Dynamic Potential Polarization Research Articles

Fluorine-free superhydrophobic Ni/Mn-TiO2 composite coatings on carbon steel via one-step electrodeposition for enhanced durability and corrosion resistance

The application of superhydrophobic coatings on carbon steel (CS) surface represents an effective strategy for mitigating corrosion in these materials. This study presents the preparation of superhydrophobic Ni/Mn-TiO2 composite (SNMT) coatings on CS substrates through a facile one-step electrodeposition technique. The formation mechanism of SNMT coatings was meticulously analyzed under varying conditions of nanoparticle types and concentration levels. The inclusion of TiO2 nanoparticles, with an optimal additive concentration of 1 g, facilitated the formation of numerous low surface energy, cauliflower-like microstructures on CS interface. Surprisingly, the results indicate that SNMT coatings maintained commendable superhydrophobicity even post-exposure to superficial damages such as tape peeling, sandpaper wear, and knife-scratch, as evidenced by a static contact angle (CA) exceeding 158° and a sliding angle (SA) below 2°. Furthermore, the corrosion inhibition efficacy of SNMT coatings was quantitatively assessed via dynamic potential polarization curves in a simulated seawater environment. The results demonstrated that SNMT coatings exhibited excellent corrosion inhibition performance in simulated seawater solution, with a protection efficiency (PE) reaching 96.5%. In conclusion, superhydrophobic surfaces can effectively inhibit the penetration of corrosive liquids. The durability and robustness of such superhydrophobic surfaces advocate for their potential widespread application in enhancing the longevity and reliability of CS in corrosive environments.

Corrosion resistance of pressure/pressureless sintered cemented carbides with/without graphene oxide in NaOH solution

The electrochemical corrosion performance of WC-Co hard alloy was studied under pressure/pressureless sintering and conditions with/without graphene oxide added. Three electrochemical testing methods were used to evaluate the corrosion behavior: open circuit potential, electrochemical impedance spectroscopy, and dynamic potential polarization. The corrosion resistance of the alloy was compared using three parameters of corrosion potential, corrosion current density, and total impedance. The corrosion mechanism was studied by observing the surface morphology of corroded alloy using scanning electron microscopy and analyzing the surface corrosion products using X-ray photoelectron spectroscopy. The results showed that pseudo-passivation phenomenon appeared in the potentiodynamic polarization curve of the hard alloy in the sodium hydroxide solution. The corrosion behavior was mainly controlled by anodic dissolution, with the dissolution of WC phase being greater than that of Co phase. The corrosion resistant properties of the pressure sintered cemented carbide are higher than that of the pressure-less sintered cemented carbide respectively in NaOH solution, mainly because pressure increases the grain size and decreases the grain boundaries of cemented carbide, which can be regarded as the dislocation wall between grains and normally attacked by the serious corrosion preferentially.

Corrosion and mechanical properties of Al/Al2O3 composites fabricated via accumulative roll bonding process: Experimental and numerical simulation

With the advancement of science and technology and the construction of metal-based composites (MMC), it became possible to achieve improved properties that were not easily available in an alloy. In fact, with the emergence of such technology, manufacturers were able to adjust the resulting materials according to their needs in such a way as to provide mechanical strength, hardness, corrosion resistance, or other desired properties. These composites were used in various aerospace, automotive, construction, and production industries. Aluminum-based composites are among the structures that have taken an important place in the industry due to their lightweight and high strength. The present study produced bi-alloy aluminum-based 1060/5083 composites fabricated with alumina particles with a Hot ARBp at T = 380 °C. Also, the effect of rolling steps on the roll bonding mechanism is investigated using numerical simulation. As the novelty of this study and for the first time, a bi-alloy 1050/5083 composites reinforced Al2O3 particles via ARB process have been produced and then, potential dynamic polarization in 3.5 Wt% NaCl solution was used to study the corrosion properties of these composites. The corrosion behavior of these samples was compared and studied with that of the annealed aluminum. The study aimed to investigate the bonding behavior between the bi-alloy layers. So, as a result of enhancing influence on the number of ARBp, this experimental investigation revealed a significant enhancement in the main electrochemical parameters and the inert character of the Alumina particles. Reducing the active zones of the material surfaces could delay the corrosion process. Results showed that the corrosion resistance of the sample fabricated after six steps improved more than 100 % in comparison with the initial annealed Al alloy. Also, the average peeling force improved from 45 N to 94 N for the sample fabricated with six steps. Moreover, at a higher number of steps, the corrosion of MMC improved. Moreover, increasing the number of ARBsteps illustrated an improvement in the wear resistance of samples. Finally, the samples' bonding interface, corrosion surface, and peeled surface were investigated using scanning electron microscopy (SEM).

