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The abundance of electrochemically noble secondary phases present in the heterogeneous microstructure of Mg alloys leads to accelerated corrosion of the surrounding Mg matrix by micro-galvanic coupling. The extent of disintegration of the large Al-Mn intermetallic particles (IMPs) present in the Mg alloy AZ31B was investigated with respect to laser processing parameters of a nanosecond pulsed Excimer laser. The parameters investigated were overall pulse per area, laser fluence (J/cm 2 ), and background pressure of Ar gas. Observation of resulting IMP dissolution, morphology, and subsequent reduction in cathodic corrosion kinetics are reported. Laser fluence and pulse per area were observed to have the largest impact on the corrosion kinetics and overall dissolution of IMPs, with the highest fluence (1.5 J/cm 2 ) and 100 or above pulse per area exhibiting an order of magnitude reduction in cathodic kinetics. [ABSTRACT FROM AUTHOR]

The corrosion behavior of the Al 0.3 Cr 0.5 Fe 2 Mn 0.25 Mo 0.15 Ni 1.5 Ti 0.3 compositionally complex dual-phase alloy was explored in a variety of electrolytes. Comparable corrosion resistance to 316L stainless steel and Ni-Cr binaries was observed in NaCl despite lower Cr concentrations. Individual elemental fates during corrosion were identified by combinations of in-situ atomic emission spectroelectrochemistry and ex-situ X-ray photoelectron spectroscopy with high-resolution surface analysis and depth profiling. A potentiostatically grown passive film was enriched in Al(III), Cr(III), Ti(IV), and Mo(VI). Al-Ti and Cr-Ti layers were suggested but significant Al, Cr, and Ti mixing was present. Proposed benefits of Al-Cr-Ti coexistence are addressed. • The passivation behavior and corrosion resistance of a dual-phase compositionally complex alloy is characterized. • Elemental fates are tracked with X-ray Photoelectron Spectroscopy and Atomic Emission Spectroelectrochemistry. • The effect of oxide aging on passive film composition and polarization resistance is evaluated. • Intermixing of Al, Ti, and Cr within the passive film is observed without significant oxide layering. • The benefits and drawbacks of Al and Ti are discussed with respect to light-weight compositionally complex alloy design. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient Machine Learning algorithm is used to assist down-selection from an otherwise prohibitively large alloy space. • An alloy having a ductile FCC matrix and an intermetallic L2 1 (Heusler phase) reinforcement is developed. • The composition is tailored to promote partitioning of passivating elements to both phases and minimize microgalvanic corrosion. • A Genetic Algorithm is used to optimize a crystal plasticity-based prediction of toughness by varying microstructural attributes. A strategy for designing compositionally complex alloys (CCAs) achieving multiple objectives is articulated. In this specific case, the objectives are low density and cost, along with good strength, ductility, and aqueous corrosion resistance. The present strategy has produced a two-phase material, having a ductile FCC matrix and a L2 1 intermetallic reinforcing phase. A machine learning algorithm has been trained using attributes of binary phase diagrams as inputs and the existing experimentally informed CCA database as output values, which efficiently predicts the phases which will result from combinations of selected elements. Corrosion resistance is achieved through tailoring the composition such that solute partitioning promotes passivity of both phases. Surprising results of composition optimization, such as preferred levels of Mn and Mo in an Al-Cr-Fe-Mo-Mn-Ni-Ti alloy are presented. While raw material cost, density, corrosion resistance, and stiffness are strong functions of alloy chemistry, the strength and ductility are highly sensitive to microstructure as well. A genetic algorithm is used to optimize a crystal plasticity-based prediction of toughness, defined as the product of ultimate tensile strength and uniform elongation, by varying microstructural attributes. Surprising dependencies of this toughness on the microstructure inputs are highlighted. Experimental results demonstrate the efficacy of the approach. [ABSTRACT FROM AUTHOR]

