Corrosion Pits Research Articles

Role of Cl/F Ions Concentration, pH and Temperature on Pitting Corrosion Behavior of 2507 Duplex Stainless Steel

In the chemical industry, 2507 duplex stainless steel is usually used for the pipes of absorption tower. The residual F− and Cl− in the tail gas could aggregate in the clean solution of ammonium hydroxide, which causes the risk of pitting corrosion. In this study, the role of Cl/F ions concentration, pH and temperature on the pitting corrosion of 2507 stainless steel is investigated by exposing to actual industrial ammonia desulfurization solution. The experimental results reveal that the 2507 stainless steel exposed the serious corrosion solution appears pitting corrosion problem. However, the 2507 stainless steel is free of pitting corrosion at the tested condition of pH value 3.59/5, temperature 80 °C/100 °C, and ion concentration 46375 ppm/80000 ppm. This study provides a fundamental data for the safety service of stainless steel used in chemical industry.

Corrosion of calcite speleothems in epigenic caves of Moravian Karst (Czech Republic)

Corrosion processes were studied in epigenic caves of the Moravian Karst (MK). Samples of naturally corroded speleothems and carbonate rocks collected in various MK caves were compared with limestone and calcite standards that were corroded under well-controlled conditions in the laboratory. Two stages of corrosion were distinguished: (1) an early stage of pitting and linear corrosion predisposed by point and line defects in the standards, and (2) an advanced stage characterized by deep corrosion of the entire standard surface. During the second stage, the internal structure of the corroded substrate remained partially preserved, however, if the water was extremely aggressive, the corrosion progressed to depth en-bloc regardless of the structure. In this paper, we (1) proposed a new corrosion mechanism based on the binding of aqueous calcium by clays and tested it experimentally in the cave, (2) characterized conditions that generally favor the formation of aggressive waters (water undersaturated with calcite) into seven categories incorporating them into a conceptual model of the karst vertical profile, and (3) discussed anthropogenic influences on these processes.

ATLAS 316, ATLAS 316L, ATLAS 316H

Abstract Atlas 316 is a chromium-nickel-molybdenum austenitic stainless steel, second only to Atlas 304 in commercial importance. The molybdenum gives Atlas 316 better overall corrosion resistant properties than type 304 austenitic stainless steel, particularly higher resistance to pitting and crevice corrosion in chloride environments. It is readily brake or roll formed, welded, soldered, and cut by both thermal and mechanical methods. The austenitic structure gives excellent toughness, even down to cryogenic temperatures. Atlas 316L, the low carbon version of Atlas 316, is highly resistant to sensitization (grain boundary carbide precipitation) and so is extensively used in heavy gauge welded components; about 5 mm, 0.2 in., and over. Atlas 316H, with its higher carbon content, has some application at elevated temperatures, as does stabilized type 316Ti. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as heat treating, machining, and joining. Filing Code: SS-1365. Producer or source: Atlas Steels.

Fatigue of Bridge Steel Wire: A Corrosion Pit Evolution Model under the Effects of Wind and Vehicles

To investigate the damage evolution behavior of corroded steel wires under the influence of alternating loads, a damage evolution model for steel wires based on the theory of continuous damage mechanics was established. The damage evolution process at corrosion pits was simulated by using the element birth and death technique in ANSYS 2020R2. Then, a certain cable-stayed bridge was chosen as the research subject, the stress–time data of the sling were computed using a traffic–bridge–wind simulation analysis model, and the influence of corrosion pit distribution on the mechanical properties and fatigue life of wires under an alternating load was discussed. The results show that, in comparison to single-pitted steel wires, double-pits distributed circumferentially across the cross-section of the steel wires lead to more severe stress concentration, accelerating the damage evolution process and significantly reducing the fatigue life of the steel wires. Conversely, the stress concentration caused by double pits distributed along the longitudinal direction of steel wire is similar to that caused by single pits, and it will be even weaker than that caused by single pits with the change in the relative distance of the double pits. Based on the calculation results of the damage evolution model of steel wire, it was found that the corrosion pit crack nucleation life of steel wire under alternating load accounts for nearly 80% of the fatigue life of steel wire, and different corrosion pit distribution modes will significantly affect the fatigue life of steel wire.

