Electrochemical Corrosion Tests Research Articles

Electrochemical, mechanical, and antibacterial properties of the AZ91 Mg alloy by hybrid and layered hydroxyapatite and tantalum oxide sol–gel coating

Abstract The corrosion and bacterial behavior of AZ91 magnesium alloy coated with sol–gel-deposited amorphous tantalum oxide and hydroxyapatite have been investigated. The objective was to assess the potential suitability of AZ91 for permanent prosthesis applications. The coatings were applied in layered and hybrid configurations and characterized using various techniques including X-ray diffractometry, Fourier transform infrared spectroscopy, scanning electron microscopy/energy dispersive spectrometry, and drop analyses. The antibacterial properties were evaluated through interactions with Staphylococcus aureus and Escherichia coli strains. Mechanical properties and adhesion were determined via linear scratch tests, and electrochemical corrosion tests were conducted in different media. The release of aluminum ions from the samples in Dulbecco’s Modified Eagle’s Medium was monitored over 28 days. The findings revealed that the amorphous tantalum oxide coating, particularly in combination with hydroxyapatite, improved antibacterial properties and positively influenced corrosion and scratch resistance. The layered and hybrid coatings demonstrated the highest corrosion resistance. The release of aluminum ions remained within acceptable levels in the tested medium. Overall, the study provides valuable insights into the potential of sol–gel coatings on AZ91 for prosthetic applications, considering antibacterial behavior, corrosion resistance, and aluminum release.

Effect of ultrasonic vibration extrusion cutting on the corrosion resistance of ultra-fine grained strips

Ultrasonic vibration extrusion cutting (UVEC), a new processing method, is proposed to prepare ultra-fine grained materials with better corrosion resistance. The mathematical models, finite element simulations, and experiments are combined and validated against each other to investigate the mapping relationships and influence mechanisms among ultrasonic amplitude, stress field parameters, microstructure, and corrosion resistance. It is found that with the increase of ultrasonic amplitude, the equivalent strain, equivalent strain rate, grain refinement degree of strip and thickness of a nanocrystalline surface layer on the side of the strip in contact with a tool (front side) increase gradually. The immersion corrosion test shows that both sides of the strip have better corrosion resistance than original matrix, and the corrosion resistance of the strip front side is better than that of strip side in contact with the extrusion block (back side). The electrochemical corrosion test shows that with the increase of ultrasonic amplitude, the electrochemical parameters are improved. It is determined that the corrosion resistance of ultra-fine grained strips prepared by UVEC is significantly improved compared with the original matrix, and the overall corrosion resistance is best at 2 μm ultrasonic amplitude.

First-principles study on surface corrosion of 6082 aluminum alloy in H+ and Cl− medium

In order to explore the corrosion mechanism of the 6082-aluminum alloy (Al alloy) in environments containing H+ and Cl−, we employ first-principle calculations to study the adsorption behaviors of H+ and Cl− on the surfaces of the Al matrix and its precipitated phases. This analysis is complemented with electrochemical corrosion tests to investigate the corrosion mechanism and the nature of the passivation film (Al2O3) formed on the 6082 Al alloy in the presence of H+ and Cl− ions. Our findings show that the adsorption energy of H+ on the Al (111) surface (-4.911 eV) is lower than that of Cl− (1.436 eV), indicating a stronger adsorption affinity for H+. Both H-Al and Cl-Al formed polar covalent bonds. For the Mg2Si (111) surface adsorption, the adsorption energies for Mg interaction with both ions (-4.829 eV for H+ and -4.893 eV for Cl−) are lower than those for Si, suggesting a stronger bond between H+ and Mg. Notably, the surface of the sample is preferentially corroded to the adsorbed Mg2Si phase, inferring its higher activity. In addition, when compared to the HCl solution, the samples in the NaCl solution exhibit a substantially lower corrosion current density(icorr) and corrosion rate. In contrast to the NaCl medium, the samples immersed in the HCl solution did not form a passivation film, leading to more active corrosion behavior with deeper corrosion pits. It is worth mentioning that the interfacial bonding between the passivation film and the underlying substrate is stronger, with an interfacial adhesion work of Al2O3 (0001)/Al (111) of 0.654298 J/m2, wherein the Al2O3 is well bonded to the surface of the 6082 Al alloy to inhibit corrosion. This study contributes a deeper understanding of the corrosion behavior exhibited by Al, thereby offering valuable insights for the design and application of high-performance corrosion-resistant Al alloys.

