Corrosion Response Research Articles

Compositional design and in vitro investigation on novel Zr–Co–Cu–Ti metallic glass for biomedical applications

Zr–Co–Cu–Al based metallic glasses (MGs) are potential material for making surgical equipment due to their ultra-high strength. However, presence of elemental Al in these alloys is not desirable due to biotoxicity. To counter this problem the present study is undertaken to design metallic glass forming composition by replacing Al with Ti. Design strategy adopted is based on thermodynamic modelling by rationalizing the effect of chemical enthalpy and atomic mismatch entropy along with statistically controlled atomic arrangement through configurational entropy. The rapid solidification technique was used to synthesize MG in melt spun ribbon form. The structural nature and glass stability of the ribbon are confirmed by X-Ray diffraction, transmission electron microscopy and differential scanning calorimetry. Corrosion response of the MG is thoroughly investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in a simulated body fluid (SBF) environment. The mechanical property of MG is evaluated using microindentation technique. Improvement in corrosion resistance is observed in all the SBF solutions along with in vitro biocompatibility study using MG-63 cell viability experiment.

(Digital Presentation) Understanding Metal Additive Manufactured Surfaces

Metal additive manufacturing (AM) is being pursued as manufacturing technique in order to shorten development cycles and reduce cost through rapid iteration and agile design. Metal AM allows for designs that were not previously possible, optimizing the balance between mechanical strength and weight. However, rough as-built surfaces do not meet engineering specifications, with roughness measurements between Sa = 5 – 60 mm. Furthermore, depending on the build angle the surface roughness varies widely within a single part. These rough surfaces result in different surface morphology and chemistry compared to other manufacturing methods which has a direct impact on the susceptibility to localized corrosion and mechanical performance. This variation is also amplified depending on the machine used to build the material. We have extensively characterized the surface roughness, and corrosion response of AM 316L stainless steel (SS) that has been built on different machines which result in significantly different surface properties.Our team is also developing environmentally friendly surface finishing techniques to reduce the surface roughness to meet specifications, increase corrosion performance, and drastically reduce the part-to-part variations. We have used optical methods to measure the surface roughness of as-built AM 316L SS, A20x (AM aluminum alloy), and Ti6-4. Aqueous and atmospheric corrosion measurements have been performed on 316L SS. Finally, EDS/SEM measurements reveal there is significant chemical segregation on the surface of the as-built material; however, surface treatment methods being developed by the group have been shown to remove this layer. Post-processing surface treatments result in a more homogeneous surface and improve the performance of the material.

(Digital Presentation) Effects of Surface Finish on the Corrosion Performance of Additively Manufactured Metals

Metal additive manufacturing (AM) is becoming a transformative technology in the manufacturing industry. The as-built surfaces produced by metal AM are very different compared to wrought material, typically resulting in very rough surfaces that have different corrosion properties. There are a large number of studies that have attempted to understand the corrosion response of metal AM. However, these studies are typically performed on materials that have been printed on a single machine. As a result, there are significant inconsistencies in the literature due to the high variability in the quality of parts manufactured on different machines. We will present work that compares the corrosion response of AM 316L stainless steel (SS) that has been printed on multiple machines. Our results have shown there is significant variability observed in the corrosion performance of metal AM parts built on different machines and within a single build plate. The observed corrosion performance is likely affected by the stability of the passive film, chemical segregation, and microstructure of the surface. We also propose that surface finishing of AM 316L SS reduces the part-to-part variations observed in the corrosion performance of the material printed on different machines and within a single build plate.This talk will discuss the corrosion properties of AM 316L SS, A20x (AM aluminum alloy), and Ti-6Al-4V parts produced by direct metal laser sintering (DMLS). The majority of our work focused on understanding the susceptibility to localized corrosion of metal additively manufactured materials with respect to build machine, surface roughness, and build angle. As a result, we also examined the corrosion performance of 316L SS built on a single instrument as we varied the build parameters. Conventional electrochemical corrosion experiments were used to characterize corrosion performance, including open circuit potential, potentiostatic electrochemical impedance spectroscopy, and potentiodynamic polarization scans. White light interferometry, optical profilometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were utilized to characterize the surface of the samples.

