Aluminum alloys are prone to pitting and intergranular corrosion during use, which greatly limits their large-scale application. This study explores micro-arc oxidation (MAO) coatings on 1.5 wt.% CNTs/2024Al composites to improve corrosion resistance. Using a Na 2 SiO 3 -NaOH electrolyte at 430 V for 12 min, MAO coatings were prepared. SEM shows denser surfaces with smaller pores in CNTs-reinforced coatings due to CNTs optimizing discharge channels. XRD confirms α-Al 2 O 3 and γ-Al 2 O 3 phases, with higher crystallinity in CNTs/2024Al coatings. EDS detects C elements, indicating CNTs participation in film formation. Electrochemical tests in 0.5 wt.% NaCl show CNTs/2024Al-MAO has a lower corrosion current density (2.63 × 10 -7 A/cm 2 ) and higher charge transfer resistance, demonstrating superior corrosion resistance. MAO with CNTs offers a viable strategy for enhancing Aluminum Matrix Composites (AMCs) durability in harsh environments

Abstract This study investigates the influence of build direction in Ti6Al4V substrates manufactured by Electron Beam Powder Bed Fusion (EB-PBF) on the performance of Plasma Electrolytic Oxidation (PEO) coatings. Because of the inherent anisotropy of additively manufactured alloys, arising from differences in thermal history between the build and transverse directions, surface treatments and coating behavior may vary. To explore this, coatings were produced in a silicate–phosphate (Si–P) electrolyte under different current densities and treatment times. The resulting coatings were characterized in terms of morphology, crystalline phase composition, and corrosion performance. The results show that, although build direction affects the initial voltage response during PEO treatment, its influence on coating thickness and porosity is minimal. X-ray diffraction revealed the presence of both anatase and rutile TiO₂ phases, with anatase formation favored at lower current densities. Importantly, PEO treatment eliminated the corrosion anisotropy observed in uncoated Ti6Al4V manufactured by EB-PBF, leading to uniform protective behavior regardless of build direction. Overall, these findings demonstrate the potential of PEO to enhance the functional performance of additively manufactured titanium alloys for biomedical and aerospace applications. In addition, they underscore the importance of electrolyte composition and process optimization in tailoring surface properties.

Abstract The inherent corrosion susceptibility of titanium alloys constrains their deployment in aggressive environments, micro-arc oxidation (MAO) represents an effective remediation strategy. In this study, ZrO2/TiO2 MAO composite films were in situ synthesized by adjusting the concentration of Zr(SO4)2 in the electrolyte, and the effect on the microstructure, mechanical properties, and corrosion resistance of the MAO films were studied. Compared with the bare TA18 substrate, the surface performance of the MAO coated TA18 improved significantly. With the introduction of Zr(SO₄)₂, the surface morphology was refined and the hardness, thickness, and wear resistance of the MAO film were improved. When the Zr(SO₄)₂ concentration is 0.75 g L⁻¹, the corrosion rate and wear rate reach their lowest values of 2.2776 × 10⁻² mpy and 0.6644 × 10⁻⁶ mm³ m⁻¹ N⁻¹.

The automotive, aerospace, biomedical, and other engineering sectors make substantial use of Ti6Al4V titanium alloy, known for its high strength-to-weight ratio, corrosion resistance, and biocompatibility, but it often suffers from poor tribological performance and low surface hardness. To increase durability, a variety of surface modification techniques have been investigated, including chemical etching, shot peening, thermal oxidation, laser surface texturing, and physical vapor deposition. However, these methods frequently entail high thermal input and mechanical stress with limited control over surface chemistry. Electrochemical methods, on the other hand, allow uniform and precise alteration of surface morphology without thermal or mechanical damage. Among these, anodization and plasma electrolytic oxidation (PEO) facilitate hardening and stress-free surfaces but suffer from passive film formation, porosity and micro-cracks, while electrochemical polishing (ECP) yields much better surface finish but at high energy cost and causes passive film formation. In this review, electrochemical machining (ECM), typically viewed as a subtractive method for material removal, is reevaluated as a process for both material removal and functional surface tailoring. Despite its application for removing material, ECM promotes valence-controlled dissolution that favours the formation of lower oxidation states of titanium. It also inhibits the formation of passive films and enables the formation of atomically smooth surfaces. The present study provides a novel theoretical framework for customizing Ti6Al4V surfaces with improved functional and morpho­logical properties by integrating ECM with anodization, PEO and ECP within the broader paradigm of electrochemical surface engineering.

