Site-Specific Hydroxide Formation and Corrosion on Mg Nanocrystals.

The present study has been conducted to clarify the local corrosion of solid oxide at the slag surface where the dissolution of solid oxide into the slag results in the reduction of its surface tension through direct observation of the local corrosion in SiO2(s)-(FetO-SiO2) slags. The results obtained are as follows: (1) The major part of the local corrosion zone occurs in the meniscus region of the slags which is called “slag film”. (2) The film has two types of characteristic movement. One is a rotational movement around the specimen surface on the initial stage of the local corrosion of the rod specimen; Another is an up and down movement of the whole slag film all at once along the specimen surface on the developed stage of the local corrosion of the rod specimen, and on the whole stage of the corrosion of the prism specimen. (3) Linear rate of corrosion, dL/dt, at the most corroded portion in the local corrosion zone increases with increasing temperature and FetO content. dL/dt at the corner of the prism specimen is \sqrt2 times as large as that at the plane. In a word, the cross section of the prism specimen keeps a square during the whole stage of the corrosion. For the rod specimen. dL/dt decreases with increasing initial diameter of the specimen. (4) A mechanism of the local corrosion for the present slag system has been estimated qualitatively from the standpoints of the Marangoni effect of the slag film induced by the dissolution of the specimen into the slag, and the wetting between the specimen and slag.

Measurements of weight gains and film capacities of zirconium and zirconium alloys in steam and oxygen at atmospheric and high pressures are reported. At best, the behavior of resistant alloys and of Van Arkel zirconium in steam inhibited with boric acid is comparable to that of Van Arkel zirconium in oxygen. It is concluded that in steam, but not in oxygen, the pressure drop due to the flow of gas through porous oxide is a significant factor in the effects observed. Alloying elements, and also boric acid inhibition, decrease the film cracking or porosity which, with unalloyed zirconium, leads to very rapid corrosion in high‐pressure steam. With some more resistant materials there appears to be a compensation effect whereby films formed in high‐pressure steam are less porous than those formed at atmospheric pressure.Detailed topographical studies of the early stages of film growth and breakdown on Van Arkel zirconium in steam and in oxygen are described. In addition to uniform film growth, at rates varying with grain orientation, rapid localized attack is found in steam. Such attack is accelerated by an increase of pressure and appears to be diminished by additions of copper and by boric acid inhibition. This localized corrosion is considered to be due to the same type of film failure as is responsible for cracking or porosity in thicker, more uniform, films at a later stage of corrosion. The implications of the findings for the development of steam‐resistant alloys are considered.

Revisiting the effects of molybdenum and tungsten alloying on corrosion behavior of nickel-chromium alloys in aqueous corrosion

With the recent advances in the variational multiscale (VMS) methods, computational ow analysis in aerospace, energy, and transportation technologies has reached a high level of sophistication. It is bringing solutions in challenging problems such as the aerodynamics of parachutes, thermo-fluid analysis of ground vehicles and tires, and fluid-structure interaction (FSI) analysis of wind turbines. The computational challenges include complex geometries, moving boundaries and interfaces, FSI, turbulent flows, rotational flows, and large problem sizes. The Residual-Based VMS (RBVMS), Arbitrary Lagrangian-Eulerian VMS (ALE-VMS) and Space-Time VMS (ST-VMS) methods have been successfully serving as core methods in addressing the computational challenges. The core methods are supplemented with special methods targeting specific classes of problems, such as the Slip Interface (SI) method, MultiDomain Method, and the ST-C data compression method. We provide and overview of the core and special methods. We present, as examples of challenging computations performed with these methods, aerodynamic analysis of a ramair parachute, thermo-fluid analysis of a freight truck and its rear set of tires, and aerodynamic and FSI analysis of two back-to-back wind turbines in atmospheric boundary layer flow. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Computational flow analysis is now playing a key role in aerospace, energy and transportation technologies, bringing solution in challenging problems such as aerodynamics of parachutes, thermo-fluid analysis of ground vehicles and tires, and fluid–structure interaction (FSI) analysis of wind turbines. The computational challenges include complex geometries, moving boundaries and interfaces, FSI, turbulent flows, rotational flows, and large problem sizes. The Residual-Based Variational Multiscale (RBVMS), ALE-VMS and Space–Time VMS (ST-VMS) methods have been quite successful serving as core methods in addressing the computational challenges. The core methods are supplemented with special methods targeting specific classes of problems, such as the Slip Interface (SI) method, Multi-Domain Method, and the “ST-C” data compression method. We describe the core and special methods. We present, as examples of challenging computations performed with these methods, aerodynamic analysis of a ram-air parachute, thermo-fluid analysis of a freight truck and its rear set of tires, and aerodynamic and FSI analysis of two back-to-back wind turbines in atmospheric boundary layer flow.

