Electrochemical Corrosion Behavior Research Articles

Microstructure and Electrochemical Corrosion Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting

Microstructure and Electrochemical Corrosion Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting

Electrochemical synthesis, physical properties and corrosion behavior of electropolymerized polyaniline films developed on 316L stainless steel

AbstractPolyaniline (PANI) films may be developed on metallic substrates by a variety of electrochemical techniques. In the present work, PANI films were electrodeposited on AISI 316L stainless steel substrates by cyclic voltammetry (CV), chronoamperometry (CA), and chronopotentiometry (CP) with the objective of comparing the efficacy of each method, based on the integrity of the developed films. Cyclic voltammetry and anodic polarization were used to determine optimal electrodeposition parameters for the development PANI films using the CA and CP methods. The structure and morphology of the coatings were characterized by scanning electron microscopy, energy‐dispersive x‐ray spectroscopy, Fourier‐transform infrared spectroscopy, and ultraviolet–visible spectroscopy. Among the evaluated techniques, CV led to the formation PANI films with the best homogeneity as well as the lowest number of defects, such as cracks or pores. Subsequently, the corrosion resistance of AISI 316L steels with and without PANI was compared in a physiological saline solution (0.9% NaCl). Potentiodynamic polarization tests indicated that the PANI‐coated samples exhibited lower corrosion current density values (0.012 vs. 0.018 μA/cm2) and lower passive current density values (0.04 vs. 0.06 μA/cm2) in comparison to the bare AISI 316L steel. Additionally, long‐term monitoring by electrochemical impedance spectroscopy revealed that PANI films consistently exhibited superior polarization resistance up to 32 days of exposure in the 0.9%NaCl solution (233,000 vs. 207,000 Ωcm2).

Effect of hot-rolling process on the microstructure, mechanical and corrosion behaviors of dual-phase Co-based entropic alloys

Two compositions from dual-phase Co-based entropic alloys with high corrosion resistance were chosen, and the effect of hot-rolling process on the microstrcture, mechanical property and corrosion resistance was investigated in this work. The processing parameters were designed and optimized by CALPHAD calculations. For the case of hot-rolled alloys, fcc + hcp dual-phase structures were confirmed by different characterization techniques, including XRD, ECCI, and EBSD. After testing various mechanical properties and electrochemical corrosion behaviors at room temperature, the hot-rolled alloys exhibit an outstanding mechanical and corrosion resistance property. The hot-rolling process improves the electrochemical corrosion resistance slightly and promotes hardness as well as strength-ductility greatly. The experimental characterizations provide plentiful information about microstructure, crystallographic orientation, lattice misorientation, grain boundaries, and so on. More details for the strengthening and hardening mechanisms could be obtained from the EBSD analysis. The current work shed lights on the design of new alloy recipe as well as the synthesis of novel grade dual-phase entropic alloys with excellent combination of mechanical properties and corrosion resistance which could be applied in harsh environments.

Electrochemical corrosion behavior and passive film properties of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy coating prepared by laser cladding

The phase composition, microstructure morphology, and corrosion behavior of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy (EHEA) coatings produced via laser cladding were investigated. The research delved into discerning the phase structures and microstructural variations of the EHEA coatings concerning differing Nb compositions. The findings highlighted a direct correlation between Nb content and the volume fraction of the eutectic structure, specifically the FCC/Laves phases. Electrochemical evaluations, including diverse tests such as potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization, Mott-Schottky measurements, and X-ray photoelectron spectroscopy, revealed distinct corrosion behaviors among the EHEA variants. Notably, the Fe2Ni2CrV0.5Nb0.2 coating exhibited relatively superior corrosion resistance compared with Fe2Ni2CrV0.5Nbx (x=0.4,0.6,0.8) coatings, attributed to its lower corrosion current density (Icorr) and the formation of a thicker passive film with prolonged passivation duration. Conversely, the Fe2Ni2CrV0.5Nb0.8 coating, characterized by increased eutectic structures and grain boundary density, yielded a thicker yet non-uniform passive film with higher vacancy defects. This comprehensive exploration into the corrosion behavior and passive film properties of these EHEA coatings provides a reference for designing materials that hold promising implications for future corrosion-resistant material development in industrial parts repair applications.

