Corrosion Resistance Of Alloy Research Articles

Effect of Anodic Oxidation Pulse Voltage on Antibacterial Properties and Biocompatibility of Ti-Ag Alloy

For the application of titanium and titanium alloys in orthopedic implant materials, the antibacterial properties and cell biocompatibility determine whether the implant surgery is successful. In this study, a functional anodic oxidation (AO) coating was successfully prepared to modify the surface of Ti-Ag alloy. The surface characteristics of the anodized Ti-Ag alloy were analyzed using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The corrosion characteristics of Ti-Ag samples were tested by an electrochemical workstation. In addition, the antibacterial properties and cell activity were studied by the plate count method and MC3T3-E1 cell staining. The results indicate that the AO process can generate a multi-functional TiO2/Ag2O coating with a large number of block and flower-like structures on the surface of a Ti-Ag alloy. When the AO voltage of the sample is 120 V, the maximum roughness is 0.73 μm and the minimum wetting degree is 23°, which improves the biocompatibility. The corrosion test results show that AO treatment can improve the corrosion resistance of a Ti-Ag alloy. The oxidation voltage is 20 V and the coating has the best corrosion resistance. The corrosion open circuit potential (Eocp) is 107.621 mV and the corrosion current density (icorr) is 2.241 × 10−8 A·cm−2. This coating can promote ion release and show more than 99% of a strong antibacterial ability against S. aureus. The results of the compatibility evaluation by cultured cells showed that the multifunctional coating formed by the anodic oxidation process did not cause cytotoxicity and promoted the adhesion of MC3T3-E1 cells.

Machine Learning-Assisted Prediction of Corrosion Behavior of 7XXX Aluminum Alloys

High-strength and lightweight 7XXX Al alloys are widely applied in aerospace industries. Stress corrosion cracking (SCC) in these alloys has been extensively discussed, and electrochemical corrosion should be brought to the forefront when these materials are used in marine atmospheric environments. This work obtained the corrosion potentials (Ecorr) and corrosion rates of 40 as-cast 7XXX Al alloys by potentiodynamic polarization tests and immersion tests, respectively; then, chemical compositions and physical features were used to build a machine learning model to predict these parameters. RFR was used for the prediction model of Ecorr with the features Cu, Ti, Al, and Zn, and GPR for that of the corrosion rate with the features of specific heat, latent heat of fusion, and proportion of p electrons. The physical meaning and reasonability were discussed based on the analysis of corrosion morphology and precipitated composition. This work provides a reference for the design of corrosion-resistant 7XXX Al alloys and shows a method of conducting corrosion mechanism evaluation by using machine learning.

Synergistic Enhancement of Strength, Ductility, and Corrosion Resistance of Ti6Al4V Alloy Through Low Cu Doping and Hot Extrusion

A Cu-containing Ti6Al4V alloy is considered an ideal biomedical material due to its excellent antibacterial properties. However, the addition of Cu leads to a mismatch in strength, ductility, and corrosion resistance, which hinders their further application. To address this issue, the study utilized low Cu doping and hot extrusion to optimize the material’s properties. The results showed that the primary lamellar structures were transformed into equiaxed grains, with an average grain size reduced from 10 μm to 300 nm. The nanoequiaxed grains had a homogeneous elemental composition and a stronger base texture, with orientations aligned with the extrusion direction. As a result, synergistic strengthening in terms of strength, ductility, and corrosion resistance was achieved. The film resistance increased from 127 kΩ·cm2 to 325 kΩ·cm2, the ultimate tensile strength (UTS) increased from 1,030 MPa to 1,330 MPa, and the elongation increased from 7% to 21%. These improvements were attributed to the nanostructure and basal texture, which facilitated the formation of a thicker passive film and reduced pitting corrosion, thereby enhancing corrosion resistance. Additionally, the nanoequiaxed grains could provide grain boundary strengthening and texture strengthening on UTS and ensure uniform deformation for elongation.

Albumin suppresses oxidation of TiNb alloy in the simulated inflammatory environment.