Preparation and Properties of Mo/Ti/Sn Conductivity Conversion Coatings on 6063 Aluminum Alloy

ABSTRACTConductivity chromium‐free conversion coatings on aluminum substrates were achieved by utilizing Na2SnO3 and Mo/Ti solutions. The composition and morphology of the coatings were characterized using XPS, SEM, EDS, AFM, and Raman spectroscopies. The corrosion behavior of the coatings in 3.5‐wt% NaCl solution was investigated through a dynamic potential polarization method and EIS analysis. Mott–Schottky and UV–Vis analyses were used to determine the semiconductor properties of the coatings, including carrier concentration and band gap. The results revealed that the main components of the coating were Al2O3, SnO2, MoO3, and MoO2 and the coating presented a double‐layer structure, including a transition layer close to the substrate and a compact layer on the surface. The coating also exhibited the properties of a p‐type semiconductor. The electrical contact resistance value of adding Na2SnO3 decreased from 0.4331 to 0.1343 Ω/in2 (in 200 psi), while the band gap decreased from 2.281 to 2.232 eV.

Construction of Smart Coatings Containing Core-Shell Nanofibers with Self-Healing and Active Corrosion Protection.

With increasingly severe metal corrosion, coating preparation with high-performance corrosion protection has attracted more attention. Herein, the encapsulation of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) as well as the self-healing agent linseed oil (LO) in polyvinyl alcohol (PVA) and chitosan (CS) shells were realized by coaxial electrospinning, which was recorded as PVA/CS@LO/8-HQ core-shell nanofibers. PVA/CS@LO/8-HQ nanofibers were employed to promote the high-performance corrosion protection of the epoxy coating. The anticorrosion mechanism was that the change of the local pH on the metal surface stimulated the release of 8-HQ from the nanofibers, which were then chelated with iron ions to form a complex. When cracks occurred and caused rupture of the nanofibers, LO was released and reacted with oxygen to cure them so that the cracks could be healed autonomously. The dynamic potential polarization curves showed that the corrosion inhibition efficiency of the compound inhibitor LO + 8-HQ reached 87.54%, 90.31%, and 85.57% at pH = 3, 7, and 11, respectively, higher than that of the single corrosion inhibitor. Density functional theory calculations revealed that the LO and 8-HQ combination, forming a hydrogen bond interaction, promoted the adsorption of inhibitors on the steel surface. Scanning Kelvin probe and electrochemical impedance spectroscopy proved the self-healing corrosion protection properties of the epoxy coating. These results demonstrated that embedding PVA/CS@LO/8-HQ nanofibers in the coating could obtain self-healing properties, and promote the mechanical and corrosion protection of epoxy coating.

Synthesis and evaluation of Schiff base as corrosion inhibitor for carbon steel in 1 M HCl solution

Purpose The main purpose of the present study is to introduce new Schiff bases as corrosion inhibitor for carbon steel in 1 M HCl. The inhibitory activity of Schiff base was also assessed. Design/methodology/approach 2,2′-((1Z,1′Z)-((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))diphenol was synthesized and it’s performance as an inhibitor was then investigated in 1 M HCl. The inhibition of this compound was studied and evaluated by the chemical methods of electrochemical impedance spectroscopy, electrochemical potential dynamic polarization and Atomic Force microscopy (AFM) method. The thermodynamics parameters were investigated for corrosion of carbon steel in both the absence and presence of Schiff base. Findings The results of the tests showed that this compound has a good performance as an inhibitor and the percentage of inhibition on steel corrosion will increase with increasing concentration and it will reach 70% in the presence of 2 × 10−3 M of this inhibitor. Polarization tests indicated that this compound will act as a mixed inhibitor. Nyquist curves showed that the addition of this substance to the solution increased the charge transfer resistance and decreased the capacity of the double layer. The absorption of the new Schiff base on steel follows Langmuir adsorption isotherm, and the amount of free energy of adsorption indicates the spontaneous adsorption of this inhibitor. Using AFM investigations, the results of electrochemical methods were confirmed. Originality/value Incorporation of a new Schiff base into 1 M HCl is a promising approach for protecting the carbon steel against corrosive solution.

