All galvanized items are dressed in accordance with the Australian Standard for hot- dip galvanizing. Sharp edges and dags are removed, however runs and general roughness of the zinc surface will remain. The result of high gloss and smoothness when paint has been applied over extruded metal, planed timber or pre-galvanized sheet, wire and tubing will not necessarily be achieved when applied to an item that has been hot-dip galvanized. To achieve the smoothness required for a paint-finish standard, additional dressing may be required before powder coating or painting.
Please note: if undertaking further dressing of items, care must be taken not to damage the zinc coating with heavy or excessive grinding.
In order to provide a sound substrate for a duplex coating, the galvanized surface will require abrasive blasting or application of a suitable primer.
Abrasive blasting
In order to create a suitable surface for paint coatings to adhere to newly hot-dip galvanized coatings, an abrasive sweep or brush-blast may be used.
- Blast material should have a particle size no larger than 0.5mm or between 200 to 500 microns. Aluminium/magnesium silicate, limonite and other suitable mediums can be used.
- Blast pressure should not exceed 40psi to ensure the minimum amount of zinc oxide is removed.
Paint coatings should be applied as soon as possible after abrasive blasting.
It is important this operation is performed carefully as the removal of excessive zinc will compromise the quality of the hot-dip galvanized coating.
If hot-dip galvanized coatings are abrasive blasted in an incorrect manner, the coating will delaminate or peel. As this procedure is a form of mechanical damage, we do not accept responsibility should peeling or delamination occur.
Wet brush or spray
The painting of hot-dip galvanized steel requires different paint systems and preparation than uncoated steel. Not all paint types will adhere to a hot dip galvanized coating and as paint formulas vary from one manufacturer to another, a technical expert in the paint field should be consulted.
Powder coating
Powder coatings are applied by the electrostatic spraying of dry powders that are then heat-fused at moderate temperatures to form a continuous, homogeneous coating. To ensure surface treatment applications used at Hunter Galvanizing do not interfere with the powder-coating process, purchase orders supplied with items should clearly state that a powder coating will be applied after galvanizing.
Please Note: Hunter Galvanizing cannot be held responsible for the integrity of the galvanized coating on any item once a subsequent process outside of our control has commenced.
