Which Materials Can Be Vacuum-Metallized? A Complete Guide to Suitable Substrates

Vacuum metallization offers exciting opportunities for manufacturers, enabling premium-looking products to be created from lightweight, cost-efficient base materials. But which materials are best suited for the technology? Which plastics can be metallized, and is it possible to apply the process to metal surfaces as well? This comprehensive guide answers these key questions.

The Basics: Why the Substrate Matters

During vacuum metallization, metal vapor—typically aluminum—is evaporated in a vacuum and deposited evenly onto the substrate. For the coating to be durable, uniform, and visually appealing, the material must meet several criteria:

• Heat resistance: the material must withstand the temperatures present inside the chamber
• Surface quality: a smooth, non-porous surface ensures uniform coating
• Adhesion capability: with proper primer layers, the metallic coating must bond reliably

Thermoplastics: The Most Common Materials for Metallization

Thermoplastic polymers are ideal for vacuum metallization. These materials soften when heated, harden when cooled, and provide an excellent base for metallic coatings.

Polypropylene (PP)

One of the most popular plastics for metallization. Lightweight, durable, cost-effective, and widely used in packaging, automotive interiors, and household applications.

Properties:

• Good chemical resistance
• Low density
• Excellent price–performance ratio
• Wide range of molding options

Applications: cosmetic bottles, plastic caps, interior automotive parts, handles for household tools

ABS (Acrylonitrile–Butadiene–Styrene)

Extremely popular due to its outstanding mechanical properties and smooth surface. Impact-resistant, easy to process, and ideal for high-quality metallic finishes.

Properties:

• Excellent impact resistance
• Smooth, glossy surface
• Good heat resistance
• Easy to machine

Applications: automotive decorative parts (chrome-effect grilles, emblems), electronic housings, toys, decorative furniture components

Polystyrene (PS)

A lightweight, rigid, inexpensive plastic widely used for metallization. Common in packaging and decorative products.

Properties:

• Rigid structure
• Available in transparent or colored variants
• Cost-efficient production
• Good surface quality

Applications: cosmetic packaging, decorative elements, Christmas ornaments, mirror frames

Other Metallizable Plastics

• PET (Polyethylene terephthalate): bottles, containers, packaging
• PMMA (Acrylic): optical components, premium covers
• PC (Polycarbonate): automotive light housings, protective covers
• PE (Polyethylene): packaging materials, bottles

Metallizing Metals: When Metal Gets Metal

Surprisingly, not only plastics but also metal substrates can be vacuum-metallized. This is useful when a metal part needs enhanced decoration, coloration, or protection.

Why Metallize Metal?

• Corrosion protection: e.g., aluminum coating on steel components
• Aesthetic enhancement: creating different metallic tones
• Optical performance: enhanced mirror reflection
• Cost-efficiency: inexpensive metal parts upgraded with a premium finish

Example: Ceiling lamp housings

Ceiling lamp bodies (steel or aluminum) can be metallized to achieve a flawless mirror finish, improving both aesthetics and light reflection efficiency.

Other Applications:

• Automotive metal decorations
• Light fixtures and reflectors
• Decorative items and jewelry
• Metal furniture accessories

Surface Preparation: The Key to Success

Even if a material is suitable in theory, proper surface preparation is essential. This typically includes:

1. Cleaning: removal of dust, grease, contaminants
2. Priming: applying a special primer layer to ensure adhesion
3. Drying: ensuring the primer cures properly

Precise preparation ensures that the metallic layer is durable, uniform, and defect-free.

Protective Topcoats

After metallization, protective lacquers can be applied to provide:

• Scratch resistance
• UV protection
• Improved chemical resistance (e.g., against perfumes or alcohol)
• Long-lasting surface gloss

UV-Cured Coatings: for maximum resistance, UV-curable protective lacquers offer superior performance.

Which Materials Cannot Be Metallized?

Certain materials are unsuitable or only partially suitable for vacuum metallization:

• Thermoset plastics (duroplastics): insufficient heat resistance
• Silicone: poor adhesion
• Rubber and elastomers: flexibility incompatible with metallic coatings
• Porous or rough surfaces: cause inconsistent coatings
• Moisture- or gas-emitting materials: problematic in vacuum conditions