Slow Corrosion Rate Research Articles

Investigation of Copper Addition on Corrosion Behavior of a Ferrous Based Shape Memory Alloy for Biomedical Implant Applications

Permanent biomedical implants pose several issues in long term scenarios like infections, inflammation, implant fracture, tissue damage, cancerous tumors formation, and skin allergies. Biodegradable biomedical implants are a new interest that function by degrading internally after achieving the implant goal. Shape memory alloys like Nitinol and Iron based shape memory alloys have applications in biomaterials due to the excellent property of super elasticity and shape memory effect respectively with the ease of small surgery requirement. To achieve biodegradability, the alloy composition is to be set while not compromising other properties such as biocompatibility, mechanical properties, shape memory properties, and magnetic properties. Slow corrosion rates of Fe-Mn alloys are reported and alloying addition, surface modifications, and novel manufacturing techniques are suggested to overcome this problem. In this study, the effect of addition of copper addition effect on the degradation behavior of Fe-30Mn-5Si is investigated. Austenite is the major phase present in both samples and small amounts of martensite are also present. For 10% copper, an additional copper rich phase is formed along the grain boundaries as it was beyond the solubility limit of iron matrix. The electrochemical corrosion test shows that 10% Cu addition resulted in 1.72 times higher corrosion rate than that of 5% Cu addition. As 5% Cu addition is within the solubility limit of iron matrix, and it forms a solid solution with iron that creates a passive layer during corrosion testing results in slower degradation.

Effects of Mo Addition on Microstructure and Corrosion Resistance of Cr25-xCo25Ni25Fe25Mox High-Entropy Alloys via Directed Energy Deposition.

Highly entropy alloys (HEAs) are novel materials that have great potential for application in aerospace and marine engineering due to their superior mechanical properties and benefits over conventional materials. NiCrCoFe, also referred to as Ni-based HEA, has exceptional low-temperature strength and microstructural stability. However, HEAs have limited corrosion resistance in some environments, such as a 3.5 wt% sodium chloride (NaCl) solution. Adding corrosion-resistant elements such as molybdenum (Mo) to HEAs is expected to increase their corrosion resistance in a variety of corrosive environments. Metal additive manufacturing reduces production times compared to casting and eliminates shrinkage issues, making it ideal for producing homogeneous HEA. This study used directed energy deposition (DED) to create Cr25-xCo25Ni25Fe25Mox (x = 0, 5, 10%) HEAs. Tensile strength and potentiodynamic polarization tests were used to assess the materials' mechanical properties and corrosion resistance. The mechanical tests revealed that adding 5% Mo increased yield strength (YS) by 20.1% and ultimate tensile strength (UTS) by 9.5% when compared to 0% Mo. Adding 10% Mo led to a 32.5% increase in YS and a 20.4% increase in UTS. Potentiodynamic polarization tests were used to assess corrosion resistance in a 3.5-weight percent NaCl solution. The results showed that adding Mo significantly increased initial corrosion resistance. The alloy with 5% Mo had a higher corrosion potential (Ecorr) and a lower current density (Icorr) than the alloy with 0% Mo, indicating improved initial corrosion resistance. The alloy containing 10% Mo had the highest corrosion potential and the lowest current density, indicating the slowest corrosion rate and the best initial corrosion resistance. Finally, Cr25-xCo25Ni25Fe25Mox (x = 0, 5, 10%) HEAs produced by DED exhibited excellent mechanical properties and corrosion resistance, which can be attributed to the presence of Mo.

Effect of Laser Energy Density on the Properties of CoCrFeMnNi High-Entropy Alloy Coatings on Steel by Laser Cladding

High-entropy alloys (HEAs) have emerged as a novel class of materials with exceptional mechanical and corrosion properties, offering promising applications in various engineering fields. However, optimizing their performance through advanced manufacturing techniques, like laser cladding, remains an area of active research. This study investigated the effects of laser energy density on the mechanical and electrochemical properties of CoCrFeMnNi HEA coatings applied to Q235 substrates. Utilizing X-ray diffraction (XRD), this study confirmed the formation of a single-phase face-centered cubic (FCC) structure in all coatings. The hardness of the coatings peaked at 210 HV with a laser energy density of 50 J/mm2. Friction and wear tests highlighted that a coating applied at 60 J/mm2 exhibited the lowest wear rate, primarily due to adhesive and oxidative wear mechanisms, while the 55 J/mm2 coating showed increased hardness but higher abrasive wear. Electrochemical testing revealed superior corrosion resistance for the 60 J/mm2 coating, with a slow corrosion rate and minimal passivation tendency in contrast to the 55 J/mm2 coating. The comprehensive evaluation indicates that the HEA coating with an energy density of 60 J/mm2 exhibits exceptional wear and corrosion resistance.