Electrodeposition of nanotubes for corrosion inhibition: Dual role as superhydrophobic matrix and nanocontainer for storing-releasing corrosion inhibitor

The lotus leaf-inspired superhydrophobicity to prevent metal corrosion has garnered significant interest. The prevailing approach employs micro/nanoscale matrices to trap air and support water, resulting in short-term effectiveness due to air dissolution. Basic zinc carbonate nanotube (BZC NT), created via electrochemical anodization, dually achieves superhydrophobicity and contains 1-dodecanethiol as corrosion inhibitor for zinc. During the immersion under the water phase, the release of 1-dodecanethiol enables a corrosion inhibitor-air cushion, which is remarkably distinguished from the typical single air cushion formed in the superhydrophobic matrix. Using scanning Kelvin probe, the local micro-zone surface potential of Zn increases about 286 mV after being covered by superhydrophobic BZC NT (SHS BZC NT), exhibiting the high decrement of atmospheric corrosion tendency. Through typical electrochemical corrosion tests, the |Z|lf (lf = 0.036 Hz) of SHS BZC NT is about 9.78 × 106 Ω cm2, and the value is ca. 3 orders of magnitude larger than pure Zn (1.46 × 103 Ω⋅cm2). After soaking in a strong alkaline solution (pH = 11) for 24 h, the inhibitive efficiency of SHS BZC NT is 99.99%, demonstrating high corrosion inhibition effect.

An Experimental High-Throughput to High-Fidelity Study Towards Discovering Al–Cr Containing Corrosion-Resistant Compositionally Complex Alloys

Compositionally complex alloys hold the promise of simultaneously attaining superior combinations of properties, such as corrosion resistance, light-weighting, and strength. Achieving this goal is a challenge due in part to a large number of possible compositions and structures in the vast alloy design space. High-throughput methods offer a path forward, but a strong connection between the synthesis of an alloy of a given composition and structure with its properties has not been fully realized to date. Here, we present the rapid identification of corrosion-resistant alloys based on combinations of Al and Cr in a base Al–Co–Cr–Fe–Ni alloy. Previously unstudied alloy stoichiometries were identified using a combination of high-throughput experimental screening coupled with key metallurgical and electrochemical corrosion tests, identifying alloys with excellent passivation behavior. The alloy native oxide performance and its self-healing attributes were probed using rapid tests in deaerated 0.1-mol/L H2SO4. Importantly, a correlation was found between the electrochemical impedance modulus of the exposure-modified air-formed film and self-healing rate of the CCAs. Multi-element extended x-ray absorption fine structure analyses connected more ordered type chemical short-range order in the Ni–Al 1st nearest-neighbor shell to poorer corrosion resistance. This report underscores the utility of high-throughput exploration of compositionally complex alloys for the identification and rapid screening of a vast stoichiometric space.Graphical

Properties of Ni-B/B Composite Coatings Produced by Chemical Reduction

The paper presents the results of research on composite Ni-B coatings with embedded particles of boron produced by a chemical reduction method and their influence on the mechanical, tribological, and corrosion properties of produced materials. Boron was used in two forms: an alloy component and nanoparticles incorporated into the Ni-B matrix. The coatings were deposited from a bath at different concentrations of dispersion phase. The paper also presents the characteristics of the used boron particles. Results of morphology and surface topography (SEM) as well as the structure (XRD) of the produced coatings are presented. The mechanical properties of the produced coatings, like Knoop hardness, Martens hardness, and indentation hardness, as well as the modulus of elasticity, were determined. The tribological tests were carried out using the ball-on-disc method. Electrochemical corrosion tests were conducted by the potentiodynamic method. The adhesion of the coatings to the substrate was evaluated by the scratch test method. Consequently, this investigation yielded a novel material in the form of Ni-B/B composite coatings, exhibiting significantly improved mechanical and tribological properties compared to Ni-B coatings without embedded particles of the dispersion phase.

