I picked up a very clean frame for my commando. it was sandblasted and primed. There is some surface rust. What would be the best way to remove it other than sandblasting? Should I just use POR 15 or something similar? I'll get some better pictures tomorrow.
You should remove the rust rather than covering it. I used a rust converter, Ospho, on some rusty parts and it worked pretty good.
Remove any heavy rust and then use a paint brush to paint the Ospho on and let it sit overnight. The rust will turn black. Then use a wire brush and/or wire wheel to clean that off. It came off pretty easy for me. A second application if necessary, then wash and dry it.
I used a paint on primer instead of spray on so I could work it into any hard to reach areas but whatever works best for you.
I second a product like Ospho. I scrub lightly rusted areas like I see on your new frame with a green scuffing pad soaked in Ospho. It will remove 99% of that light rust. I would then paint the frame with Rustoleum (rusty metal primer, then black). I’m not a fan of POR 15 unless you want rust blisters under the paint a few years later.
Southern Polyureathane’s “black” is also a very good product for chassis coating.