Galvanic Corrosion of E690 Offshore Platform Steel in a Simulated Marine Thermocline

Marked changes in temperature, pH, dissolved oxygen (DO) content, and nutrient content typically occur in marine thermoclines, which are key factors that affect the corrosion of metals. Offshore platforms require marine metals to be exposed to deep-sea environments and thus increase their penetration into the marine thermocline. This study investigates the galvanic corrosion of E690 steel in a marine thermocline using a simulated marine thermocline (SMT). Specifically, the corrosion of E690 steel was analyzed using the wire beam electrode (WBE) technique, linear polarization (LP), corrosion morphology, and weight loss measurement. Results indicated that the SMT had a stable multilayer structure, and the variations in temperature, DO, pH, and nutrient concentration in the SMT were similar to those in the natural marine thermocline. There were two forms of E690 steel corrosion in the SMT: galvanic corrosion and seawater corrosion. The corrosion rate of seawater corrosion was influenced by the DO concentration. Galvanic corrosion occurred after the intrusion of E690 steel into the marine thermocline. The driver of galvanic corrosion was the difference values for Ecorrs of E690 steel at various depths of the marine thermocline. The Ecorr of E690 steel was influenced by the temperature, pH, and DO of the seawater, in the following order: DO >> T > pH. The continuous reduction in Ecorr with depth contributed to large-scale galvanic corrosion, and the oscillation variation in Ecorr with depth was the reason for small-scale galvanic corrosion. The primary anodic regions of galvanic corrosion were located in the area with the fastest temperature variation in the thermocline, and the position of the anodic regions rose with time. The anodic regions gradually expanded with time. The proportion of galvanic corrosion in the average corrosion rate could increase up to approximately 80% in the stable anodic region. There were many hemispherical corrosion pits on the surface of the single electrodes that were at the depths of 75 cm, 105 cm, and 135 cm. These single electrodes comprised a long-term, sustainable anodic region of galvanic corrosion.

Influence of corrosion on ultra-low cycle fatigue performance of steel butt-welded joints with various welding methods

Preferential corrosion of welded joints in steel structures has been observed in a wide range of scenarios and should receive enough attention. The current work focuses on the corrosion and ultra-low cycle fatigue (ULCF) behavior of low-alloy steel weld joints. Firstly, 1600 h neutral salt spray (NSS) tests were conducted on welded joints made by different welding methods, and then topography scanning of corrosion pits was carried out. It was found that the welded region is more susceptible to corrosion. Dynamic polarization curves of the welded joints were measured, and the results show that the self-corrosion potential of the welded region is lower than that of the base metal (BM) region, while the corrosion current density is higher than that of the BM region. Subsequently, cyclic tests were carried out on the corroded weld joints. The results show that corrosion can cause a maximum reduction of 11.79% in yield load and 20.87% in ultimate load of the welded joints. Corrosion has slight influence on the energy dissipation capacity of welded joints, but the maximum reductions in ULCF life could reach 77.31% due to corrosion. Fractography analysis further shows that secondary cracks, map cracks, and intergranular brittle fracture, apart from more common fatigue fracture, ductile fracture, and quasi-cleavage fracture, appear on the fracture surfaces. Supplementary numerical simulation was conducted to enable a better understanding of the failure processes. In the simulation, a geometric modeling method using topography scanning data of corrosion surface was proposed. By using the proposed modeling approach, together with Chaboche cyclic plasticity constitutive model and cyclic void growth model (CVGM) for capturing fracture behavior, the predicted results show an acceptable agreement with the experimental ones.

