Dissolution Of Alloys Research Articles

Nanoporous Pt and Ru catalysts by chemical dealloying of Pt-Al and Ru-Al alloys for ultrafast hydrogen generation

Novel nanoporous catalysts from selective dissolution of alloys have been prepared for fast hydrogen generation from chemical hydrides. Pt and Ru have been used as precious metals in the alloys, while the nonprecious metal is Al. The alloy composition has been arranged by sputtering power of Al, which is varied from 200 to 400 W for Pt-Al and Ru-Al alloys. The influence of particle size on the sputtering power of Al has been demonstrated. The particle size of the Pt nanoparticle decreases from 900 to 90 nm when the sputtering power of Al is increased from 200 to 400 W. However, the particle size of the Ru nanoparticle decreased from 610 to 55 with the same increase in Al sputtering power. The hydrolysis reaction rate of NaBH4 scales with the sputtering power of Al and has been raised from 20 to 90 L min−1gcatalyst−1 for Pt while it increases from 23 to 110 L min−1gcatalyst−1 for Ru. The BET analysis has demonstrated that the measured surface areas of the Pt and Ru nanoparticles are approximately 55.5 and 151 m2 g−1, respectively. Joint like morphology providing the porous structure has been clearly concluded by TEM analysis. The average pore sizes are 1 and 10 nm for the Ru and Pt nanoparticles, respectively. In this study, fast hydrogen generation with lower activation energies of 31.7 and 32.1 kJ mol−1 has been achieved for the Pt and Ru nanoparticles, respectively. The critical parameters demonstrating the high catalytic activity in the hydrolysis reaction of NaBH4 are reported for the catalysts developed by the dealloying process.

Effect of fluoride on the corrosion behavior of nanostructured Ti-24Nb-4Zr-8Sn alloy in acidulated artificial saliva

The surface of titanium dental implants is highly susceptible to aggressive fluoride ions in the oral environment. Nanotechnology has proven an effective approach to improve the stability and corrosion resistance of titanium by applying a passive film. In this study, we investigated the effects of fluoride on the corrosion behavior of nanostructured (NS) Ti-24Nb-4Zr-8Sn (Ti2448) alloy in acidulated artificial saliva (AAS) at 37 °C, and then conducted comparisons with its coarse grained (CG) counterpart. Electrochemical techniques, such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS), as well as surface analysis including X-ray photoelectron spectroscopy (XPS) with argon ion sputtering, and scanning electronic microscopy (SEM) were employed to evaluate the effects of fluoride on sensitivity to pitting and the tolerance of Ti2448 to fluoride in AAS solution. The results demonstrate that corrosion current density increased with F− concentration. In all respects, the NS Ti2448 alloy presented corrosion resistance superior to that of its coarse grained (CG) counterpart at low F− concentrations (≤0.1%). Furthermore, a high content of F− (1%) was shown to promote the active dissolution of both alloys by increasing the rate of corrosion. Following immersion in the fluoridated AAS solution for 60 days, a tissue-friendly compound, Ca3(PO4)2, was detected on the surface of the NS when F− = 0.01% and Na2TiF6 was identified as the main component in the corrosion products of the CG as well as NS Ti2448 alloys when F− = 1%. High concentrations of F− produced pitting corrosion on the CG alloy, whereas NS Ti2448 alloy presented general corrosion in the form of lamellar separation under the same conditions. These findings demonstrate the superior corrosion resistance of the NS Ti2448 alloy as well as lower pitting sensitivity and higher tolerance to fluoride due mainly to grain refinement.

Pyrazole, pyrazolone and enaminonitrile pyrazole derivatives: Synthesis, characterization and potential in corrosion inhibition and antimicrobial applications

Six pyrazole and pyrazolone derivatives namely: 3-amino-1-phenyl-5-pyrazolone (1), 3-amino-1-(2,4-dinitrophenyl)-5-pyrazolone (2), 1H-pyrazole-3,5-diamine-4-(2-phenyldiazenyl) (3), 1-phenyl pyrazole-3, 5-diamine, 4-[2-(4-methylphenyl) diazenyl] (4), 1H-pyrazole-3,5-diamine, 4-[2-(4-methylphenyl) diazenyl] (5), 5-amino-1,3–diphenyl-1H-pyrazolecarbonitrile (6) were synthesized and evaluated as corrosion inhibitors for copper alloy dissolution in basic medium. Corrosion inhibition evaluation was performed using weight loss, polarization and electrochemical impedance measurements. The results showed that the prepared compounds have high efficiency as corrosion inhibitors for dissolution prevention of copper in NH4OH solution at pH of 9. The prepared compounds were evaluated for their antimicrobial activities against gram positive and gram negative bacteria using inhibition zone diameter measurements. The results revealed that the synthesized compounds have higher antibacterial activities than the conventional bactericide agents. The results of the antimicrobial activities and the corrosion inhibition tendencies of these compounds were correlated to their chemical structures.