Corrosion resistance of Cu-Fe deformation processed in situ alloy in chloride ion environment

To assess the corrosion resistance of Cu-Fe deformation in situ alloys in a chloride ion environment, Cu-Fe alloys with varying Fe contents (5 wt%, 10 wt%, and 14 wt%) were prepared using vacuum induction melting, and the impact of Fe content on the corrosion resistance was examined. The corrosion morphology and corrosion products were analyzed, and the corrosion rate, corrosion period, dynamic potential polarization curves, electrochemical parameters, and electrochemical impedance spectra with different Fe contents were determined. However, the corrosion resistance of Cu-Fe alloys initially increased with an increase in Fe content before decreasing, with Cu-10 wt% Fe alloys (95% reduction rate) exhibiting the best corrosion resistance. As the Fe content increased, the amount of primary Fe phase gradually increased and became more densely distributed. This led to an increase in the dense oxide film on the surface, thereby enhancing the corrosion resistance of the material. Moreover, with a further increase in Fe, the primary Fe phase exhibited coarsening and non-uniform distribution. This resulted in the oxide film becoming looser, leading to a decreased corrosion resistance of the alloy.

EVOLUTION OF WEAR AND CORROSION RESISTANCE OF Bi ALLOY-LAMINATED Al/TiO2 COMPOSITE STRIPS FABRICATED VIA APB PROCESS

In this study, Bi alloy AA1100/TiO2/AA5083 composites were produced by accumulative press bonding (APB) for the first time. In the first step, two bars of aluminum alloys 1100 and 5083 with 5[Formula: see text]wt.% of uniformly scattered TiO2 particles were stacked together and pressed with a 50% reduction ratio. Then, this process was continued up to six steps. Corrosion properties of composites were studied by potential dynamic polarization and electrochemical impedance spectroscopy measurement in 3.5[Formula: see text]wt.% NaCl solution. So, in this investigation and as its novelty, a considerable improvement was revealed in the main electrochemical parameters as a result of enhancing the influence of APB steps and the inert character of the particles. Moreover, using the wear test, the wear resistance of these bi alloy composites has been studied vs the APB steps. Also, the wear and electrochemical experiments showed that corrosion and wear resistance of samples were improved by the APB steps by 70% and 34%, respectively.

Preparation and Performance of Micro-Arc Oxidation Coatings for Corrosion Protection of LaFe11.6Si1.4 Alloy.

The microstructure, corrosion resistance, and phase-transition process of micro-arc oxidation (MAO) coatings prepared on LaFe11.6Si1.4 alloy surfaces in different electrolyte systems were systematically investigated. Research has demonstrated that various electrolyte systems do not alter the main components of the coatings. However, the synergistic action of Na2CO3 and Na2B4O7 more effectively modulated the ionization and chemical reactions of the MAO process and accelerated the formation of α-Al2O3. Moreover, the addition of Na2CO3 and Na2B4O7 improved the micromorphology of the coating, resulting in a uniform coating thickness and good bonding with the LaFe11.6Si1.4 substrate. The dynamic potential polarization analysis was performed in a three-electrode system consisting of a LaFe11.6Si1.4 working electrode, a saturated calomel reference electrode, and a platinum auxiliary electrode. The results showed that the self-corrosion potential of the LaFe11.6Si1.4 alloy without surface treatment was -0.68 V, with a current density of 8.96 × 10-6 A/cm2. In contrast, the presence of a micro-arc electrolytic oxidation coating significantly improved the corrosion resistance of the LaFe11.6Si1.4 substrate, where the minimum corrosion current density was 1.32 × 10-7 A/cm2 and the corrosion potential was -0.50 V. Similarly, after optimizing the MAO electrolyte with Na2CO3 and Na2B4O7, the corrosion resistance of the material further improved. Simultaneously, the effect of the coatings on the order of the phase transition, latent heat, and temperature is negligible. Therefore, micro-arc oxidation technology based on the in situ growth coating of the material surface effectively improves the working life and stability of La(Fe, Si)13 materials in the refrigeration cycle, which is an excellent alternative as a protection technology to promote the practical process of magnetic refrigeration technology.

Effect of Scanning Strategy on the Manufacturing Quality and Performance of Printed 316L Stainless Steel Using SLM Process.