Literature data has shown that reactive oxygen species (ROS), generated by immune cells during post-operative inflammation, could induce corrosion of standard Ti-based biomaterials. For Ti6Al4V alloy, this process can be further accelerated by the presence of albumin. However, this phenomenon remains unexplored for Ti β-phase materials, such as TiNb alloys. These alloys are attractive due to their relatively low elastic modulus value. This study aims to address the question of how albumin influences the corrosion resistance of TiNb alloy under simulated inflammation. Electrochemical and ion release tests have revealed that albumin significantly enhances corrosion resistance over both short (2 and 24 h) and long (2 weeks) exposure periods. Furthermore, post-immersion XPS and cross-section TEM analysis have demonstrated that prolonged exposure to an albumin-rich inflammatory solution results in the complete coverage of the TiNb surface by a protein layer. Moreover, TEM studies revealed that H2O2-induced oxidation and further formation of a defective oxide film were suppressed in the solution enriched with albumin. Overall results indicate that contrary to Ti6Al4V, the addition of albumin to the PBS + H2O2 solution is not necessary to simulate the harsh inflammatory conditions as could possibly be found in the vicinity of a TiNb implant.

Exploring the impact of Al alloying on microstructure and hot nitric acid corrosion resistance of Ti-xAl (x=0, 1, 2, 3, 4, 5) alloys

Enhancing the corrosion resistance of titanium alloys in hot nitric acid environments is imperative for advancing spent fuel reprocessing. Here, we explored the impact of Al alloying on microstructure and corrosion resistance of Ti-Al alloys via experimental assessments and theoretical computations. Results indicated that Al alloying induced a comparable Widmanstatten structure and increased hardness. Electrochemical findings demonstrated the optimal corrosion resistance for the alloy with 4 wt% Al. DFT computation presented the highest WF and the lowest EF for Ti-4Al alloy, indicative of superior thermodynamic stability. Eventually, a mechanistic understanding of Al alloying on nitric acid corrosion resistance was proposed.

The influence of La and Ce additions on the solidification of alloys from the Al–Fe system

AbstractAluminium alloys are popular in modern applications due to their lightweight, high strength and ductility. Alloys in the 8xxx series have similar properties to those in the 1xxx series, but are stronger, are more malleable and have higher stiffness. The addition of rare earths (RE) can refine the as-cast microstructure and, as a result, can increase the corrosion resistance and mechanical properties of aluminium alloys at room and high temperatures. The effects of rare earth (Ce and/or La) additions to Al-1.4Fe alloys were investigated. Thermal analysis of the solidification behaviour of the reference alloy showed the occurrence of three reactions corresponding to the formation of α-Al, eutectic (α-Al + AlxFey) and Fe intermetallics, respectively. The results showed similar reactions for the Ce- and/or La-modified alloy, but at slightly different temperatures, indicating a change in the forming phases due to the addition of Ce and/or La. In all cases, the microstructures were typically hypoeutectic, consisting of the primary α-Al and the eutectic (α-Al + AlxFey). The effect of grain refinement of the primary α-Al grains of the as-cast alloy was observed by the addition of RE, while La showed the strongest effect. The effect of the RE additions showed no obvious differences in the morphology of the eutectic AlxFey, although they were present in these phases. When Ce and/or La were added, (α-Al + Al11Ce3) and/or (α-Al + Al11La3) eutectics were formed, while Fe was not detected in these eutectics.

Corrosion resistance study of ZIF-67/Co-Fe LDHs composite coating on the surface of AZ31 magnesium alloy micro-arc oxidation film

Magnesium (Mg) alloys can be applied in many fields, but their poor corrosion resistance limits their widespread applications. This study prepared a zeolitic imidazolate framework (ZIF-67)/Co-Fe layered double hydroxides (LDHs) composite coating on micro-arc oxidation (MAO) coated Mg alloy AZ31. The surface, interface, and corrosion resistance of the composite coating were studied. The results demonstrate that the ZIF-67/LDHs composite coating showed lower corrosion current density icorr (1.31×10−8 A∙cm–2) than AZ31 (5.20×10−5 A∙cm–2), MAO (1.16×10−7 A∙cm–2) or LDHs (7.78×10−8 A∙cm–2). After immersing in a 3.5 wt% NaCl solution for 14 days, its icorr still remained the lowest, exhibiting excellent corrosion resistance to AZ31. It was of great significance in improving the corrosion resistance of Mg alloys, and this compositely growth technology was expected to be applied to other metals.

