A functional ceramic generated directly from the metal

PEO (Plasma Electrolytic Oxidation) is an electrochemical process that transforms the surface of a lightweight alloy part (titanium, magnesium, aluminium) into a ceramic oxide layer, with no added foreign material: the ceramic is generated from the metal itself.

Unlike an applied coating, there is no interface between the layer and the substrate: adhesion is metallurgical in nature, which greatly limits the risk of delamination.

Process principle

The treatment takes place in an electrolytic bath where the part, immersed under increasing voltage, goes through several successive regimes:

  1. Anodizing — formation of a thin, compact oxide film, without discharge.
  2. Breakdown — beyond a threshold voltage, the native oxide gives way and the first micro-discharges ignite across the entire surface.
  3. Micro-arc regime — this is the useful zone of the process: each micro-discharge locally melts the oxide, which instantly re-solidifies on contact with the bath, progressively building up the ceramic layer.
  4. Arcing — at too high a voltage, discharges become rare but highly energetic, gouging large craters and potentially cracking the layer. This regime should be avoided.

Materia Nova controls the process to stay within the micro-arc regime window, which guarantees a homogeneous, high-quality layer.

The resulting layer

The PEO treatment produces a ceramic bilayer:

  • A dense inner layer, under one micron, which acts as a barrier and provides corrosion resistance.
  • A porous outer layer, thicker, which gives the surface its appearance and roughness, and which can be sealed or functionalized depending on the intended application — for example to integrate antibacterial agents or promote cell adhesion in biomedical applications.

The total thickness, typically between 5 and 30 µm, can be adjusted via the treatment duration and the applied electrical profile.

Properties achieved

  • Hardness and wear resistance — the ceramic layer is significantly harder than the bare metal, with greatly enhanced scratch resistance.
  • Corrosion and erosion resistance — provided by the dense inner layer, which acts as a barrier; the outer porosity can be sealed to further reinforce this protection. In this respect, PEO is an alternative to conventional anodizing treatments, with the advantage of complying with REACH regulatory requirements.
  • Mechanical performance — the layer grows from the metal itself, with no applied interface, which limits the risk of delamination.
  • Biological functionalization — surface porosity can be leveraged to promote osseointegration or confer antibacterial properties, notably through the integration of specific additives into the layer.

Multiple customization levers

Several parameters allow the characteristics of the resulting layer to be adjusted:

  • Composition and conductivity of the electrolytic bath, including the addition of functional additives (antibacterial agents, metal salts, etc.)
  • Applied voltage and current
  • Frequency and duty cycle of the signal
  • Grade and composition of the treated alloy

This combination of levers opens the way to tailor-made developments, whether for functional properties (hardness, corrosion, wear, biocompatibility) or for the aesthetic effects sought by certain sectors, such as watchmaking and luxury goods.

Applications

  • Technical parts requiring increased resistance to wear and corrosion
  • Components for watchmaking and luxury goods, with possibilities for aesthetic customization (colours)
  • Biomedical devices (dental implants, stents, osteoarticular prostheses), to promote osseointegration and limit the risk of infection
  • Aeronautical components, as an alternative to conventional anodizing treatments for anti-corrosion and anti-erosion protection
  • More broadly, any application where metallurgical adhesion and the absence of solvents or regulated compounds (hexavalent chromium, etc.) are an advantage

Materia Nova has recent PEO equipment, combined with in-depth expertise in electrolyte formulation acquired on other processes (electrolytic deposition, cyanide-free gilding and silvering). This technology is at the heart of several of our collaborative research projects.

contact us