Fatigue performance and alternate coupling mechanism of ZL114A aluminum alloy under corrosion-fatigue alternating

This paper investigates the fatigue performance of ZL114A cast aluminum alloy through laboratory corrosion-fatigue alternating test conducted under simulated tropical marine humid-hot atmosphere. The study examines the impact of different alternating frequency on the fatigue properties of the aluminum alloy. At the same time, the micro morphology of the specimen surface and fatigue fracture were observed, and the damage mechanism under the alternating action of corrosion-fatigue was analyzed. The concept of ‘fatigue impact factor’ in alternating test was proposed to reflect the effect of fatigue on corrosion in alternating process. The results show that the increase of alternating frequency leads to an extended fatigue life for the alloy, following a power function relationship. Pitting is identified as the primary form of corrosion damage on specimen surfaces, with multi-crack initiation observed in fatigue fractures. It is found that the fatigue impact factor exponentially increases with each alternating cycle during testing. In early alternating cycles of test, the presence of fatigue inhibits corrosion by promoting passivation of corrosion pits; however, in later alternating cycles, propagation of fatigue cracks accelerates growth in size for these corrosion pits which subsequently promotes further corrosion.

Effect of corrosion pit distribution of rebar on pore, and crack characteristics in concrete

This research paper delves into the impact of corrosion-induced changes, particularly pit distribution, on pore structures and crack propagation in concrete subjected to galvanostatic accelerated corrosion. Two samples with different pit configurations were investigated—one with larger and spread pits, the other with smaller and localized ones. Various characterizations methods were applied including X-ray Computed Tomography (CT), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDS), and Raman spectroscopy. The 3D CT images reveals dynamic changes in pore volumes, pit expansion, emergence of new pores at cement-aggregate interfaces, and distinctive crack formation patterns. Image analysis accurately quantifies corrosion products, highlighting their dependence on pit presence and characteristic. The sample with larger pit volume experiences exclusive initial formation of iron hydroxides, while small pit volume contains both iron oxides and hydroxides simultaneously. Raman spectroscopy shows the dynamic interplay of iron oxides and hydroxides, marking an evolution from oxides to hydroxides within the cement paste. Crack formation analysis reveals distinct patterns in samples with high pit dispersion, including cracks originating from pores near reinforcing bar pits, larger cracks diffusing corrosion products outward, and zipper cracks emerging from distant interconnected pores. Conversely, low pit content sample exhibits a different crack pattern with varying origins and narrower apertures. The temporal evolution of cracks in this sample appears simultaneous, possibly linked to ongoing corrosion processes. Elemental mapping indicates elevated corrosion product volumes within and around cracks, possibly due to water migration into the concrete matrix. These insights deepen our understanding of concrete deterioration mechanisms, guiding strategies to enhance structural integrity and durability in critical infrastructure.

Enhancing tribo-mechanical, microstructural morphology, and corrosion performance of AZ91D-magnesium composites through the synergistic reinforcements of silicon nitride and waste glass powder

