Electrochemical Corrosion Behavior Research Articles

Mechanical and Electrochemical Corrosion Behaviors of Porous Ti-6Al-4V Alloys Prepared by an Electrochemical Sintering Approach

Titanium alloys have been widely used in bone implants, but the mechanical properties, elastic modulus mismatch between bone and metal, and stress shielding effects can occur. However, porous materials can effectively overcome this problem. In recent years, porous structures have attracted enough attention from researchers. Adjustment of the porous structure may make the titanium alloys better able to meet the requirements of the implant. In this study, we have successfully prepared Ti-6Al-4V alloys by combining powder metallurgy with electrolysis in molten salt. At the same time, CaCl2 was used as a sacrificial space holder to adjust the porosity and porous structure. The Ti-6Al-4V alloys prepared by this method contain 29%–60% porosity and elastic modulus has been controlled between 1.8 GPa to 7.8 GPa, which is suitable for cancellous bone, trabecular, and other parts with low elastic modulus. In addition, the higher porosity also showed better corrosion resistance in the Hank’s solution. The potentiodynamic polarization curves show that the corrosion resistance increases significantly with an increase in porosity.

Study on the structure, growth pattern and corrosion behavior of CoCrFeNiAl high entropy alloy coatings - base on hollow cathode effect

The surface of TC18 titanium alloy was coated with a CoCrFeNiAl HEA coating using double-glow plasma surface metallurgy. The structure, phase, and growth mode of the coating were investigated, along with its electrochemical corrosion behavior. The prepared HEA coating, under the influence of the hollow cathode effect and non-equilibrium diffusion, exhibits a composite structure consisting of a deposited layer and an interdiffused layer. It demonstrates robust metallurgical bonding with the substrate, and it exhibits a hardness of 12.66 GPa and an elastic modulus of 158.52 GPa, along with exceptional hardness and high elastic modulus. The primary phase of the coating consists of an FCC solid solution, with a minor presence of Ni3Al and Al8Cr5 phases. TEM results demonstrate that hollow cathode enhanced sputtering effectively refines the grain structure on the substrate surface. The high entropy alloy coating, characterized by a significant abundance of nanocrystalline and amorphous structures, is obtained under the bombardment of high-energy particles. Gradually increasing from the interface to the deposited layer, there is an augmentation in the content of nanocrystals. The transition from the substrate to the sedimentary layer comprises three distinct regions: a surface fine crystal region, a nanocrystalline structure region, and a nanocrystalline and amorphous precipitated phase-rich region. In 3.5 wt% NaCl solution, the electrochemical corrosion rate of the coating is 1.36 × 10−1 μm·year−1, which is about ten times lower than that of the substrate. Moreover, pre-soaking forms a stable oxide film on the coating's surface, effectively preventing corrosion and demonstrating its remarkable corrosion resistance.

Al Clad CF/Al Composite Fabricated by a One-Step Liquid–Solid Infiltration–Extrusion Process: Electrochemical Corrosion and Mechanical Behavior

Al Clad CF/Al Composite Fabricated by a One-Step Liquid–Solid Infiltration–Extrusion Process: Electrochemical Corrosion and Mechanical Behavior

The precipitation and corrosion behaviour of cast Al–Mg–(0.7, 1.3) Li–Cu alloys

Achieving the development of ultra-light Al–Li alloys with high strength and excellent corrosion resistance is always a challenge. In this study, the precipitation characteristics and electrochemical corrosion behaviours after isothermal aging of cast Al–Li alloys with two different Li contents were comparatively analysed. The results showed that the increase in Li content from 0.7 wt-% to 1.3 wt-% retarded the peak hardening and improved the Al–Li alloy hardness and strength by promoting the precipitation of the S′ (Al2CuMg) and T1 (Al2CuLi) phases. Besides, the galvanic coupling corrosion of the alloying element Cu with the aluminium matrix was reduced by more Li addition, thus improving the corrosion resistance of the alloy.

Investigation on electrochemical corrosion behavior and mechanical properties of Fe-nano particles produced by high-energy ball milling technique

Abstract This study focuses on converting iron particles from grinding sludge, after removing impurities, into Fe-nanoparticles using high-energy ball billing. The goal is to examine the corrosion behaviors and mechanical properties of these Fe-nanoparticles. Nanostructured Fe-powder was synthesized through a process involving 10 h of high-energy ball milling, followed by conventional hot pressing and sintering. Structural and microstructural properties were thoroughly examined using techniques such as X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental diffraction spectroscopy. Upon sintering, SEM and TEM analyses unveiled the formation of a nanostructured alloy within the samples. Notably, the milled sample exhibited high hardness value, measuring at 155 HV. However, it is noteworthy that the un-milled sample demonstrated superior compression strength compared to its milled counterpart. Furthermore, the corrosion behavior of the samples was evaluated through electrochemical corrosion studies. Interestingly, the sample subjected to 10 h of milling (coin number 5) displayed a significantly lower corrosion rate, measuring at 1.3921 mm/year, suggesting enhanced corrosion resistance attributed to the nano structuring process.

