Micro-arc Oxidation Technology Research Articles

Investigation on surface properties of AZ31 magnesium alloy modified by micro-arc oxidation and cathodic deposition techniques

Cathodic deposition (CD) technology, as a surface treatment technology, is widely used to prepare surface protective layers of non-valve metals. However, due to the presence of a dense oxide film on the surface of valve metal, during the CD process, this dense oxide film will hinder the contact between ions in the electrolyte and the substrate surface, making CD deposition technology unsuitable for valve metal. In this paper, valve metal AZ31 Mg alloy was first treated by micro-arc oxidation (MAO) technology, and then CD treatment was performed using ethylene glycol organic solution as electrolyte. This method not only solves the problem that CD technology cannot be applied to valve metals and successfully prepares a coating with excellent friction and corrosion resistance, but also explores a new solution as a CD electrolyte. By comparing with the samples after CD treatment in deionized water solution and the samples after MAO, the results show that after CD treatment in deionized water solution, only the porosity (8.572 %) and coefficient of friction (COF) (0.403) of the coating were improved, but after CD treatment in ethylene glycol solution, the coating surface had the lowest porosity (4.263 %), the highest hardness (265.2 HV), and the smallest COF (0.362). Electrochemical tests further showed that the sample had the lowest corrosion current density (5.6099 × 10−10 A/cm2) after CD treatment in ethylene glycol electrolyte. The coating prepared by this method can be widely used in aerospace, medical equipment and other fields due to their excellent friction and corrosion resistance, and can increase the service life of Mg alloy parts. However, this method is currently more suitable for the processing of small parts. This study not only provides a valuable strategy for improving the performance of MAO coatings, but also provides a new direction for the application of CD technology on valve metals.

Relationship between the B4C reinforcement content and the properties of MAO films on the B4C/Al matrix composites

Thermal control coating is necessary for the B4C/Al matrix composites (AMCs) used in nuclear power field. Micro-arc Oxidation (MAO) technology is a suitable method to prepare thermal control coating on B4C/AMCs, but the B4C reinforcements has a great influence on the MAO process. In this paper, the effects of the B4C content on the spark discharge, microstructure and properties of the MAO films were studied by a Dual-channel Oscilloscope, Scanning Electron Microscopy (SEM) and Electrochemical Impedance Spectroscopy (EIS). The results indicate that the spark discharge in the early stage of oxidation is inhibited with the increase of the B4C particles in AMCs, but the effect declines in the later stage. Also, the compactness and blackness of the MAO films reduce due to the negative effect of the B4C particles on the oxidation process, but the lowest emissivity of the MAO film is still higher than 0.85, which can still meet the general requirement for thermal control coatings in actual applications.

Corrigendum to: “Recent Patents of Micro-arc Oxidation Technology”

A typographical error appeared in terms of repetition of sentences in the manuscript titled “Recent Patents of Micro-arc Oxidation Technology”, 2024; 18(6): e300423216386 [1]. <p> Original: Liu et al. [90] provided a method for micro-arc oxidation of electrolytes and reducing the brittleness of microporous ceramic film. By adding chitin nanowhiskers and Nacetylated chitosan into the electrolyte, the toughness of the ceramic film is improved, and bending brittleness and fragmentation are prevented. <p> Li et al. [91] provided an electrolyte for micro arc oxidation self-lubricating composite ceramic coating. The friction and wear properties of the composite ceramic coating were improved by adding nano additives and micro MoS2 powder into the conventional electrolyte. <p> Liu et al. [90] provided a method for micro-arc oxidation of electrolytes and reducing the brittleness of microporous ceramic film. By adding chitin nanowhiskers and Nacetylated chitosan into the electrolyte, the toughness of the ceramic film is improved, and bending brittleness and fragmentation are prevented. <p> Li et al. [91] provided an electrolyte for micro arc oxidation self-lubricating composite ceramic coating. The friction and wear properties of the composite ceramic coating were improved by adding nano additives and micro MoS2 powder into the conventional electrolyte. <p> Corrected: Liu et al. [90] provided a method for micro-arc oxidation of electrolytes and reducing the brittleness of microporous ceramic film. By adding chitin nanowhiskers and Nacetylated chitosan into the electrolyte, the toughness of the ceramic film is improved, and bending brittleness and fragmentation are prevented. <p> Li et al. [91] provided an electrolyte for micro arc oxidation self-lubricating composite ceramic coating. The friction and wear properties of the composite ceramic coating were improved by adding nano additives and micro MoS2 powder into the conventional electrolyte. <p> The original article can be found online at https://www.eurekaselect.com/article/131347

Synergistic Effect of Polyurethane on Pore-Sealing and Lubrication of Microarc Oxidation Coating.