Electrochemical properties of MnSe inclusions and improving the pitting corrosion resistance of stainless steel via Se microalloying

Controlling the electrochemical properties of non-metallic inclusions is of substantial interest in the design of corrosion-resistant alloys. To the best of our knowledge, the dissolution and pitting corrosion behavior of selenide inclusions in stainless steels and the improvement of the pitting corrosion resistance of type 304 stainless steels via Se microalloying have not been investigated. In this study, stainless steel specimens containing artificial MnS and MnSe inclusions were fabricated via spark plasma sintering to systematically investigate their electrochemical properties. The superior pitting corrosion resistance and dissolution resistance of MnSe to those of MnS were demonstrated. The results obtained from the sintered specimens were applied to improve the pitting corrosion resistance of type 304 stainless steels via Se microalloying. Adding a trace amount of Se (0.005 mass%) altered the readily soluble sulfide inclusions to dissolution-resistant selenide-type inclusions, resulting in improved pitting corrosion resistance of type 304 stainless steel.

Structural, Electrical and Corrosion Properties of Bulk Ti-Cu Alloys Produced by Mechanical Alloying and Powder Metallurgy.

Binary Ti100-x-Cux (x = 1.6 and 3.0 wt.%) alloys were produced by the application of mechanical alloying and powder metallurgy processes. The influence of the copper concentration in titanium on the microstructure and properties of bulk alloys was investigated. The synthesized materials were characterized by an X-ray diffraction technique, scanning electron microscopy, and chemical composition determination. The electrochemical and corrosion properties were also investigated. Cold compaction and sintering reduced the content of α-Ti content in Ti98.4-Cu1.6 and Ti97-Cu3 alloys to 92.4% and 83.7%, respectively. Open Circuit Potential measurements showed a positive shift after the addition of copper, suggesting a potential deterioration in the corrosion resistance of the Ti-Cu alloys compared to pure Ti. Electrochemical Impedance Spectroscopy analysis revealed significant improvement in electrical conductivity after the addition of copper. Corrosion testing results demonstrated compromised corrosion resistance of Ti-Cu alloys compared to pure Ti. In summary, the comprehensive investigation of Ti100-x-Cux alloys provides valuable insights for potential applications in biosensing.

Effect of 0.3 at. % Ce on the corrosion resistance of Fe40Ni20Co20Cr20 high-entropy alloy in 3.5 wt% NaCl solution

The impact of trace Ce doping on the pitting behavior of Fe40Ni20Co20Cr20 high-entropy alloy in a 3.5 wt% NaCl solution was examined. The results indicate that the addition of trace Ce elements leads to a notable reduction in grain size and improved corrosion resistance of the alloy, the critical pitting potential of the alloy increased to 428 mv, and the corrosion resistance of the passivation film was significantly enhanced. This improvement can be mainly attributed to the strong surface activity of Ce, which promotes the formation of Cr2O3 in the passivation film, resulting in a more stable and protective film layer. The ΔE (difference between corrosion potential and zero charge potential) of the high-entropy alloys (HEAs) was negative, indicating a decrease in the adsorption capacity of the electrochemical interface for Cl−. This reduction helps to mitigate pitting corrosion on the surface of the passivation film caused by Cl− erosion.

