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Hi @Lee777,
You’ve got three different sections there, and unfortunately, they all need to be treated slightly differently to make sure the paint system sticks properly and lasts. It’s a bit of extra prep up front, but it will really pay off long term.
Starting with the blue primed RHS, that factory primer isn’t designed to be painted over, so it needs to be sanded back to expose bare steel. Once you’ve got clean metal showing, you can prime those areas with White Knight Rust Guard metal primer to work from a sound base.
For the Duragal sections, these need a different approach. New Duragal often has oils and surface contaminants from the manufacturing process, so give it a thorough clean first, then lightly sand it to key the surface and remove any remaining slicks. After sanding, wash it down with clean water and let it dry fully. Once prepped, those sections can be primed with an SLS Etch primer, which is designed to adhere properly to galvanised steel.
The bare welds need their own attention as well. Make sure you sand them back to remove any slag or residue left from welding, then prime them with a suitable metal primer such as a White Knight True Bite primer. After that, applying a White Knight Rust Guard Cold Gal Primer Paint over the welds will help restore corrosion protection in those vulnerable areas.
Once all of that prep and priming is done, you can paint the entire pergola frame with White Knight Epoxy Enamel Satin Black. For the best finish to match your satin black windows and avoid brush marks, spraying will give the most even result. If spraying isn’t an option, using a high-quality microfibre roller and laying it off carefully with a brush will still give a very tidy finish.
It’s a bit of work, but doing each section properly will give you a durable, good-looking pergola that matches in nicely with the rest of your home.
Please let me know if you have any questions.
Mitchell
For the Duragal sections, @Lee777, 240-grit sandpaper is ideal. You’re not trying to remove the coating, just lightly key the surface and knock off any contaminants so the primer can grab properly. For the blue primed RHS, you’ll usually need something coarser to get through the factory primer. Starting with around 120 grit is a good approach to remove the bulk of it back to bare steel, then go back over it with 240 grit to smooth things out before priming. For the welds, 120 to 180 grit works well to clean them up and remove any slag, followed by a quick pass with 240 if needed.
In terms of coats, more is not always better. With primers, the goal is full, even coverage rather than thickness. You shouldn’t be able to see bare steel through the primer once you’re done. Depending on how it lays on, that’s usually one to two coats, and often two is the safer option. Once you move to the topcoat, you’re again aiming for full coverage rather than building it up excessively. With a black epoxy enamel over primer, two solid coats is usually plenty. A third coat is only worth doing if you can still see the undercoat showing through anywhere.
Adding extra coats beyond full coverage doesn’t really make the finish tougher or longer-lasting. In fact, overly thick paint can be more prone to chipping and damage. As long as each coat is applied properly and allowed to cure as per the product instructions, stopping once you’ve achieved full coverage will give you the best balance of durability and finish.
Mitchell