Investigating Pitting Behavior of Stainless-Steel for Canister in Vertical Position Using Electrochemical Acceleration Test

Stainless steel is renowned for its corrosion resistance and is widely used in constructing canisters for nuclear waste containment. These canisters are designed to endure burial in soil for over a century, making it crucial to study the long-term corrosion behavior of SS in this specific context. However, analysis of the corrosion behavior of SS is challenging due to its slow corrosion rate. Therefore, electrochemical acceleration methods are essential in studying the corrosion behavior of SS. This research employs the potentiostatic polarization test to comprehensively analyze SS pitting corrosion. The study focuses on vertically-positioned SS specimens, simulating canister conditions. Advanced microscopy techniques and simulation aid in understanding anolyte, pit depth, and pit shape behavior. Through this, the pitting propagation process of SS could be divided into four stages. Key outcomes of this study include models for absolute depth during propagation and the formation of secondary pitting. Comparative analysis with immersion tests reveals insights crucial for industrial installations safety and longevity.

Deciphering the corrosion puzzle: Nano-iron-biochar composite – Not a quick fix for metal immobilization in peat soils

The use of zero-valent iron nanoparticles in the remediation of metal-contaminated soils has received considerable attention. Upon introduction into the soil, zero-valent iron particles corrode into iron oxides, known for their high adsorption capacity for potentially toxic metals. While limited research has directly compared zero-valent iron micro- and nanoparticles, it is important to investigate whether particle size contributes to effective soil remediation. This study focuses on elucidating the comparative kinetics of iron corrosion using iron powder and a nano-iron-biochar composite. In a model experiment, these materials were exposed to a cellulose/biochar mixture and peat for five months. Mössbauer spectroscopy, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, and transmission electron microscopy with electron diffraction were used to analyze the corrosion products. The results show a slow corrosion rate in the nano-iron-biochar composite in cellulose due to the protective effect of biochar on the embedded iron nanoparticles. In addition, iron corrosion in peat was inhibited, likely due to the presence of humic substances. Transmission electron microscopy after five months of corrosion revealed round metal particles encased in a graphite capsule with visible channels. Large dissolved organic matter molecules in the peat likely block these channels, inhibiting metallic iron corrosion. Consequently, the nano-iron-biochar composite emerges as a slow-reacting option for immobilizing soil metals in peat. This study highlights the need for further research involving long-term field experiments.

Preparation and characterization of supersonic plasma sprayed Al–Al2O3–Cr2O3 composite coatings on magnesium alloy substrate

Magnesium alloys have poor wear and corrosion resistance, which limits their wider industrial applications. In order to improve wear and corrosion resistance, Al–Al2O3–Cr2O3 composite coatings with different Al, Al2O3 and Cr2O3 compositions were prepared on magnesium alloy substrate using supersonic plasma spraying technology. The surface morphology, porosity, and microstructure of Al–Al2O3–Cr2O3 coatings were analyzed. The wear and corrosion resistance of Al–Al2O3–Cr2O3 coatings were evaluated. The results showed the surface morphology of the composite coating was flat, and the cross-sectional structure had a layered structure with close interlayer bonding, and also the structure was uniform and fine. The A70A15C15 coating exhibited the lowest porosity (0.56 %), whereas the porosity of A30A35C35 coating was the highest (only 1.61 %). The wear resistance of the composite coating increased with increasing Al2O3–Cr2O3 compositions, and the A30A35C35 coating showed the best wear resistance, with a 90.58 % reduction in volume wear rate when compared with that of the magnesium alloy substrate. Based on electrochemical impedance spectroscopy testing, the A50A25C25 coating had the slowest corrosion rate and best electrochemical corrosion resistance. Therefore, the preparation of the Al–Al2O3–Cr2O3 coating by supersonic plasma spraying on magnesium alloy substrate is a promising technique for improving its wear and corrosion resistance.