Corrosion behavior of novel Ti6422 alloy with equiaxed structure and lamellar structure in HCl solution

This study systematically investigated the electrochemical corrosion and static immersion corrosion behavior of the novel Ti6422 (Ti-6Al-4V-2Mo-2Fe) alloy with equiaxed (EM) and lamellar structure (LM) in HCl solution. The differences in corrosion performance between EM and LM samples were analyzed based on the characteristics of the passive film and substrate microstructure. Results indicated that the LM sample contained higher contents of TiO₂, Al₂O₃, and MoO₃ with higher stability compared with the EM sample, and the thickness of passive film was approximately twice that of the EM sample. Additionally, the donor density of LM sample was lower than EM sample. These findings indicate that the passive film on LM samples is thicker, with fewer defects and higher density. Electrochemical corrosion results revealed that the corrosion current of LM samples was lower and the polarization resistance was higher than these of EM samples, both suggesting superior corrosion resistance of LM samples. Immersion corrosion further confirmed that the LM sample had a lower corrosion rate. The enhanced corrosion resistance in LM samples was primarily due to higher content of corrosion-resistant β phase. Conversely, the numerous micro-galvanic cells between αs precipitates and adjacent β phase in EM samples weakened the corrosion resistance. Overall, these results demonstrated that regulating microstructure through heat treatment is an effective strategy for improving corrosion resistance of titanium alloys.

Investigation of the microstructural characteristics of laser-cladded Ti6Al4V titanium alloy and its corrosion behavior in simulated body fluid

Laser cladding technology has a wide range of potential industrial applications in the surface strengthening, repair and reuse of orthopedic implants. By employing this technique to conduct same-material surface restoration and enhancement on titanium alloys, it demonstrates significant developmental potential. However, the microstructure of laser additively manufactured titanium alloy differs significantly from that of traditional titanium alloys, which affects its corrosion resistance in human body fluids. To compare the corrosion resistance differences between the cladding layer and the substrate, this study investigates the microstructure of multi-pass laser cladding Ti6Al4V (TC4) titanium alloy and analyzes the corrosion morphology and corrosion products of the cladding layer in simulated body fluids (SBF). By comparing the electrochemical corrosion behavior of laser cladding with that of traditionally manufactured TC4, this research reveals the differences in corrosion resistance between the two titanium alloys. The research demonstrates that the microstructure of cladding primarily consists of prior-β grains and continuous grain boundary α phase, along with a complex basketweave structure composed of fine acicular α phase and lamellar α phase. Additionally, due to the complex thermal cycling process, the acicular α' colonies within the prior-β grains. These features enhance the cladding layer’s resistance to plastic deformation and increase microhardness, though with some uneven distribution. Interestingly, the TC4 cladding layer forms a porous passivation layer after corrosion, primarily composed of a TiO2 passivation film and deposits of hydroxyapatite and other phosphates. Due to the lower β-phase content, finer grains with higher energy states, and a greater proportion of high-angle grain boundaries (HAGBs) in the cladding layer, it exhibits higher electrochemical activity. As a result of these microstructural differences, the corrosion resistance of the TC4 cladding layer in SBF is inferior to that of TC4 manufactured using traditional techniques.

Effect of laser-induced grain growth on the electrochemical and immersion corrosion behavior of electrochemical deposited Ni coatings

In this study, the introduction of laser irradiation during the electrochemical deposition of Ni coatings was employed to investigate the evolution of surface morphology, microstructure, and residual stress. Furthermore, the impact of laser on corrosion performance was examined through electrochemical and immersion corrosion tests. The results showed that introducing a laser resulted in a uniform electrochemically deposited particle size distribution, and the shape evolved from granular to pyramidal. However, the average grain size increased from 0.4 ± 0.1 μm to 0.6 ± 0.3 μm after adding laser, and the grain morphology also transformed from equiaxed to columnar grains. In addition, the surface roughness increased from 34 ± 3 nm to 122 ± 16 nm compared to not adding a laser. The internal stress changed from 54 ± 17 MPa to −113 ± 19 MPa, indicating that the original tensile stress evolved into compressive stress. Electrochemical and immersion corrosion indicate that after adding laser, the passive current density decreased from 3.8 × 10−6 A·cm−2 to 6.9 × 10−7 A·cm−2 (reduced by approximately 81.8 %), indicating a significant improvement in corrosion resistance. This is attributed to the stability and density of the passive film. Although the average grain size and surface roughness increase, the uniformity of surface deposited particles improves the uniformity of electrochemical distribution, accelerates the formation of uniformly dense passive film, and limits the expansion of corrosion pits under the combined action of compressive stress.