In this study, the effects of Z-0°, Z-67°, Z-90°, I-67°, and S-67° scanning strategies on the surface morphology, microstructure, and corrosion resistance of the specimens in SLM316L were systematically studied. The results show that the partition scanning path can effectively improve the manufacturing quality of the specimen, reduce the cumulative roughness layer by layer, and increase the density of the specimen. The scan path of the island partition of the fine partition is better than that of the strip partition; moreover, the 67° rotation between each layer reduces the accumulation of the height difference of the melt pool, fills the scanning gap of the previous layer, and improves the molding quality of the sample. Electrochemical tests were performed in an aqueous solution of NaCl (3.5 wt%), including open-circuit potential (OCP), dynamic potential polarization, and electrochemical impedance spectroscopy (EIS). The results show that the specimen with a 67° rotation between each layer achieves stability of the surface potential in a short time, and the I-67° specimen exhibits good corrosion performance, while the Z-0° specimen has the worst corrosion resistance.

Quantitative Characterization of Passivation Process of Steel Reinforcement in Concrete towards Durability against Anticorrosion Based on Electrochemical Methods

The passivation behavior of steel reinforcements in concrete is significantly influenced by the environment, concrete pore solution, and the passive film formed on the steel surface. The present study used electrochemical methods to successfully characterize the passivation process of steel reinforcements in concrete. The passivation behavior of commonly used HRB400 steel reinforcement material in concrete was studied using various electrochemical parameters quantitatively. As the soaking test time increased, the OCP gradually increased and stabilized after 5 days, indicating that the steel electrode transitioned from an active state to a passive state in the simulated liquid environment of concrete. The steel reinforcement developed a protective passive film that reduced its tendency to corrode. According to EIS, after soaking for one day, the steel electrode showed significant early passivation, indicated by an increase in its arc diameter. The WE arc gradually increased in the first 5 days of immersion, suggesting dynamic passive film formation and development. Beyond 5 days, the passive film stabilized with minimal further changes in its impedance spectrum, indicating carbon steel electrode passivation. The working electrode’s impedance increased significantly on the fifth day, and gradually increased slightly after 10 days, indicating comprehensive coverage by the oxide film. Attributed to the growth and development of the oxide film, the electrode resistance reached a relatively stable state after the fifth day. The shift in corrosion potential offers an indication of the level of passivation of the steel reinforcements. The decrease in the anode Tafel slope and increase in the corrosion potential indicate the formation and stabilization of an oxide film on the steel surface, which is beneficial for its long-term durability in concrete structures. By analyzing the OCP, EIS, and dynamic potential polarization curve method data, it is possible to gain insights into the passivation behavior of steel reinforcements in concrete structures. This study aims to provide a basis for optimizing the corrosion protection of steel reinforcements in concrete structures. The significance of this study lies in a deep understanding of the passivation behavior of steel bars in concrete, providing a theoretical basis for improving the durability and lifespan of steel bars in concrete structures.

Synthesis, Corrosion Inhibition Efficiency in Acidic Media, and Quantum Chemical Studies of Some Hydrazine Derivatives

In this work, four hydrazone Schiff base derivatives N-(2,4-Dinitro-phenyl)-N’-(1H-pyrrol-2-ylmethylene)-hydrazine (1a), N-Benzo [1,3] dioxol-5-ylmethylene-N’-(2,4-dinitro-phenyl)-hydrazine (1b), (E)-5-((2-(2,4-dinitrophenyl)hydrazono)methyl)-2-hydroxybenzoic acid (1c) and (E)-1-(2,4-dinitrophenyl)-2-(2-methoxybenzylidene)hydrazine (1d) were synthesized by reaction of four aldehydes namely pyrrole-2-carboxaldehyde, piperonal, 5-formylsalicylic acid, and o-vanillin with 2,4-dinitrophenyl hydrazine to produce the final compounds 1a, 1b, 1c, and 1d, respectively. These four compounds were investigated as corrosion inhibitors in aqueous mild acidic static solution. FTIR, HNMR, and elemental analysis were used to elucidate the chemical structure of the synthesized inhibitors. Using potential dynamic polarization measurements, these inhibitors’ efficiency in preventing C-steel corrosion in 1.00 M HCl was studied. The results of the experiments revealed that 1×10−3 M is the ideal concentration for 1a, 1b, 1c, and 1d, and that the corresponding inhibition efficiencies for these subunits were 80.70%, 91.30%, 91.34, and 88.80%, respectively. The best corrosion inhibitors were compounds 1b and 1c. Furthermore, studies suggested that these substances are mixed-type inhibitors and that the efficiency of the inhibition is strongly correlated with their quantity. Quantum paraments included Dipole moment, energy band gap (ΔE), value of energy of lowermost unoccupied molecular orbital (ELUMO), and energy of high most occupied molecular orbital (EHOMO) using Molecular Operating Environment MOE, Gaussian, and HyperChem software packages were determined which demonstrated strong agreement between algorithmic and practical findings.