The present investigation has employed recycled waste glass powder (WGP) and silicon nitride (Si3N4) as reinforcing-agents within AZ91D-matrix composites. The composites were fabricated by employing the vacuum stir casting technique to mitigate the effects of oxidation and to ensure homogeneity, uniformity, and superior wettability among the AZ91D-matrix and reinforcements. A microscopic study provided confirmation of a uniform dispersion of WGP and Si3N4 particles throughout the AZ91D-matrix. The tensile strength of the AZ91D/WGP/Si3N4 composites rise with the inclusion of WGP particulates by up to 1.5 percent in AZ91D/7.5% Si3N4. However, the tensile strength of the AZ91D/9%Si3N4 composite have showed maximum value as compared to other chosen formulations/combinations in the current investigation. The tensile strength of AZ91D/1.5% WGP/7.5% Si3N4 composites has strengthened up to 12.13 percent with the comparison of base alloy AZ91D-matrix. In A1 formulated composite, the amount of WGP particulate has enhanced the hardness of the AZ91D-alloy by up to 1.5 percent. Findings, nevertheless has exhibited that the A6 formulated composite had superior outcomes in terms of hardness. The incorporation of “reinforcing-constituent particulates” with 1.5%WGP + 7.5%Si3N4 combination within the AZ91D-matrix, has further increased fatigue-strength by around 57.84 percent. A weight-loss of 0.312 mg was being unveiled for the A1 formulated fabricated composite. The weight-loss for the A6 formulated fabricated composite, however, was reported to be 0.294 mg. At 5 N loads, 2 m/s sliding speed, and 1000 m of sliding distance, the developed 1.5%WGP/7.5%Si3N4/AZ91D composites was reported to have a rate of wear, and frictional coefficient of 0.0025 mm3/m and 0.315, respectively. The investigation employing scanning electron microscopy (SEM) identified the presence of corrosion pits on the surfaces that had undergone corrosion. These pits were found to be a result of localised surface assaults occurring in corrosive environments. Additionally, SEM pictures of the worn surfaces indicated the emergence of microcracks, which may be associated to the conditions of cyclic loading. Moreover, the tensile-fractography examination for the developed 1.5%WGP/7.5%Si3N4/AZ91D composites has exhibited the brittle fracture failure, including cracks and debonding phenomena. In addition, the EDS spectra-analysis have revealed an apparent existence of the observed Mg-peak, Si-peak, Al-peak, Ca-peak, and O-peak for the 1.5%WGP/7.5%Si3N4/AZ91D composites. Furthermore, the utilisation of X-ray diffraction analysis effectively determined the existence of hard phases inside the AZ91D-matrix, which significantly contributed to the reported enhancement in wear resistance. The development of harder-phases has included, α-Mg, Al12Mg17, SiO2, Si3N4, MgO, and CaO phases within the composite has been accountable for the enhancement of the tribomechanical, and wear-resistance characteristics of the AZ91D/WGP/Si3N4 composites. The Si3N4 has been discovered to have a substantial impact on enhancing mechanical performance and raising the resistance to wear.

Trends in Longer-Term Corrosion Loss of Magnesium Alloys

The corrosion of magnesium alloys is often considered to differ in behaviour and development with time from most other metals and alloys because they show evolution of hydrogen right from first exposure. However, data extracted from the open literature indicate that magnesium alloys develop corrosion mass-loss trends with time that are consistent with the so-called bimodal pattern, which is topologically similar to those of other alloys. Examples are given of such trending for magnesium alloys under immersion, half-tide and various atmospheric exposure conditions. The critical roles of corrosion pitting and its development into localised corrosion are discussed. For high-purity magnesium alloys, the transition to longer-term corrosion, which is rate-controlled by the hydrogen evolution cathodic reaction, occurs quickly, within days. Comments are made about the application of measurements of hydrogen evolution and of electrochemical methods to make rapid estimates of shorter-term corrosion rates.

Study on the mechanism and correlation of double-pit pitting in ductile iron IN625 laser cladding layer

With its excellent strength and toughness, ductile iron is widely utilized in marine applications, including ship propellers, rudders, ship cabin pumps, valves, and pipes. Laser cladding is an emerging environmentally-friendly surface-strengthening technology. Numerous corrosion pits on the cladding layer surface accelerate the corrosion failure process. It is of great significance to quantitatively reveal the evolution of microscopic corrosion transients on the cladding layer and to analyze the interaction mechanism between adjacent corrosion pits. In this article, a cladding layer of IN625 was prepared on the surface of QT600 ductile iron. The microscopic morphology and Energy Dispersive Spectroscopy (EDS) were used to observe the cladding layer. The relationship among ion concentration, ion migration, pH, electrode potential and corrosion rate was analyzed by numerical simulation. Electrochemical corrosion experiments were conducted using the CorrTest electrochemical workstation. The results show that the IN625 cladding layer can effectively improve the corrosion resistance of QT600 ductile iron. The polarization curves show that the corrosion current density decreases by two orders of magnitude, and the corrosion rate decreases by 395.5 times after laser cladding. This study can provide new ideas and methods to enhance the service performance enhancement of ductile iron laser cladding layers in marine environments.