THE CORROSION INHIBITION EFFECT ON THE ALUMINUM ALLOY AZ91C'S FATIGUE BEHAVIOR IN THE SALINE ENVIRONMENT

Investigations were made into the fatigue in the magnesium alloy AZ 91C cast in corrosive fluids and air at varied NaCl solution concentrations. Fatigue specimens will be subjected to surface stress testing in corrosive conditions with a stress amplitude of 75 MPa both after and before coating. To comprehend the behavior of the magnesium material, its fatigue life, corrosion product (X-ray spectra), and fracture properties will be examined. The corroding medium (NaCl) has been found to significantly shorten the fatigue life of the magnesium alloy AZ91C. Chemical conversion treatment was applied to the AZ91C alloy to improve corrosion resistance and corrosion fatigue resistance. MgSnO3 was found in the XRD patterns of the stannite-treated AZ91C alloy, and this treatment slightly improved the alloy's corrosion resistance in an alkaline stannite solution with a pH of 7. H2O and SEM images demonstrate that chloride ions can penetrate the substrate through porous structures.

The Study on Corrosion Resistance of Ti-6Al-4V ELI Alloy with Varying Surface Roughness in Hydrofluoric Acid Solution

The corrosion resistance of titanium alloy poses a crucial challenge, significantly affecting its prospect for service and application. The present study aimed to investigate the corrosion resistance of Ti-6Al-4V ELI alloys with varying surface roughness in hydrofluoric acid solution, in order to assess the influence of roughness on their corrosion resistance performance. The weight loss percentage, surface morphology evolution, and roughness variation of Ti-6Al-4V ELI alloys before and after exposure to hydrofluoric acid corrosion were characterized. While the weight loss and weight loss percentage of the Ti-6Al-4V ELI alloy increased with prolonged corrosion, the overall weight loss rate decreased. The accumulation of TiF3 phases and depletion of the Ti-6Al-4V ELI matrix mutually led to the alterations of the surface roughness. Due to the inability to prevent fluoride ions from contacting with the Ti-6Al-4V ELI alloy, continuous corrosion occurred in hydrofluoric acid. Based on these experimental results and analysis, the corrosion mechanism of the Ti-6Al-4V ELI alloy corroded by hydrofluoric acid solution was elucidated. Furthermore, an analysis was conducted to explore the influence of corrosion time on mechanical properties by analyzing the decay in compressive properties of the Ti-6Al-4V ELI titanium alloy after hydrofluoric acid corrosion treatment. The bearing capacity of the Ti-6Al-4V ELI alloy deteriorated over the corrosion time.

Addition of molybdate ions to the anodizing bath to improve the corrosion resistance of clad 2024-T3 alloy anodized in tartaric-sulfuric acid

In the present investigation molybdates ions (MoO4−2) were added to a tartaric‑sulfuric acid (TSA) bath, which was employed to anodize AA2024-T3 clad samples. The incorporation of Mo into the anodized layer was investigated by different techniques: X-ray photoelectron spectroscopy (XPS), glow-discharge optical emission spectroscopy (GDOES), Rutherford backscattering spectrometry (RBS) and scanning electron microscopy (SEM), while the corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) techniques in neutral (0.5 M) and acidic (0.1 M, pH = 4.0) NaCl solutions. The different characterization techniques indicate that small amounts of the modifier were incorporated into the anodized layer, while the SEM analysis confirmed that the morphology of the layer was not changed, although it was thicker when anodized in the Mo containing bath. Evaluation of corrosion resistance by EIS in both media showed that samples anodized in the molybdate containing bath were more corrosion resistant and durable. Fitting results of the electric equivalent circuit indicate that this may be a consequence of a thicker barrier layer for these samples.

Effect of heat treatment on the microstructure and in-situ corrosion behavior of SLM-NiTi alloys

As a medical implant material, NiTi must have good corrosion resistance in order to adapt to the complex environment in the human body. However, the impact of heat treatment on the corrosion resistance of NiTi alloys prepared by selective laser melting (SLM) remains unclear. This work investigates the effect of heat treatment on the microstructure and corrosion behavior of SLM-NiTi alloys through in-situ corrosion methods. The results indicate that the overall corrosion resistance of SLM-alloy is enhanced after heat treatment. This enhancement is attributed to the gradual transformation of HAGBs to LAGBs, reduction in dislocation density. Combined with electrochemical tests, the passivation film Rf increased, the passivation film on the alloy surface was denser, so the grain boundaries were more stable. Furthermore, the B19’ phase content increased significantly and was concentrated in the grains with GOS < 1. Pitting sources can form within these grains, leading to pitting corrosion. This work provides a theoretical basis for the preparation of high corrosion resistance SLM-NiTi alloys.

