Incentives for Using LEIM in the Investigation of Corrosion Initiation on Organic Coated Alloys

Numerical Models ◽

Physical Phenomenon ◽

Product Formation ◽

Coated Metal ◽

Aqueous Environments ◽

Damage Process ◽

Experimental Process ◽

Measurement Artifact ◽

AbstractLocal electrochemical impedance mapping and spectroscopy (LEIM/S) have become important tools for the investigation of local electrochemical breakdown events associated with the degradation of organically coated metals in aqueous environments. LEIM/S of organic coated metal substrates has revealed local degradation events that are distributed spatially and temporally. These observations provide support to a number of long-standing theories, as well as provide new insight into the damage process. The local changes in impedance observed at early stages of immersion support the presence of virtual pores, while the metastability of impedance peaks representing the local changes provide evidence of healing via corrosion product formation. Each of these are long-standing theories used to explain global electrochemical impedance measurements. This paper will provide an overview of some of the events observed using LEIM and examine these results in the context of recent analytical and numerical models. Models used to predict the electric field above an equipotential disk electrode support the interpretation of most experimental LEI data as being representative of chemical and physical phenomenon and not a result of measurement artifact. However, certain features may be an artifact of the finite nature of the experimental process. The interpretation of LEIM events in view of current experimental and modeling results will be discussed.

A Brief Insight into Microbial Corrosion and its Mitigation with Eco-friendly Inhibitors

Journal of Bio- and Tribo-Corrosion ◽

10.1007/s40735-021-00563-y ◽

2021 ◽

Vol 7 (3) ◽

Author(s):

M. Lavanya

Keyword(s):

Wide Spectrum ◽

Present Review ◽

Electrochemical Reactions ◽

Microbial Corrosion ◽

Engineering Applications ◽

Microbially Influenced Corrosion ◽

Catastrophic Failures ◽

Chemical Strategies ◽

AbstractCorrosion results from the electrochemical reactions between the metal and its existing environment. Corrosion results in severe and expensive damage to a wide spectrum of industries. When microbes are involved in corrosion it is seldom possible to economically evaluate its impact. Microbially influenced corrosion is recognized to cause catastrophic failures contributing to approximately 20% of the annual losses. In many engineering applications, microbially influenced corrosion control is of prime importance. Expensive, toxicity and sometimes, even ineffectiveness of the current chemical strategies to mitigate microbially influenced corrosion have shifted the interest towards eco-friendly inhibitors. The present review discusses microbial induced corrosion in various metals and its inhibition through eco-friendly inhibitors. In addition, the study also reviews the morphological and electrochemical impedance results.

The Detection And Mapping Of Defects In Organic Coatings Using Local Electrochemical Impedance Methods

MRS Proceedings ◽

10.1557/proc-411-31 ◽

1995 ◽

Vol 411 ◽

Author(s):

S. R. Taylor ◽

M. W. Wittmann

Keyword(s):

Organic Coatings ◽

Single Frequency ◽

Probe Design ◽

Coating Failure ◽

Local Electrochemical Impedance Spectroscopy ◽

Physical Defects ◽

Steel Substrates ◽

ABSTRACTCoating failure initiates as a local event at defects which can result from chemical heterogeneities in the resin or physical defects such as bubbles, underfilm deposits, or pinholes. The ability to detect, map the location, as well as make quantitative in-situ measurements of coating heterogeneities will help identify the source of failure (i.e. coating chemistry, method of application, cure schedule, etc.) and provide insight into the mechanisms of coating degradation. This study used a 5 electrode arrangement to perform local electrochemical impedance spectroscopy (LEIS) on coated steel substrates. Using single frequency measurements, LEIS could successfully detect and map both intentional chemical heterogeneities and physical defects such as subsurface bubbles, underfilm deposits, and pinholes. Efforts to optimize probe design and instrumentation are ongoing.