Development of in-situ Zn–3Cu–10ZnO composite prepared by high-pressure solidification for orthopedic applications

Biodegradable zinc (Zn)-based composites are considered to be the next generation of promising orthopedic implant materials due to their degradability and the multiple functionality of combining metal and ceramic phases. However, its clinical bone-implant application is seriously limited due to their poor interface binding ability and mechanical properties. Herein, we developed the biodegradable in-situ Zn–3Cu–10ZnO composite through powder metallurgy using Zn and copper (Cu) powder combined with hot forging, followed by the high-pressure solidification (HPS) process for bone-implant application. Microstructural characterization showed that the HPS process can densify composite, form a uniform distribution of fine ZnO particle, and increase Cu atom solid solubility in the Zn matrix. Mechanical test revealed that the HPS composite exhibited a high compression performance with a compressive yield strength of 340.8 MPa, an ultimate compressive strength of 514.2 MPa, and a failure strain of ≥70%. The HPS composite exhibited the lowest corrosion rate of 25.8 μm/y and 44.3 μm/y measured by electrochemical corrosion and immersion tests, respectively, among these composites. Moreover, the diluted extracts of HPS composite with a concentration of ent% showed a higher cytocompatibility among these composites and better antimicrobial capability than those of the as-cast pure Zn. Accordingly, the HPS Zn–3Cu–10ZnO composite is expected to be a potential biodegradable material for orthopedic applications.

Tribological properties and sulfuric acid corrosion resistance of laser clad CoCrFeNi high entropy alloy coatings with different types of TiC reinforcement

CoCrFeNi, directly added TiC (D-TiC) and in-situ synthesized TiC (I-TiC) reinforced CoCrFeNi high entropy alloy coatings (HEACs) were prepared on the surface of 316 stainless steel (SS) by laser cladding (LC). The HEACs all achieved a dense and uniform structure, the TiC distributed at the grain boundaries (GBs) reduced the dilution rate of the HEACs, and the I-TiC composite coating realised a fine and diffuse distribution of the reinforcing phase compared to the D-TiC HEAC. The introduction of TiC dramatically refined the grain size of HEA system and inhibited the formation of high angle grain boundaries (HAGBs), with the average grain size decreasing from 23.6 µm in the TiC-free HEAC to 12.3 µm in D-TiC HEAC and 9.3 µm in I-TiC HEAC, and the proportion of low angle grain boundaries (LAGBs) of D-TiC and I-TiC composite coatings was even as high as 64.8% and 70.4%. As a result, the density of geometrically necessary dislocations (ρGND) in TiC-containing coatings also increased greatly, and ρGND in CoCrFeNi, D-TiC and I-TiC HEACs were 0.55 × 1015, 1.08 × 1015 and 1.27 × 1015 m−2, respectively. The highest average microhardness values of 420.2 ± 6 HV0.2 was achieved with I-TiC HEAC, which relied on TiC precipitation in a nucleation-growth mode. In electrochemical corrosion tests, the introduction of TiC also provided additional channels for ion diffusion. The ordered and dense passivation film of the I-TiC composite coating impeded sulfuric acid attack effectively, with an Icorr value of only 2.28 × 10−2 ± 0.8 μA/cm2, which was less than that of the substrate as well as the other two HEACs. In both dry sliding friction and wear and corrosive wear experiments, abrasive wear was the dominant wear pattern of I-TiC HEAC due to the increase in local stresses caused by the "point-to-point" contact between the TiC particles and the friction pair. Thanks to the diffuse and homogeneous distribution of the TiC reinforcing phase, I-TiC HEAC exhibited the best tribological performance in both dry sliding friction and wear or corrosive wear experiments with specific wear rates as low as 0.05 mm3/Nm in air and 0.06 mm3/Nm in sulfuric acid.