Microstructure and electrochemical corrosion behavior of TA2 with nano/micro TiC particle reinforcement

TA2 pure titanium (Titan Grade 2-EN) is commonly used in marine and biomedical applications due to its outstanding biocompatibility and resistance to corrosion. Nevertheless, the limited hardness of TA2 presently reduces the service life of the components. Directed energy deposition (DED) technology can improve the properties of conformal materials, opening up new possibilities. In this work, 8% micro-TiC/TA2, 8% nano-TiC/TA2, and 4% micro/4% nano-TiC/TA2 composites were fabricated by DED to investigate the effects of different scales of TiC reinforcement on the properties of TA2. The majority of micro-TiC remaining unmelted in the composite, exhibiting only a small amount of micro-TiC dissolution. In comparison, the nano-TiC/TA2 displays a conspicuous dendritic structure with well-developed dendritic growth, boasting up to three dendrites. In contrast, the 4%micro/4%nano-TiC/TA2 exhibits a mixed crystal morphology, characterized predominantly by dendritic growth along the unmelted TiC, with other TiC phases also present in the deposited layer. Performance tests demonstrated that TiC can increase the microhardness of titanium. The 4% micro/4% nano-TiC/TA2 composite achieved the highest average microhardness of 542 HV0.2, representing a 160.58% increase compared to TA2. Additionally, the composites demonstrated improved corrosion resistance relative to TA2, with the 8% micro-TiC/TA2 composite exhibiting the best corrosion resistance. This outcome can be attributed to the effective physical barrier properties of the micron-sized TiC.

The effect of Al on the corrosion resistance of binary Mg-Al solid solutions: Combining in-situ electrochemistry with combinatorial thin films

The effect of varying Al concentrations on the electrochemical corrosion resistance of binary Mg-Al solid solutions thin films under alkaline immersion conditions was investigated via a combination of in-situ flow-cell, scanning vibrating electrode technique and microscopy analysis. These spatially resolving characterization techniques are employed along the Al concentration gradient of the combinatorically grown thin films enabling efficient screening of the Al concentration dependent electrochemical corrosion behaviour. The analysis revealed an increasing corrosion resistance with increasing Al concentration, as a consequence of Al induced hydroxide reinforcement. Specifically, the addition of >4 wt.% Al decreases the corrosion current density in the range of 70–90 % compared to pure Mg.

Electrochemical corrosion behaviour of Co–Cr–Mo–W alloy and its surface anodic oxide film in artificial saliva

Electrochemical corrosion behaviour of Co–Cr–Mo–W alloy and its surface anodic oxide film in artificial saliva

Corrosion property investigation of laser-cladding copper coating in the simulated nuclear waste disposal solution

To explore the efficient corrosion protection for the nuclear waste storage containers, pure copper coatings were successfully prepared on the 20# steel pipe surface using an infrared laser system under different laser powers. The study was conducted on the copper coatings, encompassing the surface quality, defects, microstructure, elemental distribution, phase composition, and corrosion products. The electrochemical and immersion corrosion behavior of the copper coatings in simulated nuclear waste disposal solutions was analyzed. The pure copper coating prepared by 2800 W laser power has fewer amounts and smaller sizes of defects inside the coating with only a slight fusion of Cu and Fe elements at the interface, which exhibits the highest corrosion potential and the smallest self-corrosion current density. During the immersion corrosion process, pores and unfused defects inside the coating, as well as the pits formed by galvanic coupling corrosion, lead to enhanced acidity inside these defects, resulting in a higher corrosion rate. As the immersion time proceeds, the corrosion rate slows down gradually and the content of Cu2+ corrosion product increases significantly.