Microarc oxidation (MAO) is a widely used surface treatment technology. However, its processing inevitably leads to the presence of micropores, microcracks, and other defects in the MAO coating. These defects lead to suboptimal tribological performance and diminished corrosion resistance of the MAO coating. Thus, this study proposed a new pore-sealing method with environmental protection and high efficiency. Polyurethane reactive (PUR) composite coating was prepared on the surface of MAO coating. The sealing effect of the PUR sample was analyzed using scanning electron microscopy (SEM). The molecular structure and elemental changes of the coating were analyzed using X-ray photoelectron spectroscopy (XPS). The tribological properties were analyzed using a tribological testing machine, and the corrosion resistance was tested using an electrochemical workstation. The test results show that the lubricity and corrosion resistance of PUR sample are improved significantly compared with MAO coating. When the mass fraction of PUR is 3 wt %, the PUR sample shows the best lubrication performance, and the coefficient of friction decreases by 70.8%. Compared with the traditional sealing technology, this experimental method is simple and low-cost and has a wide application prospect, which promotes the development of MAO technology.

PROSPECTS FOR THE USE OF MICROARC OXIDATION IN THE PRODUCTION OF AVIATION AND AUTOMOTIVE COMPONENTS

This article discusses the prospects for the application of microarc oxidation (MAO) technology in the aviation and automotive industries. The MAO process allows the creation of durable, wear-resistant and corrosion-resistant coatings on the surface of metal parts, which significantly increases their durability and performance characteristics. Technological aspects of MAO are discussed, including surface preparation features, selection of electrolytes and control of process parameters. Examples of successful application of MAO in the production of aviation and automotive components are given. Also, directions for further research and development of the technology are explored, including the creation of new materials, combined coatings and the study of the durability of coatings under real operating conditions. The article emphasizes the importance of MAO as a promising technology for improving the reliability and efficiency of vehicles and equipment.

Topographical hard protective coating for joint replacement implants

Joint replacement surgery, essential for managing joint diseases, requires improvements in tribocorrosion performance to ensure surgical success and longevity of joint implants. Transition-metal light-element (TMLE) compound coatings, known for their high hardness and chemical stability, have been extensively researched and applied for surface protection of joint implants. However, these coatings typically lack a lubrication phase, leading to high friction coefficients and severe corrosion wear, which makes long-term effective protection challenging. A promising approach is to utilize the natural lubricating proteins present in body fluids, which are continuously available and can thus address long-term service issues of TMLE coatings. In this work, we utilized micro-arc oxidation (MAO) technology to develop an underlying morphology, then conformally deposited a TiB2 layer, resulting in a cratered dual-layer TiB2/MAO coating. This unique cratered dual-layer structure not only preserves the high hardness and wear resistance of TiB2 but also aims to (1) absorb wear particles to prevent abrasive wear and (2) increase surface energy to optimize protein lubrication capacity. Consequently, the TiB2/MAO coating exhibits low friction coefficients and wear rates in protein-containing simulated body fluids. Furthermore, the dual-layer TiB2/MAO coating demonstrates excellent corrosion resistance and biocompatibility. This dual-layer coating design synergistically combines the superior intrinsic properties of material with unique structural construction, while also harnessing continuously available external proteins as lubricants to further optimize performance, thereby introducing an advanced strategy for developing protective coatings for implant materials.

A Liquid Metal-Based Temperature-Responsive Low-Toxic Smart Coating for Anti-Biofouling Applications in Marine Engineering.

Titanium alloys have been widely used in marine engineering fields. However, because of high biocompatibility, they are vulnerable to biofouling. In this work, based on the micro-arc oxidation technology and spontaneous galvanic replacement reaction, a temperature-responsive low-toxic smart coating consisting of liquid metal particles is designed to control the release of Ga3+, Cu2+, and Cu1+ ions in different temperatures. This technology can ensure the full release of active ingredients within the target temperature range, intelligently maintaining the excellent anti-biofouling performance, while saving active ingredients. After being immersed in culture media with Sulfate-Reducing Bacteria (SRB) for 14 days at 10, 20, and 30°C, at the optimal activity temperature of 30°C for SRB, the best sample releases the highest amounts of Ga3+, Cu2+, and Cu1+ ions, demonstrating a 99.9% bactericidal rate. When the temperature decreases to 10°C, the activity level of SRB is very low, and the smart coating can also reduce the released ions correspondingly, still with a 97.3% bactericidal rate. The remarkable anti-biofouling performance is attributed to the physical damage and lethal ions interaction. Furthermore, the best sample exhibits good corrosion resistance. This work presents a design route for smart anti-biofouling coatings for temperature-responsive.