Biodegradable Zn−1wt.%Mg(−0.5wt.%Mn) Alloys: Influence of Solidification Microstructure on Their Corrosion Behavior

The development of biodegradable Zn-based alloys for implants that effectively mimic the functionality of native bone throughout the healing process is a multifaceted challenge; this is particularly evident in the task of achieving appropriate corrosion rates. This work explores the incorporation of 0.5wt.%Mn into a Zn−1wt.%Mg alloy, with focus on the relationship between corrosion behavior and microstructure. Electrochemical corrosion tests were carried out in a 0.06 M NaCl solution using as-solidified samples with two distinct microstructural length scales. Mn addition was found to induce significant electrochemical active behavior. Localized corrosion was predominant in interdendritic regions, with the ternary alloy exhibiting a higher susceptibility. For both alloys, the coarsening of the microstructure promoted a slight inclination to accelerate the corrosion rates in both biodegradable Zn alloys. The corrosion rate showed an increase of about nine-times with Mn addition for coarser eutectic spacings, while for finer ones, the increase was by about 22 times.

Laser Shock Peening Improves the Corrosion Resistance of an E690 High-Strength Steel Cladding Layer.

To investigate the effect of laser shock peening parameters on the corrosion resistance of an E690 high-strength steel cladding layer, NVE690 high-strength steel powder was selected for testing at various power densities of pulse lasers. The surface roughness and residual stress of the treated samples were measured, and the microstructure morphology of the sample surface was observed. The electrochemical corrosion tests were conducted with an electrochemical workstation to measure the electrometer polarization, obtain the impedance curve, and observe the electrochemical corrosion. As the laser power density increased, the surface grains of the E690 high-strength steel cladding layer continued to refine until nanocrystals formed, and the residual compressive stress on the surface increased. The residual compressive stress on the surface rendered the passivation film stable and dense; furthermore, the refinement of surface grains inhibited the initiation and propagation of microcracks. The positive shift of the corrosion potential increased from -1.004 to -0.771 V, the corrosion current density decreased from 114.5 to 5.41 μA/cm2, the radius of the impedance spectrum curve increased, and the peeling pits, as well as corrosion micropores on the surface, gradually became no longer evident after electrochemical corrosion. After laser shock treatment, the corrosion resistance of the cladding layer sample was substantially improved.

Picosecond laser remelting of electrodeposited Ni[sbnd]P coating: Parameters optimization and electrochemical corrosion behavior

Excessive P content (≥ 10 wt%) easily leads to cracks on the surface of electrodeposited NiP coatings, causing rapid deterioration of corrosion performance. This study uses picosecond laser remelting (LR) technology to close cracks and improve corrosion performance. The influence of the laser parameters on the quality of laser-remelted (LRed) coatings in ambient air is discussed in detail, and the corrosion performance is evaluated through electrochemical corrosion tests. The results indicated that the scanning rate, laser power, and repetition frequency significantly affect the degree of crack closure and LRed defects. For cracks of similar sizes, both multiple-LR with a lower power (10.4 W, five times) and single-LR with a higher power (19.2 W, once) achieved an excellent crack closure. After single-LR, the surface roughness increased from 3.9 ± 0.3 nm to 33.4 ± 3.2 nm. In addition, the LRed layer crystallized from the initial amorphous state. Although the energy-dispersive spectroscopy results indicated that the oxidation behavior during the LR process was insignificant, X-ray photoelectron spectroscopy showed that the surface composition evolved from Ni/Ni–P compounds to Ni–POx after LR. Electrochemical corrosion tests indicated that the corrosion current density decreased approximately three times from 9.19 × 10−6 to 2.91 × 10−6 A/cm2 after LR. Moreover, the corrosion mechanism shifted from the original stress corrosion to pitting corrosion. Thus, the LR technology can effectively improve the corrosion performance and reduce the issues caused by cracks.