The effect of Te concentration in molten FLiNaK salt on the corrosion and mechanical properties of 304 stainless steel was investigated. The corrosion depth of samples after the immersion tests for 48 h at 600 ℃ decreased with increasing Te concentration. Likewise, the sample after the immersion test containing 1.0 wt% of Te (1.0 wt% Te sample) showed less reduction in mechanical properties than the 0.1 wt% Te sample. We hypothesize that the condition for a Cr-oxide layer that has the protective property is fulfilled underneath the Ni-Fe rich layer which is formed by the selective leaching of Cr. • In molten FLiNaK salt, the corrosion depth was decreased with increasing Te content. • Mechanical properties of the corroded samples were recovered in higher Te concentration. • Chromium oxide was formed at grain boundaries in higher Te concentration. • This chromium oxide wasn't dissolved into the FLiNaK and had a protective property. • In lower Te content, it is not enough Te to promote making the protective layer. [ABSTRACT FROM AUTHOR]

The effect of the Cr content on the corrosion behavior in a series of single-phase non-equiatomic Ni 38 Fe 20 Cr x Mn 21-0.5x Co 21-0.5x (6 < x < 22 at%) multi-principal element alloys (MPEAs) was investigated in acidified NaCl solutions. Comparisons were made with binary solid solution Co-Cr, Ni-Cr, and Fe-Cr alloys over a similar range of Cr contents. The corrosion behavior was evaluated using in-situ AC and DC electrochemical methods and ex-situ surface sensitive characterization techniques. Passivity and various levels of local corrosion resistance were obtained in the MPEA with 10 at% Cr or above. The binary Ni-Cr alloys with 12–30 at% Cr behaved similarly. The MPEA with 6 at% Cr and binary alloys with 5, 6, or 10 at% Cr were marginally passive or active and underwent localized corrosion during both linear sweep voltammetry and potentiostatic hold experiments. Passive films formed during potentiostatic hold experiments were characterized with X-ray photoelectron spectroscopy and atom probe tomography. Cr cation enrichment in the passive films was observed for all alloys and similar enrichment factors were obtained as a function of Cr content regardless of whether MPEA or binary alloy except for the Fe-Cr alloy. Moreover, passive current density was correlated with the Cr cation fraction in the passive film. The degree of Cr enrichment was attributed to a combination of thermodynamic and kinetic factors, such as selective chemical dissolution of alloying elements as well as limitation due to solute depletion at the metal oxide interface in alloys with a bulk Cr content ≤ 10 at%. [Display omitted] [ABSTRACT FROM AUTHOR]

A three-dimensional (3-D) granular model that has the capability of predicting time-dependent intergranular corrosion (IGC) damage propagation depths in AA5083-H131 exposed to 0.6 M NaCl solution under potential control is presented. The geometry of grains and degree of sensitization (DoS) of grain boundaries were utilized as inputs, organized in a database, which informed the model to produce IGC depth distributions. The dependencies of IGC depth with exposure time, DoS, and orientation of propagation, both in terms of propagation kinetics and damage morphology, are outputs from the model. The model was calibrated by comparing outputted damage depths to IGC depth data from experiments. Model validation was achieved by comparing the predicted to experimental IGC depths based on image analyses of metallographic cross-section of AA5083-H131 exposed under the same conditions. The relevance and limitations of the current version of the model are discussed. [ABSTRACT FROM AUTHOR]

The relationship between microstructure, composition and the localized corrosion resistance of a low carbon Cr-Ni-Mo martensitic-ferritic stainless steel was investigated. Four heat treatments were selected to examine the effect of varying tempered Martensitic-Ferritic microstructures on localized corrosion susceptibility. The pitting potential for each heat treatment was determined in deaerated 192 g/L NaCl electrolyte saturated with CO 2 (pH: 3.8) at 65 °C. Austenite reversion and other microstructural transformations associated with tempering had a detrimental effect on the pitting potential. The resulting chemical and structural inhomogeneities decreased the pitting potential. [Display omitted] • A complex MFSS was assessed as a function of heat treatment producing variations in steel microstructure. • Pitting potential was detrimentally affected by austenite reversion during tempering process. • For materials tempered at higher temperatures, pitting initiation occurred at previously reversed areas depleted in Cr/Mo. • In the as quenched condition pitting initiation occurred at lath boundaries and prior austenite grain boundaries. • Low tempering temperature led to initiation sites corresponding to the as quenched condition and inside reversed areas [ABSTRACT FROM AUTHOR]