Formation of corrosion-based ZVMg nanoparticles for reductive degradation of high-level trichloroethylene in aqueous solution

This study discovered that nanosized zero valent magnesium (nZVMg) could be formed during the electrochemical corrosion of microsized ZVMg (mZVMg) in aqueous solution. It is observed that the nZVMg particle sizes were less than 50 nm with the specific surface area of 54.63 m2/g after it was corroded for 96 h (ZVMg96) at the expense of losing about 60 wt% Mg0. However, the XPS characterization indicated the thickness of Mg(OH)2 layer over ZVMg96 being less than 5 nm, accompanied by the faster electron transfer rate but slower corrosion rate than mZVMg. Most importantly, the removal efficiency of 82 % under high-level trichloroethylene (TCE) at 100 mg/L was achieved by ZVMg96 within one hour relative to 48 % by mZVMg. The rate constant normalized by surface area was 3.11 × 10−2 L/m2/h by ZVMg96 due to the high surface energy of nanoparticles. The degradation products were dependent on the initial TCE concentrations, with environmentally friendly and biodegradable degradation products being generated via hydrodechlorination, hydrogenation and polymerization pathways according to the density functional theory calculations. ZVMg corroded for 14 days illustrated a long-term chemical stability and excellent degradation performance, demonstrating significant application potential in remediating the TCE plumes in groundwater.

Interfacial Engineering Boosts Highly Reversible Zinc Metal for Aqueous Zinc-Ion Batteries.

Zinc metal is emerging as the promising anode for aqueous Zn-ion batteries. However, corrosion and undesirable Zn dendrite growth limit their practical application in the large-scale energy storage area. Herein, a mountain-valley micro/nanostructure is successfully fabricated on the surface of the Zn anode via a femtosecond-laser filament texturing (FsLFT) technique. Beneficial from the large surface area and spontaneously generated ZnO coating layer, the FsLFT-Zn electrode demonstrates a slow corrosion rate with a current density of 0.62 mA cm-2 and a stable cycle life over 3000 h under 1 mA cm-2, superior to the original Zn anode. Simulation of the electric fields reveals that the enlarged surface area is responsible for the outstanding performance of the FsLFT-Zn electrode. This study not only proposes a novel strategy to suppress dendrite growth toward highly stable AZIBs but also opens a new avenue to solve similar issues in other metal batteries.

Remarkably slow corrosion rate of high-purity Mg microalloyed with 0.05wt% Sc

We report that the corrosion resistance of Mg is significantly improved by adding 0.05wt% Sc. Corrosion rates evaluated from weight loss values after room-temperature immersion in 0.6 M NaCl solution for two weeks were 0.27 and 4.0 mm y −1 for the high-purity Mg samples with and without microalloyed 0.05wt% Sc, respectively. The beneficial effect of Sc microalloying on the corrosion resistance of Mg is discussed in connection with Sc-induced microstructural modifications.

Pulse Electrodeposited Super-Hydrophobic Ni-Co/WS2 Nanocomposite Coatings with Enhanced Corrosion-Resistance

The hydrophobicity and corrosion resistance of composite coatings can be effectively improved by changing the electrodeposition method and adding inorganic nanoparticles. In this work, the incorporation of WS2 nanoparticles significantly increased the surface roughness of Ni-Co coatings. The best hydrophobicity and corrosion resistance of the Ni-Co/WS2 nanocomposite coatings (water contact angle of 144.7°) were obtained in the direct current electrodeposition mode when the current density was 3 A/dm2 and the electrodeposition time was 50 min. Compared with direct current electrodeposition, the pulsed current electrodeposition method was more conducive to improving the electrodeposition performance of the nanocomposite coatings. Under the conditions of a current density of 3 A/dm2, pulse duty cycle of 70%, and pulse frequency of 1000 Hz, the nanocomposite coatings reached a superhydrophobic state (water contact angle of 153.8°). The nanocomposite coatings had a slower corrosion rate and larger impedance modulus in this state, and thus the corrosion resistance was superior. The wetting state of the Ni-Co/WS2 nanocomposite coating surface was closer to the Cassie–Baxter model. The protective air layer formed by the layered rough microstructures significantly reduced the actual contact area between the liquid and the substrate, achieving excellent hydrophobic and corrosion resistance properties.