Potentiometric C2H4-Selective Detection on Solid-State Sensors Activated with Bifunctional Catalytic Nanoparticles

Chemosensors ◽

10.3390/chemosensors9100274 ◽

2021 ◽

Vol 9 (10) ◽

pp. 274

Author(s):

Fidel Toldra-Reig ◽

Jose Manuel Serra

Keyword(s):

Solid State ◽

Impedance Analysis ◽

Selective Detection ◽

Catalyst Nanoparticles ◽

Cross Sensitivity ◽

Car Exhaust ◽

Catalytic Nanoparticles ◽

Oxidation Properties ◽

This work presents a solid-state ionic-based device to selectively detect C2H4 in car exhaust gases. The sensor consists of 8YSZ as the electrolyte and two electrodes: Fe0.7Cr1.3O3/8YSZ and LSM/8YSZ. The main aim of this work is to optimize the catalytic behavior of the working electrode to C2H4 and reduce cross-sensitivity toward CO and H2O. Several catalyst nanoparticles were infiltrated to tailor C2H4 adsorption and electrochemical oxidation properties while diminishing adsorption and conversion of other gas components such as CO. The infiltrated metal catalysts were selected, taking into account both adsorption and redox properties. Infiltration of Ti or Al, followed by a second infiltration of Ni, enabled the selective detection of C2H4 with low cross-sensitivity toward CO and H2O in a moist gas environment. Further insight into potentiometric C2H4 sensing is achieved by electrochemical impedance analysis of the electrodes activated with bifunctional catalysts.

How atmospheric escape sculped the evolution of the Martian CO2 atmosphere over time

10.5194/epsc2021-599 ◽

2021 ◽

Author(s):

Manuel Scherf ◽

Herbert Lichtenegger ◽

Sergey Dyadechkin ◽

Helmut Lammer ◽

Raven Adam ◽

...

Keyword(s):

Numerical Models ◽

Atmospheric Escape ◽

Ion Escape ◽

Thermal Escape ◽

Partial Pressures ◽

Argon Isotopes ◽

Atmospheric Loss ◽

4.1 Ga ◽

Insight Into ◽

Volcanic Outgassing

Mars likely had a denser atmosphere during the Noachian eon about 3.6 to 4.0 billion years ago (Ga). How dense this atmosphere might have been, and which escape mechanisms dominated its loss are yet not entirely clear. However, non-thermal escape processes and potential sequestration into the ground are believed to be the main drivers for atmospheric loss from the present to about 4.1 Ga. To evaluate non-thermal escape over the last ~4.1 billion years, we simulated the ion escape of Mars' CO2 atmosphere caused by its dissociation products C and O atoms with numerical models of the upper atmosphere and its interaction with the solar wind (see Lichtenegger et al. 2021; https://arxiv.org/abs/2105.09789). We use the planetward-scattered pick-up ions for sputtering estimates of exospheric particles including 36Ar and 38Ar isotopes, and compare ion escape, with sputtering and photochemical escape rates. For solar EUV fluxes &#8805;3 times the present-day Sun (earlier than ~2.6 Ga) ion escape becomes the dominant atmospheric non-thermal loss process until thermal escape takes over during the pre-Noachian eon (earlier than ~4.0 - 4.1 Ga). If we extrapolate the total escape of CO2-related dissociation products back in time until ~4.1 Ga, we obtain a theoretical equivalent to CO2 partial pressure of more than ~3 bar, but this amount did not necessarily have to be present and represents a maximum that could have been lost to space within the last ~4.1 Ga. Argon isotopes can give an additional insight into the evolution of the Martian atmosphere. The fractionation of 36Ar/38Ar isotopes through sputtering and volcanic outgassing from its initial chondritic value of 5.3, as measured in the 4.1 billion years old Mars meteorite ALH 84001, until the present day can be reproduced for assumed CO2 partial pressures between ~0.2-3.0 bar, depending on the cessation time of the Martian dynamo (assumed between 3.6-4.0 Ga) - if atmospheric sputtering of Ar started afterwards. The later the dynamo ceased away, the lower the pressure could have been to reproduce 36Ar/38Ar. Prior to ~4.1 Ga (i.e., during the pre-Noachian eon), thermal escape should have been the most important driver of atmospheric escape at Mars, and together with non-thermal losses, might have prevented a stable and dense CO2 atmosphere during the first ~400 million years. Our results indicate that, while Mars could have been warm and wet at least sporadically between ~3.6-4.1 Ga, it likely has been cold and dry during the pre-Noachian eon (see also Scherf and Lammer 2021; https://arxiv.org/abs/2102.05976).