Hydrogen uptake, diffusivity and trap binding energy were determined for the nickel–copper–aluminum alloy Monel K-500 (UNS N05500) in several conditions. The total atomic hydrogen (H) concentration increased from 0 to 132wppm as the hydrogen overpotential decreased to −0.5V in alkaline 3.5% NaCl electrolyte at 23°C. The room-temperature H diffusion coefficient ranged from 0.9 to 3.9×10−14 m2 s−1 for single-phase solid solution, aged, and cold worked then aged microstructures. Diffusivity was independent of lattice H concentration but depended weakly on metallurgical condition, with slower H diffusion after aging. The apparent activation energy for H diffusion was in the range of 29–41±1.5kJmol−1 at the 95% confidence level. The lower value approached nearly perfect lattice transport, while the high value was strongly influenced by traps of low-to-intermediate strength. Atomic hydrogen trapping at metallurgical sites, strongly suggested to be spherical-coherent γ′ (Ni3Al) precipitates, was evident in the aged compared to the solution heat treated+water-quenched condition. Both thermal desorption and classical Oriani trap state analyses confirmed that the apparent hydrogen trap binding energy interpreted as Ni3Al (10.2±4.6kJmol−1) interfaces was significantly less than the activation energy for perfect lattice diffusion (25.6±0.5kJmol−1) in this nickel-based alloy system. [ABSTRACT FROM AUTHOR]

[Display omitted] The oxide film formed on a corrosion-resistant multi-principal element alloy 38Ni-21Cr-20Fe-13Ru-6Mo-2W (at. %) was characterized via transmission electron microscopy and atom probe tomography. Oxidation in air at 600°C for 1080 minutes resulted in a complex, layered film with multiphase inner and outer oxide scales, and localized recrystallization in the underlying base alloy. The outer oxide scale is dominated by two phases: a Ni-Fe spinel (≈NiFe 2 O 4) and a Ni-rich monoclinic phase (NiMoO 4). The inner oxide consists of a near surface Ni-Fe-Cr spinel and RuO 2 , and semi-continuous Cr 2 O 3 with oxygen-rich Ru-Mo metal inclusions. Local recrystallization and concomitant elemental partitioning in the base alloy was influenced by a high dislocation density in the as-prepared sample surface. [ABSTRACT FROM AUTHOR]

• The dissolution behavior of oxide films on Type 316L stainless steel in FLiNaK salt was investigated. • The oxide film formed on Type 316L SS is unstable in molten FLiNaK salt at 700 °C. • The oxide dissolution rate is calculated to be 0.85 nm/h at 700 °C in molten FLiNaK salt. • The O2− in FLiNaK could react with 316L stainless steel to form FeCr 2 O 4 at the grain boundary of the steel. The corrosion behavior of oxide films grown on Type 316L stainless steel (SS) in molten FLiNaK (LiF-NaF-KF: 46.5−11.5−42 mol.%) salt was investigated. The results show that the oxide film formed on Type 316L SS is unstable and can only temporarily protect materials from corrosion in molten FLiNaK salt. Based on the electrochemical impedance spectroscopy, the oxide dissolution rate is calculated to be 0.85 nm/h at 700 °C in molten FLiNaK salt. After the oxide film dissolved, Cr and Fe are selective dealloyed from the steel, leading to intergranular corrosion of Type 316L SS in molten fluoride salt. [ABSTRACT FROM AUTHOR]