Platinum–carbon nanotube reinforced hydroxyapatite ceramic coatings on Ti6Al4V implant via plasma electrolytic oxidation: Enhanced surface and biological characteristics

Plasma electrolytic oxidation coating for aluminium and glass-fibre polyamide 6 bonding

Plasma electrolytic oxidation of aluminium using conventional anodizing precursors and electrolytic colouring with Cu, Sn and Ni

77The Dual Role of Precipitated Phases in Discharge Behavior During the Plasma Electrolytic Oxidation of Mg Alloys

The effect of in-situ incorporation of CuO and MnO2 particles into Al2O3 coatings by plasma electrolytic oxidation of aluminum on their photocatalytic performance

Corrigendum to “Wear and corrosion resistance of AZ31B magnesium alloy micro-arc oxide coatings by laser surface remelting” [Vacuum 240 (2025)114435

In-situ fabrication of durable corrosion-resistant ZrO2/Al2O3 coating on 3D-printed AlSi10Mg via two-step micro-arc oxidation

To enhance the wear and corrosion resistance of Zr alloy components in marine engineering, this study investigated the influence of the applied voltage (ranging from 470 to 620 V) on the morphology, structure, and properties of ceramic coatings formed on a Zr alloy substrate by Micro-arc Oxidation (MAO) in a silicate–phosphate composite electrolyte. The results showed that with increasing voltage, the coating thickness increased (from 15.12 to 52.80 μm) and the surface roughness increased (from 1.12 to 4.89 μm), while both the surface and cross-sectional porosity first increased and then reached their minimum values at 620 V (1.61% and 5.75%, respectively). Phase analyses indicated that the coatings consisted mainly of monoclinic ZrO2 (m-ZrO2), along with minor amounts of SiO2, ZrSiO4, and Zr3(PO4)4. The coating prepared at 620 V exhibited optimal performance: its hardness was 1.98 times that of the substrate, the wear volume decreased by approximately 87%, the self-corrosion potential shifted positively by 539 mV, the corrosion current density decreased by nearly two orders of magnitude, and the polarization resistance increased by approximately two orders of magnitude. These results demonstrate a substantial improvement in the service performance of Zr alloys for marine applications.

This study explores the effect of potassium permanganate (KMnO4) concentration on the microarc oxidation (MAO) coatings of high-purity copper. Results show that the KMnO4 addition reduces overall porosity but enlarges individual pores. The resulting manganese oxides increase coating thickness, hardness, roughness, and impart transient hydrophobicity. Tribological tests confirm improved wear resistance under high loads. Although larger pores slightly reduce corrosion resistance, the coating still protects the substrate. Additionally, the coating growth mechanism is clarified, providing a basis for optimizing MAO coatings on pure copper through secondary processing.

Diabetes mellitus is a globally prevalent metabolic disorder that impairs wound healing and bone regeneration, compromising outcomes in implant therapies that rely on osseointegration. Advances in precision medicine and bioengineering have driven the development of functionalized implant surfaces to overcome these limitations. Among them, bioactive glass (BG) coatings have emerged as promising candidates to enhance biological responses. Building upon this rationale, we unveiled the osteoinductive potential of a BG-based coating synthesized via plasma electrolytic oxidation (PEO) and its effects on peri-implant bone regeneration in a diabetic rat model. Titanium implants were treated with PEO using a formulation mimicking BG composition (∼45.0 Si, 24.5 Ca, 24.5 Na, 6.0 P; m/v %), and the resulting coating was characterized. Implants with a sandblasted and acid-etched (SLA) surface served as the control. In vivo evaluation was conducted in Wistar rats with streptozotocin-induced diabetes mellitus, followed by tibial implant placement. At 14 and 28 days postimplantation, samples were harvested for histological, immunohistochemical, micro-CT, and histomorphometric analyses. Physicochemical characterization confirmed the synthesis of the PEO-BG coating, which exhibited enhanced surface roughness and wettability compared to SLA controls. A significantly greater area of newly formed bone, increased bone-implant contact, and favorable bone turnover were noted in the PEO-BG group. The expression profiles of BMP-2, RANKL, OPG, and OCN indicated modulation of osteogenic and inflammatory pathways consistent with accelerated bone repair. These findings demonstrate that PEO-BG coating confers robust osteoinductive potential, enhancing peri-implant bone regeneration under compromised diabetic conditions, and highlight its potential for translational application in high-risk populations.

