So I've been trying to find a rust converter to neutralize the rust on parts I cannot remove or otherwise clean. Recently here in canada our benevolent overlords in the Fed severely restricted household chemicals, making things as mundane as WD40 banned. (They did this by expanding the definition of 'volatile organic compound' to include "participating in atmospheric chemical reactions", which is absurd as it sounds. They could plausibly ban nitrogen for such a crime) All the rust converters are of course phosphoric acid and immediately vanished off the market, even amazon dropped them here.
There is one brand still in stock locally though, Rust Mort, which is 15-25% advertised acid content, at 200 bucks a gallon. However I know of dairy farm acid cleaners at much higher concentration for peanuts. I checked every farm supply place, every industrial cleaner place and any other supplier I could. Nobody carries this stuff.
But in the US of course, I can find 85% phosphoric acid at 20 bucks a gallon. Five times the concentration at a 10th of the price off the shelf, come and get it!
After spending the day trying to find a supplier, I found that place, which will ship it to me. But they only sell a palette of 4, and with shipping it'll be 300 bucks for some spicy fruit juice. Still a significant bargain, but boy does it not feel like it.
Y'all yankees don't know how good you got it. I just wish I knew to buy some on my Oregon trip.