Corrosion Mode Research Articles

Angiogenesis-osteogenesis coupling and anti-osteoclastogenesis zoledronate intermixed calcium silicate metal-organic/inorganic hybrid coating on biodegradable zinc-based intramedullary nails for osteoporotic fracture healing

Osteoporotic (OP) fractures remain a tough clinical challenge owing to their impaired healing outcome, which requires novel biomaterials with osteogenicity for effective healing. Metallic zinc (Zn) is attracting increasing attention for biodegradable intramedullary nails (IMNs) for OP fracture healing thanks to their comprehensive mechanical properties, biosafety, and bioactivity. However, the multiple biofunctions required for OP fracture healing have not been fully met by Zn. Herein, a zoledronate (ZA)-mediated calcium-zinc silicate (Ca(Zn)Si) metal-organic/inorganic hybrid coating was fabricated on Zn-based IMN by coordination chemistry driven via interactions between ZA and Ca2+/Zn2+ as well as in-situ directional growth of Ca(Zn)Si phase. The ZA&Ca(Zn)Si hybrid coating exhibited a homogeneous micro/nanostructure with a granular morphology, which prevented premature fracture failure of IMN in rat femur by ameliorating corrosion mode and decreasing degradation rate of the Zn matrix. More importantly, this hybrid coating enabled sustained release of Zn2+/Ca2+/Si4+ and ZA in the long term, achieving a remarkable effect on vascularized bone regeneration. The coated IMN enhanced angiogenesis–osteogenesis coupling through autocrine and paracrine effects between endothelial cells and bone marrow mesenchymal stem cells. Osteoclastogenesis was repressed by Zn2+ and ZA. This approach offers a new strategy for surface-engineering of biodegradable metals for bone fracture healing.

Tensile capacity degradation of randomly corroded strands based on a refined numerical model

In this study, we develop a sophisticated numerical model to analyze the axial tension behavior of seven-wire steel strands subjected to corrosion by employing the ANSYS finite element software. The axial tensile performance of steel strands subjected to random corrosion is examined, and the model's accuracy is validated by comparing it with experimental results. The corrosion degree in the steel strands is quantified by the mass loss rate χ, which denotes the ratio of the mass lost due to corrosion to the total mass. The reduction factor θ is employed to characterize the diminished axial tensile performance of the steel strands following corrosion. Two corrosion modes under random corrosion in steel strands were proposed, with lower bound formulas for the θ-χ distribution derived for each. In Mode I, the largest corrosion depth is prespecified. Mode II is characterized by destructive cross-sectional corrosion. As the corrosion intensifies, the corrosion pits can expand indefinitely across the wire's cross-section, potentially leading to significant loss or complete corrosion of a section of the steel strand. The finite element analysis indicates that the wire diameter and the corrosion pit depth affect θ-χ. The element size, steel strand length, and lay length have minimal impact.

Probing and monitoring multiple forms of localised corrosion occurring concurrently on pipeline steels in marine environments

An electrode array probe, with a novel approach, has been specifically designed to enable the in-situ field monitoring of multiple forms of localised corrosion of steel exposed to marine environments. The initiation and propagation of localised corrosion within the crevice area as well as at the steel weldment were visualised and evaluated over one-year field exposure at two different marine locations in Australia. The results show the varied initiation and propagation behaviour of crevice corrosion and weldment corrosion on steel, which provide experimental evidence for ‘bi-modal’ behaviour and the change-over of corrosion modes in extended periods of marine exposure.

Progressively advantageous long-term corrosion profile of Mo over Mg, Zn, and Fe from the perspective of biodegradable metals

Long-term corrosion profile of molybdenum was studied in three different simulated body fluids up to 28 days, compared with magnesium, zinc, and iron from the perspective of biodegradable metals (bio-metals). Their corrosion rate, mode, products and surface characteristics were comprehensively fathomed. Strikingly, Mo showed progressively advantageous long-term corrosion behavior with the smallest corrosion rate, and most importantly, more uniform mode, as compared with the other three bio-metals. It also performed bilaterally under the simulated inflammatory and bovine serum protein added conditions, with different corrosion progressions. These findings provide an optimistic outlook in opting molybdenum as a new type of bio-metal.

