Steel yourself – can I use powder on steel?
Powder Coating steel – the do’s and don’ts.
Powder coating aluminum is pretty straightforward. The AAMA coating specifications outline what you can expect from any organic coating applied to architectural aluminum, and warranties up to 20 years are supplied when applied to properly pretreated aluminum by a certified applicator. Easy.
But what about steel?
Navigating coatings for steel is simply not as clear cut, and there are often many questions. Can you use environmentally responsible powder coatings on steel? Are there limitations? Will you get a warranty? Should you spec a primer? Are their limitations on colors and effects?
Check out our ten most frequently asked questions about powder coating steel and the answers you need to ensure your coated steel performs to the highest standards and looks great!
1. Can you powder coat steel?
You’ve probably already guessed the answer to this one (otherwise a top “ten” would be pointless!) but yes, you can absolutely powder coat steel. Powder coatings are used on steel used in a wide variety of applications from high quality windows and doors, to structural pieces. Outside of the architectural industry all sorts of steel applications are powder coated, many of them exterior, including aerial work platforms, cranes and trailers. Architectural grade powders for steel include high performance Fluoropolymers, high performance Super Durables and interior grade Standard Polyesters.
2.What types of steel can be powder coated?
Most types of steel can be powder coated. Some types are easier than others and the pretreatment might vary depending on the type of steel and whether it is and exterior or interior application, but steel can be powder coated and the powder is actually applied in the same way. It’s a factory applied finish; the steel is prepped, the powder is electrostatically applied and then cured in an oven. Simple.
3. What type of preparation should be performed on the steel before powder coating?
For any exterior use, the preparation or pretreatment, of steel is incredibly important. The most common concern when using steel is corrosion. Proper preparation and pretreatment is the first step in trying to prevent corrosion. To be honest, it’s not as simple as the great pretreatment options that exist for aluminum, but good substrate prep on steel is still essential. Depending on the type of steel you are using, zinc, iron phosphate or zirconium pretreatment can be used, or if sandblasting is the method of prep, a white metal blast. After pretreat or blast, a zinc rich powder primer should be applied
4. Should I use a primer on steel?
For exterior applications, absolutely. For interior applications, it’s not as essential in terms of weathering, but does help add a layer of protection and provides a good, smooth surface to powder coat. The good news is it’s not a chrome based primer. High performance liquid coatings MUST use chrome based primer – they simply don’t perform without it (and yes, it’s the nasty variety – bad for people and the environment). Powder coatings never require chrome based primers. For steel substrates used in exterior applications we recommend a zinc rich IFS powder primer to add another level of corrosion protection before the IFS powder top coat is applied.
5. Does the system require a certified steel prep or applicator?
Applying powder to steel is not a proprietary application system, however for exterior pieces, to ensure good pretreatment and application a certified applicator is recommended. It’s slightly different to coating aluminum due to the warranty issues involved (see below), however as good substrate prep and application is so important in preventing corrosion and maintaining color and gloss over time, having a coater who knows what they are doing and has a good quality preparation and application system and oven is a no brainer.
6. Are there limitations on colors and effects?
The great news here is the answer is not really! The rules for coating aluminum still apply. So, for exterior applications where high performance Fluoropolymers are required, some of the brighter pinks/purples, oranges and reds are more difficult to achieve. This is simply because the pigments that will meet the 20 year color retention requirements in these brighter shades are not available. Other than that there is a lot of choice and mica/metallics and some textures are also available.
With Super Durables or interior grade Standard Polyester powders, the world is your oyster! There’s a huge range of colors and effects available – at IFS we have over 55,000 colors in our database so there’s plenty to choose from!
7. Are the environmental benefits of powder the same if applied to steel?
For the most part, yes! The benefits of the actual coating – no VOCs, no toxic compounds, no toxic waste created in manufacture or application, no chrome required, etc. are exactly the same. Where it may differ slightly to powder coating aluminum is in the number of coats. Adding a zinc rich powder primer obviously adds another layer of coating – and this may add another cure cycle which means more energy used. However IFS has developed IFS Co-cure, which uses clever formulation technology so that 2 coats of high quality IFS powder can be applied with only one cure cycle. Talk to your IFS representative to see if this is available for your application.
8. What are the steel section size limitations?
Really the only limitation is the size of the powder coaters’ oven. Many coaters working with steel parts have extremely large ovens for this reason.
9. Will I get a warranty for coating performance on steel?
The simple answer in this case, unfortunately, is no. At least not from the coating manufacturer, though the applicator may provide a warranty. The reason for this is to do with the substrate and the corrosion problems that can occur with steel, more than the coating. On aluminum, the coating is designed to deliver specified levels of salt spray and humidity resistance and will do so as long there is a quality application and proper pretreatment is in place. The pretreatment is incredibly important in providing corrosion protection. With steel, the issue of corrosion is much bigger, and so while the coating is exactly the same product as applied to aluminum, the pretreatment options are not the same.
10. Can I touch up powder coatings on steel?
Yes! Just like on aluminum, spray on coating in an aerosol can is available to touch up powder coated applications. They are liquid solutions – imagine how difficult it would be to cure powder on site – and they work great!
There is so much information and expertise available to you from IFS, so if we haven't answered your questions here or you need more information on IFS architectural powder coatings talk to your IFS representative or contact us.