Influence of ultrasonic power modulation on the optimisation of aluminium alloy micro-arc oxidation coating properties

Conventional micro-arc oxidation (MAO) technology, due to the randomness and transient nature of arc discharge, produces coatings with numerous defects, poor abrasion resistance, and inadequate ability to effectively block the intrusion of corrosive media. In this paper, ultrasonic-assisted technology was used to study the effect of different ultrasonic power regulation on the performance optimization of MAO coating on 6061 aluminum alloy. The coating microstructure and elemental composition were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometer, and its hardness, wear resistance, corrosion resistance and other properties were tested. The results show that the prepared coating has the characteristics of high hardness, good wear resistance and excellent corrosion resistance under the assistance of ultrasonic power of 50 W. This is mainly attributed to the cavitation effect, mechanical effect and thermal effect generated by the corresponding ultrasonic power, which effectively enhances the surface quality, performance and service life of the coating. This study provides valuable insights into the interaction between ultrasound power and the resulting MAO coatings, and has important implications for optimizing ultrasound-assisted processes and improving coating properties.

Growth mechanism and performance of MAO-AO composite coating obtained by two-stage process

Titanium alloys, with the high specific strength and low elastic modulus, are currently the research focus of many applications. Various surface treatments have been applied with the intention of improving their wear and corrosion resistance. Micro-arc oxidation (MAO) technology originated from anodic oxidation (AO) technology, which has the advantages of simple process, high efficiency and environmentally friendly electrolyte. However, due to the micro-arc discharge effect, MAO coatings inevitably show the characteristic of high porosity. In this study, post-treatment of MAO coatings using AO was proposed to obtain a composite coating with both high hardness and low roughness and porosity thereby compensating for the defects of MAO coatings. After preparation, each sample was analyzed and characterized. The results indicated that AO was main conducted in the discharge channel of MAO coating and an amorphous phase coating with the matrix oxide as main component was grown in situ. The composite coating showed a slight increase in thickness and significant reduction in roughness than MAO coating and with superior wear and corrosion resistance. In conclusion, this study provides new idea and data support for improving the performance of MAO coatings, which is expected to be widely used in the field of surface treatment.

Recent Patents of Micro-arc Oxidation Technology

Abstract: Micro-arc oxidation (MAO) is a new surface treatment technology that can improve wear resistance, corrosion resistance, high voltage insulation, and other metal properties. Therefore, this technology is widely used in automobile manufacturing, aerospace, ship anti-corrosion, medical equipment, sewage treatment, and other fields. This paper reviews the representative patents of micro-arc oxidation technology at home and abroad. The micro-arc oxidation processing device, the process method of micro-arc oxidation processing, the power supply and electrical parameters of micro-arc oxidation, the preparation of electrolytes, and the methods of anticorrosion and protection of metal surface are analyzed. The development trend of micro-arc oxidation technology in the future is discussed. Micro-arc oxidation is a simple, green, and environment- friendly surface treatment technology, and there will be more patents in the field of micro- arc oxidation in the future.

Study on micro-arc oxidation coating of copper pretreated at high temperature

Micro-arc oxidation (MAO), also known as plasma electrolytic oxidation (PEO), is a surface treatment technology widely used in valve metals. As a widely used non-valve metal, copper is generally not easy to prepare MAO coating on its surface. In this paper, from the principle of MAO, the black coating was successfully prepared on the surface of pure copper by using high temperature pretreatment method and MAO technology, and the surface morphology and composition of the coating are characterised in detail. Friction experiments show that the MAO coatings formed by copper after high-temperature pretreatment at 300 °C have better wear resistance. The water contact angle test and electrochemical experiments show that the 300 °C sample has a higher water contact angle and excellent corrosion resistance. This study expands the surface treatment method of copper and provides a new idea for MAO technology in the surface treatment of other non-valve metals.