High‐Nitrogen Nickel‐Free Stainless Steel: An Attractive Material with Potential for Biomedical Application

Metal materials such as stainless steel, cobalt‐based alloy, and NiTi alloy used in clinic contain a certain amount of nickel (Ni) for the structure stability. Nickel ions can gradually dissolve into the human body even with much slow corrosion rate, causing allergic, inflammation, local tissue proliferation, and other adverse reactions to some people. To avoid these adverse effects of nickel, a new high‐nitrogen nickel‐free stainless steel (HNNFSS) using nitrogen and manganese instead of nickel to stabilize the austenite structure is developed, which exhibits much better mechanical properties, good corrosion resistance, and biocompatibility. Compared with the conventional orthopedic metal implants, the adhesion strength of HNNFSS implant with the surrounding tissue in animal is found to be stronger with new bone formation, promoted by both alkaline phosphatase (ALP) and osteocalcin (OCN) expressions. The vascular stent made of HNNFSS shows lower restenosis rate compared with the traditional 316L stainless steel stent, which is attributed to the promotion of endothelial cell and inhibition of smooth muscle cells, and superior blood compatibility. In conclusion, results from large number of studies show that high‐nitrogen nickel‐free stainless steel as a new kind of high‐performance biomedical metallic material possesses great application potential.

Enhancing the corrodibility of biodegradable iron and zinc using poly(lactic) acid (PLA) coating for temporary medical implant applications

Iron (Fe) and zinc (Zn) are attractive materials for fabricating temporary implants. However, for some applications, the use of these materials is limited by their relatively slow corrosion rates. This study investigates the use of poly(lactic) acid (PLA) coating to control corrosion rates of biodegradable pure Fe and Zn in a physiological environment. PLA accelerated the degradation of both Fe and Zn, attributed to the occurrence of localized acidic environments at the metal-coating interface generated by the hydrolytic decomposition of the polymer. Corrosion enhancement favoured an amorphous polymer structure (poly (dl-lactide)), low molecular weight, and thicker coatings. Polarization and immersion tests indicated an optimum coating thickness (Fe = 15 μm, Zn = 10 μm) at which maximum corrosion acceleration is achieved, as determined by the interaction of the rate of polymer hydrolysis and metal surface passivation.

Surface Modification of Pure Zinc by Acid Etching: Accelerating the Corrosion Rate and Enhancing Biocompatibility and Antibacterial Characteristics.

Zinc (Zn) has recently been identified as an auspicious biodegradable metal for medical implants and devices due to its tunable mechanical properties and good biocompatibility. However, the slow corrosion rate of Zn in a physiological environment does not meet the requirements for biodegradable implants, hindering its clinical translation. The present study aimed to accelerate the corrosion rate of pure Zn by utilizing acid etching to roughen the surface and increase the substrate surface area. The effects of acid etching on surface morphology, surface roughness, tensile properties, hardness, electrochemical corrosion and degradation behavior, cytocompatibility, direct cell attachment, and biofilm formation were investigated. Interestingly, acid-treated Zn showed an exceptionally high rate of corrosion (∼226-125 μm/year) compared to untreated Zn (∼62 μm/year), attributed to the increased surface roughness (Ra ∼ 1.12 μm) of acid-etched samples. Immersion tests in Hank's solution revealed that acid etching accelerated the degradation rate of Zn samples. In vitro, MC3T3-E1 cell lines in 50 and 25% conditioned media extracts of treated samples showed good cytocompatibility. Reduced bacterial adhesion, biofilm formation, and dispersion were observed for Staphylococci aureus biofilms cultured on acid-etched pure Zn substrates. These results suggest that the surface modification of biodegradable pure Zn metals by acid etching markedly increases the translation potential of zinc for various biomedical applications.