Prediction of Lithium Deposition By Electrochemical Noise Method in Li-Ion Batteries

Electrochemical noise measurement methods have established a significant presence in corrosion literatures and through these measurements, it becomes feasible to discern the corrosion mode and make a clear distinction between localized and uniform corrosion types, particularly when examined alongside post-mortem studies.In recent years, the increase in the use of lithium-ion batteries demands that the tests to be performed on the batteries are faster, easier, cheaper and, if possible, non-destructive and non-perturbing. While some electrochemical noise studies on batteries have commenced, the existing literature on this subject is limited and questionable. Electrochemical noise measurement, in Lithium based batteries has the potential to serve as a non-invasive diagnostic tool for assessing battery health. One of our previous studies has demonstrated an increased voltage noise in non-rechargeable batteries with Li/MnO2 chemistry upon exposure to a short circuit, indicating detectable morphological changes in metallic lithium due to non-homogenous depletion of lithium anode through electrochemical noise measurement.In Lithium-Ion batteries, lithium deposition refers to the undesired formation of metallic lithium, commonly in the form of dendrites, on the battery’s anode during charge and discharge cycles. This phenomenon is a consequence of uneven lithium-ion plating and stripping, leading to localized overplating. This growth of lithium dendrites poses significant risk, including internal short circuits, compromised battery integrity, and the potential for thermal runaway. These issues can result in reduced battery performance, safety concerns, and shortened cycle life. Effectively addressing lithium deposition is essential for enhancing the safety and reliability of lithium-ion batteries in various applications.Similarly to our previous publication, the electrochemical noise method shows promise as a non-invasive approach to investigate the understand deposition of metallic lithium by monitoring the voltage noise during charge and discharge cycling of batteries. For this purpose, NMC/Graphite pouch and coin cells are employed. In this presentation, we will delve into the details of electrochemical noise in lithium-based batteries, discussing the method’s reliability in assessing lithium deposition in NMC/Graphite lithium-ion batteries and presenting preliminary results. Figure 1

Corrosion Behavior of Cu-Ni-Fe-Mn-Cr Alloy in 3.5 wt% NaCl Solution

A novel Cu-10Ni-1.7Fe-0.5Mn-0.2Cr alloy was fabricated and exposed to a neutral 3.5 wt% NaCl solution for various days. The corrosion performance, corrosion film, and corrosion mode of the alloy were investigated in detail. The results suggested that the average corrosion rate reduced from 0.082 mm/a for 1-d immersion sample to 0.037 mm/a for 30-d immersion sample. The reduction in corrosion rate was mainly attributed to the progressive thickness and densification of the corrosion film, leading to increasing the resistance of the corrosion film with the prolonged exposure time. Low-valent oxides and chlorinated compounds were generated over the 1-d immersion sample surface, while high-valent oxides and hydroxide compounds were developed over the 30-d immersion sample surface. The mature corrosion film typically composed of Cu2O, CuO, Cu2(OH)3Cl, γ-FeOOH, MnO2, and Cr2O3. Eventually, the alloys suffered from selective corrosion and intergranular corrosion after a long exposure time in NaCl solution.

Correlating corrosion modes with the microstructure of the 2XXX series alloys: A comparative approach

In this study, the localized corrosion susceptibility of AA2050‐T84, AA2198‐T851, and AA2024‐T3 alloys was compared by immersion in three test solutions, specifically sodium chloride solution (3.5% NaCl), EXCO solution, according to ASTM G34‐18, and a solution for intergranular corrosion (IGC) test recommended by ASTM G110‐15 and via scanning vibrating electrode technique (SVET). The results showed higher susceptibility of AA2050‐T84 alloy to all types of corrosion tested compared to the other studied 2XXX series alloys. Corrosion penetration was deeper in the AA2050‐T84 due to its microstructural characteristics as a difference in the micrometric Cu‐Rich intermetallic particle distribution on the surface and related to the distribution of the T1 (Al2CuLi) phase.

Osteogenerative and corrosion-decelerating teriparatide-mediated strontium–zinc phosphate hybrid coating on biodegradable zinc–copper alloy for orthopaedic applications