Ionic liquids with trichloride anions for oxidative dissolution of metals and alloys.

Ionic liquids (ILs) with trichloride anions ([Cl3]-) combined with different cations were synthesised by bringing chlorine gas into contact with the corresponding chloride (Cl-) ILs at room temperature. These trichloride ILs safely store chlorine and are useful as oxidising agents for dissolution of various metals and alloys under mild conditions.

Kinetic study on compositional variations of inclusions, steel and slag during refining process

A steel-slag-inclusion-alloy-refractory-air multiphase model, which combined the kinetic analysis and the consideration of fluid flow in argon-stirred ladle, was established to investigate the compositional changes during refining process. The steel-slag reaction, the steel and inclusion reaction, the refractory-steel reaction, the refractory dissolution into the slag, the reoxidation of the molten steel, the removal of inclusions by floating, and the alloy dissolution were all considered in the current model. The stirring energy, the average speed of the molten steel in the plume, the horizontal speed of the molten steel in the open eye, the speed of the molten steel near the side wall, the speed of the molten steel at the bottom of the ladle and the volume fraction of the plume were obtained by mathematical simulation. The mass transfer coefficient of the molten steel is obtained by mathematical simulation. Meanwhile, it is assumed that the mass transfer coefficient of inclusions is influenced by the temperature. The calculation results are in accordance with the experimental ones. The influence of different slag compositions, different gas flow rates, and different inclusion diameters on system compositions were also investigated using the current model. It is indicated that the content of T.O. in the molten steel was influenced by the gas flow rate and the removal rate of inclusions goes up with the increasing inclusion diameter.

Study of Chemical Dissolution of Cu98Be Alloy in Solutions Based on FeCl3

Process of chemical dissolution of beryllium bronze in various electrolytes was studied. Taking into account complex formation processes during chemical etching in solutions based on FeCl3 the ionization rate and selectivity of dissolution of Cu98Be alloy components was determined. It was shown that uniform and high rated chemical dissolution of beryllium bronze is possible in acidic medium in presence of Fe3+ ion-oxidizer and chlorine ions. An optimal etching solution composition was proposed. The surface morphology of the beryllium bronze electrode after etching in the investigated solutions was studied. An absence of passivation on the alloy Cu98Be surface was shown and salt and oxide nature of the grains of compounds formed on the electrode surface after chemical etching was proved.

The Electrochemical Dissolution Behavior Research of Titanium Alloy underDifferent Electrolyte

Titanium alloy Ti6Al4V material is widely used in industrial production. In order to obtain high surface quality of titanium alloy and clarify the electrochemical processing and dissolution characteristics of titanium alloy,in this paper, titanium alloy in the NaCl electrolyte, NaNO3 electrolyte and the two mixed electrolyte was used to study the electrochemical polarization of titanium alloy at low current density by electrochemical workstation. The dynamic behavior and polarization curves of the dissolution of titanium alloy were obtained. At the same time, the dissolution behavior of titanium alloy at high current density was studied by side-flow parallel plate electrolytic processing method. The dissolution law and surface morphology of titanium alloy were obtained. Fractal calculation of titanium alloy dissolution at different current density was carried out by using pixel - covered fractal dimension method. The results show that the surface morphology of titanium alloy at different current density shows different characteristics, and there are more pit-like dissolution phenomena in NaNO3 electrolyte. The pitting corrosion phenomenon of titanium alloy in NaCl electrolyte is more obvious. But it effectively reduces pitting corrosion and pit-like dissolution in both the mixed solution and high current density, the quality of surface of electrochemical machining for titanium alloy is improved.