• Investigate electrochemical properties of a model sputtered oxide as a surrogate to a reactor material oxide. • Sputtered oxide showed an enhanced corrosion resistance than the thermally formed oxide in Cl− containing electrolytes. • Significantly increased electronic defect density for the thermally oxidized Fe compared with sputtered oxide. The electrochemical stability and corrosion behavior of the thermally pre-oxidized and sputter deposited variant of an oxide single-crystalline Fe thin film were compared. Thermal oxides formed Fe 2 O 3 over an inner layer of Fe 3 O 4 while the sputtered oxides were found to have grown Fe 3 O 4 instead of the target stoichiometry of Fe 2 O 3. Oxide films of both types were stable in pH = 9.3 borate buffer solution, however, were altered in pH = 9.3, 0.1 M NaCl solution in the case of thermally pre-oxidized Fe thin film. The stability of the oxide differed in pH = 4, 0.1 M NaCl where sputtered Fe films were more stable against acidic chemical dissolution than the thermally formed Fe oxide film. These differences were traced by AC/DC electrochemical analysis including electronic defect densities, and molecular identity characterized by ex-situ X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Element redistributions after initial oxidation of a Ni 38 Cr 22 Fe 20 Mn 10 Co 10 (at.%) multi-principle element alloy at 120 °C and 300 °C is captured via in situ atom probe tomography. All cations contribute to the oxide in both conditions, consisting of a Cr-rich inner oxide and a Fe, Mn, Co and Ni-rich outer oxide. At lower temperature, Ni tends to be trapped at the outer/inner oxide interface, while Ni enriches at the oxide/metal interface at higher temperature in tandem with Cr metal depletion. These observations confirm oxidation of complex alloys involves the formation of metastable, multi-layered oxide films, with a distinct tendency for solute trapping. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Distinguishing capacitance from an oxide and that double layer in RTIL by EIS. • Quantitative information about the interfacial properties of a metal/oxide/RTIL. • Methodology can be used in non-aqueous environments. The frequency-dependent impedance of a metal/oxide/room temperature ionic liquid (RTIL) interface was separated into oxide layer (C ox) and double layer (C dl) capacitances using electrochemical impedance spectroscopy (EIS). A pre-formed oxide of known initial thickness on Fe-20 at.% Cr was investigated in 1-ethyl-3-methylimidazolium methanesulfonate ([Emim][MeSO 3 ]) RTIL + aqueous mixtures. The oxide thickness was calculated from C ox using the complex capacitance representation and the power-law model. The result was additionally verified by cross-sectional analysis using transmission electron microscopy. The C dl calculated from the constant-phase element (CPE) was distinguishable from C ox for Fe-20Cr, which enables monitoring of the interfaces of structural metals with oxide layers in RTILs containing water. [ABSTRACT FROM AUTHOR]

• Electrochemical Impedance Spectroscopy (EIS) was employed to investigate the impedance behavior of thermal-oxidized iron in liquid lead-bismuth-eutectic. • The impedance of the oxide film increases with increasing oxidizing temperature, due to the formation of a thicker scale and fewer defects. • Increasing the oxidation time at a constant temperature can reduce the defect concentration in the oxide film and improve the resistivity of the oxide scale in LBE. • EIS is a promising in-situ method to investigate the electrical properties and integrity of the oxide scales in liquid LBE in real-time. The impedance behavior of pre-oxidized iron in liquid lead-bismuth eutectic (LBE) at 200 °C is studied using electrochemical impedance spectroscopy. The structures and resistance of oxide grown on iron oxidized in air at different temperatures and durations are compared. The results show that the resistance of the oxide film increases with increasing oxidizing temperature, due to the formation of a thicker scale and fewer defects. At the same temperature (600 °C), increasing the oxidation time can also reduce the defect concentration in the oxide film and improve the impedance of the oxide scale in LBE. [ABSTRACT FROM AUTHOR]

