Why Does Arc Spray Galvanising Only Work on Certain Metals?

Metal in New ZealandArc spray galvanising is a type of metal spraying procedure that protects metals from corrosion and degradation. It is the process of spraying a prepared surface with small, molten particles of zinc or a zinc alloy. This creates a uniform coating that completely envelops the metal.

Companies like Euro-Blast NZ Ltd use the arc spray galvanising technique for steel and iron products. Architectural elements, such as fences, grates and steel staircases often use galvanised metals. The process creates a highly effective barrier coating against moisture and offers a clean surface for any subsequently applied top coats and sealants. Not all metals, however, can be galvanised.

How Arc Spray Galvanising Works

The ‘arc’ in arc spray galvanising refers to the energised wires that are fed through a feeder, and into the gun head of the spraying device. One wire has a positive charge, while the other has a negative charge. It forms an arc that meets in the middle, which creates intense heat.

The heat created by these wires melts the zinc in the feeder, which is then sprayed onto the prepared surface. The droplets hit the surface of the metal and flatten upon contact, creating a thin layer of molten metal on the surface. As the droplets spread out, they harden and create a strong mechanical bond with the metal underneath.

Only Certain Metals Work

Since the arc spray galvanising forms a mechanical bond, or a chemical bond, with the metal, it is not suitable for just any kind of metal. Galvanising works well on iron and steel because the chemical structure of these metals are compatible with the zinc used in the spraying process.

The zinc will not adhere to metals that it is not compatible with. For example, metals, such as aluminium or alloys that contain silicon will react negatively to the zinc. It will reject the zinc, and it will simply flake off the surface. It will also not adhere to materials, such as plastic.

Arc spray galvanising is a sophisticated chemical process that requires a deep understanding of the materials used. This is why the process is only effective for specific applications.

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