Microhomology Selection for Microhomology Mediated End Joining in Saccharomyces cerevisiae

Genes ◽

10.3390/genes10040284 ◽

2019 ◽

Vol 10 (4) ◽

pp. 284 ◽

Cited By ~ 3

Author(s):

Kihoon Lee ◽

Jae-Hoon Ji ◽

Kihoon Yoon ◽

Jun Che ◽

Ja-Hwan Seol ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Budding Yeast ◽

Product Formation ◽

Dna Breaks ◽

End Joining ◽

Base Pairs ◽

Circular Chromosome ◽

Proximal Side ◽

Selection For ◽

Microhomology-mediated end joining (MMEJ) anneals short, imperfect microhomologies flanking DNA breaks, producing repair products with deletions in a Ku- and RAD52-independent fashion. Puzzlingly, MMEJ preferentially selects certain microhomologies over others, even when multiple microhomologies are available. To define rules and parameters for microhomology selection, we altered the length, the position, and the level of mismatches to the microhomologies flanking homothallic switching (HO) endonuclease-induced breaks and assessed their effect on MMEJ frequency and the types of repair product formation. We found that microhomology of eight to 20 base pairs carrying no more than 20% mismatches efficiently induced MMEJ. Deletion of MSH6 did not impact MMEJ frequency. MMEJ preferentially chose a microhomology pair that was more proximal from the break. Interestingly, MMEJ events preferentially retained the centromere proximal side of the HO break, while the sequences proximal to the telomere were frequently deleted. The asymmetry in the deletional profile among MMEJ products was reduced when HO was induced on the circular chromosome. The results provide insight into how cells search and select microhomologies for MMEJ in budding yeast.

Fatigue Failure Behaviour Study of Automotive Lower Suspension Arm

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.462-463.796 ◽

2011 ◽

Vol 462-463 ◽

pp. 796-800 ◽

Cited By ~ 1

Author(s):

Nawar A. Kadhim ◽

Shahrum Abdullah ◽

Ahmad Kamal Ariffin ◽

S.M. Beden

Keyword(s):

Finite Element ◽

Fatigue Life ◽

Numerical Models ◽

Good Alternative ◽

Analysis Tool ◽

Element Analysis ◽

Finite Element Software ◽

Life Model ◽

Experimental Process ◽

Behaviour Study

Fatigue life of automotive lower suspension arm has been studied under variable amplitude loadings. In simulation, the geometry of a sedan car lower suspension arm has been used. To obtain the material monotonic properties, tensile test has been carried out and to specify the material mechanical properties of the used material, a fatigue test under constant amplitude loading has been carried out using the ASTM standard specimens. Then, the results used in the finite element software to predict fatigue life has been evaluated later to show the accuracy and efficiency of the numerical models which they are appreciated. The finite element analysis tool is therefore proved to be a good alternative prior to the further experimental process. The predicted fatigue life from the simulation showed that Smith-Watson-Topper model provides longer life than Morrow and Coffin-Manson models. This is due to the different consideration for each strain-life model during life calculations.

Using electrochemical impedance spectroscopy to predict the corrosion resistance of unexposed coated metal panels

Progress in Organic Coatings ◽

10.1016/j.porgcoat.2009.04.009 ◽

2009 ◽

Vol 66 (1) ◽

pp. 8-34 ◽

Cited By ~ 33

Author(s):

F. Louis Floyd ◽

Sundaresan Avudaiappan ◽

Jason Gibson ◽

Bhaumik Mehta ◽

Pauline Smith ◽

...

Keyword(s):

Corrosion Resistance ◽

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Coated Metal ◽

Metal Panels

Low frequency bottom reverberation in a Pekeris waveguide with Lambert’s rule

Journal of Computational Acoustics ◽

10.1142/s0218396x16500016 ◽

2016 ◽

Vol 24 (02) ◽

pp. 1650001 ◽

Cited By ~ 5

Author(s):

Michael A. Ainslie ◽

Dale D. Ellis ◽

Chris H. Harrison

Keyword(s):