Zinc–copper (ZnCu) alloys recently showed great potential as biodegradable materials for bone implants thanks to their excellent mechanical strength, biosafety, and promising bioactivities. However, bare ZnCu alloys exhibited poor cytocompatibility and osteointegration. Moreover, the biological functions of ZnCu remain to be corroborated. Herein, the teriparatide (PTH)-mediated strontium–zinc phosphate (SrZnP) organic–inorganic hybrid coating was fabricated on the surface of ZnCu substrate via a chemical conversion method to contain the release of Zn ions and improve biofunctionality in osteogenesis. The characteristics of the hybrid coating were optimised by adjusting the amount of PTH molecules added. A dense and homogenous coating with micellar crystal micro-/nano-structure was obtained. The coated samples showed a significantly decreased corrosion rate and a more uniform corrosion mode, effectively suppressing the release of Zn2+. Additionally, the coated ZnCu enhanced the proliferation of bone marrow mesenchymal stem cells (BMSCs), promoted the expression of alkaline phosphatase and the formation of calcium nodules, and upregulated the levels of osteogenic-related genes. More important, the hybrid coating activated the classic osteogenic signalling pathway of BMP-2/Smad1/Runx2 and Sirt1/Runx2 to induce the osteogenic differentiation of BMSCs. These appealing features can be mainly attributed to the constituents of released Zn2+, Sr2+, and PTH molecules in the control, as well as the unique topographical characteristics of the coatings. Taken together, the PTH&SrZnP hybrid coating could be a promising option for surface modification of biodegradable metallic Zn for orthopaedic applications.

Corrosion behavior of Hastelloy alloys and stainless steel in the molten chloride salt NaCl-CaCl2-CeCl3

ABSTRACT Compatibility tests are carried out on Ni-based Hastelloy alloys and stainless steel under the influence of the molten chloride salt NaCl-CaCl2-CeCl3 to investigate the corrosion behavior of molten salts with structural materials. Weight change measurements before and after the reaction tests show that the Hastelloy alloys have better corrosion resistance than stainless steel. The effects of molten salt purification on the corrosion behavior in the Hastelloy alloys are explored. The composition of the reacting phases is identified from transmission electron microscopy analysis and the corrosion mode is homogeneous corrosion with Cr and Fe diffusion, followed by Mo and Ni elution.

Effect of Sulfide Addition on the Corrosion Mechanism of Copper in Saline Groundwater Solution

The interaction of copper with sulfide-containing simulated saline groundwater is studied by electrochemical techniques (voltammetry, current-time transients, and electrochemical impedance spectroscopy, EIS) complemented with surface and cross-sectional microscopic observations and energy dispersive spectroscopic analyses. Both experimental findings and quantitative interpretation of EIS data using previously published kinetic models indicate that no continuous adherent barrier-type layer is formed on Cu in sulfide-containing groundwater, thus precluding the possibility of the development of localized corrosion modes.

The uniform corrosion of biodegradable Mg alloy induced by protein addition in Hanks’ balanced salt solution

The localized corrosion caused by the interphase potential differences and incompleteness of the corrosion product layer results in the premature failure of Mg alloys. In biomedical applications, understanding about the corrosion behavior of Mg alloys in complex environment is still insufficient. In this work, mechanical tests after corrosion were employed to indirectly but generally reflect the localized corrosion of Mg alloy in the protein-containing electrolytes. The results reveal that protein alters the Mg corrosion mode to uniform corrosion and an appropriate amount of protein is beneficial for maintaining its mechanical bearing capacity. This work is helpful for understanding the corrosion behavior of Mg alloys and consummating degradation evaluation systems for Mg alloys.

Electrochemical and hot corrosion behaviour of annealed AlCoCrFeNi HEA coating over steel

The ability to endure extreme corrosion in challenging environments is reduced in stainless steel. This can be addressed by appropriate surface modification techniques to redefine the surface with the required properties. The characteristics of the atmospheric plasma sprayed AlCoCrFeNi High Entropy Alloy (HEA) on SS316l are presented in this study. The coating characterisation revealed uniform coating with homogeneous deposition of gas-atomized AlCoCrFeNi HEA spanning for 150 µm. The coated substrates were further annealed for 2 h at 400 °C, 550 °C, 700 °C and 850 °C and the annealing at 550 °C offered enhanced microstructure. Annealing the coated sample at 550 °C offered a 46% improvement in microhardness against the uncoated sample post-annealing. The electrochemical corrosion tests showcased improved corrosion resistance after annealing through the formation of a protective oxide layer and the influence of HEA. Hot corrosion tests at 900 °C resulted in 10.1%, 8.49%, and 10.36% improved corrosion resistance for the coated sample annealed at 550 °C than the coated sample pre annealing and 44.09%, 44.25%, and 42.09% than the uncoated sample pre annealing under three salt mixtures respectively. The microstructural analysis examines various corrosion modes and verifies the presence and formation of protective oxide layers.