Glass-forming ability and properties of Hf-Cu-Ni-Al-Ag bulk metallic glasses

A new Hf-based Hf-Cu-Ni-Al-Ag glassy alloy was synthesized to be formed by copper mold casting. The influence of Ag addition on the properties of Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%) glassy alloys was studied by differential scanning calorimeter, X-ray diffractometer, quasi-static compression, and electrochemical corrosion test. The experimental results show that adding Ag can improve the thermal stability and glass-forming ability of glassy alloys. The Hf48Cu29.25Ni9.75Al12Ag1 exhibits the best glass-forming ability with a critical diameter of 12 mm and the highest compressive strength (2363 MPa) among glassy Hf48Cu29.25Ni9.75Al13-xAgx (x=0-5at%). The total plastic deformation of Hf48Cu29.25Ni9.75Al12Ag1 before fracture approaches 4%. In addition, there is a passivation interval of about 3 V for Hf48Cu29.25Ni9.75Al12Ag1 glassy alloy in 1 mol/L H2SO4 solution, which makes the passivation film more stable and increases the corrosion resistance. In 1 mol/L KOH solution, the corrosion tendency and rate decreased with the addition of Ag content, leading to increased corrosion resistance.

In vitro corrosion behavior of the extruded Mg–4Zn–1Mn alloy in different physiological solutions for biomedical applications

The extruded Mg–4Zn–1Mn alloy was prepared and its in vitro corrosion behavior in different physiological solutions of simulated body fluid (SBF), artificial saliva (AS) and artificial urine (AU) was investigated for biomedical applications. The microstructural characterization by optical microscope (OM), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) showed that the alloy with an average grain size of approximate 20 ​μm was mainly composed of α-Mg matrix phase along with some MgZn2 and α-Mn precipitates. The results of electrochemical corrosion and immersion corrosion tests revealed a distinct corrosion behavior for the alloy in different solutions with increasing immersion time. The corrosion morphologies were featured with flocculent precipitates in the SBF, flower-like clusters in the AS and columnar crystals in the AU. The alloy exhibited highest corrosion resistance and lowest corrosion rate in the AS compared with the SBF and the AU, which was attributed to the formation of a stable corrosion products layer.

Taguchi optimization of tribological properties and corrosion behavior of self-lubricating Al–Mg–Si/MoS2 composite processed by powder metallurgy

Self-lubricating aluminum matrix composites (AMCs) can be used to reduce the wear and coefficient of friction (COF) in automotive engine components in which the use of liquid lubricants is not desirable. High temperatures accelerate the oxidation and thermal degradation of a liquid lubricant. In this study, we used powder metallurgy (PM) technique to prepare self-lubricant (MoS2)-based Al–Mg–Si AMCs, designated as Al–Mg–Si–xMoS2 (x in wt.%; x = 1.5, 2.0, 30, 3.5, and 4.0). The dry sliding wear properties were assessed using a pin-on-disk tribometer at various applied loads (20–50 N) and sliding distances (1000–3000 m), based on the Taguchi model (L9). Furthermore, electrochemical corrosion tests such as open circuit potential (OCP) and potentiodynamic polarization (PDP) were performed in a 3.5 wt% NaCl medium. The morphology of the Al–Mg–Si–xMoS2 composites was observed through scanning electron microscopy and energy dispersive spectroscopy to clarify the particle distribution and chemical composition. The results indicated that the addition of MoS2 to Al–Mg–Si decreased the wear and COF and increased the corrosion resistance, compared with those of the pristine Al–Mg–Si matrix alloy under same operating conditions. As the sliding distance increased to 250 m, the COF fluctuated, but it stabilized as the distance approached 3000 m. The effects of the load and reinforcement concentration were more significant than those of the sliding distance and track diameter, as predicted by the Taguchi model and analysis of variance methods.

