Powder for Outdoor Products

Q: We are a custom coater that has been applying powder for around three years. We have been doing almost all indoor products but we are getting an increasing number of requests to coat outdoor parts. We have a 5-stage iron phosphate washer and we are not confident that we can supply products that will hold up when exposed to outdoor conditions. Can you comment on our ability to do outdoor work and also give us advice on what we need to change in order to be able to take on this work? 

A: I can answer your questions, but let me first point out that I do not know much about how you run now or just what type of work you want to be able to do. A 5-stage iron phosphate washer could be adequate if you do a lot of other things to ensure good corrosion resistance. For example, what are your typical quality standards? Do you regularly have a lot of quality measurements that you use? Do you test for corrosion resistance? Do you ever apply two coats or use a primer coat? What level of quality can you get now?

In addition to measurement of the current quality, a clear definition of “outdoor” product would be helpful. There is a big difference between a screen door in Ohio and a boat dock in Florida. You also did not mention if the products you want to coat are made of steel or some other metal. These are all factors that should be considered when determining the best course of action. Based on the information you have supplied, here are some things to keep in mind.

For starters, iron phosphate does not add much corrosion resistance. It can do a nice job of creating a neutral surface and good bonding of powder when applied over a clean surface but does not stand up to corrosive elements very well. If your washer is built of stainless steel, you may be able to change to an enhanced zirconium oxide product that will improve your corrosion resistance. This would be adequate for lighter-duty applications that are not exposed to extreme conditions.

If this is not practical, then you will have to enhance corrosion resistance by adding a primer or second layer of topcoat. That would require running the part through twice or setting up another booth and gel oven. A second layer of coating can add substantially to performance. A blast on steel plus a zinc-rich primer can get you a much more extreme level of performance.

Since the liability factor of coating for outdoor performance is much more challenging than indoor work, I suggest you proceed very cautiously. Consult with your chemical supplier, make sure you have the right quality measurement in place and test any changes to be sure they are effective. Avoid extreme performance such as architectural aluminum or seacoast installations. Tread carefully!