Effect of chemically accelerated vibratory finishing on the corrosion behavior of Laser Powder Bed Fusion 316L stainless steel

As-built surface morphology and texture of Additively Manufactured (AM) metal parts reduce their mechanical and corrosion properties. One chemically accelerated vibratory finishing (CAVF) technique employs a chemically-based stepwise process to gradually remove surface roughness without the need for significant manual manipulation. While this procedure is effective at producing smooth surfaces, the corrosion response of the resulting surface is unknown. This study evaluates the effect of this surface finishing technique on the corrosion response and mechanisms of 316L stainless steel fabricated using Laser Powder Bed Fusion (L-PBF) AM techniques. The results show that the CAVF process does not obviously change the microstructure but imparts residual compressive stresses on the surface which improve the breakdown potential compared to other specimens evaluated. Further, the process removed surface Cr3C2 precipitates formed during heat treatment. CAVF improves surface finish and mechanical properties with an added benefit of enhancing the corrosion response of processed parts.

Base material location dependence of corrosion response in friction-stir-welded dissimilar 2024-to-5083 aluminum alloy joints

The effects of the base material (BM) location on the mechanical properties and the exfoliation corrosion performance of friction-stir-welded (FSWed) dissimilar 2024-to-5083 aluminum alloy joints were investigated. Scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), tensile tests and electrochemical experiments were conducted. The results revealed that the BM location had little effect on the tensile properties of the joints. The grain orientation spread (GOS) value of 2024 alloy side was lower than that of 5083 alloy side. Intergranular corrosion occurred mainly on the 2024 alloy side, while the grain interior of the 5083 alloy side was corroded due to the higher GOS value and dislocation density. The FSWed dissimilar joints with a superior exfoliation corrosion resistance could be achieved when the 5083 aluminum alloy with better corrosion performance was positioned on the retreating side.

Assessing Mg/Si3N4 biodegradable nanocomposites for osteosynthesis implants with a focus on microstructural, mechanical, in vitro corrosion and bioactivity aspects

Magnesium-based biodegradable implant materials for the osteosynthesis process (fixation or stabilizing of a fractured bone) are on the verge of being used clinically. However, the rapid degradation of magnesium-based materials in the physiological environment results in a loss of mechanical integrity before the complete healing of the fracture site. To address this issue, the present study used Silicon Nitride (Si3N4) nanoparticles to improve the in-vitro degradation resistance along with the mechanical strength and ductility of Magnesium. The Si3N4 nanoparticles were homogeneously reinforced in the pure Magnesium matrix through the ultrasonic-assisted stir casting method. Moreover, the effect of Si3N4 nanoparticles on microstructure, mechanical, in-vitro corrosion and bioactivity response of Mg/Si3N4 nanocomposites was studied. Notably, the inclusion of 1.0 vol% Si3N4 nanoparticles increased tensile strength by 1.4 times and ductility by two times. In addition, the elastic modulus of Mg/Si3N4 nanocomposites is within the range of local cortical bone elastic modulus. In-vitro immersion experiments in simulated physiological fluids revealed a 2.2-fold reduction in degradation rate compared to pure Magnesium. Moreover, the addition of Si3N4 nanoparticles enhanced the in-vitro bioactivity, as the surface of the nanocomposites showed a high needle-like Ca–P apatite layer with a 1.41 Ca/P ratio of the deposited layer close to hydroxyapatite's Ca/P ratio (1.64). Overall, this study provides the basis for the fabrication of stable yet completely biodegradable Mg/Si3N4 nanocomposite bone implants for the osteosynthesis process.

Deposition of Aluminide Coatings onto AISI 304L Steel for High Temperature Applications.

