Galvanizing steel is a cathodic protection system as well as a direct barrier to its immediate atmospheric conditions. Cathodic protection is used in corrosive conditions in order to protect the surface of the parent metal. This is achieved by sacrificing atoms of a more reactive metal than the parent metal itself.
In order to paint galvanized steel correctly, it is necessary to de-grease and then sweep blast the surface to remove 10 microns of zinc using an aluminium oxide abrasive medium. The use of a high quality duplex painting system must then be applied. Duplex painting systems are two pack systems consisting of a primer with a hardener and a topcoat with a hardener. It is advised to consult with professional coating specialist.
After approximately 1 year it is possible to paint galvanized steel without any special washing treatments. The removal of all oily residues dust and dirt is all that is required before painting. A good quality acrylic roof type paint is advised due to its excellent ultra violet resistance. (UV stable) Its always advised to speak to a paint professional before.
The utilisation of an electro static coating process to paint galvanized steel has not been very successful, this is due to the use of acid baths to etch the surface which causes gassing when placed in the curing oven.
Once the zinc has been applied to the steel the zinc surface changes three more times once exposed to the environment.
Zinc oxide (ZnO)
Zinc hydroxide( Zn(OH)2 )
Zinc carbonate (ZnCO3)
RAPTOR products have a ten year workmanship and corrosion guarantee.