Investigation on electrochemical corrosion behavior of Cu-14Fe -(0, 0.05)Ce alloys

This work thoroughly investigated the electrochemical corrosion behaviors of Cu-14Fe-(0, 0.05) Ce alloys. Experimental findings revealed that the addition of Ce did not change the phase constituent, but refined α-Fe phase particle from 0.30 ± 0.04 to 0.22 ± 0.03 μm and increased its content from 1.24% to 2.17%. With the increase of corrosion time, adding Ce could increase the linear polarization resistance by up to 3 times, and correspondingly the corrosion rate was reduced to half. Moreover, Ce addition contributed to the densification of corrosion products. The α-Fe phase preferentially underwent anodic dissolution reaction, generating corrosion product Fe2O3. The increase of soaking time resulted in the occurrence of anodic dissolution of Cu-matrix phase, along with the formation of Cu2O and Cu2Cl(OH)3.

The electrochemical corrosion behavior and antibacterial properties of Cu-xFe alloy

Copper-based alloys have garnered significant attention for their potential in antimicrobial applications aimed at mitigating medical-related infections. Nonetheless, the alloying elements in conventional copper alloys frequently exhibit biotoxicity. This study explored the corrosion behavior, antimicrobial activity, and ion release of Cu–Fe alloys with varying iron contents and aging treatment. The results indicate that increasing the iron content in Cu–Fe alloys and applying appropriate aging treatment can enhance both the antibacterial efficiency and corrosion rate. Transmission electron microscopy (TEM) observations revealed a corrosion mechanism in which dispersed iron phases act as nucleation sites. These nanoscale precipitates increase the Cu/Fe interfacial area, thereby promoting ion release at the interface. Furthermore, in-situ scanning electron microscopy (SEM) revealed that corrosion products are more likely to detach in iron-rich segregated areas, which effectively promotes the sustained release of copper ions.

Influence of Ni content on electrochemical corrosion and tribological behavior of Cu-10Sn coatings by laser cladding

In this work, Cu-10Sn-xNi (x = 0, 3, 6, 9, and 12 wt%) alloy coatings were prepared using laser cladding technology. The influence of Ni content on the phase composition, microstructure, crystallographic characteristics, microhardness, electrochemical corrosion, dry sliding wear and corrosive wear behavior of the coatings were studied. The results indicated that the coatings formed good metallurgical bond with the substrate. The coatings were composed primarily of the α-Cu matrix and small γ precipitates. The Ni element effectively reduced component segregation, and with the increased of Ni content, the grain size in the coating was significantly refined, resulting in fine equiaxed grains. Under the effect of fine grain strengthening, the Cu-10Sn-12Ni (C12NS) coating achieved a higher microhardness of approximately 222.9 ± 5.3 HV0.2. In the electrochemical corrosion test, the increased in the number of grain boundaries significantly reduced the corrosion resistance of the Cu-10Sn-xNi coatings. The Cu-10Sn-6Ni (C6NS) coating exhibited excellent corrosion resistance, with an Icorr of only 1.37 μA/cm2. The results of the dry sliding wear test showed that under the influence of the hardness gradient between the hard precipitate phase and the soft matrix of the coating, the C6NS coating achieved satisfactory wear resistance with a specific wear rate of 3.30 × 104 μm3/Nm. Meanwhile, due to the good corrosive resistance, the C6NS coating showed the best tribological performance in 3.5 wt% NaCl environment, and the specific wear rate was 1.58 × 104 μm3/Nm.

The Study of the Electrochemical Corrosion Behavior of Cu-30%Fe Nanoalloy

In this work, we have developed Cu-Fe alloys with a nanometric structure through the process of mechanosynthesis. We then followed the formation mechanism of these alloys and proceeded with a crucial step, which is cold compaction. We have elaborated Cu-Fe alloys with a nanometric structure by mechanosynthesis and following the mechanism of formation of these alloys, the we employed various analytical techniques to characterize the structural and microstructural properties of our powders. The X-ray diffraction method (XRD) was used to calculate the structural parameters, while laser granulometry was employed to study the evolution of particle size. Scanning electron microscopy (SEM) was then utilized to examine the morphology of the powders. Additionally, we investigated the electrochemical behavior of our alloys, focusing on their corrosion resistance. Electrochemical impedance spectroscopy (EIS) was performed in the frequency range of 10 kHz to 15 mHz to evaluate the corrosion performance.

Electrochemical Corrosion Behavior and the Related Mechanism of Ti3SiC2/Cu Composites in a Strong Acid Environment.