Effect of simulated inflammatory conditions and potential on dissolution and surface oxide of CoCrMo alloy: In situ electrochemical atomic force microscopy study

Inflammation may develop in association with implantation of hip replacements and the inflammatory state of the local body fluids may affect the corrosion of metallic biomaterials like CoCrMo alloy. In this study CoCrMo alloy surfaces were imaged using in situ electrochemical atomic force microscopy (ECAFM) to evaluate oxide film morphology and surface dissolution while immersed in phosphate buffered saline (PBS) solution or simulated inflammatory (SI) solutions across a range of potentials. The SI solution explored here consisted of a 30 mM hydrogen peroxide (H2O2) modified PBS solution. Analysis of ECAFM images, surface roughness and potentiostatic polarization current density data exhibited a correlated relationship between surface oxide morphology, loss of passivity and electrochemical behavior CoCrMo alloy. ECAFM results showed that the presence of H2O2 altered oxide film behavior, leading to positive shifts of open circuit potential (OCP) to 0.32 V (vs Ag/AgCl), higher current density and significantly altered oxide film topography compared to PBS only case. Surface morphology, surface roughness (Ra) and current density exhibited strong potential- and time-dependent behaviors. Significant surface oxide formation on alloy and carbides were observed, followed by dissolution of CoCrMo alloy as potentials were increased above 0.5 V. Carbide boundaries and metal grain boundaries were preferential sites for oxide dissolution at transpassive potential ranges. Formation and evolution of new oxides were directly imaged at 0.65 V in PBS solution. New oxides formed and covered the surface in 10 min at 0.65 V. However, they were less protective compared to the passive oxide films at OCP condition. Simulated inflammatory solutions raise alter corrosion behavior of CoCrMo alloys.

Inhibition effect of underpotential deposition of metallic cations on aqueous corrosion of metals

Abstract The experimental results reported so far for the inhibition effect of underpotential deposition (UPD) of metallic cations on aqueous corrosion of metals are criticized and discussed based on the prerequisite for UPD. The inhibition effect of Pb2+, Cd2+, Zn2+ or Mn2+ on hydrogen evolution or hydrogen absorption on Armco iron or various steels is classified into three potential regions: bulk deposition, UPD and adsorption of metallic cations without discharging. Moreover, the inhibition effect of Pb2+, Tl+ or Sn2+ on anodic dissolution of pure Fe, Ni or Ni-base alloys in acidic solutions is ascribed to the UPD of these metallic cations. Particularly, in situ X-ray absorption spectroscopy (XAS) for Pb-UPD on Ni has indicated that the electro-deposited Pb species on the Ni surface is metallic to form partly surface alloy and the metallic Pb blocks the active dissolution sites of Ni to inhibit the anodic dissolution. In contrast, in situ XAS for Sn-UPD on Ni has indicated that the electro-deposited Sn species is not only bonded with Ni atoms but also bonded with oxygen atoms and that the anodic dissolution of Ni is inhibited by the oxygenated Sn species on Ni.

The kinetics of transpassive dissolution chemistry of stainless steels in nitric acid: The impact of Si

Atomic emission spectroelectrochemistry was used to monitor the elemental dissolution of two stainless steels during transpassive polarization. A 304LN stainless steel (X2 CrNiN 18-10) was compared with a 3.5 wt% Si rich stainless steel (X1 CrNiSi 18-15-4) so as to elucidate the effect of Si on the dissolution mechanism. The enrichment in Si shifted the cathodic reaction to lower potentials explaining that in hot and concentrated nitric acid containing oxidizing species, 304LN SS corrodes more rapidly due to the transpassive break of passivity, while the 3.5 wt% Si SS remains passive. However, when polarized into the transpassive domain, preferential grain boundary corrosion was observed for the 304LN but not for the 3.5 wt% Si SS, despite having similar current densities. Congruent alloy dissolution was observed in the transpassive domain with the stoichiometry of Fe(III), Cr(VI) and Ni(II) yielding a faradaic yield of 100% at early times. For longer times, with the 304LN, the faradaic yield drop to 70% indicative of intergranular dissolution in which the cations released in the intergranular space were not detected by the ICP-AES. Transmission electron microscopy coupled with energy dispersive spectroscopy showed that the interface of the 3.5 wt% Si SS enriches in Cr during a polarization in the transpassive domain of the steel. No similar enrichment was detected for the 304LN.

Reaction rates and prediction of thermal instability during aluminum alloy 6061 dissolution

ABSTRACTChemical kinetics of dissolution of aluminum alloy 6061 was investigated for the processing of Pu-238 for deep space missions. The rate of dissolution was measured by the heat release and appeared to be controlled by the rate of release of Al(OH)4− from the metal surface. Rates of reaction were measured from 273 to 365 K, giving an activation energy of 72 ± 13 kJ⋅(mol Al)−1 and a pre-exponential factor of 5 ± 3 × 109 dm3mol−1min−1. Minor alloying elements did not appear to affect the reaction kinetics. The average heat of dissolution was −360 ± 70 kJ⋅(mol NaAlO2)−1. When extrapolated to an infinitely dilute solution of aluminum, kJ⋅(mol NaAlO2)−1.