Investigation on the Corrosion Resistance of 3003 Aluminum Alloy in Acidic Salt Spray under Different Processing States

3003 aluminum alloy exhibits commendable corrosion resistance, ease of processing, and good formability, rendering it extensively utilized across many industrial sectors. In this study, the corrosion behavior of 3003 aluminum alloy in a homogenized state and after hot extrusion deformation in an acidic salt spray environment for different times was studied. The microstructure of the 3003 aluminum alloy in the homogenized state and after hot extrusion was characterized using scanning electron microscopy (SEM), optical microscope (OM), laser scanning confocal microscope (LSCM) etc., while electrochemical methods were employed to study the difference in corrosion resistance between these two states. The results show that corrosion pits on the surface of the homogenized 3003 aluminum alloy increase with time, and corrosion extends along the second phase arrangement, while the hot extruded 3003 aluminum alloy mainly exhibits corrosion pit extension. The grain size of the homogenized 3003 aluminum alloy is larger than that of the hot extruded state, and the second phase is distributed in a reticular pattern. Hot extrusion deformation ensures not only a uniform distribution of the second phase in the 3003 aluminum alloy but also a reduced grain size, an increased grain boundary density, a heightened electrochemical activity in acidic environments, and an augmented pitting density. Compared with the homogenized 3003 aluminum alloy, the pitting density, maximum pitting depth, and weight loss of the hot extruded state are increased.

Analytical modeling of particle size effect on impact wear deformation characteristics of ductile materials

AbstractThis study aims to analytically predict the material impact wear rate and improve the prediction accuracy and applicability of existing impact wear prediction models. The ABAQUS software was used to numerically model and analyze the erosion pit morphology and stress distribution characteristics. Micromorphological testing was used to investigate the impact wear damage mechanism, and an improved impact wear prediction model was developed by introducing the particle size. The results show that the maximum von Mises stress in the impact area of the target material can reflect the severity of the damage to the target material. The peak stress varies with the impact angle. The target material significantly absorbs the energy of small particles at higher impact angles and large particles at vertical impacts. The depth of the hardened layer resulting from particle impact increases from 3 to 10 μm with increasing impact angle. When the impact angle is unchanged, the depth of the hardened layer increases by 3% to 5% with an increase in particle size. The hardened layer limits further plastic deformation of the metal material. Comparing the analysis results with the experimental results reveals that the proposed formula that uses the size factor can predict the volume loss of plastic metallic materials with different particle sizes, impact angles, and impact velocities more accurately.

Study on corrosion characteristics of reinforcing bars in concrete under industrial SO2 environment

Sulfur dioxide (SO2) is the primary pollutant in industrial atmospheres, leading to significant damage to industrial buildings. The corrosion caused by SO2 in concrete, including neutralization and solid phase volume expansion, poses particular concerns. However, there is a lack of research on the electrochemical behaviour and corrosion mechanisms of reinforcing bars embedded in concrete. This study conducted indoor simulations of reinforced concrete specimens exposed to industrial SO2 corrosion utilizing an SO2 testing chamber. The corrosion behavior of the reinforcing bars was monitored through half-cell potential, weak polarization, and electrochemical impedance spectroscopy (EIS). Additionally, the corrosion mechanisms of the reinforcing bars under SO2 exposure were investigated using scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), X-ray diffraction (XRD), and Raman spectra. The results demonstrated a consistent correlation between variations in corrosion potential (Ecorr) and corrosion current density (icorr) of steel rebars in different types of concrete. The corrosion rates of the reinforcing steel in C1 (w/b=0.57), C2 (w/b=0.47), and C3 (w/b=0.37) concrete exceeds 0.1 μA/cm2 after 42, 72, and 90 days of SO2 corrosion, respectively. At this time, the ratio of the depth of neutralization to the thickness of the protective layer is 0.51–0.65. The rust exhibits a layered structure with a presence of S elements adsorbed and deposited on the surface of the rust layer. Moreover, the research has identified the accumulation of S elements within corrosion pits, which can be attributed to localized acidification reactions. The rust products identified include iron hydroxide (FeOOH), and iron oxide (Fe2O3), rozenite (FeSO4·4 H2O). The formation of FeSO4·4 H2O in corrosion pits suggests that significant localized corrosion on the surface of reinforcing bars in concrete under the impact of SO2.