The electrochemical corrosion behaviors of Ti3SiC2/Cu composites in harsh media including dilute HNO3 and concentrated H2SO4 were studied in detail and the related corrosion mechanisms were explored. Under open-circuit potential, the corrosion resistance of Ti3SiC2/Cu in dilute HNO3 was worse than that in concentrated H2SO4. In dilute HNO3, Ti3SiC2/Cu exhibited a typical passivation character with a narrow passivation interval. During the corrosion process, the dissolution of Cu-Si compounds resulted in the destruction of the passivation layer on the surface. Additionally, with the increasing of the potentials, the oxidation of Cu and Si atoms led to the generation of the oxide film again on the surface. In concentrated H2SO4, the Ti3SiC2/Cu composite was covered by a double-layered passivation layer, which was composed of an internal layer of TiO2 and an external layer of Cu2O and SiO2. This was because Cu diffused into the surface and was oxidized into Cu2O, which formed a denser oxidized film with SiO2. In addition, it was found that Ti3SiC2/Cu has better corrosion resistance in concentrated H2SO4.

Study on corrosion resistance of arc sprayed Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings in salt spray environment

AbstractTo study the corrosion behavior of Zn–Al pseudo alloy coatings with different Al contents, Zn–xAl (x = 19, 27, and 37) pseudo alloy coatings were prepared by the wire arc spraying technique using Zn and Al wires with different diameters. This study investigated the microstructure, electrochemical corrosion behavior, and corrosion morphology and products of the as‐sprayed coatings after the salt spray test in 5 wt% NaCl solution. The results exhibited that the Zn–Al pseudo alloy coatings with higher Al content form denser corrosion products (Zn5(OH)8Cl2·H2O and Zn–Al layered double hydroxide) with stronger self‐shielding effect against corrosive media, thus provide better long‐term corrosion protection. Besides, electrochemical reactions are controlled by mass transfer until corrosion for 24 h, and then by a combination of mass transfer and diffusion for 96 h. Overall, it can be concluded that the Zn–37Al pseudo alloy coating in this study shows great potential to protect steel substrates from corrosion.

Investigation of supercritical CO2 corrosion behavior of X80 carbon steel in pipelines: An in situ experimental and DFT study

The electrochemical corrosion behavior of X80 carbon steel was investigated in a supercritical CO2 (sCO2) environment at 60 ℃ and 9 MPa, by in-situ experiments and density functional theory (DFT) calculations, revealing the corrosion mechanism. For in situ electrochemical measurements, two novel CO2-rich and H2O-rich cells were developed to replace the traditional three-electrode cell. Electrochemical impedance spectroscopy revealed distinct differences in the corrosion behavior between CO2-rich and H2O-rich environments during the later stages of testing. In H2O-rich environments, as corrosion time increased, the corrosion product layer gradually changed from porous to dense, eventually forming a protective layer. In CO2-rich environments, corrosion occurs mainly in areas where water condenses to form FeCO3. Simultaneously, microscopic calculations provided evidence for the three-step sCO2 hydrolysis mechanism and the formation of FeCO3 products.

In-situ electrochemical corrosion behavior of oil well tubing in CO2-containing highly mineralized oilfield produced water: Revealing the effect of temperature

In-situ electrochemical corrosion behavior of oil well tubing in CO2-containing highly mineralized oilfield produced water: Revealing the effect of temperature

Microstructure and corrosion behaviour of metal copper parts formed by laser shock

The effects of laser shock forming (LSF) on material microstructure evolution and its electrochemical corrosion behaviour were investigated. Results show that high-density dislocations and stacking faults are formed on the laser-irradiated surface layer of parts. The laser-irradiated surface of the parts subjected to two-shot LSF exhibited better corrosion resistance, with a 2-fold decrease in the passive current density, 3.5-fold increase in the charge resistance, and ∼12-fold thicker passive film compared with the undeformed sheet. The formation of nano-grains, compressive residual stresses, and a dense Cu2O oxidation film during LSF contributed to the improved corrosion resistance of the LSF-fabricated copper parts.

Machine learning-assisted prediction and interpretation of electrochemical corrosion behavior in high-entropy alloys

In this study, machine learning (ML) models were successfully employed to predict the short-term electrochemical corrosion behavior of high-entropy alloys (HEAs) based on their chemical compositions. Considering the vast compositional space of HEAs, which restricts the development of corrosion-resistant HEAs, and the lack of non-destructive methods to qualitatively assess their corrosion resistance, this work represents a significant advancement in the field. The “three-step” method was applied to select the optimal feature set from 38 features, and six ML regression models were trained and compared. The eXtreme Gradient Boosting (XGBoost) and Gradient Boosting Decision Tree (GBDT) algorithms demonstrated the highest predictive accuracy (R2 = 81.02 % and 84.64 %, respectively) among the six algorithms. The model’s robust generalization capabilities were confirmed through validation on an additional dataset. Moreover, the interpretability of the model was enhanced by employing two analysis methods, which revealed that pH as an environmental factor, electronegativity difference and average electronegativity as empirical parameters, and the concentrations of Cr and Cu as compositional parameters have the most significant impact on the corrosion resistance of HEAs. The proposed methodology and framework have the potential to optimize alloy composition, facilitating the design and development of new corrosion-resistant HEAs.

