Quelles différences entre MAO et PEO en structure de couche et durabilité ?

Fundamental Process Differences and Coating Formation

Micro-Arc Oxidation (MAO) and Plasma Electrolytic Oxidation (PEO) are closely related technologies, and in modern terminology, PEO is widely recognized as the advanced, highly controlled evolution of traditional MAO. Both processes are electrochemical surface treatments that use high-voltage plasma discharges to convert the metal surface into a dense, ceramic oxide layer. They are applicable to lightweight metals such as aluminum, magnesium, and titanium.

The essential distinction lies in the precision of electrical control. While MAO systems typically rely on simpler high-voltage AC or unipolar power supplies to generate plasma discharges, PEO systems employ sophisticated, digitally modulated electrical regimes—such as bipolar pulsed currents with controlled frequency, duty cycle, rise time, and current density. This fine control governs plasma energy distribution, oxide growth rate, and local thermal effects. As a result, PEO produces more uniform, engineered coatings and offers substantially improved functional performance—making it the preferred process for high-end applications where our Arc Anodizing service may be required.

Coating Structure and Morphology

Coating morphology is one of the clearest differentiators between MAO and advanced PEO processes.

A traditional MAO coating often exhibits a distinct three-layer structure:

• Inner barrier layer: Thin, dense oxide directly formed at the metal–oxide interface.

• Intermediate compact layer: Thicker but relatively heterogeneous, with localized densification and micro-cracking.

• Outer porous layer: Rough, with larger discharge craters and sintered molten particles caused by uncontrolled arc events.

These characteristics result from the more violent, less regulated plasma discharges inherent to MAO systems.

In contrast, a modern PEO system—using optimized, pulse-controlled electrical parameters—produces:

• More uniform plasma events with lower energy per discharge.

• Finer microstructure with reduced crater size and fewer molten ejections.

• Lower porosity and more homogeneous oxide distribution.

• Smoother transitions from the dense inner layer to the outer surface.

The result is a significantly more refined composite ceramic coating with improved structural integrity and reduced risk of delamination or crack propagation.

Comparative Durability and Performance

The structural improvements of PEO translate into measurable performance advantages:

Hardness and Wear Resistance: Both MAO and PEO produce extremely hard ceramic surfaces, but the finer and denser microstructure of PEO coatings allows them to reach higher and more consistent hardness values—often >1500 HV. This delivers exceptional abrasive and adhesive wear resistance, outperforming many thermal spray coatings and substantially surpassing standard hard anodizing.

Corrosion Resistance: With lower porosity and minimized micro-cracking, PEO coatings offer superior corrosion resistance. In standardized Post-Process validation tests such as ASTM B117 Salt Spray, well-sealed PEO coatings frequently exceed 1000 hours of protection without pitting—making them suitable for marine, automotive, and aerospace exposure conditions.

Adhesion and Mechanical Integrity: Unlike deposited coatings, MAO and PEO both form a metallurgically bonded oxide layer grown outward from the substrate. PEO’s more uniform microstructure reduces internal stress concentrations, delivering:

• Higher adhesion strength

• Improved resistance to mechanical shock

• Superior fatigue performance

These attributes are critical for components that undergo Post Machining, dynamic loading, or assembly-induced stress.

Application Selection and Industrial Relevance

For standard applications requiring moderate wear and corrosion resistance, a conventional MAO coating may meet performance needs at a lower cost. However, for industries where consistent, long-term reliability is mission-critical—such as aerospace structures, drivetrain systems, medical instruments, and next-generation automotive components—PEO is the preferred high-performance solution.

Its advanced microstructural uniformity, coating density, and superior mechanical characteristics make PEO the most reliable option within the spectrum of plasma electrolytic oxidation technologies.