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That sounds pretty easy. Do you have any experience with that method ?
Do I need a plastic or metal swimming pool? How long must the frame soak in the acid. And in which concentration or strongth, I have seen oxalic acid is sold in 1 Gramm Pills.

You get the stuff at a marine supply store. I hope you have one there. If not you might be able to get it online. Cheap, like ten dollars for more than what you need to do the job. Just dilute it according to the directions. It's mild stuff for bleaching the wood on boats. Plastic tarp or a shower curtain over a brick frame or a hole will do if you don't have a tub. It will get rid of surface rust, but the pitting will still be there.

Thank you. I will give it a try next week.

There's more info if you search online. It's nowhere near a rechrome job, but I've seen pretty good results. Stay away from Naval Jelly. That stuff turns the rust area black due to the chemical reaction it produces. It will look uglier than before.