Corrosion properties of submerged friction stir modified as-cast nickel-aluminum bronze (NAB) compositions

This study aimed to analyze the effects of adding alloying elements and cooling medium during friction stirring on the electrochemical and immersion corrosion properties. The results showed that the addition of nickel and iron prevented the formation of an unfavorable phase γ2 and instead produced intermetallic compounds κ in the microstructure. Friction stir processing (FSP) helped refine and homogenize the coarse and inhomogeneous structure of the casting, and also eliminated casting defects, whether performed in air or underwater conditions. The polarization and electrochemical impedance tests revealed that, in most cases, FSP led to a decrease in electrochemical and short-term corrosion behaviors as compared to the as-cast specimens, under the impact of alloy composition and active cooling. However, the weight loss immersion tests indicated that the friction stir processed alloys, particularly those processed underwater, demonstrated the best long-term corrosion properties. It was observed that the corrosion product film created on all models after immersion had a similar composition.

Electrochemical corrosion and product formation mechanism of M42 high-speed steel in NaH2PO4-Na2SO4 passivating electrolyte

High-speed steel (HSS) rolls operate in harsh conditions, making them vulnerable to surface degradation. Material removal technology for repairing defective HSS roll surfaces is the most effective way to maintain their integrity and reduce production costs. Electrochemical corrosion machining, with its excellent machining capabilities, offers a promising method for repairing HSS roll surfaces. However, the outer working layer of these rolls is made of premium HSS containing passivating metallic elements, complicating its corrosion behavior, particularly in passivating electrolytes. To elucidate the corrosion behavior and uncover the underlying mechanisms of corrosion and product formation of HSS during electrochemical corrosion machining, this study investigates the electrochemical corrosion process and behavior of M42 HSS used in rolls within a NaH2PO4-Na2SO4 passivating electrolyte. Metallographic etching experiments indicated that M42 HSS comprises a tempered martensitic matrix along with M2C and M6C eutectic carbides. Characteristics of oxidative reactions for M42 HSS in the electrolyte were observed in cyclic voltammetry. By conducting anodic polarization tests, along with thermodynamic analysis and characterization techniques, the entire electrode system was thoroughly examined, including corrosion phenomena, varying processes, and underlying mechanisms of corrosion and product formation. Notably, this study is the first to construct a Pourbaix diagram for the M42 HSS-H2PO4−-SO42−–H2O system. The thermodynamic analysis revealed that the applied potential variation significantly influences corrosion behavior of M42 HSS, confirming by the characterization results. The adsorption phenomenon on the cathodic surface requires a higher potential (such as 6 V) to occur. Electrochemical reactions primarily occur on the anodic surface, while the cathodic surface (or in the electrolyte) mainly engages in chemical reactions with no electronic participation. Furthermore, the electrochemical corrosion process of HSS is driven by one or more corrosion mechanisms, such as galvanic corrosion, pitting, or intergranular corrosion. Therefore, these findings from this study contribute to the development of repairing HSS roll surfaces based on electrochemical corrosion machining in future engineering applications.

Study on microstructure and electrochemical corrosion behavior of ζ-FeZn13 phase layer in hot-dip galvanized coating

In this study, the electrochemical corrosion behavior of outburst and flat ζ-FeZn13 phase layers was investigated using scanning electron microscopy, field emission scanning electron microscopy, electrochemical workstation, and Raman spectroscopy instrument. The ζ phase layer is composed of the η phase, coarse ζ phase, and fine ζ phase. Their corrosion potential is Eη-Zn=-1.140±0.003 V, Efine-ζ=-1.052±0.003 V, and Ecoarse-ζ=-1.036±0.002 V. The presence of fine ζ phases can form a thick passivation film on the surface of the coating. The thickness of the passivation film for the outburst and flat ζ phase layers is 5.31 nm and 6.47 nm, respectively. The more uniform the distribution of fine ζ phases, the thicker the passivation film. The corrosion types of the outburst phase layer are mainly local corrosion and pitting corrosion, and the flat phase layer is mainly uniform corrosion. The corrosion products of η phase are ε-Zn(OH)2, 4Zn(OH)2.ZnCl2, Zn5(CO3)2(OH)6, and Zn5(Cl2)(OH)8.H2O. The corrosion products of ζ phase are Fe2O3, ZnO, and Zn(OH)2.