A series of single phase Ni 38 Fe 20 Cr x Mn 21–0.5x Co 21–0.5x multi-principal element alloys (MPEAs) were fabricated and their localized corrosion behavior was tested in 0.6 M NaCl solution. These MPEAs were found to be susceptible to localized corrosion, exhibiting pitting at room temperature, as indicated by positive hysteresis loops and low repassivation potentials observed in cyclic potentiodynamic polarization experiments. The pitting resistance increased with increasing Cr content. Interestingly, even the MPEAs with low chromium content, Ni 38 Fe 20 Cr 6 Mn 18 Co 18 and Ni 38 Fe 20 Cr 10 Mn 16 Co 16 , exhibited passivity and localized corrosion. The passivity observed in these low chromium MPEAs is likely derived from their relatively high nickel content. Crystallographic pit morphology was observed in most of these MPEAs, suggesting the absence of a salt film on the dissolving pit surface. Such crystallographic pit morphology indicates that the pit growth in most of these MPEAs was under charge-transfer/ohmic control. [ABSTRACT FROM AUTHOR]

• The onset of sub-critical cracking during slow strain rate tensile (SSRT) testing is assessed. • Hydrogen diffusion alone cannot explain measured intergranular fracture depths. • A new phase field formulation is developed for the coupled hydrogen-deformation problem. • Simulations indicate the onset of sub-critical cracking well before specimen failure. • Sub-critical cracking is shown to obfuscate the interpretation of SSRT metrics. The onset of sub-critical crack growth during slow strain rate tensile testing (SSRT) is assessed through a combined experimental and modeling approach. A systematic comparison of the extent of intergranular fracture and expected hydrogen ingress suggests that hydrogen diffusion alone is insufficient to explain the intergranular fracture depths observed after SSRT experiments in a Ni–Cu superalloy. Simulations of these experiments using a new phase field formulation indicate that crack initiation occurs as low as 40% of the time to failure. The implications of such sub-critical crack growth on the validity and interpretation of SSRT metrics are then explored. [ABSTRACT FROM AUTHOR]

We report experimental results on the composition and crystallography of oxides formed on NiCrMo alloys during both high-temperature oxidation and aqueous corrosion experiments. Detailed characterization using transmission electron microscopy and diffraction, aberration-corrected chemical analysis, and atom probe tomography shows unexpected combinations of composition and crystallography, far outside thermodynamic solubility limits. The results are explained using a theory for nonequilibrium solute capture that combines thermodynamic, kinetic, and density functional theory analyses. In this predictive nonequilibrium framework, the composition and crystallography are controlled by the rapidly moving interface. The theoretical framework explains the unusual combinations of composition and crystallography, which we predict will be common for many other systems in oxidation and corrosion, and other solid-state processes involving nonequilibrium moving interfaces. [ABSTRACT FROM AUTHOR]

Traveling waves of excitation arise from the spatial coupling of local nonlinear events by transport processes. In corrosion systems, these electro-dissolution waves relay local perturbations across large portions of the metal surface, significantly amplifying overall damage. For the example of the magnesium alloy AZ31B exposed to sodium chloride solution, we report experimental results suggesting the existence of a vulnerable zone in the wake of corrosion waves where local perturbations can induce a unidirectional wave pulse or segment. The evolution of these segments, combined with the absence of rotating spiral waves, imply subexcitable dynamics for which the segments' open ends tangentially retract. Using a simple excitable reaction-diffusion model, we identify parameters that replicate these experimental observations. Under these conditions, small protected disks act as wavebreakers, disrupting continuous fronts, which then shrink and disappear. We further explore different placement schemes of these wavebreakers to optimize potential corrosion mitigation. For constant surface coverage, many small wavebreakers prove more effective than a few large ones. A comparison of triangular, square, rectangular, hexagonal, aperiodic Penrose, and random lattice geometries indicates that triangular placements of wavebreakers are generally the optimal choice, while rectangular and random lattices perform poorly. Although wavebreakers were not demonstrated experimentally in this study, these findings provide concrete design guidance for the protection of alloy surfaces prone to wave-mediated corrosion., (© 2025 Author(s). Published under an exclusive license by AIP Publishing.)