Effect of Nb Addition on Corrosion Resistance of U-6Zr Alloys

The fuel element plates in a research reactor can be exposed to an acidic, neutral, or alkaline environment based on its surroundings. This study aimed to investigate the effect of Nb addition on the corrosion properties of U-6Zr alloys in various environments. U-6Zr-xNb alloys (U-6Zr-2Nb, U-6Zr-5Nb, and U-6Zr-8Nb) with different Nb compositions of 2, 5, and 8 wt%, respectively, were prepared and cut into smaller pieces. The pieces were then mounted with chemical resin equipped with copper wire cables and metallography prepared by grinding using sandpaper with grit sizes ranging from 320 to 1200. The electrochemical corrosion tests used in this work were the polarization test and Tafel extrapolation method. In the first step of corrosion testing, the corrosion potential and polarization resistance were measured using standard settings from a voltage range of −0.02 to 0.02 V with a scanning rate of 0.05 mV/s. In the next step, a destructive method, called the Tafel extrapolation method, was used. Corrosion tests were carried out on U-6Zr-xNb alloys (x = 2, 5, 8) under various environmental conditions using electrochemical methods. Polarization resistance test and Tafel extrapolation methods revealed that the U-6Zr-2Nb alloy exhibited good corrosion resistance in an acidic HNO3 environment with a pH of 1.18. The best corrosion resistance of the U-6Zr-5Nb alloy was observed in demineralized water. Meanwhile, the U-6Zr-8Nb alloy showed the best corrosion resistance in an alkaline NaOH environment with a pH of 11.02. It can be concluded that the higher Nb composition added to U-6Zr alloys, the better their corrosion resistance in higher pH environments.

Correlation between welding structure and corrosion behavior of high strength low alloy (HSLA) ship steel in Cl--containing solutions

The high-strength low-alloy (HSLA) steel industry is in great demand due to the continued growth of the ship and marine sectors. The microstructure of HSLA steel is greatly influenced by both the heat input during welding and the variations in salinity resulting from changes in climate. This paper presents the development of HSLA ship steel using a vacuum electric arc furnace and heat treatment techniques. Electrochemical corrosion tests were conducted on the substrate, heat-affected zone, and fused zone of HSLA ship steel. The results showed that the heat treatment process can improve the microstructure homogeneity of the HSLA ship steel, eliminate chemical composition segregation, refine the grain, and promote the formation of the microstructure of pearlite and ferrite. The welded interface structure was uniform and free from defects or inclusions. The metallographic microstructure of the fused zone showed a massive distribution of grain boundary ferrite, martensite, and granular bainite, and that of the heat-affected zone displayed superheated characteristics consisting of pearlite and acicular ferrite. The interlocking microstructure of the base material enhanced performance in a 4.2 % NaCl solution. The corrosion resistance of the heat-affected zone and fused zones of HSLA ship steel deteriorated. Grain boundary ferrite may be related to the inferior corrosion resistance of the heat-affected zone, while the coarse microstructure of granular bainite led to the serious corrosion resistance in the fused zone of HSLA ship steel.

Accelerated optimization of chromium coating microstructures for nuclear fuel applications through electrochemical corrosion testing

Corrosion of zirconium alloy fuel cladding in nuclear reactors is one of the main limiting factors to component lifespan. Protective coatings may be applied to reduce the corrosion rate during regular operation and can have the added benefit of mitigating follow-on risks associated with loss-of-coolant accidents. This study considers the use of electrochemical testing to rapidly evaluate the corrosion protection of chromium coatings on zirconium alloys. By correlating these electrochemical testing results with the microstructural characteristics and mechanical properties of the coating, it is possible to qualitatively predict the performance of these coatings during long-term autoclave testing and eventual in-reactor use. A series of chromium coatings were deposited using cathodic arc physical vapor deposition (CA-PVD) with varying substrate bias. Electrochemical testing showed that the coatings provided improvements in corrosion protection over the uncoated baseline zirconium alloys, with further improvements observed for substrates to which voltage bias was applied. This is attributed to the increased adatom mobility during the deposition process, allowing for the development of a dense, uniform microstructure of the chromium coating. These results were compared to autoclave exposure data over a 56-day period to show the effectiveness of electrochemical testing towards predicting significant differences in corrosion resistance under regular operating conditions. This approach provided limited qualitative insight on long-term performance in its present state, but shows promise for further development.

