Pre-Treatment, metal preparation or surface preparation is either chemical or mechanical treatment in order to provide a perfect finish to powder coated items.
This includes the removal of dirt, grease and oils using chemicals. These may be applied simply by wiping or spraying. The chemicals used will differ dependant on the base metal.
This could be either abrasive scratch brushing or blasting. This erases both impurities and improves the surface by removing scratches or irregularities. Once mechanical cleaning is completed, surface coating must be undertaken quickly to avoid corrosion on the metals.
A conversion coating is applied in order to prevent corrosion before powder coating application, to promote good adhesion of the powder and to extend the life of the final finish. The type of coating is dependent on the base metal.
TYPICAL PRE-TREATMENT PROCESSES
Stage 1: Pre-Clean
All parts are hung individually on our track system in the preparation area before being steam cleaned to remove grease and dirt. Once parts are hung on the track system and cleaned they are not touched by hand until the powder coating has been applied and has cooled.
Stage 2: Acid-Etch
An acid etch which is used to remove any remaining grease or oil which can remain on galvanised parts. It is also used to remove white rust and oxidation from mild steel.
The acid etch is diluted to the desired strength before being evenly applied to parts using a hand spray system, it is then left in place for the required time, before being evenly applied to parts using a hand spray system.
Stage 3: Removal of Acid Etch
All parts are then steam cleaned to remove the acid etch from surface.
All parts are then inspected to ensure there is no remaining debris.
Stage 4: Application of Primer
A primer is applied to ensure a good adhesion between the surface of the parts and the powder coating.
The primer is diluted to the desired strength before being evenly applied using a hand spray system, the primer is a dry in place substance and is not removed from the parts.
Stage 5: Drying
Treated parts are then moved along the track system into the oven for drying and curing at a temperature of 190°C (+/- 5°C) for 15 minutes. Parts are then removed from the oven and moved along the track system into the spraying area and allowed to cool.
The complete process depends on the material to be coated.
MILD STEEL PRE-TREATMENT