Wetting, droplet evaporation and corrosion behavior of various composite and textured materials

Experimental studies were conducted on the evaporation rate of a droplet located on the surfaces of various composite and textured materials with different wettability at varying surface temperatures. The maximum droplet evaporation rate was recorded on a textured Cu–SiC composite material with superhydrophilic properties. The minimum droplet evaporation rate corresponded to a superhydrophobic AlMg3 substrate obtained using laser texturing with subsequent hydrophobization procedure. An increase in surface temperature led to a significant deterioration of hydrophobicity for a superhydrophobic substrate and a deterioration of hydrophilicity for a superhydrophilic substrate. As a result, with increasing temperature, the influence of the droplet geometry determined by surface wettability on the droplet evaporation rate for these substrates sharply decreases. Advancing and receding dynamic contact angles, as well as contact angle hysteresis were obtained on all studied substrates. It is generally accepted that a hydrophobic surface exhibits less contact angle hysteresis than a hydrophilic one. However, Cu-SiС composite substrate with a textured hydrophobic surface exhibited the opposite behavior. The contact angle hysteresis on the hydrophobic textured surface was found to be four times higher than that on the hydrophilic polished one. A mechanism was proposed that explains the high contact angle hysteresis and four hysteresis time modes. The minimum hysteresis value corresponded to the superhydrophobic AlMg3 substrate. Anti-corrosion properties were studied for all substrates under consideration. The minimum corrosion current corresponded to a copper substrate with a graphene coating, as well as a superhydrophobic AlMg3 substrate. For a given substrate, there are two corrosion modes with a three-fold difference in the corrosion current. In addition, the wettability behavior of different surfaces was examined using molecular dynamics simulations. The simulation results were found to be consistent with the experimental data.

Effect of water vapor content on the corrosion mechanism of HR3C in simulated oxy-coal combustion environment

The corrosion performance of the HR3C steels covered with salt deposition (Na2SO4:K2SO4 = 1:1) was investigated under various water vapor content at 700 °C. Results show that the HR3C alloy undergoes severe pitting and sulfidation in a dry corrosive atmosphere (0.5SO2-4O2-CO2) and the corrosion products are peculiarly prone to peel off. In comparison, the corrosion behavior is gradually mitigated with increasing water vapor content. In highly humid corrosive gas (0.5SO2-4O2-20H2O-CO2), the corrosion degree is remarkably faint and the dominant corrosion mode is oxidation. The mechanism responsible for the transition of corrosion mode as water vapor content varied is discussed in detail.

Effect of building orientation on the in vitro corrosion of biomedical Zn-Cu alloys prepared by selective laser melting

Zn-Cu alloys as biodegradable materials have been successfully fabricated by selective laser melting (SLM) method. XRD, EBSD, electrochemical and immersion tests have been conducted to investigate the effect of building direction on microstructure and in vitro degradation behaviors. Finer grains and more CuZn5 precipitates are found on vertically built Zn-Cu alloy, which results in a higher degradation rate than horizontally built one in both electrochemical and immersion tests. The corrosion mode includes general corrosion and pitting. The moderate corrosion rates of SLM Zn-Cu make them suitable for cardiovascular stents and the corrosion rate is controllable by fabricating methods.

Observations of Atmospheric Corrosion Testing on Heated Austenitic Stainless Steel Surfaces: Exploring the Role of Inert Dust Particulates and Seawater

Relevant atmospheric corrosion laboratory testing environments were developed to explore the influence of inert dust and seawater on the corrosion susceptibility of stainless steel in spent nuclear fuel dry storage conditions. Measurements from dust collected on in-service dry storage canisters were applied to develop exposure conditions. Three atmospheric exposure conditions, two static and one cyclic, were examined with three different surface coverages: co-deposited large dust and seawater, co-deposited small dust and seawater, and solely seawater. Stainless steel coupons representative of spent nuclear fuel dry storage canister material were subjected to the various corrosion environments, with the results from exposures up to 1 year presented here. Post exposure, corrosion damage was analyzed using optical microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Initial observations are presented herein, and potential implications with respect to the influence of inert dust particles on corrosion susceptibility are summarized. In general, the co-deposition of dust and salt resulted in larger pits and exhibited mixed modes of corrosion that were not observed in the no-dust conditions (i.e., crevicing, filiform, and pits within pits). The presence of the inert dust may influence brine spreading and/or act as crevice formers, leading to enhanced corrosion. This study highlights the significance of incorporating dust particulate(s) beyond the deliquescent chemistries to fully evaluate atmospheric corrosion severity.

The Study on Fatigue Crack Growth Rate of 4130X Material under Different Hydrogen Corrosion Conditions.