Corrosion at the Steel–Medium Interface

Corrosion on the interface between a metal alloy, such as steel, and a wet, permeable non-metallic medium is of considerable practical interest. Examples include the interface between steel and water, the atmosphere or concrete, as for steel reinforcement bars; between metal and soil, as for buried cast iron or steel pipes; deposits of some type, as in under-deposit corrosion; and the interface with insulation, protective coatings, or macro- or micro-biological agents. In all cases, corrosion initiation depends on the characteristics of the interfacial zone, both of the metal and the medium, and the spatial variability. For (near-)homogeneous semi-infinite media with good interfacial contact, the pitting, crevices and general corrosion of the metal will be largely controlled by the metal (micro-)characteristics, including its inclusions, imperfections and surface roughness. In other cases, these may be overshadowed by the macro-characteristics of the medium and the degree of interfacial contact, possibly with severe resulting corrosion. Where the build-up of corrosion products can occur at the interface, they will dominate longer-term corrosion and govern the long-term corrosion rate. For media of finite thickness, diffusion issues and material deterioration may also be involved. The practical implications are outlined. It is argued that with the presence of a suitable medium, it is possible to achieve negligible long-term corrosion but only if certain practical actions are taken.

Corrosion behavior and magnetocaloric property of pure phase La1-xCexFe11.5Si1.5 (x=0.1,0.2,0.3) compounds

To further study the corrosion mechanism of pure phase La(Fe,Si)13, Ce were added into the LaFe11.5Si1.5 compounds to facilitate phase formation and improve corrosion resistance and magnetic properties. The corrosion test conducted on the pure phase La1-xCexFe11.5Si1.5 (x = 0.1, 0.2, 0.3) revealed a significant number of minute corrosion pits with irregular shapes such as round, square and triangular after only 1 h of corrosion in tap water. However, in the case of La0.7Ce0.3Fe11.5Si1.5 compound, the number of corrosion pits was significantly lower. Potentiodynamic polarization curves showed that Ecorr goes up from −0.76 V to −0.59 V, and the Icorr goes down from 4.92 × 10−6 A/cm2 to 2.46 × 10−6A/cm2 as a result of Ce addition from 0.1 to 0.3. With the increase of Ce content, the corrosion resistance of La1-xCexFe11.5Si1.5 compounds was improved. Adding Ce element in the LaFe11.5Si1.5 compounds can also enhance the magnetocaloric effect. Significant extra spike-shaped peaks were observed on the M-H curves of La0.8Ce0.2Fe11.5Si1.5 and La0.7Ce0.3Fe11.5Si1.5, indicating a strong first-order magnetic phase transition. Furthermore，-△SM values improved from 21.2 J/kg K to 51.6 J/kg K by increasing Ce from 0.1 to 0.3.

Experimental Investigation of the Evolution Process of Suspended Pipelines through River Bottoms under Unsteady Flow Conditions

One of the major geological hazards that can cause harm to long-distance oil and gas pipelines are water-induced disasters. These disasters are quite common and widespread. Pipelines that cross river channels are at a higher risk of facing damage due to flood-induced erosion. To shed light on the evolution pattern of riverbeds adjacent to pipelines under the influence of unsteady flow conditions, a flume model test was conducted, and the underlying mechanisms of local scour were elucidated. The experimental results demonstrate that pipelines are more susceptible to suspension during flood conditions. The suspension process of pipelines under flood conditions could be broadly divided into five stages. In comparison to constant flow conditions, the evolution process of local scour and the suspension of pipelines under unsteady flow lacked the erosion pit expansion stage, and the scour duration was shorter. Each stage exhibited distinct erosion characteristics, and both the peak flow rate and the number of flood peaks significantly impacted the maximum range and depth of the erosion pit. During pipeline-laying projects, selecting a covering layer with a larger particle size can enhance the erosion resistance of the riverbed around the pipeline. The study of the local erosion process of underwater crossing pipelines under unstable flow conditions can provide a reference for pipeline engineering design and riverbed pipeline protection strategies.