Electrochemical corrosion and tribocorrosion behavior of CrN and CrAlN coatings in artificial seawater

AbstractThis study investigated the corrosion and tribocorrosion behavior of CrN and CrAlN coatings deposited on steel through direct current magnetron sputtering. Additionally, the effects of Al addition on the microstructure, corrosion inhibition, and tribocorrosion behavior of CrN coatings were evaluated. Compared with the CrN coating, the CrAlN coating exhibited a denser columnar crystal structure and a higher hardness of 23.8 GPa. The CrAlN coating reacted with water to form Al2O3 and Cr2O3 films, which enhanced its corrosion resistance. Moreover, the addition of Al enhanced the wear resistance of the CrN coating and reduced the material loss due to corrosion, wear, and their synergistic effects. The CrAlN coating exhibited a low corrosion current density of 1.14 × 10−8 A/cm2, indicating a 92% reduction compared with the CrN coating. Furthermore, under either open circuit potential or anodic accelerated tribocorrosion conditions, the CrAlN coating featured significantly lower total material loss and synergistic material loss than the CrN coating, demonstrating higher corrosion and tribocorrosion protection.

Experimental investigation of electrochemical and mechanical properties of stainless steel 309L at different built orientation by cold metal transfer assisted wire arc additive manufacturing

In this article, a multi layered wall of stainless steel 309 L (ER309L) material was WAAM printed over a substrate, at optimized parameters using gas metal arc welding as heat input source assisted by cold metal transfer machine, aiming to evaluate mechanical and electrochemical properties at different built orientations i.e., 0°, 30°, 45°, 60°, and 90°. Wall samples were cut-out by wire cut electric discharge machine to compare their properties. Microstructural properties and phases were confirmed by Scanning Electron Microscopy, Energy-Dispersive Spectrometry (EDS) and X-ray diffractometry (XRD), as they change on melting and solidification along the building direction. Columnar dendrite and vertical ferritic grains were observed through an optical microscope. SEM images suggests the presence of Widmanstatten austenite laths forming δ/γ duplex phase. Element distribution by EDS was further verified by Schaeffler’s diagram. XRD pattern confirms various elements and their phase compositions. The tensile strength and yield strength of samples decreased with increase in orientation angle, which is attributed to decrease in the inter-layer length which restricts the slipping of grains and reestablishment of the residual forces., tableau software was used to theoretically predict values for 45° sample as it broke outside the gauge length. electrochemical properties and corrosion behaviour were studied by electrochemical impedance spectroscopy (EIS) and Potentiodynamic polarization (PDP) where in highest Rct=170 Ω and lowest corrosion rate, 0.56 mils per year (MPY) was observed for 45° is attributed to diffusion of chromium to the metal-solution interface forming a passive film. The corrosion rate range 0.48–2.7 MPY, advocates SS309L have a uniform passive film. The properties studied certifies that WAAM printed stainless steel component can be exploited for critical applications.

Study on corrosion characteristics and mechanism of laser powder bed fusion of Mg–Zn–Zr alloy

Laser Powder Bed Fusion (LPBF) presents novel opportunities for the processing and manufacturing of magnesium (Mg) alloys. However, Mg alloys consistently face challenges with poor corrosion resistance. Consequently, it becomes imperative to delve into the corrosion behavior and mechanisms of Mg alloys formed through LPBF. This paper investigated the electrochemical corrosion behavior, the distribution of corrosion products, and the corrosion mechanism of LPBF ZK60 Mg alloy. The results show that the corrosion current density (Icorr) value of LPBF ZK60 Mg alloy is 3.76 μA∙cm−2. The hydrogen evolution in Hank's solution steadily increases with immersion time and reaches a stable state after 24 h. The corrosion rates calculated based on hydrogen evolution and weight loss are 2.1 mm/y and 2.4 mm/y, respectively. The corrosion resistance of LPBF ZK60 Mg alloy is predominantly affected by three factors: uneven microstructure, internal crack defects, and precipitate phases. The melt pool boundary is identified as a corrosion-vulnerable zone, which extends into the columnar crystal zone after corrosion. Crevice corrosion occurs at microcracks, and the precipitate phases within the grains and matrix induces galvanic corrosion. These findings suggest that the corrosion resistance of LPBF ZK60 Mg alloy may be regulated through targeted measures, such as eliminating cracks, achieving microstructure homogenization, and controlling the precipitate phases (including quantity, composition, and distribution).