The nickel aluminides are commonly employed as a bond coat material in thermal barrier coating systems for the components of aeroengines operated at very high temperatures. However, their lifetime is limited due to several factors, such as outward diffusion of substrate elements, surface roughness at high temperatures, morphological changes of the oxide layer, etc. For this reason, inter-diffusion migrations were studied in the presence and absence of nickel coating. In addition, a hot corrosion study was also carried out. Thus, on one set of substrates, nickel electrodeposition was carried out, followed by a high activity pack aluminizing process, while another set of substrates were directly aluminized. The microstructural, mechanical, and oxidation properties were examined using different characterization techniques, such as SEM-EDS, optical microscopy, XRD, optical emission spectroscopy, surface roughness (Ra), and adhesion tests. In addition, the variable oxidation temperatures were employed to better understand their influence on the roughness, degree of spallation (DoS), and morphology. The results show that AISI 304L substrates do not respond to aluminizing treatment, i.e., no aluminide coating was formed; rather, a nearly pure aluminum (or alloy) was observed on the substrate. On the contrary, successful formation of an aluminide coating was observed on the nickel-electrodeposited substrates. In particular, a minimum amount of migrations were noted, which is attributed to nickel coating. Moreover, the scratch test at 10 N load revealed neither cracking nor peeling off, thereby indicating good adhesion of the aluminide coating before oxidation. The as-aluminized samples were oxidized between 700 °C to 1100 °C in air for 8 h each. The degree of spallation showed an incremental trend as temperatures increased. Likewise, oxide morphologies showed temperature dependence. On the other hand, average surface roughness (from Ra = 2.3 µm to 5.8 µm) was also increased as temperatures rose. Likewise, the mass gain showed linearity as temperatures increased during oxidation. The hot corrosion responses of electrodeposited-aluminized samples were superior among all specimens. An extensive discussion is presented based on the observations noted above.

Corrosion behavior of Mg-Zn-Zr-RE alloys under physiological environment – Impact on mechanical integrity and biocompatibility

Benefits of RE addition on Mg alloys strength and corrosion resistance are widely reported but their effects on biodegradability and biocompatibility are still of concern. This paper investigates the effect of RE additions on biodegradability of Mg-Zn alloys under simulated physiological conditions. In this context, two commercial Mg-Zn-Zr-RE alloys, namely ZE41 and EZ33, with same RE addition but different concentrations are studied in Hank's Balanced Salt Solution (HBSS) at 37 °C and with pH of 7.4. Weight-loss, hydrogen evolution, real-time in-situ drop test, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization are deployed to study corrosion characteristics. The mechanical integrity of both alloys is assessed by mechanical testing post immersion. Furthermore, in vitro biocompatibility is evaluated by indirect cytotoxicity tests using NIH3T3 cells. Results reveal that although both alloys showed similar microstructure, size and distribution of precipitates played a significant role on its corrosion response. EIS and open circuit potential results show stable film formation on EZ33, while ZE41 showed passive layer formation followed by its deterioration, over the analyzed time period. Using real-time drop test, it was shown in ZE41 alloy that both T-phase and Zr-rich precipitates acted as micro cathodes, resulting in an unstable surface film. In EZ33, Zr-rich regions did not influence corrosion response, resulting in better corrosion resistance that was corroborated by post-immersion surface morphology investigations. The higher degradation observed in ZE41 alloy resulted in higher drop in flexural and tensile strength compared to EZ33 alloy. In addition, cytotoxicity tests on NIH3T3 cells revealed that cell viability of EZ33 increased with increasing incubation time, contrary to ZE41, owing to its lower biodegradation behavior and despite higher concentrations of REs. Present results show that an increase in RE concentration in EZ33, relative to ZE41, had a positive effect on corrosion rate that subsequently controlled alloy mechanical integrity and biocompatibility.

Corrosion Response of Carbon Steel Exposed to Dynamic H2S Aqueous Solution in the Presence of Bicarbonate Ions and Natural Aeration

Corrosion Response of Carbon Steel Exposed to Dynamic H2S Aqueous Solution in the Presence of Bicarbonate Ions and Natural Aeration

Influence of stoichiometry on the corrosion response of titanium oxide coatings produced by plasma electrolytic oxidation

In this study the corrosion mechanism leading to coating debonding in acidic environments, produced by plasma electrolytic oxidation (PEO) on Ti, is investigated through electrochemical impedance spectroscopy (EIS), potential step chronometric, and a detailed structural characterization according to the use of electron energy loss spectroscopy (EELS). It will be demonstrated that a slightly reduced oxide will enhance proton adsorption and percolation leading to oxide debonding, while the synthesis of a barrier layer mainly composed by Ti 4 + oxide bearing phases and low sulfur content will retard H + permeation enhancing H2 evolution in correspondence of the oxide surface.

