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Galvanized fencing bubbles up after powdercoat

RED I am currently powder coating a galvanized fence should I gas the product out and then hit it hot or should I let it cool completely before coating.

Rick Douthit
powdercoating job shop - Cincinnati, Ohio, USA
July 15, 2008

July 16, 2008

Before powdercoating galvanized steel, you need to pretreat it, or the powder will fall off in a short time.

I'm not sure what you mean by "gassing it out", but without pretreatment it would be a waste of powder.
The pretreatment might be a chromate, a phosphate, a silane, or at minmium perhaps a phosphoric acid wash.
Adequate drying after pretreatment before applying powder is necessary.
Spraying on hot steel will only cause a thicker coating, not ensure adhesion.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

July 16, 2008

De-gas and shoot whilst the metal is still quite warm to the touch. Many European coaters use a solution called T-Wash prior to PC galvanised substrates. A good read would be to visit http://www.hdg.org.uk/103_Guidelines_-_Pre-treatment_for_Painting.php
It may give you some pointers re coating galvanised metal. It also supplies the basic formula for T-Wash and how to use.
Just a point of caution, don't confuse the bubbles due to gassing with bubbles due to back-ionisation.

Terry Hickling
Birmingham, United Kingdom

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