Evaluation of scalp hair nickel and chromium level changes in patients with fixed orthodontic appliance: a one-year follow-up study

Background and objectives: The release of metal ions from orthodontic appliances is part of the dissolution and biomechanical processes of alloys. Nickel (Ni) and chromium (Cr) are the elements commonly used in the manufacture of various components of fixed orthodontic appliances, including bands, brackets and wires. This study was aimed to measure the Ni and Cr ions levels in the scalp hair of patients treated with fixed orthodontic appliances in comparison of the control group.Materials and methods: The patient group consisted of 24 patients treated with fixed orthodontic appliances for one year, while the control group included 28 healthy individuals without orthodontic appliances. Analysis of the Cr and Ni was performed using atomic absorption spectrophotometer by graphite furnace method. The data were analyzed via student and paired samples t-test and ANOVA repeated measurement test.Results: After one year, the levels of Ni and Cr in two groups showed significant differences (0.086 ± 0.007 and 0.258 ± 0.009 µg/g for control group and 0.149 ± 0.010 and 0.339 ± 0.013 µg/g for patient group, respectively for Ni and Cr, p < .001). ANCOVA test by removing the effects of age, gender and the baseline levels of Ni and Cr showed that changes in these ions in the scalp hair of both groups after one year were statistically significant.Conclusion: Due to the slightly elevated levels of Ni and Cr ions in the scalp hair of patients treated with fixed orthodontic appliances and considering the cytotoxic and allergic effects of these ions, changing the ingredients in fixed orthodontic appliances is suggested for the future.

In Situ Electrochemical-AFM Study of Local Dissolution Processes of Al x Co Cr Fe Ni High-Entropy Alloys

The multiple compositionally-equivalent high-entropy alloys (HEAs) have shown remarkable potential in structural and energy-related applications. Their intrinsic random arrangement of elements results in homogeneous chemical distribution, which is expected to be beneficial for improving the corrosion resistance. However, with the increased Al content in the objective Al x CoCrFeNi (x = 0.3, 0.5, and 0.7, molar ratios) HEAs, the multi-phase microstructure with chemical segregations is inevitable. The microstructure changes from single FCC solid-solution to FCC + disordered/ordered BCC phases. The FCC and disordered BCC phases are (Cr, Co, Fe)-rich, while ordered BCC phase is (Al, Ni)-rich. This chemical segregation would lead to the localized corrosion, which evidently impact the corrosion resistance. To investigate the detailed localized corrosion mechanism, the in-situ electrochemical-AFM (EC-AFM) measurements are performed at consecutively applied anodizing potentials in a 3.5 wt.% NaCl solution in the present study. The topography changes on the surface at micro/sub-micro scale are monitored in real-time. The results show that in the single phase Al0.3CoCrFeNi alloy, at the passive region, the surface roughness increases slightly due to the formation of oxide film. While increasing the potential continuously, deposition of the corrosion products results in increased sample roughness. At the active potential region, severe local dissolution is observed as the onset of pitting. For the Al0.5CoCrFeNi alloy, the FCC matrix performs similar corrosion behavior as the single FCC phase of the Al0.3CoCrFeNi alloy. However, the active potential is easier to reach due to the preferential formation of pits at the FCC/BCC phases boundaries. For the Al0.7CoCrFeNi alloy, the critical breaking down potential of passive film decreases dramatically. No pitting-like corrosion is observed, but a large amount of selective dissolution occurred at the FCC and BCC phase boundaries at the active potential region. Local selective dissolution of the (Al, Ni)-rich ordered BCC phases is observed as well. The XPS results indicate that the oxide film with the higher Cr content is more protective, therefore, pitting and selective corrosion prefer to initiate at the (Al, Ni)-rich phases. Moreover, the trenches formed along the phase boundaries indicate that the galvanic cell formed between the FCC and BCC phases accelerate the alloy dissolution as well. Overall, in situ EC-AFM is shown to be a useful tool to explore details of the anodic oxidation/dissolution behavior of the Al x CoCrFeNi HEAs. The in-depth understanding of the local dissolution activity and corrosion behavior obtained in the present study is of importance for the future design of high performance HEAs. Figure 1. In situ EC-AFM images of (a-c) Al0.3CoCrFeNi, (d-f) Al0.5CoCrFeNi, and (g-i) Al0.7CoCrFeNi HEAs at increasing potentials. Figure 1