A wide range of metals and minerals are currently used in battery and energy technology, meaning that an increasing number of these commodities are being considered as potentially viable primary products by the minerals industry. A select group of these minerals and elements that are vital for energy and battery technologies, including Al, Cr, Co, Cu, graphite, In, Li, Mn, Mo, the rare earth elements (REEs; primarily Dy and Nd), Ni, Ag, Ti, and V, are also likely to undergo rapid increases in demand as a result of the move toward low- and zero-CO2 energy and transportation technology (often termed the energy transition) driven by climate change mitigation and consumer and investor concerns and demands. Increased levels of mineral exploration, discovery, and production will be needed to meet this rising demand. However, several of these key metals and minerals are produced as co- and by-products of other elements. This means that their production is inherently linked to the production of main product elements that may not undergo similar increases in demand, creating issues related to security of supply. It is also not simple to just produce more metal and minerals given the environmental, social, and governmental challenges the global mining industry currently faces. Finally, there are uncertainties over exactly what technologies will dominate the energy transition, meaning that robust demand predictions are still relatively problematic. Quantifying these and other uncertainties and addressing issues over by-and coproduct supply will help ensure that mineral deposits are used sustainably. In addition, understanding the deportment and processing behavior of key critical metals and minerals that are produced as by- or coproducts of main metals such as copper will allow these to actually be extracted from mineral deposits being mined now and into the future rather than be lost to waste. Both of these are vital steps in terms of ensuring that future increases in metal and mineral demand can be met. The impact of these changes on metal and mineral demand and pricing also needs to be examined to ensure the economics of these changes relating to the energy transition are fully understood. All of this means that the mineral industry must act and plan for this transition accordingly in coordination with governments and other organizations. This is especially true given the long lead-in times related to the vast majority of mineral exploration and mining projects compared to the potentially rapid increase in demand for certain battery and energy metals and minerals. This is somewhat analogous to the technology sector, where software (analogous to battery and energy technology) can advance rapidly, creating significant demand that puts pressure on associated hardware (in this case, the development of new mines or changes in mineral processing) that advances more slowly. Failing to ensure mineral and metal supply meets increasing (and potentially rapidly varying) demand may lead to situations where demand far exceeds supply, causing preventable issues related to supply chain continuity and further delaying climate change mitigation, with potential global consequences.

The influence of copper upon the atmospheric corrosion of iron

With the development of the global economy and the increase in environmental awareness, energy technology in transportation, especially the application of energy storage technology in rail transportation, has become a key area of research. Rail transportation systems are characterized by high energy consumption and poor power quality due to the more flexible regulation capability of energy storage technology in these aspects. This paper summarizes the latest research results on energy storage in rail transportation systems, matches the characteristics of energy storage technologies with the energy storage needs of rail transportation, and analyzes the operation of energy storage systems in different scenarios. The adaptability of batteries, supercapacitors, and flywheels as energy storage systems for rail transportation is summarized and compared. The topologies and integration methods of various energy storage systems are studied. The control strategies under each control of rail transportation are summarized and proposed. The future development direction of energy storage system for rail transportation prospects and the corresponding reference is provided for the engineering of energy storage technology in the field of rail transportation.

Sensitized AA5083-H2 aluminum alloy was exposed to chloride-laden thin-film electrolyte at ambient temperature (20%–85% relative humidity) and the local Volta potential measured, in-situ and in real-time, using the Scanning Kelvin Probe Force Microscopy, with the intention to elucidate the earliest stage of localized corrosion. Positive Volta potentials vs alloy matrix were measured for magnesium silicides in ambient air, which, however, underwent a severe nobility loss during corrosion, causing their nobility to invert to active potentials (negative) relative to the alloy matrix. The reason for the nobility inversion was explained by the preferential dissolution of Mg2+, which resulted in an electropositive surface. Aluminides, both with and without silicon, were seen to form the main cathodes at all exposure conditions. The local alloy matrix next to closely-separated aluminides were seen to adopt the Volta potential of the neighbor aluminides, which, hence, resulted in local corrosion protection. The phenomenon of nobility adoption introduced in this work raises questions regarding the anode-to-cathode ratio, which was observed to change during corrosion, and the resulting impact to localized micro-galvanic corrosion. This work further demonstrates that it is necessary to measure the Volta potential during corrosion to reflect the true relationship between the Volta potential and corrosion potential or breakdown potential.

