47025

Is "pre heating" essential for powdercoating? [England] 

November 13, 2007

Hi there,
I'm setting a new plant with iron phosphate dip, which is then polyester powdered coated
I'm used to pre heating my work to ensure even cure, any gassing, thicker powder topcoat.
Will I still need to preheat?
My product is multi thickness steels ranging from 1mm-5mm thick, its situated outside and open to the elements would you recommend a zick rich primer process also.
I need my product to last and long term paint finish is essential, please please advise me on how to accomplish this.
Many thanks

Carl (a worried manufacturer)

Carl Ordidge
Buyer, designer. - Warwick, England

For external uses, steel that is powdercoated only will, not last very well.
And Iron phosphate seems the lowest possible pretreatment to use!
For long lasting in an outdoor environment you should consider to galvanize and then polyester powdercoat.
But this requires a competent pretreatment (Iron phosphate won't do, Zinc phosphate, chromate, or silane are suitable).

PC only will end up like all the cheap imported steelwork that you can see outdoors rusting away, powder peeling off, looking really sad after even some months only.

Geoff Crowley    galvanizing &    powder coating shop Glasgow, Scotland

 

Carl,

I personally believe that iron phosphate is the most widely used type pretreatment in the world. Iron phosphate does a good job and is fair priced. This is a good combination, however, you have to use the proper pretreatment for the end use. Powder coat can fail if the pretreatment is not controlled. If you have heavily soiled wash tanks or improper ph's, or improper dwell times, you will not have an appropriate surface in which to apply the topcoat. If this happens, the topcoat and it's performance will suffer.

Generally, most comapanies do not pre-heat the susbstrate because you get very uneven topcoats and you use way too much powder. When you use too much powder, you violate the powder manufacturers specifications to get the ultimate topcoat performane and cosmetics. Usually the reason for pre-heat is to get powder applied into recessed areas that are difficult to get powder into, or on MDF board where pre-heat is required.

If you control your pretreatment, and use the correct powder for the end use, you will get exceptional results. The important thing is to get the powder to adhere to the substrate which really means your iron phosphate. It's only as good as your pretreatment. If you use tap water for a final rinse and it has alot of high solids in it, your topcoat performance will also suffer. I could go on forever, but you get the messege.

Bob Utech - Brooklyn Park, MN

Editor's note:      Mr. Utech is    the author of --