Applications of Microplasma Oxidation
Microplasma oxidation (MPO), also known as micro-arc oxidation, is a surface treatment technology that uses plasma discharge to trigger a chemical reaction on the surfaces of light metals such as aluminum, magnesium, and titanium, forming a ceramic oxide film. Its application has gradually expanded from aerospace to various fields, including automotive, medical, and electronics. Compared with traditional anodizing, MPO films can reach thicknesses of 5-100μm, with hardness exceeding HV1000 and a bond strength exceeding 50MPa with the substrate. They provide comprehensive properties such as wear resistance, corrosion resistance, and insulation. In the automotive industry, MPO technology is used to treat the surface of aluminum alloy pistons in engines. The resulting ceramic film can withstand temperatures exceeding 300°C and fuel corrosion, increasing piston wear resistance by two times and reducing oil consumption by 30%. Application data from one automaker shows that the overhaul mileage of engines treated with MPO has been increased from 300,000 kilometers to 500,000 kilometers.
In the medical device field, microplasma oxidation technology provides an ideal surface modification solution for magnesium and titanium alloy implants. By forming a bioactive ceramic film, it significantly improves the biocompatibility and osseointegration capabilities of the materials. MPO treatment of the surface of titanium alloy artificial joints forms an oxide film containing hydroxyapatite, with a surface roughness Ra of 1.5-3μm, which facilitates the attachment and growth of bone cells. Animal experiments have shown that osseointegration time is 40% shorter than that of untreated samples, and the implant loosening rate is reduced to below 1%. As a biodegradable metal, magnesium alloy has broad application prospects in fracture fixation devices, but its rapid degradation rate has limited its use. MPO technology forms a dense magnesium oxide-aluminum oxide composite film on the surface, which can control the degradation rate to 0.1-0.2mm per month, matching the speed of bone healing. MPO-treated magnesium alloy bone screws developed by a medical device company have achieved gradual degradation over 6-12 months in clinical use, avoiding the painful need for secondary surgery for removal.
The electronics industry is leveraging the high insulation and wear resistance of microplasma oxide films, applying them to aluminum alloy heat sink components and insulating brackets, addressing the insufficient insulation strength of traditional anodic oxide films. The oxide film formed on the surface of MPO -treated aluminum alloy heat sinks boasts a breakdown voltage exceeding 5000V and a thermal conductivity of 150-200W/(m · K) . Its use in LED lamp heat sinks prevents short circuits while ensuring efficient heat dissipation, extending the lamp’s service life to over 50,000 hours. At the junction between the metal midframe and the glass cover of smartphones, MPO technology can produce a 10-20μm insulating ceramic film, replacing traditional tape insulation. This film is not only thinner (reduced by 0.3mm ) but also withstands high-temperature welding and drop shock. Using this technology on a certain brand of mobile phone, the reliability of the midframe-to-screen connection increased by 60%, and the after-sales failure rate dropped to below 0.5%.
In marine engineering and shipbuilding, microplasma oxidation technology provides an excellent anti-corrosion solution for aluminum and magnesium alloy components. The ceramic film it forms resists long-term seawater corrosion without the need for additional coating. After 10,000 hours of immersion in artificial seawater, the corrosion rate of aluminum alloy yacht outboard motor components treated with MPO was only 0.001mm/year, far lower than the 0.01mm/year of anodizing treatment, and no surface pitting was observed. MPO treatment and sealing of magnesium alloy cabin components in ships can last for over 10 years in high-humidity, high-salinity environments, eliminating the need for regular maintenance of traditional anti-corrosion coatings. Comparative experiments at a marine research institute showed that MPO-treated aluminum seawater pipes had a service life three times that of galvanized steel pipes and were 50% lighter, significantly reducing the vessel’s energy consumption.
The application of microplasma oxidation technology in mold manufacturing replaces traditional chrome plating by forming a high-hardness, high-temperature-resistant ceramic film on the surface of aluminum alloy molds, addressing the environmental pollution and insufficient wear resistance of chrome plating. MPO treatment increases the surface hardness of aluminum alloy die-casting molds to HV800-1000 and temperature resistance to over 500°C. In zinc alloy die-casting production, mold life is extended from 50,000 to 150,000 cycles. Improved demolding performance eliminates the need for frequent release agent applications, increasing production efficiency by 20%. In the plastic mold industry, the low surface energy of MPO film (water contact angle above 90°) enables self-cleaning capabilities, reducing the surface roughness Ra of molded parts to 0.05μm, reducing subsequent polishing steps. A mold factory’s application case shows that the qualified rate of PET preform molds treated with MPO has increased from 95% to 99.5%, saving hundreds of thousands of yuan in scrap costs annually. With the reduction of process costs and the miniaturization of equipment, the application scope of microplasma oxidation technology will be further expanded and become one of the mainstream technologies for light metal surface treatment.