In situ nano- to microscopic imaging and growth mechanism of electrochemical dissolution (e.g., corrosion) of a confined metal surface

Reactivity in confinement is central to a wide range of applications and systems, yet it is notoriously difficult to probe reactions in confined spaces in real time. Using a modified electrochemical surface forces apparatus (EC-SFA) on confined metallic surfaces, we observe in situ nano- to microscale dissolution and pit formation (qualitatively similar to previous observation on nonmetallic surfaces, e.g., silica) in well-defined geometries in environments relevant to corrosion processes. We follow "crevice corrosion" processes in real time in different pH-neutral NaCl solutions and applied surface potentials of nickel (vs. Ag|AgCl electrode in solution) for the mica-nickel confined interface of total area ∼0.03 mm2 The initial corrosion proceeds as self-catalyzed pitting, visualized by the sudden appearance of circular pits with uniform diameters of 6-7 μm and depth ∼2-3 nm. At concentrations above 10 mM NaCl, pitting is initiated at the outer rim of the confined zone, while below 10 mM NaCl, pitting is initiated inside the confined zone. We compare statistical analysis of growth kinetics and shape evolution of individual nanoscale deep pits with estimates from macroscopic experiments to study initial pit growth and propagation. Our data and experimental techniques reveal a mechanism that suggests initial corrosion results in formation of an aggressive interfacial electrolyte that rapidly accelerates pitting, similar to crack initiation and propagation within the confined area. These results support a general mechanism for nanoscale material degradation and dissolution (e.g., crevice corrosion) of polycrystalline nonnoble metals, alloys, and inorganic materials within confined interfaces.

Effect of Ge addition on wettability, copper dissolution, microstructural and mechanical behavior of SnCu–Ge solder alloy

This paper explores the effects of Germanium (Ge) addition on the wetting behavior, copper dissolution, IMC formation, microstructure and mechanical behavior of SnCu alloy. Static copper dissolution was conducted as a function of contact time and in the temperature range of 260–300 °C. The results show that the Ge doped alloy has the lowest copper dissolution rate compared to SnCu, SAC305, and very much comparable with SnPb solder thus making it suitable alloy for the wave soldering process. Two solderability standards measurement (JIS vs. IPC) have been executed on different surface finishes such as OSP, ENIG, ImAg commonly used in industrial soldering process. The results showed that addition of Ge significantly improves the wetting/spread performance for all the surface finishes (ENIG, OSP and ImAg). Contact angles range from 17°–30°, the lowest contact angles being observed on ENIG surface. Microstructural analysis showed Ge addition refine the grain structure of SnCu–0.01Ge alloy. A thin IMC layer was observed, and IMC growth was not significant after multiple reflows as compared to Sn–Cu alloy. Similarly, Ge addition increases the hardness value due to uniform microstructure of SnCu–Ge alloy. The tensile testing results also showed an increase in tensile strength and tolerable ductility.

Understanding multi-element alloy passivation in acidic solutions using operando methods

The kinetics of passivation and dissolution of many corrosion resistant engineering alloys remain incompletely characterized. Clarification of such kinetics and the unique role of alloying elements were investigated upon Ni-22% Cr and Ni-22% Cr-6% Mo, wt%, in an acidic chloride-free sulfate environment using simultaneous electrochemistry, on-line Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS), and Single Frequency-Electrochemical Impedance Spectroscopy (SF-EIS). The combination of methods enabled in-operando tracking of the total current densities for (i) oxidation, (ii) cation ejection by multiple paths, and (iii) oxide film growth during non-steady state passivation. An improved and physically accurate interpretation of passivation processes is presented and clarifies and alters the frequently made assumption that Cr2O3 is the dominant oxide on Ni-Cr alloys throughout oxidation.

Electrochemical and microstructural investigations on an as-cast and solution-annealed Al–Mg–Sn–Ga alloy as anode material in sodium chloride solution

In this research, the electrochemical properties of a stir cast Al-0.65Mg-0.15Sn-0.05Ga (wt.%) alloy as an anode material in 3 wt.% NaCl solution was examined by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion behavior of the material was also evaluated using self-corrosion rate, hydrogen evolution, open circuit and closed circuit potentials, and anode efficiency measurements. In addition, the microstructure of the material was studied using scanning electron microscopy (SEM) and the intermetallic particles were analyzed by energy dispersive spectrometer (EDS). The results showed that tin inclusions were formed within the grains and along the grain boundaries and the dissolution of aluminum substrate was occurred preferentially around these particles leading to form round pits. The dissolution of alloy was accompanied by hydrogen gas evolution from cathodic tin particles. Polarization measurements showed active behavior with considerably negative corrosion potential value without any passive region. The obtained impedance results showed an increase in the impedance values due to the coverage of anode surface by reaction products during immersion. A sample of the alloy which was subjected to homogenizing annealing at 570 °C showed more active behavior by providing more negative open and closed circuit potential values and improved anode efficiencies at higher impressed currents, but evolved higher amounts of hydrogen compared to the as-cast anode.