Micro-arc oxidation (MAO) coatings were produced on commercially pure titanium Grade 2 using a composite electrolyte containing sodium phosphate (Na3PO4) and sodium silicate (Na2SiO3), while varying the applied voltage. The surface morphology, phase composition, and structural features of the coatings were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The coatings exhibited a characteristic crater-like microporous surface morphology associated with the micro-arc discharge process. XRD analysis confirmed the formation of mixed TiO2 phases in the anatase and rutile modifications, with higher voltages promoting the growth of the thermodynamically stable rutile phase. Corrosion and tribological properties were evaluated in a 3.5 wt.% NaCl solution using potentiodynamic polarization and a ball-on-disc test configuration, respectively. The results revealed a substantial improvement in both corrosion resistance and wear performance compared with bare titanium. The coating formed at 300 V demonstrated the highest wear resistance due to its denser microstructure, whereas the coating produced at 350 V exhibited the lowest friction coefficient and the greatest corrosion resistance, attributed to the increased rutile content. Overall, MAO coatings fabricated in the phosphate–silicate electrolyte effectively enhance the combined operational properties of titanium and can be recommended for applications requiring improved wear and corrosion resistance.

In this study, oxide coatings with layered double hydroxide (LDH) nanosheets were prepared on AZ91 magnesium alloy by a one-step low-voltage microarc oxidation (MAO) process. The microstructure and composition of the coatings were characterized using SEM, EDS, XRD, FT-IR, and XPS. The corrosion protection performance of the coatings was evaluated by electrochemical analysis and hydrogen evolution tests. The results showed that oxide coatings with Mg-Al-LDH nanosheets are successfully produced by microarc oxidation at a voltage of less than 100 V. The coating with a higher density of Mg-Al LDH nanosheets exhibited enhanced corrosion resistance. Moreover, after modification with stearic acid, the coatings displayed high hydrophobicity and corrosion resistance.

This study evaluated the surface functionalization of a non-equiatomic TiZrNbTaMo high-entropy alloy (HEA) by micro-arc oxidation (MAO) in Cu-rich electrolytes to tailor its performance for biomedical implants. The Cu content was varied, and the resulting coatings were investigated for their morphology, phase constitution, chemical structure, wettability, and cytocompatibility. X-ray diffraction (XRD) measurements of the substrate indicated a body-centered cubic (BCC) matrix with minor HCP features, while the MAO-treated samples depicted amorphous halo with sparse reflections assignable to CaCO3, CaO, and CaPO4. Chemical spectroscopic analyses identified the presence of stable oxides (TiO2, ZrO2, Nb2O5, Ta2O5, MoO3) and the successful incorporation of bioactive elements (Ca, P, Mg) together with traces of Cu, mainly as Cu2O. MAO treatment increased surface roughness and rendered a hydrophilic behavior, which are features typically favorable to osseointegration process. In vitro cytotoxic assays with MC3T3-E1 cells (24 h) showed that Cu addition did not induce harmful effects, maintaining or improving cell viability and adhesion compared to the controls. Collectively, MAO in Cu-rich electrolyte yielded porous, bioactive, and Cu-incorporated oxide coatings on TiZrNbTaMo HEA, preserving cytocompatibility and supporting their potential for biomedical applications like orthopedic implants and bone-fixation devices.

Photocatalytic active MgO/MgAl2O4 coatings doped with rare earth elements (Sm, Tb, Pr, Gd, and Nd) formed on AZ31 magnesium alloy by plasma electrolytic oxidation

To investigate the osteogenic potential of a novel composite coating -micro-arc oxidation combined with polydopamine and nanoclay (MAO-PDA-NC)- on titanium substrates, coatings were fabricated via micro-arc oxidation (MAO) and impregnation techniques. Pure titanium (TI) was the control, while MAO-PDA-NC-coated titanium functioned as the experimental specimen. After surface characterization, a 5 mm critical-sized calvarial defect model was established bilaterally in rat skulls. Titanium implants were randomly allocated to the defect sites, either uncoated or coated with MAO-PDA-NC. The regenerative response was assessed through micro-computed tomography, histological analysis, immunohistochemistry, and immunofluorescence. Results demonstrated that MAO-PDA-NC-modified titanium significantly enhanced new bone formation, exhibiting anti-inflammatory and regenerative properties. These characteristics show broad application prospects in the field of implant surface modification.

Corrosion behavior and formation mechanism of plasma electrolytic oxidation coatings on 1060 aluminum alloy in Si(OC2H5)4-(NaPO3)6-NaOH electrolyte