Microstructure and properties of a MAO/PA/MoS2 composite coating formed on 6063 aluminum alloy by micro arc oxidation

Different self-sealing and lubricating composite coatings were produced on 6063 Al alloy using micro arc oxidation (MAO) with MoS2 and/or phytic acid (PA) incorporated into the base electrolyte. The tribological properties and electrochemical corrosion behavior of the coatings were detailed investigated in this paper. The results showed that the coefficient of frictional (CoF) of MAO/MoS2 coating decreased 29.6 % compared to that of the pure MAO coating due to the excellent self-lubricating of MoS2. Meanwhile, the CoF of MAO/PA/MoS2 coating reduced 39.5 % attributed to a thicker and more compact coating obtained by the addition of PA as an intermediate chelating agent besides the self-lubricating effect of MoS2 particles. The pores were sealed by MoS2 during MAO process due to the electrodeposition effect which resulted in a positive shifting of the corrosion potential. However, the improvement of corrosion resistance for the MAO/MoS2 coating was limited as the intrinsic defects in MoS2 lattice preferred to form micro galvanic cell. The corrosion current density of the MAO/PA/MoS2 coating was three orders of magnitude lower than that of pure MAO coating. The thin PA layer produced at the substrate/coating interface of the MAO/PA/MoS2 coating can act as a barrier to suppress the galvanic corrosion, inducing the best corrosion resistance of the coating.

Electrochemical corrosion behavior of 7075 aluminum alloy with different ultrasonic surface rolling microstructures

7075 Al alloy is strengthened by ultrasonic surface rolling process (USRP), and the process parameters are changed to regulate the microstructure. The thickness, grain size and distribution of different strengthening layer are characterized in detail by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The influence of different strengthening structures on their electrochemical corrosion behavior are studied using scanning Kelvin probe (SKP) and electrochemical impedance spectroscopy (EIS). The results show that the average grain size of untreated Al alloy is 2.89 μm, the surface SKP potential is low and fluctuates greatly, and has high sensitivity to pitting corrosion. After USRP treatment, the surface roughness of 7075 Al alloy decreases, the grain size is significantly refined and shows a gradient distribution, SKP potential in the strengthening area increases and becomes more stable, the passive film on the surface thickens, the density of pits significantly decreases, and the corrosion resistance is improved. Besides, the samples with thicker plastic deformation layer and surface nanocrystallization (average size of 39.9 nm) exhibit better performance compared to other samples.

Electrochemical investigation of electrophoretically deposited graphene-oxide coating on AZ31 alloy prepared using in-house synthesized few-layer graphene-oxide nanosheets

Magnesium and its alloys possess low density and superior specific strength making it a potential structural metal to be used in different engineering fields. However, its proneness to corrosion limits its applications. In this novel study, an eco-friendly graphene-oxide coating was prepared on AZ31 magnesium alloy via electrophoretic deposition to enhance its anti-corrosion properties. Scanning electron microscopy coupled with energy dispersive spectroscopy, atomic force microscopy, and scratch test were adopted to investigate surface morphology, roughness, chemical composition, and adherence of the coating. The corrosion behaviour of graphene-oxide coated alloy was studied using potentio-dynamic polarization and electrochemical impedance spectroscopy tests in 3.5 wt% NaCl and Borate Buffer solutions. The obtained results demonstrate that the coating developed on AZ31 alloy is smooth and adherent with the hardness of the as-deposited coating measuring as high as 6.0 GPa. In addition, the electrochemical corrosion behaviour studies revealed that the coating significantly increased the corrosion potential (Ecorr) of the alloy towards more noble values (−0.65 V < Ecorr < −0.35 V), with the coated alloys possessing a charge transfer resistance nearly two orders of magnitude greater than their non-coated counterparts. Consequently, the corrosion rate of the coated alloy decreased substantially, indicating that the coating exhibits exceptional corrosion resistance (0.045–0.09 mm/a in 3.5 wt% NaCl and 0.002–0.006 mm/a in Borate Buffer). These findings challenge the conventional beliefs that graphene exhibits strong cathodic behaviour towards anodic materials such as AZ31 alloy. Thus, the outcomes not only have the potential to revolutionize the advancement of graphene-oxide coatings for corrosion resistance but could also possibly expand AZ31 alloy’s applications in the aerospace and automotive sectors.

The influence of microstructural evolutions on electrochemical corrosion and passive behavior in precipitation-strengthened high-entropy alloys

Effects of microstructural evolutions on electrochemical corrosion properties and passive film characteristics of precipitation-strengthened (Ni2Co2FeCr)92Al4Nb4 high-entropy alloys (HEAs) were investigated in a saline environment. Compared with single-phase FCC alloys, the appearance of nano-sized L12 particles increases the metastable pitting activities and slightly reduces the pitting potential, while the lamellar D019 phase further deteriorates the localized corrosion resistance. The chemical composition and oxide state of passive films are closely related to the different precipitation scenarios. The corrosion morphologies of the single-phase and L12-strengthened alloys are dominated by pitting, whereas the intergranular corrosion (IGC) and intragranular dealloying-like corrosion occur in the D019-strengthened alloy.

