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topic 214

Powder Coating Exterior Aluminum Fences


(1996)

Our powder coated flat black outdoor aluminum fence is having a problem with the black paint coming off onto our hands after only two years from the date it was installed. We have found out that the powder coating was a silicate-filled epoxy rather than polyester. Can you tell me if polyester is the preferred powder coating for outdoor use in the industry and what can be done to correct the problem.

John Marin



(1996)

Epoxy powders are not suitable for outdoor use as they are not UV stabilized. Polyester powders are in fact ideally suited for this purpose. I would recommend that John dismantles his fence and has the epoxy coating removed(either by chemical stripping or abrasive blasting),The fence should undergo a multiple stage cleaning and pretreatment process which should include a chromate or chromate phosphate conversion coating(chrome free conversion coatings are now available) prior to polyester powder application and cure. This method should give a quality finish with excellent adhesion and weatherability.

Paul Abbott

(1999)

Regardless of whether it is an epoxy, hybrid, or polyester, powdercoat will still breakdown leaving a chalky residue.  The epoxy & hybrid will of course breakdown quicker.  powder is still only a paint, in fact it is a wet paint before it is dried and converted to powder.  All paints, including powder, require maintenance to prevent the attack from the environment, particularly the harmful UV rays from the sun.

Michael Lind
- Queensland, Australia

(2005)

As a manufacturer of a galvanized and powder coated pipe fence, I have to disagree with Mike. Although most powder coating will turn chalky, The reason for this is that they do not have enough UV inhibitors. We ran into this in early stages of R&D and now with a much better powder coat do not have this problem. I have some black fence ON the Gulf of Mexico (for about 5 years) in the salt water and haven't had any fading or chalking.

Monty Taylor
- Covington, Oklahoma



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