Improvement in corrosion resistance of AZ91D Mg alloy in simulated body fluid by cerium-based/stearic acid composite coatings

Magnesium alloys have attracted attention due to their biocompatibility and biodegradability. In this work, composite coatings are developed to potentially improve the corrosion resistance of AZ91D Mg alloy in simulated physiological fluid. Cerium-based/stearic acid coatings were prepared by electrodeposition combined with a simple immersion method. The effect of stearic acid bath concentration on the contact angle and corrosion resistance of the composite coatings was evaluated. The results showed that the stearic acid treatment increased the hydrophobicity of the surfaces of the cerium-based simple coatings. The use of an appropriate stearic acid concentration is a key for the fabrication of hydrophobic surfaces. The duplex coatings were demonstrated to protect the substrate from corrosion in Ringer solution.

Enhanced Wear and Corrosion Resistance of AZ91 Magnesium Alloy via Adherent Si-DLC Coating with Si-Interlayer: Impact of Biasing Voltage

Magnesium alloys are the lowest-density structural metals with a wide range of applications, such as aircraft skins, engine casings and automobile hubs. However, its low surface hardness and non-corrosion resistance in natural environments limit its wide range of applications. In this work, Si-DLC coatings (Si: 15 at.%) are fabricated on AZ91 alloy using a hollow cathode discharge combined with a DC bias voltage from 0 to −300 V to increase the deposition rate and modulate the structure and properties of the coatings. The Si interlayer with a thickness of around 0.6 µm is deposited first to enhance the adhesion. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used to investigate the effect of DC bias on the microstructure evolution of Si-DLC coatings. Meanwhile, corrosion and wear resistance of the coatings at various bias voltages have been investigated using electrochemical workstations and pin-on-desk wear testers. It is shown that the bias-free coating has a loose structure and is less resistant to corrosion and wear. The bias coating has a compact structure, small carbon cluster size, high chloride ion corrosion resistance, and high wear resistance against Al2O3 spheres. The corrosion potential of the coating bias at −300 V is −0.98 V, the corrosion current density is 1.35 × 10−6 A·cm−2, the friction coefficient is 0.08, and the wear rate is 10−8 orders of magnitude. The formation of SiC nanocrystals and high sp3-C, as well as the formation of transfer films on the surface of their counterparts, are the main reasons for the ultra-high wear resistance of the bias coatings. The wear rate, coefficient of friction, and corrosion rate of the coating are 0.0069 times, 0.2 times, and 0.0088 times that of the AZ91 alloy, respectively. However, the bias coating has only short to medium-term protection against the magnesium alloy and no long-term protection due to cracks caused by its high internal stress.

Comparative study of CaO and CaCO3 on microstructure refinement, mechanical and corrosion resistance of AM60 alloy

Grain refinement is a crucial technique for enhancing the mechanical properties and corrosion resistance of magnesium alloys. In this study, the addition of 0.3 wt% CaO and 0.3 wt% CaCO3 successfully refined the AM60 alloy, resulting in a significant reduction in the average grain size from 326 μm to 96 μm (when adding CaCO3). The refined grain size of the as-cast AM60 alloy led to an increase in both tensile strength and yield strength to 118.2 MPa and 72.6 MPa, representing a respective increase of 35% and 23% compared to the alloy without the refiner. As results of EBSD, it is verified that the basal slip system (0001)<112‾0> has a higher Schmid factor after adding CaO, which indicates that this system has higher activity. The substitution reaction between CaO and Mg can produce synergistic effects from the solute effect of Ca and the nucleating effect of residual CaO, which play an important role in grain refinement. Due to the fine grain size and diffuse distribution of the second phase in the AM60-CaCO3 alloy and the thermal decomposition of CaCO3, which consumes the aluminum element in the matrix, the content of the β-phase (Mg17Al12) is reduced. Consequently, this reduces the electric coupling effect between the β-phase and the magnesium matrix. The AM60-CaCO3 alloy exhibited the most superior corrosion resistance, achieving a corrosion rate of only 1.01 mm y−1, representing a 48.9% reduction in corrosion rate compared to the AM60 alloy.