Microstructure and Properties of Monolayer Ta and Multilayer Ta/Ti/Zr/Ta Coatings Deposited on Biomedical Ti-6Al-4V Alloy by Magnetron Sputtering

Two types of coatings, i.e., monolayer Ta and multilayer Ta/Ti/Zr/Ta coatings, were deposited on biomedical Ti6Al4V (TC4) alloy by magnetron sputtering to improve its performance. To evaluate the effect of the two coatings on the alloy properties, the microstructure, composition, mechanical and tribological properties, in vitro biocompatibility, and corrosion resistance were investigated. The results showed that α-Ta exists in the monolayer Ta coating, while α-Ta and β-Ta phases coexist in the multilayer Ta/Ti/Zr/Ta coating. The multilayer Ta/Ti/Zr/Ta coating possessed the highest hardness and the monolayer Ta coating had the lowest friction coefficient compared to the Ti6Al4V alloy. The friction and wear tests revealed that the anti-wear performance of the Ta coating is the best, followed by that of the Ta/Ti/Zr/Ta coating, while the anti-wear performance of TC4 alloy is relatively poor in comparison with the Ta and Ta/Ti/Zr/Ta coatings. The wear resistance of the multilayer Ta/Ti/Zr/Ta coating under low normal load is better than that under high load normal load. Finally, the in vitro and electrochemical corrosion tests showed that the Ta coating modification provides better biocompatibility and corrosion resistance than those of the uncoated Ti6Al4V alloy.

Influence of CrFeCoNiCu high-entropy alloy and ultrasonic stirring on the thermal, electrochemical and mechanical properties of Zn-30Sn high-temperature solder alloy

In this study, the thermal, electrochemical and mechanical properties of Zn-30Sn solder alloy with different contents of CrFeCoNiCu high-entropy alloy (HEA) (0, 0.5 and 1 wt%) were investigated. At the same time, ultrasonic stirring was introduced into the melting process. The results suggested that the addition of HEA could refine the microstructure and the Zn matrix phases accelerated to dissolve to form more precipitation phases with the increase of HEA content from 0 to 1.0 wt%. The application of ultrasound could make the distribution of the phases disperse and facilitate the formation of dense and uniform corrosion products during the corrosion process. The electrochemical corrosion test and tensile test results showed that the ultrasonically treated Zn-30Sn solder alloy containing 1.0 wt% HEA had the lowest corrosion current density (Icorr = 1.11 μA·cm−2), the highest ultimate tensile strength (101.13 MPa) and yield strength (25.55 MPa), indicating that the corrosion resistance and mechanical properties were most outstanding. Moreover, the melting temperature of the composite solder alloys was slightly decreased from 379.5 °C to 377.5 °C.

Exfoliated carbon nitrides for corrosion prevention in radiators: Temperature-dependent corrosion analysis

This article outlines the preparation and exfoliation of graphitic-carbon nitride (GCN) by thermal polymerization technique using urea proceeded by the hydrothermal approach for the application of corrosion resistance in radiators. The prepared sample was characterized by using various methods. X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the purity of GCN, and Surface morphology results revealed the formation of spherical-shaped GCN. Herein, graphitic carbon nitride (GCN) was synthesized to enhance its corrosion-resistance performance on mild steel (MS) under a seawater atmosphere. The corrosion behaviour of the graphitic-carbon nitride (GCN) synthesized by the hydrothermal method was examined by conducting electrochemical corrosion tests in a 3.5% NaCl medium under three different temperatures. The excellent temperature dependant electro-catalytic activity of the prepared GCN was analysed. The hydrothermal exfoliation process highly enhances the structural, optical, and electrochemical properties like corrosion resistance and stability of the prepared GCN. This study demonstrates that hydrothermally exfoliated GCN exhibits low corrosion rates and high electrochemical corrosion resistance, which could be a potential candidate for corrosion inhibitors in radiators.