Effect of alloying with Ni, Cr and Al on the atmospheric and electrochemical corrosion resistance of ferritic ductile cast irons

The corrosion control of ductile cast irons becomes a technological challenge when supplying castings to customers due to the high reactivity of this alloy in contact with air. An interesting alternative to the protective systems such as coatings or corrosion inhibitors included in packaging processes is the chemical modification of the cast alloys by means of alloying elements addition which are able to improve the corrosion resistance of ductile cast irons. Ni, Cr and Al added to the cast alloys significantly affect their structure and properties, among them their corrosion response, when exposed to air. It has been observed that Ni and Al improve the corrosion behaviour while Cr additionally promoted pearlite and carbides formation. The results from the corrosion tests performed on ductile cast iron alloys which contain these three elements are discussed in the present work.

Effect of the oxidation reaction interface on the accelerated corrosion behaviour of Al–Mg–Si alloy

ABSTRACT Oxide films for Al–Mg–Si alloys with various aluminium oxide contents from 65.99 to 80.97% and thicknesses ranging from 1.7 to 5.1 μm were obtained. The effect of the oxidation reaction interface on the accelerated corrosion behaviour of Al–Mg–Si alloy has been investigated by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electron probe microanalyzer (EPMA), accelerated corrosion tests and electrochemical tests. Accelerated corrosion tests indicated that incomplete oxide films reduced the corrosion resistance even with increasing oxide film thickness and Al2O3 content in a solution containing 30 g L−1 NaCl and 10 mL HCl (ρ = 1.19 g mL−1). The thicker oxide film effectively inhibited corrosion behaviour, while the thinner oxide film disappeared and its substrate suffered corrosion after immersion for 6 h, corresponding to the dissolution of oxide film and shedding of second-phase practices on interfaces. Accelerated corrosion response of various oxidation reaction interfaces was built by an equivalent electrochemical circuit.

Designing the microstructural constituents of an additively manufactured near β Ti alloy for an enhanced mechanical and corrosion response

Additive manufacturing of near β-type Ti-13Nb-13Zr alloys using the laser powder bed fusion process (LPBF) opens up new avenues to tailor the microstructure and subsequent macro-scale properties that aids in developing new generation patient-specific, load-bearing orthopedic implants. In this work, we investigate a wide range of LPBF parameter space to optimize the volumetric energy density, surface characteristics and melt track widths to achieve a stable process and part density of greater than 99 %. Further, optimized sample states were achieved via thermal post-processing using standard capability aging, super-transus (900 °C) and sub-transus (660 °C) heat treatment strategies with varying quenching mediums (air, water and ice). The applied heat treatment strategies induce various fractions of α, martensite (α', α'') in combination with the β phase and strongly correlated with the observed enhanced mechanical properties and a relatively low elastic modulus. In summary, our work highlights a practical strategy for optimizing the mechanical and corrosion properties of a LPBF produced near β-type Ti-13Nb-13Zr alloy via careful evaluation of processing and post-processing steps and the interrelation to the corresponding microstructures. Corrosion studies revealed excellent corrosion resistances of the heat-treated LPBF samples comparable to wrought Ti-13Nb-13Zr alloys.

Correction to: Microstructure, mechanical, in vitro corrosion and biocompatibility response study of as-cast and as-rolled Mg–5Zn–0.5Zr alloy

Correction to: Microstructure, mechanical, in vitro corrosion and biocompatibility response study of as-cast and as-rolled Mg–5Zn–0.5Zr alloy

In vitro corrosion response of CoCrMo and Ti-6Al-4V orthopedic implants with Zr columnar thin films

This study focuses on the functionalized modification of Ti-6Al-4V and CoCrMo alloys substrates widely used by the biomedical domain as total joint replacements (TJRs) of the hip and knee. To improve the corrosion resistance of these devices, nanostructured columnar zirconium (Zr) thin films were produced by oblique angle deposition (OAD) using DC magnetron sputtering to model the particular design of the joint. The influence of the angular distribution of the incoming particle flux on the resulting film morphology (column tilt angle, porosity) and electrochemical behavior was studied by varying the substrates inclination angle θ from 15 to 90°. The experimental deposition process was reproduced by kinetic Monte Carlo (kMC) models. With the increase of the flux incidence angle α from 0 to 70°, the film thickness and the column tilt angle β vary in agreement with the theoretical models. Additionally, the corrosion behavior of uncoated and Zr-coated alloys (CoCrMo and Ti-6Al-4V) was compared through open circuit potential chronopotentiometry and electrochemical polarization test in NaCl 0.9% solution at 37 °C. It was found that the corrosion protection was successfully improved by the presence of the films. The variation of the corrosion behavior with the flux incidence angle is explained by the changes in the film density.

