How does PVD vacuum metallisation work? Step-by-step process
A practical guide to physical vapor deposition (PVD) technology.
Vacuum metallisation PVD (Physical Vapor Deposition) is an advanced technology for depositing ultra-thin metallic coatings on various substrates. At ELMAL, we use thermal resistance evaporation, where aluminum is vaporized in a vacuum chamber and then deposited on the surface of parts — plastics, glass, or metal. The result is a mirror-like, uniform metallic coating with high reflectivity (up to 92-95%), used in the automotive, lighting, cosmetics, and decorative industries.
Stage 1: Application of the base coat (basecoat)
The vacuum metallisation process starts before the parts enter the coater. A base coat (basecoat) is applied to the cleaned elements — mostly made of plastics like ABS, PC, PP, or PE. The base coat serves a dual function: it smooths out the surface microporosities of the plastic, providing an ideal substrate, and creates a chemical adhesion layer for the vaporized metal. The quality of the base coat directly affects the final gloss and durability of the metallic layer. After application, the parts are thermally or UV cured.
Stage 2: Plasma activation – Glow Discharge
After loading the parts into the vacuum chamber of the coater, a crucial surface preparation step takes place — plasma activation, known as Glow Discharge. A small amount of working gas (argon) is introduced into the chamber, and a high voltage of several thousand volts is applied. The ionization of argon leads to low-temperature plasma, whose ions bombard the surface of the parts with high energy.
Glow discharge performs two tasks simultaneously: first, it removes organic residues and moisture; second, it activates the polymer surface, creating free radicals that drastically increase the material's surface energy. As a result, the vaporized aluminum adheres to the substrate with excellent adhesion.
Stage 3: Metal evaporation in high vacuum
The central stage of PVD vacuum metallisation is thermal metal evaporation. Inside the working chamber of the coater, a high vacuum is maintained (typically 10-5–10-6 mbar), which means that the pressure is billions of times lower than atmospheric pressure. Under these conditions, the so-called mean free path of atoms — the average distance an atom travels without colliding with other molecules — exceeds the distance between the evaporation source and the metallized details.
At the center of the chamber is a resistive evaporator — a heating element made of tungsten, through which a high-intensity current (hundreds of amperes) flows. An aluminum wire is placed on the tungsten boat or spiral, which melts under heat and passes into the gas phase. The released aluminum atoms move in straight lines in the vacuum and deposit evenly on all exposed surfaces of the parts, creating a nanometer-thick coating with excellent chemical purity and a mirror finish.
To ensure uniform coating, the parts are placed on a rotating planetary carousel. Each part performs a circular motion (around the central evaporator) and a rotation (around its own axis), ensuring that the aluminum layer deposits evenly even on elements with complex geometry.
Stage 4: Application of the protective lacquer (topcoat)
The deposited layer of pure aluminum is extremely thin (typically 50-150 nm) and would quickly oxidize and scratch without additional protection. Therefore, the final step of the metallisation process is the application of a protective lacquer — the topcoat. This lacquer protects the metallic layer from UV radiation, moisture, atmospheric corrosion, and minor mechanical damage.
It is at the topcoat stage that various color effects can be achieved. Transparent topcoat gives a classic high-gloss silver chrome effect. Colored lacquers, on the other hand, allow for gold, brass, copper, titanium, and colors like red, blue, green, or black chrome.
What materials can be vacuum metallized?
The PVD technology used at ELMAL allows obtaining a mirror metallic coating on almost any stable material. Most often, we metallize elements made of plastics: ABS, polycarbonate (PC), polypropylene (PP), polyethylene (PE), polystyrene (PS), as well as glass, ceramics, and metals. The maximum dimensions of a single element for vacuum metallisation in our plant should not exceed 900 × 300 × 300 mm.
Why is PVD vacuum metallisation eco-friendly?
Unlike traditional electroplating, PVD vacuum metallisation is fully eco-friendly. The process does not generate toxic waste, does not use harmful hexavalent chromium (Cr6+) or aggressive chemical baths. The only 'waste' is residual aluminum deposited on chamber shields, which is recycled. As a result, vacuum metallisation is classified as Green Technology — an ideal solution for companies seeking ecological alternatives to electroplating.
PVD vacuum metallisation is a precise, multi-stage process requiring specialized equipment and experience. At ELMAL Sp. z o.o., we execute vacuum metallisation orders using the industrial KOLZER DGK36 coater, guaranteeing parameter repeatability and the highest quality of mirror coatings. If you are looking for vacuum metallisation services or have questions about the process — contact us.