Hot corrosion and electrochemical behavior of NiCrAlY, NiCoCrAlY and NiCoCrAlYTa coatings in molten NaCl-Na2SO4 at 800 °C

The NiCrAlY, NiCoCrAlY and NiCoCrAlYTa coatings were prepared on a Ni16Cr13Co4Mo alloy by the D-gun spray technique. The hot corrosion behaviors of the coatings were investigated in molten NaCl-Na2SO4 at 800 °C through electrochemical measurements including potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky plots. The corrosion layers of the coatings were characterized by electron probe micro-analysis (EPMA), auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The results showed that all the corrosion layers of the three coatings displayed the electronic structure of n-p heterojunction. However, the NiCoCrAlY coating had the slowest corrosion rate because Co reduced the carrier density of the corrosion layer and improved the corrosion layer resistance (Rl). The Co sulfides effectively inhibited the internal sulfidation. Ta ion could occupy the Al2O3 lattice and increase the carrier density of the corrosion layer. The hot corrosion of NiCrAlY coating was the most severe since the (Cr, Al) sulfides along the Al2O3 stringers promoted the formation of black bumps on the coating.

Enhancement of mechanical properties and corrosion resistance of Mg–2Zn–0.5Zr–1.5Dy (mass%) alloy by a combination of heat treatment and hot extrusion

AbstractTo enhance the mechanical properties and poor corrosion resistance of magnesium alloy in vitro, the as‐cast Mg–2Zn–0.5Zr–1.5Dy (mass%) magnesium alloy was subjected to two types of extrusion treatment, one is hot extrusion (denoted as ET alloy), the other is heat treatment followed by hot extrusion (denoted as HE alloy). The microstructure, mechanical properties, and corrosion behaviors of these extruded alloys are assessed. The results show that the HE alloy has superior mechanical properties and a slower corrosion rate than the ET alloy. The yield strength and elongation of the HE alloy reach 287 ± 10 MPa and 17.6 ± 0.5%, respectively, and its corrosion rate is only 0.59 ± 0.16 mm year−1. After hot extrusion, microscale and nanoscale second‐phase exist in the extruded alloys, and the nanoscale second‐phase can improve their mechanical properties by second‐phase strengthening. However, the presence of microscale second phase can cause galvanic corrosion and result in poor corrosion resistance. The HE alloy has good properties due to it containing more nanoscale second‐phase and fewer microscale second‐phase.

Influence of Particle Concentration on the Elemental Penetration Region and Properties of Ni-P-SiC Composite Coatings Prepared through Sandblasting and Scanning Electrodeposition on 45 Steel Surfaces

Ni-P-SiC composite coating was prepared on 45 steel surfaces through sandblasting and scanning electrodeposition to explore the relationship between element penetration region and composite coating properties. The single-factor control variable method with particle concentration as the research variable was used. Results showed that with the gradually increasing concentration of SiC nanoparticles, a trend of first increasing and then gradually decreasing was observed for the surface and cross-sectional microstructure of the coating, interpenetration ability of the elements, adhesion performance, and corrosion resistance. The best deposition quality of the coating was obtained when the concentration of SiC nanoparticles was 3 g·L−1. For cross-sectional microstructure, the scratch test revealed that the maximum coating thickness was 17.3 μm, the maximum range of elemental penetration region was 28.39 μm, and the maximum adhesion of the composite coating was 36.5 N. The electrochemical test showed that the composite coating had a −0.30 V self-corrosion potential and 8.45 × 10−7 A·cm−2 self-corrosion current density, the slowest corrosion rate. In addition, the composite coating had the best corrosion resistance and the largest impedance arc radius corresponding to an equivalent impedance value R2 of 3108 Ω.

Modifications on porous absorbable Fe-based scaffolds for bone applications: A review from corrosion and biocompatibility viewpoints.

Iron (Fe) and Fe-based scaffolds have become a research frontier in absorbable materials which is inherent to their promising mechanical properties including fatigue strength and ductility. Nevertheless, their slow corrosion rate and low biocompatibility have been their major obstacles to be applied in clinical applications. Over the last decade, various modifications on porous Fe-based scaffolds have been performed to ameliorate both properties encompassing surface coating, microstructural alteration via alloying, and advanced topologically order structural design produced by additive manufacturing (AM) techniques. The recent advent of AM produces topologically ordered porous Fe-based structures with an optimized architecture having controllable pore size and strut thickness, intricate internal design, and larger exposed surface area. This undoubtedly opens up new options for controlling Fe corrosion and its structural strengths. However, the in vitro biocompatibility of the AM porous Fe still needs to be addressed considering its higher corrosion rate due to the larger exposed surface area. This review summarizes the latest progress of the modifications on porous Fe-based scaffolds with a specific focus on their responses on the corrosion behavior and biocompatibility.

