Powder Coating vs. Liquid Paint

A. Hi Ryan. If this is a mass production item, I think it should probably be electrocoated with epoxy followed by powder coating with polyester; but getting the parts electrocoated may be a logistical problem if it's a onesy-twosy product because electrocoating is done in specialized automated processing lines.

Wet painting is not necessarily better or worse than powder coating, and often the same coating material is applied by the two methods. If the coating is flaking it's possible that the housings were solvent wiped instead of properly phosphated.

Luck & Regards,

A. Hi. The corrosion resistance of wet and powder coated paint is not significantly different -- many times they use essentially the same pigments, resins, fillers, etc. -- it's just that powder coating usually tends to be a bit thicker. Because you anticipate touch ups, I'd probably go with the wet.

More important is the pretreatment; if properly phosphatized it will be far superior to solvent wiped, so if you can get precoated sheet I think you'll be better off than doing a field applied primer. But direct burial and probable use of fertilizer in a planter are two strikes against you, so I believe you should strongly consider either pre-galvanizing & phosphating, or phosphating & e-coating before considering either the wet paint or the powder coating.

Luck & Regards,

A. Good question. I can't get anyone to directly answer this either. Seems there are too many variables, however, I talked to a very knowledgeable exhibitor at Coating 2003 who gave me the best answer I've heard. He explained that he dealt with a manufacturer that needed 1500+ hours salt spray and they used liquid paint. The application of the liquid paint required very technical methods and professional applicators using instruments for film thickness and consistency during application, among other things.

As I understand it, if you can achieve this kind of application then liquid paint probably gives better salt spray for this high hour result but that powder coating provides a lesser but still good result more consistently and easily.

I'm far from an expert and I would like to hear from the experts on this one. I'm only looking for an understanding for myself so that I can honestly answer the question for my powder coating customers.

A. We have gone through the same problems when finishing steel sculptures that were displayed outside. The biggest problem we found was the u.v. protection the material provided. Powder coat will look good for a time, but it goes flat from oxidation when exposed for a prolonged time. marine paint does a better job if you get the right type of paint that has the u.v. protection in it. If it doesn't, you might want to consider clear coating your project. Any of the big automotive paint makers carry this kind of product. Also, looking at the big picture, if you ever need to repair any of these poles, you can refinish them on sight with a much better finish and blend if needed.