Letter 24110

Kynar vs. Powder coating  

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I have four cast iron bollards scheduled to be installed (exterior) at our Harlingen Campus.
The department wants a Kynar Finish. I believe that a Powder Coating will provide an equal if not better finish and will last long.

I need data that I can use to prove my opinion. Can you help?

Tom J
University - San Antonio, Texas

Dear Tom:

Kynar is PVDF based coating which is guaranteed for 20 years of environmental exposure. Normal powder coatings are nowhere near it - to the best of my knowledge. I am afraid, you may not find what you are looking for.

Gurvin Singh Coatec India - Mohali, Punjab, India

Would any one tell me more details about "Kynar" & its application..... thanks

Atul Bhide
jobshop / applicator - Mumbai, India

Hi Tom,

With the correct pretreatment and application, powder coatings are available with a guarantee for 25 year environmental exposure. These powder coatings have been available for a long time and are common in Europe. Hope this helps.

Drew Devlin
- North Lincolnshire, U.K.

Is Powder coating on steel as effective as on aluminum for preventing corrosion and maintaining color uniformity and luster? Exterior exposure.
For how long?

joe mercolino
ceilings - Los Angeles, California

Hi, Atul. Kynar is a powder coating, but it is thermoplastic rather than thermoset, and usually applied at far greater thicknesses than typical thermoset powder coatings. I have only seen Kynar coatings applied at one shop, so I am not really an expert on them, but they were applied from a fluidized bed rather than by electrostatic spray; my book knowledge supports that this is the typical approach.

Joe, please read Drew's entry very carefully because it implies some stuff that experts like him realize, but most people don't: it's all about the pretreatment! If appropriate and high quality powder coatings are applied to properly pretreated materials, the durability will be excellent. But no matter how exotic the paint or powder, if the pretreatment isn't good, the coating will be crummy. Steel parts require a well done phosphatizing step and possibly electropainting before powder coating. Good luck.

Ted Mooney, P.E.  finishing.com Brick, New Jersey

what is the difference between thermoset and thermoplastic treatment for powder coating?

zia ullah khan
- Dubai . U.A.E.

July 2008 Hi, Zia. Thermoset plastics are plastics that cure into a different state than they started in. Sort of a one-way street. Once they are set they can never return to their original condition, you can't usefully melt them. Thermoplastic materials are plastics that soften with heat, repeatedly. If you formed a block of thermoset plastic, it would stay in that shape forever; if you formed a block of thermoplastic material you could, in theory at least, form it into a different shape the next time you applied heat. When it comes to using these plastics in powder coating, the biggest differences seems to be that thermoset materials can be thin (a few mils) whereas thermoplastic coatings are much heavier; and thermoset materials are usually applied by electrostatic spray, while thermoplastics are usually applied by fluidized bed. Regards, Ted Mooney finishing.com Brick, New Jersey June 4, 2009 PVDF or kynar being a brand name, is a coating that can carry a lengthy warranty relating to color & gloss retention. A schedule of loss is applied to the product. mechanical failure is generally not part of that. Warranties never apply to steel products. My advice is to sandblast the item white, handle minimally with clean gloves, Zinc prime, checking substrate temperature, powder coat with a finish product of SD quality polyester or TGIC free Sd polyester. Read any warranty. The 7 p's apply to powder coating. Prior Proper Planning Prevents Piss Poor Performance. Also know that Kynar or PVDF is not usually the recommended product on traffic & heavy contact areas by the reps I have dealt with. This comment is a personal opinion & not extended as fact. Sheldon Pineo - Fort Myers, Florida