Multi-scale corrosion behavior of Al/Ti/Fe multi-interfaces composites

In this study, we are presented a thermodynamics and kinetics model to reveal the corrosion sensitivities of Al/Ti/Fe multi-interface composites. The model demonstrates that impurity elements (Mn) and interface intermetallics alter the electrochemical polarization behavior of the Al and Fe layers, leading to a shift to cathodic control. Additionally, intermetallic compounds, which are formed at the interface enhance wear resistance and modify its electrochemical corrosion behavior. This study provides new insights into the interface corrosion mechanism of multi-interface composites and offers directions to improve the multi-interfaces composites corrosion resistance, which is an important step for future fabrication and applications of multi-interface composites.

The electrochemical corrosion behavior of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy with different initial microstructures

The corrosion behavior of Ti-5Al-5Mo-5V-1Cr-1Fe titanium alloy with different initial microstructures was investigated by conducting a series of electrochemical tests. Based on the experimental data, the effects of NaCl solution concentration and corrosion time on the electrochemical polarization curves, corrosion rates, electrochemical impedance spectroscopy (EIS), and impedance of the alloy with two initial microstructures were analyzed. The assessment of the corrosion current density (Icorr) and corrosion rate (CR) for the alloy under different corrosion conditions reveals a general pattern of initial decrease followed by increase in their values with extended corrosion time and elevated solution concentration, whereas the capacitive reactance arc exhibits an opposite trend. For alloys with initial equiaxed microstructures, the Icorr value is 0.1892 μA/cm2, and the CR value is 0.000413 mm/year; these values are lower than those of 1.298 μA/cm2 and 0.002842 mm/year for alloys with initial lamellar microstructures. Whereas the capacitive reactance arc and the impedance value are greater for the titanium alloy with initial equiaxed microstructure. Based on the adsorption kinetics principles, the effects of temperature on corrosion rate of alloys with different initial microstructures at a consistent concentration were analyzed. Compared to the alloy with initial lamellar microstructure of 3054 kJ/mol, the alloy with initial equiaxed microstructure had an activation energy of 4155 kJ/mol. As the temperature rises, the rate of corrosion tends to increase. The results suggested that the alloy with initial equiaxed microstructure presented the superior corrosion resistance than the alloy with the initial lamellar microstructure. Additionally, the corrosion morphologies after polarization of the alloy were characterized. And the results show that the surfaces of titanium alloys with initial lamellar microstructure display a comparatively greater incidence of pitting corrosion upon assessment of the corrosion morphology.

A Comparative Study on the Electrochemical Corrosion Behaviour of Biomedical β-Titanium Alloy with TiAlV and Titanium in Hank’s Physiological Solution and the Impact of Reactive Oxygen Species and Immersion Time

A Comparative Study on the Electrochemical Corrosion Behaviour of Biomedical β-Titanium Alloy with TiAlV and Titanium in Hank’s Physiological Solution and the Impact of Reactive Oxygen Species and Immersion Time

Electrochemical Deposition and Properties of Ni Coatings with Nitrogen-Modified Graphene Oxide

In this study, a method for producing nitrogen-modified graphene oxide (NMGO) using hydrothermal synthesis in the presence of triethanolamine is presented. The composition and structure of NMGO are characterized using X-ray phase analysis (XPA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and Raman spectroscopy. Ni-based metal matrix coatings (MMCs) modified with NMGO were obtained from a sulfate-chloride electrolyte in the galvanostatic mode. The process of electrochemical deposition of these coatings was studied using chronovoltammetry. The microstructure of Ni–NMGO MMCs was studied using the XPA and SEM methods. It has been established that the addition of NMGO particles into the Ni matrix results in an increase in the microhardness of the resulting coatings by an average of 1.30 times. This effect is a consequence of the refinement of crystallites and high mechanical properties of NMGO phase. The corrosion-electrochemical behavior of studied electrochemical deposits in 0.5 M sulfuric acid was analyzed. It has been shown that the corrosion rate of Ni–NMGO MMCs in a 3.5% sodium chloride environment decreases by approximately 1.50–1.70 times as compared to unmodified Ni coatings. This is due to NMGO particles that act as a barrier preventing the propagation of the corrosion and form corrosive galvanic microelements with Ni, promoting anodic polarization.