Painting metal can be a unique process that is sometimes very similar to wood or drywall and sometimes extremely different. The key to success is knowing the right prep and paint for the right application.
Just like there are a plethora of different paints in the world, there are a ton of different types of metal you may be painting and they all have their unique quirks. Aluminum, steel, galvanized steel, copper, brass, iron, none of them are the same and they all deserve a slightly different treatment.
This post was sponsored by my friends at Krylon. Krylon makes some extraordinary options for painting different types of metals and you should definitely check them out since I have used their products with great success over the years myself.
Tip #1 Prep Old Coatings
It doesn’t matter what paint you’re using or what metal you’re painting if you don’t properly prepare a previously painted surface. If you’ve got chipping or peeling paint then that has to be addressed first thing. Scrape or use a wire brush to clean the surface then sand the surface smooth. Remember that your new paint is only as good as the substrate you apply it to, so if you paint over failing paint then your new paint will be carried away with the old stuff as it fails.
Always be careful if you are working on a project that is older than 1978 because there is a chance it may have lead paint. You can read about how to properly protect yourself from lead paint in my earlier post, Lead Safe Practices.
Tip #2 Clean the Surface
When painting metal some paints will claim no cleaning or prep needed. I’m not buying it. If the surface is dusty, oily, greasy, or otherwise gross then it needs to be cleaned prior to painting. Dampen a cotton rag with TSP cleaner and wipe the surface thoroughly until you get a clean rag.
I find that sometimes after the heavy cleaning that TSP provides a quick wipe down with acetone is also helpful to remove any remaining residue. If the metal surface passes the white glove test with your rag then it’s ready for painting.
Tip #3 Scuff Shiny Metal
Maybe your metal surface is not dirty or peeling, good for you! But if it’s a shiny, super slick surface then it still needs a little help before painting. Using a pad of Steel Wool (grade 0 or 1) will scuff the surface just enough that you’ll give the paint something to adhere to which yields a longer lasting paint job.
Tip #4 Don’t Paint in Direct Sunlight
If you are painting metal outside then avoid direct sunlight during application and immediately after. Metal is a great conductor of heat and (especially in southern climates) that means the surface can get much warmer than is conducive to paint adhesion. The paint will bubble or peel almost immediately if you try painting a sun drenched hot piece of metal so plan accordingly.
I recently did an attic vent restoration project and I had to be extra careful to paint on a shady day since it was on top of my roof. Grab a shady spot or work around the sun to avoid that heat.
Tip #5 Deal With Rust
Rust is metal cancer. You can’t just paint over it and expect it will go away, I promise it won’t. Rust will continue growing under the surface, doing damage unseen until it causes bigger problems.
Deal with rust by sanding the rough spots off and then use a rust treatment or a rust inhibiting primer like Krylon’s Rust Tough to transform the rust into something that is paintable before painting metal. You may think you’ve sanded the rust off, but even though you don’t see any remaining I would still act like it’s there if you are painting a ferrous metal like steel or iron because the rust is likely still there just in microscopic scale.
Tip #6 To Prime or Not to Prime
Priming metal has some specific rules you need to know if you want your paint to last for long. Priming is always helpful to encourage adhesion of your paint, but it is not necessary in all cases so the decision is ultimately up to you. Some metals absolutely require priming and here’s the breakdown below.
Ferrous Metals: These metals should always be primed for the best and longest lasting paint job. Anything with iron content is considered a ferrous metal. The quickest way to test is if the metal responds to a magnet. Ferrous metals include:
- Wrought Iron
- Cast Iron
Stainless steel is technically a ferrous metal but it behaves completely differently and doesn’t need priming.
Non-Ferrous Metals: These metals have a built in corrosion resistance and unless they have a slick shiny surface they usually don’t require priming.
- Precious Metals (Silver, Platinum, and Gold)
- Copper, Bronze, and Brass
- Nickel, Palladium, Platinum
- Tin, Lead
Galvanized Metals: Galvanized metals present a unique challenge since they are usually steel coated with zinc as a protectant. Over years as the zinc wears off the metal may show signs of rust and need painting to keep it from rusting. In this case you CANNOT use any alkyd primer due to an odd reaction with the remaining zinc called saponification which causes very quick failure of the coating.
When painting galvanized metals you need to prime with a high-bond acrylic primer only.
Tip #7 Spray Painting or Brushing
When it comes to painting metal I’m a huge fan of spray painting over brushing because you can always get a smoother finish. My go to paint is Krylon Fusion for hard wearing projects due to its incredible adhesion and Krylon ColorMaxx for more decorative projects due to the immense color selection.
Here’s a few bonus tips for spray painting metal like a pro:
- Keep the nozzle 6-12 inches away from the surface
- Select a calm day with minimal wind
- Mask off the area using drop cloths or masking tape if needed to avoid overspray
- Paint only in a well ventilated area
- Apply 2-3 medium thickness coats of paint letting the surface dry completely between coats
- Painting too thin will leave a rough texture and not provide sufficient coverage
- Painting too thick can result in runs and drips
If you follow these 7 tips you’ll be a better metal painter than most DIYers and you’ll have a paint job that lasts for the long haul. If you haven’t tried Krylon’s line off spray paints I can’t recommend them enough. They have helped me restore everything from vintage hardware to gates to attic fans and the uses just keep coming. You can find out more about their products right here.
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I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.