Synergistic Control on Co/Cu Galvanic Corrosion and Its Application for Co Barrier Chemical Mechanical Planarization in Alkaline Slurry

Selective chelation and protective film formation were synergistically combined to achieve Co/Cu galvanic corrosion control. Chelating agent imionodisuccinic acid and protective film formation agent benzotriazole are strategically chosen for fulfilling the above proposed task in alkaline solution for Co barrier chemical mechanical planarization (CMP). Chronopotentiometry and linear dynamic potential polarization methods are used to investigate the thermodynamics and kinetics of Co and Cu corrosion. A synergistic control of Co/Cu corrosion was accomplished by judiciously balancing the power of selective chelation and protective film formation. This systematic approach can be expanded to systematically design other metal CMP slurries to fulfil the desired polishing performance.

Enhanced corrosion resistance of epoxy resin coating via addition of CeO2 and benzotriazole

The use of fillers to enhance the corrosion protection of epoxy resins has been widely applied. In this work, CeO2 and Benzotriazole (BTA) were introduced into an epoxy resin to enhance the corrosion resistance of Q235 carbon steel. SEM results indicated that the CeO2 grains were rod-like and ellipsoidal in shape, and the distribution pattern of BTA was analyzed by EDS. The dynamic potential polarization curve proved the excellent corrosion resistance of the composite epoxy resin with CeO2 and BTA co-addition; and electrochemical impedance spectroscopy test (EIS) analysis indicated the significantly enhanced long-term corrosion protection performance of the composite coating. And the optimal protective performance was provided by the coating containing 0.3 wt.% CeO2 and 20 wt.% BTA, which attributed to the barrier performance of CeO2 particles and chemical barrier effect of BTA. The formation of corrosion products was analyzed using XRD. In addition, the corrosion resistance mechanism of the coating was also discussed in detail.

Corrosion Prevention of Copper in 2.0 M Sulfamic Acid Using Novel Plant Extract: Chemical, Electrochemical, and Theoretical Studies.

Copper corrosion was suppressed when a lupine extract was immersed in a 2 M sulfamic acid (H2NSO3H) solution. Numerous methods, including mass loss (ML), dynamic potential polarization (PL), and electrochemical impedance (EIS), were employed in these experiments, in addition to theoretical computations such as density functional theory (DFT), Fukui function, and Monte Carlo simulations. Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM) were used to analyze the Cu surface's composition and determine its form. Mass loss (ML) was used to examine the inhibition rate of copper corrosion in sulfamic acid at 25 °C in the presence of lupine extract. After examining how it behaved throughout the adsorption process on copper, it was discovered that it follows the Langmuir isotherm and chemical adsorption. An analysis of the PL curves indicates that the lupine extract is a mixed-type inhibitor. It was shown that the inhibitory efficiency increased to 84.2% with increasing lupine concentration. Additionally, as the data show, the efficiency of inhibitors is diminished by increasing temperatures. Theoretical calculations and experimental data were compared using Monte Carlo simulation (MC) and density functional theory (DFT).

The effect of acetic acid on the crevice corrosion of P110 steel in simulated oilfield produced water

P110 steel, widely utilized in oil and gas operations, is renowned for its robust mechanical properties, satisfactory corrosion resistance, and significant economic advantages. This study aims to investigate the influence of acetic acid on the crevice corrosion behavior of P110 steel in simulated oilfield produced water. A comprehensive range of techniques was employed for this analysis, including dynamic potential polarization curves, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy. The results highlight that the introduction of acetic acid significantly compromises the resistance of P110 steel to crevice corrosion. As the concentration of acetic acid increases, a corresponding escalation in corrosion products outside the crevice is observed, forming a protective layer on the surface of the P110 steel beyond the crevice. These insights provide a theoretical basis for enhancing the safety performance of oil well tubing, reducing operational hazards, and mitigating environmental impact.