Study of erosion wear to concrete by different gravel particle sizes: Laboratory test and numerical simulation

Concrete bridge piers face relentless erosion from Wind Gravel Flow (WGF) in Lanzhou–Xinjiang High–Speed Railway, resulting in pronounced wear on their surfaces, which could potentially induce additional structural defects. This study aims at the erosion wear performance and its corresponding damage mechanisms in concrete under WGF, using the airborne sandblasting method as a tool for this analysis. The study suggests that the Concrete Erosion Rate (CER) intensifies parallel to increases in both erosion angle and wind speed. Low angle erosion predominantly causes surface damage through cutting, while high angle erosion results in erosion pits and cracks. Notably, CER initially rises but eventually stabilizes with varying erosion times. A widened gravel particle size interval leads to a consistent reduction in the CER, but it concurrently heightens the likelihood of erosion caused by individual gravel particles on the concrete surfaces. An expanded gravel particle size interval results in a considerable increase in both the size and depth of erosion pits on the concrete surface. On the other hand, a narrowed particle size interval contributes to a significant upsurge in the number of erosion pits, causing the CER to diminish as the particle size interval increases. A novel model adapted for concrete exposed to the windy conditions of the Gobi has been developed. The model’s accuracy has been substantiated via numerical simulations, which illustrates that an uptick in erosion wind speed considerably boosts the airflow velocity around the concrete sample. In contrast, the pressure distribution on the surface steadily decreases from the center to the periphery. As erosion wind speed increases, airflow velocity and surface pressure around the concrete specimen rise significantly. Furthermore, the surface pressure of concrete increases with a broader gravel particle size interval. In conclusion, this study provides a strong scientific and theoretical underpinning for the protection of concrete bridge piers in the wind–prone Gobi regions.

Study on the ablation behavior of C/SiC composite materials under the action of local structural thermal sources

This study uses ablation testing on C/SiC composite materials under local structured thermal sources with a wide range of heat flux densities, simulating the harsh local conditions caused by discontinuous structural interference on spacecrafts. The thermal response, ablation laws, and ablative perforation time of C/SiC composite materials are obtained under different heat flux densities. The experimental findings demonstrate that there are notable differences in the morphology of the ablation pits under various heat flux conditions. As the heat flux density increases, the temperature of the local structure heat source action center on the target surface increases, the depth and outer diameter of the erosion pits increase, and the wall surface of the erosion pits gradually tends to be smooth. Under the influence of local structural heat sources, the creation of material ablation pits and the process of material perforation are predicted using the improved Umeshmotion+ALE+birth and death element method. For various conditions, the temperature field results and ablation morphology are well predicted by the numerical simulation results. Numerical calculations can be used to analyze the thermal stress and oxidation sublimation contribution rates of targets under the action of structural heat sources.

Quantifying the influence of microstructure on the corrosion of Mg-Li alloys by using X-ray CT

The microstructure of multi-component Mg-Li alloys played a decisive role in their corrosion properties due to the potential differences between the matrix and the secondary phases. In this study, the effects of secondary phases (AlLi, AlX(Gd, Y, Mn), and Mg2Sn) on the corrosion behavior of Mg-Li alloys have been quantified by using in situ X-ray CT. The microstructure-property correlation was established between the type, morphology, distribution, and dimensions of the secondary phases and the microscopic corrosion behavior. The corrosion parameters, such as average equivalent diameter, distance, number density, and volume fraction of the secondary phases and corrosion pits, were quantified as a function of corrosion time. The dominating secondary phase was identified by combining SKPFM analysis and electrochemical testing, giving quantitative information on corrosion control by designing secondary phases.