I'm a huge fan of OA bathing for parts, but have found that frame surface rust is *far* easier - and more thoroughly - addressed with pink Naval Jelly applied thick and "worked" with a bristle brush for about 20-30 minutes before a simple rinse off -- gets you right back to bare metal. Immersion in OA will get there eventually, but I've learned that some delicate paints (looking at you, blingy 1970s italian frames) suffer discolouration from so long in the OA.