Q: We are a custom coater who has been applying powder for about three years. We manufacture almost all interior products, but we are receiving an increasing number of requests to coat exterior parts. We have a 5 stage iron phosphate washer and we are not sure we can supply products that will withstand outdoor conditions. Can you comment on our ability to do exterior work and also advise on what we need to change to be able to undertake this work?
A: I can answer your questions, but first let me point out that I don’t know much about how you currently operate or what kind of work you want to be able to do. A 5-stage iron phosphate washer might be fine if you do a lot of other things to ensure good corrosion resistance. For example, what are your usual quality standards? Do you regularly have a lot of quality metrics that you use? Do you test for corrosion resistance? Do you ever apply two coats or use one coat of primer? What level of quality can you get now?
In addition to measuring current quality, a clear definition of “outdoor” product would be useful. There’s a big difference between a screen door in Ohio and a dock in Florida. You also didn’t mention if the products you want to coat are steel or some other metal. These are all factors that need to be considered to determine the best course of action. Based on the information you provided, here are a few things to keep in mind.
For starters, iron phosphate doesn’t add much corrosion resistance. It can do a good job creating a neutral surface and good powder adhesion when applied to a clean surface, but doesn’t hold up very well to corrosive elements. If your washer is made of stainless steel, you may be able to upgrade to an upgraded zirconium oxide product which will improve your corrosion resistance. This would be sufficient for lighter applications that are not exposed to extreme conditions.
If this is not practical, then you will need to improve the corrosion resistance by adding a primer or a second coat of finish. This would require running the room twice or setting up another booth and gel oven. A second layer of coating can significantly improve performance. A blast on steel and a zinc-rich primer can give you a much more extreme level of performance.
Since the coating’s liability factor for outdoor performance is much more difficult than indoor work, I suggest you proceed with a great deal of caution. Consult with your chemical supplier, ensure you have the correct quality measure in place, and test any changes to ensure they are effective. Avoid extreme performance such as architectural aluminum or seaside installations. Tread carefully!