In-Situ Determination of Hydrogen Evolution Rate on Mg and Mg Alloy during Anodic Dissolution By Gas-Chromatographic Analysis

Mg and Mg alloys are expected to be an active material for the negative electrode of air batteries 1) because they dissolve actively in the aqueous solution at less noble potential. However, the hydrogen evolution is occurred on the Mg and Mg alloys during the anodic dissolution in the aqueous solution, which calls the negative difference effect, NDE 2, 3). It may lead to the self-discharge and loss of discharge capacity of air batteries in operation. In the present study, we determined the hydrogen evolution rate on Mg and Mg alloys during anodic dissolution by gas-chromatographic analysis. Song et al. 4) reported the hydrogen evolution behavior of Mg and Mg alloys. They 4) carried out the gas collection by using a burette vertically mounted over the funnel to estimate the volume of hydrogen gas generated on Mg alloys at different applied current density. Comparing to this, we previously developed an electrochemical cell combined with a gas chromatograph 5) to perform an in-situ determination of hydrogen evolution rate on Mg during anodic dissolution. In this system, the gas generated on the working electrode is directly delivered to a gas chromatograph by a stream of carrier gas 5), namely, the qualitative and quantitative analysis of the gas generated on the working electrode can be carried out. It enables us the analysis of gases involving nitrogen and oxygen during anodic dissolution of Mg and Mg alloys. The details of the developed system and measurement conditions are described in our previous work 5). In the present study, hydrogen evolution rate on various kinds of Mg alloys during anodic dissolution were determined by developed system and the gases evolved on Mg alloys during anodic dissolution were discriminated.

The effect of Mg-Ca-Sr alloy degradation products on human mesenchymal stem cells.

Biodegradable Mg alloys have the potential to replace currently used metallic medical implant devices, likely eliminating toxicity concerns and the need for secondary surgeries, while also providing a potentially stimulating environment for tissue growth. A recently developed Mg–Ca–Sr alloy possesses advantageous characteristics over other Mg alloys, having a good combination of strength and degradation behavior, while also displaying potentially osteogenic properties. To better understand the effect of alloy degradation products on cellular mechanisms, in vitro studies using human bone marrow‐derived mesenchymal stem cells were conducted. Ionic products of alloy dissolution were found to be nontoxic but changed the proliferation profile of stem cells. Furthermore, their presence changed the progress of osteogenic development, while concentrations of Mg in particular appeared to induce stem cell differentiation. The work presented herein provides a foundation for future alloy design where structures can be tailored to obtain specific implant performance. These potentially bioactive implants would reduce the risks for patients by shortening their healing time, minimizing discomfort and toxicity concerns, while reducing hospital costs. © 2017 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 697–704, 2018.

First-principles modeling of anisotropic anodic dissolution of metals and alloys in corrosive environments

There have been extensive experimental observations of the anisotropic corrosion behavior of metals and alloys, and their mechanisms were assumed to be correlated with the so-called surface energy or the work function. However, to date, a specified mechanism or theory to interpret anisotropic corrosion behavior remains unclear. Here, we determine the anisotropic anodic dissolution of metals and alloys in corrosive environments by developing a formula to specify the relationship between the electrode potential (U) and the current density (I) by considering the basic parameters of our defined surface energy density (Esurf/ρ) and the work function (Φ). Therefore, we build an ab initio model to evaluate the anisotropic anodic dissolution behavior of metals and alloys using the inputs obtained within density functional theory. This theory is further validated in the case of variations in the crystallographic planes of Mg. Moreover, some selected alloying additions such as Ga, Cd, Hg, In, As, and Cr are theoretically elucidated to effectively reduce the anodic dissolution rates of the Mg matrix to some extent, in close agreement with available experimental observations. This model is capable of predicting the anisotropic anodic dissolution behavior, providing a promising perspective for designing better corrosion-resistant alloys.