Corrosion is a ubiquitous failure mode of materials. Often, the progression of localized corrosion is accompanied by the evolution of porosity in materials previously reported to be either three-dimensional or two-dimensional. However, using new tools and analysis techniques, we have realized that a more localized form of corrosion, which we call 1D wormhole corrosion, has previously been miscategorized in some situations. Using electron tomography, we show multiple examples of this 1D and percolating morphology. To understand the origin of this mechanism in a Ni-Cr alloy corroded by molten salt, we combined energy-filtered four-dimensional scanning transmission electron microscopy and ab initio density functional theory calculations to develop a vacancy mapping method with nanometer-resolution, identifying a remarkably high vacancy concentration in the diffusion-induced grain boundary migration zone, up to 100 times the equilibrium value at the melting point. Deciphering the origins of 1D corrosion is an important step towards designing structural materials with enhanced corrosion resistance., (© 2023. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Corrosion is an electrochemical phenomenon. It can occur via different modes of attack, each having its own mechanisms, and therefore there are multiple metrics for evaluating corrosion resistance. In corrosion resistant alloys (CRAs), the rate of localized corrosion can exceed that of uniform corrosion by orders of magnitude. Therefore, instead of uniform corrosion rate, more complex electrochemical parameters are required to capture the salient features of corrosion phenomena. Here, we collect a database with an emphasis on metrics related to localized corrosion. The six sections of the database include data on various metal alloys with measurements of (1) pitting potential, E pit , (2) repassivation potential, E rp , (3) crevice corrosion potential, E crev , (4) pitting temperature, T pit , (5) crevice corrosion temperature, T crev , and (6) corrosion potential, E corr , corrosion current density, i corr , passivation current density, i pass , and corrosion rate. The experimental data were collected from 85 publications and include Al- and Fe-based alloys, high entropy alloys (HEAs), and a Ni-Cr-Mo ternary system. This dataset could be used in the design of highly corrosion resistant alloys.

The Flint water crisis raised questions about the factors resulting in unacceptable soluble lead concentrations in the city's drinking water. Although water treatment strategies, failure to follow regulations, and unethical behavior were all factors, knowledge deficits at the intersection of several scientific fields also contributed to the crisis. Pursuit of opportunities to address unresolved scientific questions can help avert future lead poisoning disasters. Such advances will enable scientifically based, data-driven risk assessments that inform decisions involving drinking water systems. In this way, managers and decision makers can anticipate, monitor, and prevent future lead in water crises., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

There is increasing concern regarding the biological consequences of metal release from implants. However, the mechanisms underpinning implant surface degradation, especially in the absence of wear, are often poorly understood. Here the synergistic effect of albumin and H 2 O 2 on corrosion of Ti6Al4V in physiological saline is studied with electrochemical methods. It is found that albumin induces a time-dependent dissolution of Ti6Al4V in the presence of H 2 O 2 in physiology saline. Potentiostatic polarisation measurements show that albumin supresses dissolution in the presence of H 2 O 2 at short times (<24 h) but over longer time periods (120 h) it significantly accelerates corrosion, which is attributed to albumin-catalysed dissolution of the corrosion product layer resulting in formation of a thinner oxide film. Dissolution of Ti6Al4V in the presence of albumin and H 2 O 2 in physiological saline is also found to be dependent on potential: the titanium ion release rate is found to be higher (0.57 µg/cm 2 ) at a lower potential (90 mV), where the oxide capacitance and resistance inferred from Electrochemical Impedance Spectroscopy also suggests a less resistant oxide film. The study highlights the importance of using more realistic solutions, and considering behaviour over longer time periods when testing corrosion resistance of metallic biomaterials.

Atomic hydrogen (H) was introduced into steel (AISI 1018 mild steel) by controlled cathodic pre-charging. The resultant steel sample, comprising about 1 ppmw diffusible H, and a reference uncharged sample, were studied using atomic emission spectroelectrochemistry (AESEC). AESEC involved potentiodynamic polarisation in a flowing non-passivating electrolyte (0.6 M NaCl, pH 1.95) with real time reconciliation of metal dissolution using on-line inductively coupled plasma-atomic emission spectroscopy (ICP-OES). The presence of absorbed H was shown to significantly increase anodic Fe dissolution, as evidenced by the enhanced detection of Fe 2+ ions by ICP-OES. We discuss this important finding in the context of previously proposed mechanisms for H-effects on the corrosion of steels.