I've used Evapo-Rust as well. It works, too, but it more expensive and somewhat less effective than oxalic acid, in my experience. Recently, I did an overhaul on one of my keeper frames and was concerned about rust inside the tubes. Sometimes oxalic acid can leave a residue on the paint, especially if the top/clear-coat is not real smooth. In this case, I didn't want to take any chances with the oxalic acid leaving a residue on the paint, so I got some rubber plugs and filled the frame with Evapo-Rust. Worked well, and I'd use it again in certain cases. For small parts and for frames that need a deep soaking in & out, I still prefer oxalic acid.