Analytical Solutions ◽

Time Window ◽

Numerical Models ◽

Low Frequency ◽

University Of Texas ◽

Pulse Transmission ◽

Approximate Analytical Solutions ◽

Pekeris Waveguide ◽

The University ◽

The requirement by modern navies to predict sonar performance in shallow water, whether for use in research, planning or operations, led to an initiative for the validation of reverberation models in the form of two Reverberation Modeling Workshops at the University of Texas at Austin in November 2006 and May 2008 [J. S. Perkins and E. I. Thorsos, Update on the reverberation modeling workshops, J. Acoust. Soc. Am. 126 (2009) 2208]. The problem considered here (Problem XI, from the 2006 workshop) requires the computation of reverberation versus time in a Pekeris waveguide with Lambert scattering from the seabed. Results from eigenray, normal mode and (hybrid) continuum methods are presented and compared for the time window 0.05[Formula: see text]s to 1000[Formula: see text]s after pulse transmission. Approximate analytical solutions are used to provide insight into the expected behavior of the reverberation and establish regimes of validity of numerical models. In situations where the regimes of validity of different methods coincide, the solutions of models applying these methods overlap. The overlapping solutions agree with each other within ±[Formula: see text]0.3[Formula: see text]dB. Their purpose is to provide a baseline against which future model improvements can be assessed and quantified.

A Method for Calibrating Deterministic Forecasts of Rare Events

Weather and Forecasting ◽

10.1175/waf-d-11-00074.1 ◽

2012 ◽

Vol 27 (2) ◽

pp. 531-538 ◽

Cited By ~ 11

Author(s):

Patrick T. Marsh ◽

John S. Kain ◽

Valliappa Lakshmanan ◽

Adam J. Clark ◽

Nathan M. Hitchens ◽

...

Keyword(s):

Density Function ◽

Rare Events ◽

Numerical Models ◽

Kernel Density ◽

Spatial Error ◽

Error Characteristics ◽

Probabilistic Forecasts ◽

Insight Into ◽

Kernel Density Function

Abstract Convection-allowing models offer forecasters unique insight into convective hazards relative to numerical models using parameterized convection. However, methods to best characterize the uncertainty of guidance derived from convection-allowing models are still unrefined. This paper proposes a method of deriving calibrated probabilistic forecasts of rare events from deterministic forecasts by fitting a parametric kernel density function to the model’s historical spatial error characteristics. This kernel density function is then applied to individual forecast fields to produce probabilistic forecasts.

Discrete Element Modelling of Sedimentation and Tectonics: Implications for the Growth of Thrust Faults and Thrust Wedges in Space and Time, and the Interpretation of Syn-Tectonic (Growth) Strata

Frontiers in Earth Science ◽

10.3389/feart.2021.742204 ◽

2021 ◽

Vol 9 ◽

Author(s):

Stuart Hardy ◽

Nestor Cardozo

Keyword(s):

Numerical Models ◽

Element Model ◽

Discrete Element ◽

Thrust Fault ◽

Discrete Element Modelling ◽

Thrust Faults ◽

Growth Strata ◽

Modelling Studies ◽

Mountain Belts ◽

Thrust faults, and thrust wedges, are an important part of the surface morphology and structure of many contractional mountain belts. Analogue models of thrust wedges typically provide a map- and/or side-view of their evolution but give limited insight into their dynamic development. Numerical modelling studies, both kinematic and mechanical, have produced much insight into the various controls on thrust wedge development and fault propagation. However, in many studies, syn-tectonic sediments or “growth strata” have been modelled solely as passive markers and thus have no effect on, or do not feedback into, the evolving system. To address these issues, we present a high-resolution, 2D, discrete element model of thrust fault and wedge formation and the influence that coeval sedimentation may have on their evolution. We use frictional-cohesive assemblies, with flexural-slip between pre-defined layers, to represent probable cover rheologies. The syn-tectonic strata added during contraction are frictional-cohesive and we can think of them as “mechanical growth strata” as they interact with, and influence, the growing thrust wedge. In experiments of thrust wedge development without syn-tectonic sedimentation, a forward-breaking sequence is seen: producing a typical thrust-wedge geometry, consistent with analogue and numerical models. In general, the inclusion of syn-tectonic sedimentation produces thrust wedges composed of fewer major forward-vergent thrusts and with only minor thrust activity in the foreland. In most of these models the sequence of thrust activity is complex and not simply forward-breaking. With increasing sedimentation, the frontal thrust has much greater displacement and overrides a much thicker package of earlier syn-tectonic sediments. Very high syn-tectonic sedimentation results in the formation of a single basin-bounding thrust fault and no thrust-wedge per se. At the local (outcrop) scale of individual fault-related folds, high syn-tectonic sedimentation alters fault-fold evolution by producing steeper ramps, whereas low syn-tectonic sedimentation allows shallower ramps that may flatten and propagate into the syn-tectonic strata. Implications of these results for the interpretation of thrust faults and wedges and their interaction with associated growth strata are discussed.