I'm spinning this off from the Slightly Marinated Moulton thread as I fear this might get lost otherwise:

I recently picked up a Moulton Mk.I ('65, US/Huffy model) with a later of surface rust over it. I knew I could dunk this frame in a pool of OA, but I was curious if there was an alternate method that would be less labor intensive and use less water.

In the past, I've used the "soaked rag in Goo Gone" approach for soaking a stubborn sticker, and started wondering whether an application of oxalic acid could be applied in the same manner, using the aforementioned soaked rag or paper towel to conform to the surface and suspend the solution for long enough.

I decided to give it a try on the Moulton. Here's what it looked like to start with:







I mixed up some OA (probably too much) in a 1/4" deep container of water for dipping.

With a glove, I lightly dipped a triple-folded-over paper towel into the mix, let the paper towel soak for a second, then pulled it out. (If you try this and get too much water in the mix, squeegee the excess back into the container). I layered it over the Moulton like paper mache:



I've done this twice, and each time left these on for about two hours. One of the rags in the second round had dried up by then for some reason (the others remained wet), but it did the job.

Here are the results after neutralizing with a similar rag soaked in water and baking soda, followed by a wipe with WD40, then a dry-down, Meguiars' #7, and wax. Don't let the extra steps fool you; the result you see is basically what you get at the baking soda stage; I just chose to polish and wax it to help seal the paint.



The remaining rusty areas haven't been soaked yet.





Nighttime pic for contrast:



Note that this didn't make the paint entirely smooth, of course - there's still spiderwebbing, but the stains themselves are gone. The rear fender cleaned up the best, while the front is the opposite, and shows the type of surface one could have at the end of the cleaning:




Regardless, I think this counts as a win, and a perfectly workable, alternate method of clearing up surface spiderwebbing rust in a more localized way (with less risk to waterlogging the paint and decals) than an outright OA bath.

I'm curious to see the results of anyone who tries this - I know pastorbobnlnh already mentioned to me that he's going to give this a try on his Schwinn New World.

-Kurt