Effects of plasma nitriding in the corrosion behavior of an AISI 4140 steel using a seawater medium solution

In this work, a comprehensive analysis was performed to characterize the corrosion response of untreated and nitrided AISI 4140 steel. Samples were plasma nitrided at low temperature (∼400 °C) with two different gas composition. Electrochemical impedance spectroscopy, potentiodynamic polarization in artificial seawater solution at room temperature test were performed. Nitrided samples increases hardness on surface compared to the untreated sample. Nitrided samples composed by a mixture of ε-Fe2-3N and γ′-Fe4N nitrides phases offered significant influence on anodic and cathodic polarization. Nyquist curves indicated a higher corrosion resistance of nitrided samples compared to untreated sample.

Integrated high-throughput research in extreme environments targeted toward nuclear structural materials discovery

Arguably one of the most important factors in the fast deployment of advanced nuclear reactors, with major improvements in safety, is the development and qualification of radiation and corrosion tolerant materials, that serve as the structural components in reactor cores. However, the discovery, improvement, and assessment of materials resistant to radiation and corrosion in the advanced reactors’ extreme environments is quite demanding, time-consuming, and costly, which represents a significant barrier to materials innovation and qualification for nuclear energy. This short review highlights a novel, integrated, high-throughput (HTP) research framework to develop understanding and predictive models for irradiation at high doses and molten salt corrosion responses of structural Compositionally Complex Alloys (CCAs), with the objective to accelerate materials discovery for high-temperature nuclear structural applications. Using a novel in situ alloying technique, arrays of additively manufactured bulk CCAs are processed, heat-treated, and characterized, while still attached to the build plate. Leveraging recent development in automation of heavy-ion irradiation experiments at the University of Wisconsin Ion Beam Laboratory, arrays of CCAs can be rapidly irradiated to hundreds of dpa up to 800 °C. An innovative droplet corrosion method is also used to test molten salt corrosion behavior of CCAs arrays. Automated and rapid characterization methods are used to assess the irradiation and molten salt corrosion resistance of CCAs. Finally, a brief discussion of the results is presented considering future use of machine-learning-based methods to develop useful trends and highlight features of importance. Using this novel HTP approach, a robust and reliable database containing literally hundreds of data points for irradiation and corrosion responses of CCAs can be established within a year, which is considered a significant increase in the pace of nuclear structural materials research and discovery.

Predicting the corrosion-wear response of an isolated austenite phase under anodic polarization

The wear-assisted corrosion response of a super-duplex stainless-steel from a single asperity contact was obtained using atomic force microscopy (AFM). The AFM tip applied increasing loads to an isolated surface region that was polarized to two different static potentials in the passive potential region of the alloy in a 0.6 M NaCl solution. The wear-assisted corrosion response was modeled using an interfacial film growth model to obtain consistent kinetics parameters for the austenite phase response across applied loads and polarization potentials. The average response was then fit with an Arrhenius model that suggested that the stress fields from the single asperity contact induced damage in the protective oxide but also disrupted other oxide-formation processes at the oxide-electrolyte interface, thereby slowing repassivation, and allowing increasingly high corrosion currents as the stress fields increased.

Development of a Non-Equimolar Alcrcufeni High-Entropy Alloy and its Corrosive Response to Marine Environment Under Different Temperatures and Chloride Concentrations

Development of a Non-Equimolar Alcrcufeni High-Entropy Alloy and its Corrosive Response to Marine Environment Under Different Temperatures and Chloride Concentrations

Influence of Corrosion Response on Thin Wall Debit Effect of a Hf Contained Casting Ni-Based Superalloy

Influence of Corrosion Response on Thin Wall Debit Effect of a Hf Contained Casting Ni-Based Superalloy