Self-assembled Ti3C2Tx membrane driven by Marangoni effect for anti-corrosive and anti-wear applications

The recent rise of Ti3C2Tx has extended the applications in epoxy resin due to its large specific surface area and excellent mechanical properties. Whereas, the synergy between epoxy and Ti3C2Tx restricts properties enhancements when Ti3C2Tx is subjected to random orientation and discontinuous distribution. To optimize the barrier and lubrication characteristics of Ti3C2Tx, we have successfully prepared Ti3C2Tx membrane by using the Marangoni effect self-assembled method to move Ti3C2Tx nanosheets to the same latitude and deposit them on epoxy resin for the first time. Meanwhile, micro-arc oxidation technology was adopted to enhance the bonding strength of the substrate with epoxy. Due to the effective corrosion resistance offered by the Ti3C2Tx membrane, even after 28 days of immersion, the pure epoxy coating had completely failed, while the |Z|0.01Hz value of the multilayer coating still increased by 36.5 % compared to MAO/EP/EP. Furthermore, the wear rate and the friction coefficient reduced by 58.2 % and 21.4 % in comparison to the pure epoxy coating. This exceptional lubrication property stems from the interlayer shear sliding of the expansive Ti3C2Tx nanosheets, effectively preventing direct contact between the friction ball and the epoxy.

Polyvinyl alcohol gel/micro-arc oxidation 3D-printed porous structural aluminium for oil-water separation

Traditional oil-water separation membranes still face challenges in designing membrane structures and pore sizes. In this study, we successfully prepared a PVA@MAO 3D-Al material with an internal porous structure using 3D printing technology and micro-arc oxidation (MAO). Compared to the base 3D-Al material, the fabricated PVA@MAO 3D-Al exhibits excellent wear resistance, with an average friction coefficient reduced by 66 % in dry friction and 22 % in water lubrication. In electrochemical experiments, corrosion current density decreased by an order of magnitude, indicating higher stability of PVA@MAO 3D-Al in corrosive environments. In oil-water separation experiments, PVA@MAO 3D-Al achieved separation efficiencies exceeding 97 % for mixtures of white oil, kerosene, liquid paraffin, and cyclohexane with water. Moreover, even after undergoing 600 cycles of reciprocating friction and exposure to various environmental solutions, the separation efficiency of PVA@MAO 3D-Al for white oil/water mixtures remained above 96 %, demonstrating outstanding physical and chemical stability. This suggests that PVA@MAO 3D-Al is suitable for use in extremely harsh environments. This study introduces a simple and efficient approach to manufacturing oil-water separation membranes using 3D printing technology, coupled with MAO technology to enhance the base material's performance. The combination of these techniques opens up new avenues in the field of oil-water separation.

Effect of Treatment with Microarc Oxidation Technology on Tribological Properties of Nonvalve Metal Low-Carbon Steel.

Steel is one of the most widely used alloys because of its excellent properties such as high toughness, good workability, and low cost. However, steel has weak wear resistance, which limits its range of applications and service life. We have used the microarc oxidation (MAO) technique to form an Al2O3 ceramic coating on the surface of nonvalve metal low-carbon steel, which is used to enhance the wear resistance of low-carbon steel. Tribological experiments have shown that the coefficient of friction is reduced by 26.9%, hardness is improved, and wear resistance is enhanced after MAO compared to the substrate. Through a series of characterizations, the wear mechanism of the MAO samples was found to be a complex friction mechanism including abrasive wear, adhesive wear, and friction oxidation. After MAO, the wear resistance of nonvalve metal low-carbon steel is improved. The use of steel can be extended and its service life can be prolonged. This innovative approach provides a viable solution for the development of low-carbon steel coatings.

Study on the Optimization of the Preparation Process of ZM5 Magnesium Alloy Micro-Arc Oxidation Hard Ceramic Coatings and Coatings Properties

Hard ceramic coatings were successfully prepared on the surface of ZM5 magnesium alloy by micro-arc oxidation (MAO) technology in silicate and aluminate electrolytes, respectively. The optimization of hard ceramic coatings prepared in these electrolyte systems was investigated through an orthogonal experimental design. The microstructure, elemental composition, phase composition, and tribological properties of the coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and tribological testing equipment. The results show that the growth of the hard ceramic coatings is significantly influenced by the different electrolyte systems. Coatings prepared from both systems have shown good wear resistance, with the aluminate electrolyte system being superior to the silicate system in performance. The optimized formulation for the silicate electrolyte solution has been determined to be sodium silicate at 8 g/L, sodium dihydrogen phosphate at 0.2 g/L, sodium tetraborate at 2 g/L, and potassium hydroxide at 1 g/L. The optimized formulation for the aluminate electrolyte solution consists of sodium aluminate at 5 g/L, sodium fluoride at 3 g/L, sodium citrate at 3 g/L, and sodium hydroxide at 0.5 g/L.

