This method consists of melting metal either in wire or powder form inside a flame spray gun or an electric arc gun, and then, using compressed air, spraying the molten metal over the steel, stripped beforehand with abrasive jets. The metallising process is standardised: ISO 2063 STANDARD. Zinc sprayed in this way instantaneously solidifies in contact with the steel surface and forms a zinc coating. Anti-corrosion protection is thus immediate.
Since metallising coating is slightly porous, it is recommended to apply a sealer. Moreover, the porous character of the metallised surface provides an ideal substrate for applying an additional paint layer, either for aesthetic reasons or for reinforced anti-corrosion performances. This is called a duplex system (metal coat + paint).
The coating thickness can vary between 50 to 200µm, which is ideal for long-term protection against corrosion. This flexibility also allows the applicator to adapt to all corrosion classes and to technical specifications. The process can be carried out in a workshop or on-site and is perfectly suitable for structures too large to be hot-galvanised.
Two systems are generally used for the wire:
- Metallising with an electric arc gun: this process consists of introducing two zinc or zinc-aluminium alloy wires into an electric arc spray gun. When these two wires come into contact, an electric arc forms and melts the zinc which is then sprayed using compressed air onto the surface to be metallised. Wires with finer diameter, generally 2.50mm max, are used for this type of spray gun.
- Metallising with a flame spray gun: this process consists of introducing a zinc or zinc-aluminium alloy wire into a spray gun fed with a flammable gas mixture (propane or acetylene and oxygen). The wire across the gun is melted by combustion and then sprayed using compressed air onto the surface to be metallised. Wires with larger diameter, generally starting at 3mm, are used for this type of spray gun.
ISO 2063 Standard