Manufacturing high-strength and corrosion-resistant 6063Al joints by an ultrasonic-assisted liquid and solid phase diffusion technology

High corrosion-resistance aluminum alloy joint obtained by filler metal containing Sn at relatively low temperatures is a longstanding goal for electronic products. In this research, 6063Al alloys was joined by a novel ultrasonic-assisted diffusion bonding via liquid phase and solid phase synergistic diffusion. It was performed via a hypereutectic interlayer of Zn-30Sn at 360 ℃ to joining 6063Al, obtaining a Zn-Al eutectoid structures joint. By the ultrasonic vibrating, the breaking of oxide film, the diffusing of liquid and solid state had been occurring in sequence during the joining process. It resulted in a series of diffusing phase transitions from “η-Zn phases + Sn-Zn eutectic structures” to “Zn-Al eutectoid structures + η-Zn phases”, and finally to “full Zn-Al eutectoid structures”, which were driven by the grain boundary penetration and chemical potential, respectively. The joints possessed a higher strength than the base metal. The joints with Zn-Al eutectoids have a better corrosion resistance that the tensile strength reduced 37.3% after a corroding of 72 h in 3.5 wt% NaCl solution in comparison with the soldered joints. Finally, the mechanism of ultrasonic accelerated diffusion, joint formation process and mechanism of improving corrosion resistance were discussed in detail.

Effect of Extrusion on Mechanical Property, Corrosion Behavior, and In Vitro Biocompatibility of the As-Cast Mg-Zn-Y-Sr Alloy.

The effect of extrusion on the microstructure, mechanical property, corrosion behavior, and in vitro biocompatibility of as-cast Mg-1.5Zn-1.2Y-0.1Sr (wt.%) alloy was investigated via tensile tests, electrochemical methods, immersion tests, methylthiazolyl diphenyltetrazolium bromide (MTT), and analytical techniques. Results showed that the as-cast and as-extruded Mg-1.5Zn-1.2Y-0.1Sr alloys comprised an α-Mg matrix and Mg3Y2Zn3 phase (W-phase). In the as-cast alloy, the W-phase was mainly distributed at the grain boundaries, with a small amount of W-phase in the grains. After hot extrusion, the W-phase was broken down into small particles that were dispersed in the alloy, and the grains were refined considerably. The as-extruded alloy exhibited appropriate mechanical properties that were attributed to refinement strengthening, dispersion strengthening, dislocation strengthening, and precipitation strengthening. The as-cast and as-extruded alloys exhibited galvanic corrosion between the W-phase and α-Mg matrix as the main corrosion mechanism. The coarse W-phase directly caused the poor corrosion resistance of the as-cast alloy. The as-extruded alloy obtained via hydrogen evolution and mass loss had corrosion rates of less than 0.5 mm/year. MTT, high-content screening (HCS) analysis, and cell adhesion tests revealed that the as-extruded alloy can improve L929 cell viability and has great potential in the field of biomedical biodegradable implant materials.

Sustainable smart coatings of chitosan and LDH loaded with natural inhibitors for corrosion protection of Mg AZ31 alloy

In this study, sustainable smart coatings based on chitosan and layered double hydroxides (LDH), loaded with natural anions, were developed to enhance the corrosion resistance of AZ31 magnesium alloy. The LDH was synthesized using the co-precipitation method, loaded with natural inhibitors (vanillate, gallate and citrate anions) by an anion exchange process and characterized by various techniques, such as scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis. The kinetics of inhibitor release was investigated at different pH and the results show higher rates as the pH increases. The corrosion resistance offered by the sustainable smart coatings was determined by electrochemical impedance spectroscopy and hydrogen evolution tests, while the coating morphology, before and after the corrosion tests, was analyzed by SEM and optical microscopy, respectively. All of the results demonstrated that the smart coating containing gallate ions significantly improved the corrosion resistance of AZ31 magnesium alloy.