A surface-eroding poly(1,3-trimethylene carbonate) coating for magnesium based cardiovascular stents with stable drug release and improved corrosion resistance

Magnesium alloys with integration of degradability and good mechanical performance are desired for vascular stent application. Drug-eluting coatings may optimize the corrosion profiles of magnesium substrate and reduce the incidence of restenosis simultaneously. In this paper, poly (trimethylene carbonate) (PTMC) with different molecular weight (50,000 g/mol named as PTMC5 and 350,000 g/mol named as PTMC35) was applied as drug-eluting coatings on magnesium alloys. A conventional antiproliferative drug, paclitaxel (PTX), was incorporated in the PTMC coating. The adhesive strength, corrosion behavior, drug release and biocompatibility were investigated. Compared with the PLGA control group, PTMC coating was uniform and gradually degraded from surface to inside, which could provide long-term protection for the magnesium substrate. PTMC35 coated samples exhibited much slower corrosion rate 0.05 μA/cm2 in comparison with 0.11 μA/cm2 and 0.13 μA/cm2 for PLGA and PTMC5 coated counterparts. In addition, PTMC35 coating showed more stable and sustained drug release ability and effectively inhibited the proliferation of human umbilical vein vascular smooth muscle cells. Hemocompatibility test indicated that few platelets were adhered on PTMC5 and PTMC35 coatings. PTMC35 coating, exhibiting surface erosion behavior, stable drug release and good biocompatibility, could be a good candidate as a drug-eluting coating for magnesium-based stent.

Corrosion behavior of biodegradable metals in two different simulated physiological solutions: Comparison of Mg, Zn and Fe

Bio-absorbable metals have been proposed to overcome the limitations of permanent implant materials, particularly the risk of chronic inflammation and secondary surgery for removal after healing. The most researched bio-absorbable metal is magnesium, followed by iron and zinc, but there is little work comparing the different metals under the same experimental conditions. Herein, degradation performance of Mg/Zn/Fe was investigated via immersion test (28 days) and electrochemical tests under two buffer systems, simulated body fluid solution (SBF) and Dulbecco’s Modified Eagle’s cell culture medium (DMEM). Corrosion rate was initially slower in DMEM for all metals, Mg showed the fastest corrosion rate in both SBF and DMEM. The influence of the electrolyte on the corrosion behaviour was strongest for Mg. Importantly, the ranking of the corrosion rate of the three metals changes with immersion time. Noteworthy is a strong increase of corrosion resistance of Mg with time during the first 24 h of immersion. Corrosion morphology and corrosion products were characterized with SEM, EDS, FTIR, XPS and XRD. In general, the corrosion product layers are much more uniform in DMEM, besides, the insoluble corrosion product/precipitation consisted of metallic oxides/hydroxides, phosphates and carbonates. Slower corrosion rate in DMEM solution can therefore be due to formation of a more protective precipitate layer, adsorbed amino acids, and absence of Tris-HCl that accelerates corrosion in SBF.

Effect of In on Corrosion Performance of Zn-15Al-5Cu-xIn Solders

The salt spray test has been used to study the effect of adding In on the corrosion performance of Zn-15Al-5Cu-xIn (x = 0, 1, 3, and 5, where x is the mass percentage) solder alloys. The focus was on the microstructure and corrosion properties of the alloy. The results of scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), x-ray diffraction (XRD) analysis, and differential scanning calorimetry (DSC) revealed the distributed formation of In-based solid solution. Corrosion performance tests on the Zn-15Al-5Cu-xIn solders revealed the influence of In on the corrosion performance; addition of 3% In resulted in the solder with the highest corrosion potential and slowest corrosion rate. The main reason is that more γ (CuZn4) phase with strong corrosion resistance was dispersed and distributed in the solder. Remarkably, when the In content exceeded 3%, it could enrich the dendritic zone of the grains, which could reduce the corrosion resistance of the solder alloy. It is thus concluded that the optimal In content in this alloy system is 3%.