 Galvanising and zinc spray Galvanising is the process of coating steel with a thin layer of zinc. The procedure is to briefly immerse the steel item in a bath of molten zinc (approximately 450ºC), resulting in a smooth coating of zinc approximately 50 - 100 microns thick. To protect the new zinc coating, the item is given a chromate passivating coat, which, while providing extra protection for the steel, results in a smooth surface which provides a very poor key for primers and paints. This poor key normally results in peeling paint. The zinc spray process
(also referred to as metal spray or flame
spray) involves a spray gun which melts pure
zinc wire, then uses compressed air to atomise and propel
the molten droplets onto the steel item, much like an
aerosol paint. The melting, atomising and propelling is a
continuos process, so the operator literally spray paints
the item with a fine spray of molten zinc droplets. The
droplets solidify and adhere strongly on contact with the
cold steel item, forming an even, textured coating of
pure zinc. |
