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Best finish for tubular steel park benches?
November 10, 2009
I have 2000 square 11G steel tubes 71.25" x 2" x 2" with welded end caps I need refinished. They were powdercoated with no primer at all and the paint is flaking, the bar is rusting. The tubes go to outdoor benches made of 6 tubes each and are exposed to NYC winter and salt spray from cars. Being that the finish is supposed to look nice, what is the best way to protect this material. We are investigating Hot Dipped and then powdercoated, but have found no one willing to do the work. Or would a plastisol finish be the best bet to get a nice "finished" look?
Any info would be greatly appreciated. Thanks.
- New York, NY, USA
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First of two simultaneous responses -- November 11, 2009
Proper powdercoat is still probably the best way to go. I would check to see if it was possible to grit blast the tubes clean, use a good primer and then use the correct powder for the task. There is a huge amount of powder blends on the market now. Some shops prefer to use only what they have in stock or are used to doing, rather than the best choice.
Since the ends are capped, people that have systems that require
"dipping" such as galvanizing,dipped vinyl and plastisol will not want the job as they will want to float. They may also hold a large amount of the coating inside and that is an excessive cost.
If the rust is bad, grit blasting may eat completely thru the tube. Grit blasting may be ok to remove the old paint, or you may have to use a high temp thermal process.
I would price both new and repaired as new may be cheaper. You could use galvanized tube on the new. It requires a special primer for optimum adhesion to the galvanize, or it will peel earlier than desired.
- Navarre, Florida
Second of two simultaneous responses -- November 11, 2009
Hot dipped and powder coated would be ideal. Can't find any one willing to do the work? Send them to me! We do a great job here in Australia.
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Bill Reynolds consultant metallurgist Ballarat, Victoria, Australia It is this website's profoundly sad |
November 12, 2009
So then, this would make you the first person in the history of NY that has had a project like this? :-)
If this has never been done successfully, where are you going to find the magic dust that will give you the edge? If it has been done successfully, research the process and duplicate it.
The primer for powder coating is a properly pretreated substrate, if the powder coating on the product that you have now is flaking, the substrate was not pretreated properly (is it failing before it even gets installed?) or the paint is undercured.
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Sheldon Taylor supply chain electronics Wake Forest, North Carolina |
November 16, 2009
Thank you for your responses. This product has 1 NYC winter on it. I sent one of the tubes out to a plastisol applicator, and his determination was the tube IS primed. So, he agrees it was a preparation issue. The majority of the powder on the tube is adhering very, very well, and he questions the expense of getting it off. I will get that quote soon. I will also quote new tube.
Is zinc based powder primer a good alternative to electro plate galv or hot dipped galv?
Street Furniture - NYC, NY, USA
November 17, 2009
Hi, Brian. Putting zinc on a steel item sacrificially protects it so it will not rust in a scratched area and will last longer. A zinc based primer is one way to do it, but is still easily scratched through to the steel, and not the equal of zinc plating under the paint, which is not the equal of hot-dip galvanizing under the paint -- primarily because of the weight/thickness of the zinc.
Regards,
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 Ted Mooney, P.E. finishing.com Brick, New Jersey |