Preparation and properties of micro-arc oxidation ceramic coatings using machine vision technology

In this paper, a machine vision system is combined with non-immersion micro-arc oxidation (MAO) technology, using color as a visual feature, and automatically determining the MAO process through a self-developed color image segmentation program for HSV channel. The robotic arm accurately regulates the machining position and duration. Dense ceramic oxide coatings of similar quality to the artificially prepared coatings were successfully prepared on aluminum (Al) surface. The surface morphology and elemental composition of the samples were characterized using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). The performance of the coatings was tested through thickness tests, hardness tests, and roughness tests. The tribological properties were tested by friction experiments, and its corrosion resistance was tested by electrochemical corrosion tests. The results confirm the effectiveness of a machine vision system for MAO process control, which is capable of preparing high-quality coatings comparable to manual operations. This not only solves the need for precise film formation in different application scenarios, but also provides a more efficient, controllable and innovative solution for the MAO process.

Formation of ceramic coatings on non-valve metal low carbon steel using micro-arc oxidation technology

Valve metals are metals that can undergo surface modification through micro-arc oxidation (MAO). Iron is not considered a valve metal and cannot undergo MAO. Steel is a widely used alloy due to its excellent properties, including high toughness, good workability, and low cost. However, its weak corrosion and abrasion resistance limit its range of application and service life. Al2O3 ceramic coating is formed on the surface of non-valve metal low carbon steel using MAO technology. The surface morphology and composition of the MAO coatings on non-valve metals are investigated through characterization. Tribological experiments show that the coefficient of friction of the samples obtained from the MAO power supply frequency of 1400 Hz is the smallest. After conducting a corrosion resistance test following MAO treatment, the impedance increased by three orders of magnitude and the corrosion rate decreased by one order of magnitude. The use of MAO treatment can expand the use of steel and shows promise for application to other non-valve metals.

RESEARCH AND APPLICATION OF MICROARC OXIDATION TECHNOLOGY FOR RESTORATION OF WORKING PISTON SURFACES OF FREIGHT VEHICLES

The scientific article is devoted to the study and application of micro-arc oxidation technology for the restoration of the working surfaces of truck pistons. The study includes an analysis of the physical and chemical processes occurring during microarc oxidation of aluminum alloys from which the pistons are made. The physical impact of MAO promotes the formation of a strong and stable oxide layer, leading to improved surface morphology and closure of microcracks. The results obtained confirm that this technology promotes the formation of hard coatings. The presence of microcracks and surface defects on the original surface of the aluminum alloy caused by operation is noted. After applying the micro-arc oxidation procedure, significant improved surface morphology, reduction of microcracks and removal of defects are visible, indicating the high efficiency of the process. The use of micro-arc oxidized coatings in mechanical engineering promises to increase the durability and efficiency of freight vehicles, as well as reduce repair and maintenance costs. This research represents an important contribution to the field of technological solutions for the remanufacturing of vehicle parts, providing promising prospects for industrial applications.

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.

Preparation of HA-MAO coatings on β-type alloys and its corrosion resistance in high glucose environments.

Aim to provide practical clinical guidance for the treatment of implants in diabetic patients, this study investigated the corrosion mechanism of bionic coatings containing different Ca/P ratios in diabetic environments. The bionic coatings were prepared in β-titanium alloys using micro-arc oxidation (MAO) technology and evaluated for corrosion mechanism, biocompatibility, and safety by cytotoxicity, electrochemical corrosion, and coating bonding force experiments. Ca and P from the electrolyte were integrated into the coating during MAO discharge process to form hydroxyapatite. The coating Ca/P ratio initially increased and then decreased with the electrolyte Ca/P ratio. In vitro cellular experiments demonstrated that increasing the porosity of HA-containing coatings would be beneficial to the growth of cells adhering to their surfaces. Corrosion tests revealed that the corrosion tendency of the coating at higher sugar content was more severe, and a proper elevation of the Ca/P ratio was better for the corrosion resistance of the coating. The bonding analysis of the coatings before and after corrosion showed that an increase in the Ca/P ratio would improve the bonding of the MAO coatings in higher glucose content environments, thus improving the safety of the implants in diabetic patients.