Aluminium alloy 2024-T3 (AA2024-T3), widely applied in aerospace industries, may suffer from severe localized corrosion as a result of its relatively complex and heterogeneous microstructure. The corrosion initiation in such a critical alloy is governed by dynamic processes that take place at the nanoscale. A thorough understanding of the sequential stages of corrosion initiation is of pivotal importance to developing efficient inhibition strategies and demands high resolution techniques along with the ability of real-time recording of nanoscopic events.However, to date, it has not yet been possible to unambiguously show the morphological and electrochemical characteristics during local corrosion of AA2024-T3. In particular, local corrosion initiation linked to nano-/microstructural heterogeneities, intermetallic particles (IMPs), take place relatively fast and at the nanoscopic scale, rendering the study of the early stages of corrosion experimentally virtually impossible until now. Herein, we show, for the first time, the dynamic evolution of site-specific local corrosion of AAs from early surface initiation to depth propagation at the nanoscale using a dedicated in-situ liquid phase-transmission electron microscopy (LP-TEM) experimental facility.Transmission electron microscopy (TEM), capable of revealing microstructural and compositional variations in alloys at atomic and nanoscopic scale, has been applied widely in corrosion studies but mostly ex-situ and quasi in-situ. These approaches are not straightforward as artefacts and contaminations might be introduced into the system during the ex-situ and quasi in-situ experiments, including dehydration of surfaces and therefore may not fully represent the real conditions. With recent technological advances, thanks to the development of dedicated microelectronic mechanical systems (MEMS), it is now possible to fabricate components like nanoreactors (NRs) to study complicated corroding systems at the nanoscale in-situ. In fact, NRs employed in TEM studies enable to monitor morphological and compositional evolutions in materials in-situ as a result of interaction with aggressive environments like a gas or liquid.In this study, we put efforts into providing direct evidence for the nanoscopic role of intermetallics in AA2024-T3 localized corrosion through quasi in-situ TEM and in-situ LP-TEM approaches. Quasi in-situ studies were implemented by intermittently exposing the Argon ion-milled thin samples to 0.01 M NaCl solution. For in-situ LP-TEM, the real TEM specimens (lamellae) were first fabricated out of regions of interest with a FEI Helios focused ion beam. Then, the lamellae were transferred successfully to home-made NRs using an easy-lift technique. The NRs, equipped with an electrochemical set-up, were specially designed for corrosion studies. A Cs-corrected FEI Titan TEM was employed to perform real-time studies in scanning TEM (STEM) mode. Although a good resolution is still a major challenge for in-situ LP-TEM, the results revealed that intermetallic phases regardless of their types are active and prone sites to localized corrosion attack themselves and the observations finally show and elucidate initial stages of IMP-induced pitting corrosion and copper redistribution mechanisms in AA2024-T3.

Modified electrochemical emission spectroscopy (MEES) As technique of NDT for detection localized corrosion of copper alloys in seawater

Modified electrochemical emission spectroscopy (MEES) as NDT technique for detecting localized corrosion of copper alloys in seawater

Soil is a complex environment where various forms of localized corrosion could occur on buried metal structures such as pipelines. Protective coatings and cathodic protection (CP) are widely applied as principal means of protecting buried steel pipeline from soil corrosion, unfortunately coating defects and disbondment could create some complex environmental conditions for localized corrosion to initiate and propagate. Stray currents could also cause dynamic and rapid localized corrosion on buried pipelines. This paper summarizes typical results and first-hand experiences from recent work aimed at developing corrosion probes based on an electrochemically integrated multi-electrode arrays for monitoring and understanding complex forms of localized corrosion on buried pipelines. Experimental and field testing results have demonstrated the capability of the probes to be used in laboratory research and field conditions. Evidence found on localized corrosion under disbonded coatings and stray currents illustrate some of the unique advantages of the electrode array method for visualizing and understanding localized corrosion of buried steels. It also briefly discusses needs for future work to enhance the reliability of corrosion probes as a structural health monitoring tool for early detection and diagnosis of corrosion, for providing industrial system ‘health’ alarm, for forecasting maintenance requirements, and for generating data for integrated and automated corrosion management systems.

The corrosion fatigue behavior of magnesium alloy influenced by corrosion inhibitors with the differentiated inhibition mechanisms

The effects of inclusions on localized corrosion of Zr–Ti deoxidized low-alloy steels in marine environment were investigated by various analytical techniques including scanning electron microscopy with X-ray microanalysis (SEM/EDS), confocal Raman microscopy (CRM), and in situ scanning vibrating electrode technique (SVET). It was found that complex (Zr, Ti, Al)-Ox inclusions were responsible for the initiation of localized corrosion. Localized corrosion preferentially occurred at Fe matrix adjacent to these inclusions and formed micro-gaps. In the early stage of corrosion, catalytic-occluded cells and the diffusion of chloride ions played a major role in the propagation of corrosion, further accelerating the dissolution of Fe matrix and (Zr, Ti, Al)-Ox inclusions. Combining SVET and CRM results, it revealed that the maximum anodic current density in local area gradually decreased with prolonged exposure time, indicating that corrosion products covered the steel surface and lowered the propagation rate of corrosion. In the later stage of corrosion, the barrier effect of corrosion products played an important role in inhibiting localized corrosion.