Microstructure and corrosion property of TC4 coating with Al0.5CoCrFeNi high-entropy alloy interlayer by laser cladding

In this work, TC4 coating was prepared on 45 steel surface successfully by laser cladding and Al0.5CoCrFeNi high-entropy alloys (HEA) coating was designed as an intermediate layer. Microstructure, microhardness and electrochemical corrosion characteristics of TC4/HEA composite coating were evaluated in detail. The interfaces without cracks of HEA layer/substrate and TC4 layer/HEA layer are clear and straight, and a metallurgical bonding is obtained when the line energy density is 315 J/mm2 and 180 J/mm2. A reactive layer consisted of TiAl and TiFe intermetallic compounds (IMC) is formed at TC4/HEA interface. The HEA transition layers are composed of uniformly distributed equiaxed matrix (FCC) and intercrystalline phase (BCC), while a transition from Widmanstätten structure to coarse acicular crystal was found in TC4 layer. The microhardness of HEA coating is slightly higher than the substrate and lower than the TC4 coating, and the microhardness value of TC4 layer is up to 745.8 HV0.2. Potential dynamic polarization curves test results show that a comparatively small corrosion zone is concluded for TC4/HEA composite coating sample and the corrosion resistance of the composite coating is significantly improved with an increased value of 55.9 % in Ecorr (−0.325 V) and a decreased value of 99.3 % in Icorr (0.1 μA/cm2) compared to the substrate.

Corrosion Studies of Temperature-Resistant Zinc Alloy Sacrificial Anodes and Casing Pipe at Different Temperatures.

In order to solve the problem of external corrosion of deep well casing in oil and gas fields, a new type of high-temperature-resistant zinc alloy sacrificial anode material was used. The temperature and corrosion resistance of the new anode material and TP140 casing were investigated by simulating the high-temperature working conditions of a deep well in an oil field using high-temperature and high-pressure corrosion tests and electrochemical tests. The results showed that at 100-120 °C, the corrosion rate of TP140 protected by a sacrificial anode was only one-tenth of that under unprotected conditions, and the minimum corrosion rate of TP140 protected by a sacrificial anode at 100 °C was 0.0089 mm/a. The results of the dynamic potential polarization curve showed that the corresponding corrosion current density of TP140 first increased and then decreased with the increase in temperature. The self-corrosion potential in sacrificial anode materials first increased and then decreased with the increase in temperature, and the potential difference with TP140 gradually decreased.

Study on the performance of micro-arc oxidation coatings on TA10 titanium alloy with graphite additions

To improve the corrosion resistance of the Ti–0.3Mo–0.8Ni (TA10) titanium alloy, a micro-arc oxidation coating was prepared on its surface, and the effect of different amounts of graphite addition on the structure and corrosion resistance of the coatings was studied. Through methods such as X-ray diffraction phase analysis, microscopic morphology analysis, roughness analysis, coating thickness analysis and hardness testing, it was found that the added graphite particles can react with silicon (Si) in the electrolyte to promote the formation of the silicon carbide (SiC) phase, thereby improving the surface morphology of the coatings, increasing the thickness of the coatings and improving the microhardness of the coatings. At the same time, dynamic potential polarization curve and scanning electrochemical test results show that the formation of the silicon carbide phase can increase self-corrosion potential and reduce self-corrosion current density. When the amount of graphite added is 1.0 g/l, the self-corrosion potential and self-corrosion current density are −0.129 V and 2.9 × 10−8 A/cm2, respectively. This indicates that adding graphite particles can enhance the corrosion resistance of the TA10 titanium alloy.

Growth pattern of soft-spark micro-arc oxide coating on titanium alloy in silicon anion electrolyte

Soft-spark micro-arc oxidation (MAO) is considered a potential solution for eliminating the porosity on the surface coating of titanium alloys during the MAO process. However, the mechanisms behind soft-sparking and the growth of coatings on Ti alloys are not yet fully understood. This study aimed to investigate the growth pattern of soft-spark MAO coating on titanium alloys by using sodium silicate as the electrolyte and manipulating the soft-sparking duration. The research focused on analyzing the positive and negative pulse voltage-time response curves, surface micromorphology, surface composition, cross-sectional structure, phase composition, dynamic potential polarization curve, microhardness, and thickness growth curve during the soft-spark process. The research findings revealed that soft spark discharges occurred in the plasma atmosphere near the surface of the external porous layer. The sparks penetrated the weak points of the amorphous interface layer (existing between the MAO coating and the substrate), forming filamentary discharges within the coating. This phenomenon led to the formation of a significant amount of rutile phases and bubble pores within the soft-spark coating, promoting the expansion of soft-sparks into the coating and facilitating the growth of the soft-spark coating. While the inner hardness of the soft-spark MAO film reached 1146 HV, the plasma atmosphere discharge also led to the formation of numerous filamentary channels and gas pores within the coating. Consequently, the coating's corrosion resistance did not show any improvement.