In this paper, the fatigue crack growth rates of typical pressure vessel material 4130X under different corrosion conditions are investigated, and the effects of corrosion modes and loading frequency on the fatigue crack growth rate of 4130X are discussed. The results show that under the same loading conditions, the pre-corroded crack propagation rate is increased by 1.26 times compared with the uncorroded specimens. The plastic deformation mechanism of the crack tip in air is dominated by phase transformation but the hydrogen introduced by pre-corrosion causes a small number of dislocations at the crack tip. The crack growth rate obtained by corrosion fatigue is four times that of the uncorroded specimen, and the fracture surface shows a strong corrosion effect. The molecular dynamics simulation shows that the hydrogen atoms accumulated at the crack tip make the plastic deformation mechanism dominated by dislocation in the crack propagation process, and the coupling interaction between low frequency and the corrosion environment aggravates the hydrogen embrittlement of the crack tip. In the air condition, the loading frequency has no obvious effect on the crack growth rate: when the frequency decreases from 100 Hz to 0.01 Hz and other conditions remain unchanged, the fatigue crack growth rate increases by 1.5 times. The parameter n in the Paris expression is mainly influenced by frequency. The molecular dynamics simulation shows that low frequency promotes crack tip propagation.

Corrosion behaviour of electropolished magnesium materials

Although magnesium and its alloys are promising candidates as biodegradable implant materials, the tendency for localised corrosion mechanism in physiological environment limit their biomedical application. Electropolishing is an attractive strategy for improving the corrosion behaviour of metals, but it is still largely unexplored in magnesium materials. In this study, the characterisation of electropolished surfaces of AM50 and pure magnesium was performed, focussing on their in vitro degradation behaviour in cell medium. Corrosion rates were evaluated using potentiodynamic polarisation. The surface morphology before and after the onset of corrosion was investigated by scanning electron microscopy and confocal laser scanning microscopy. The presented electropolishing process led to improved surface performances, observable by significantly lower corrosion rates (0.08 mm·year−1 in Dulbecco's modified Eagle's medium), lower arithmetical mean height (0.05 µm), lower water contact angle (25–35°) and lower micro hardness (35–50 HV 0.1) compared to mechanically and chemically treated surfaces. MgO/Mg(OH)2 could be detected on electropolished surfaces. The localised corrosion mode could be reduced, but not entirely prevented. Electropolishing shows great potential as post-treatment of magnesium-based components, but detailed tests of the long-term corrosion behaviour are an important area of future research.

Effect and simulation of tensile stress on corrosion behavior of 7050 aluminum alloy in a simulated harsh marine environment

The corrosion behavior of the 7050 aluminum alloy was investigated in the presence of high concentrations of H+ and Cl- ions simulating the marine environment of high salinity and local acidification in tropical seas. The results highlight the significant influence of tensile stress on the corrosion rate of the aluminum alloy with higher stress levels resulting in faster corrosion. Under the influence of tensile stress, corrosion pits form on the alloy surface, and their depth increases with higher levels of applied stress. It is important to note that the presence of a corrosion defect leads to a pronounced stress concentration, resulting in a much faster rate of corrosion compared to other regions. However, when subjected to low tensile stress (≤174 MPa), the corrosion at the defect exhibits uniform characteristics similar to a uniform corrosion process. Moreover, the potential at the defect shifts positively with increasing stress level. Furthermore, stress has an effect on the diffusive behavior of the aluminum alloy, leading to a higher potential at the defect center compared to its surrounding region. Nevertheless, as the tensile stress is further increased, this behavior is disrupted and stress corrosion cracking becomes the dominant mode of corrosion.

Accuracy of using Moisture Reference Years for assessing the Long-Term Moisture Performance of Wall Assemblies

Hygrothermal simulation is commonly used to understand the effects of climate loads on wall assemblies. This helps determine the risk of deterioration of wall components due to factors such as mould, wood rot, corrosion, and other modes of degradation. Owing to the lengthy computing time and high cost of undertaking simulations over extended periods of time in excess of 30 years, common practice is to select representative years, generally referred to as moisture reference years (MRYs), amongst the climate data series with the assumption that they would provide results similar to that obtained using the entire climate data series. In this study, simulations were performed for a wood-frame wall having brick veneer and fibreboard as cladding and located in 4 Canadian cities using both a 31-year climate data series and MRYs. The mould growth index on the outer layer of the sheathing panel was used as the performance indicator to permit comparing the moisture performance obtained using the long-term climate series to that obtained using MRYs. It was determined that different strategies should be implemented to analyse the MRY simulation results for different types of wall assemblies to obtain a similar conclusion as that of 31-year simulations.