialized corrosion-resistant steels. Steel coupon deployments along salinity gradients in two river systems revealed attachment by FeOB at all sites, with greater abundance of FeOB at higher salinities and on 316SS, compared to 304SS. This may be due to the presence of molybdenum in 316SS, potentially providing a selective advantage for FeOB colonization. A novelZetaproteobacteriaspecies,Mariprofundus erugo, was isolated from these stainless steel samples. Genes for molybdenum utilization and uptake and reactive oxygen species protection were found within its genome, supporting the evidence from our FeOB abundance data; they may represent adaptations of FeOB for colonization of surfaces of anthropogenic iron sources such as stainless steel. These results reveal environmental conditions under which FeOB colonize steel surfaces most abundantly, and they provide the framework needed to develop biocorrosion prevention strategies for stainless steel infrastructure in coastal estuarine areas.IMPORTANCEColonization of FeOB on corrosion-resistant stainless steel types (304SS and 316SS) has been quantified from environmental deployments along salinity gradients in estuarine environments. Greater FeOB abundance at higher salinities and on the more-corrosion-resistant 316SS suggests that there may be a higher risk of biocorrosion at higher salinities and there may be a selective advantage from certain stainless steel alloy metals, such as molybdenum, for FeOB colonization. A novel species of FeOB described here was isolated from our stainless steel coupon deployments, and its genome sequence supports our environmental data, as genes involved in the potential selectiveness toward surface colonization of stainless steel might lead to higher rates of biocorrosion of manmade aquatic infrastructure. These combined results provide environmental constraints for FeOB colonization on anthropogenic iron sources and build on previous frameworks for biocorrosion prevention strategies.