A bit of a curve-ball, but I bought some of this an age ago:

https://www.trade1st.co.uk/trade-str...FYrLtAodwzUAAA

It worked wonderfully for it's intended purpose (removing graffiti) but recently I used it on a small section of old-school powder-coat. I left it on for 20 minutes or so, after which the coat slid off - I barely needed to touch it.

For something that's safe/non-solvent/smells of apples, it's ridiculously powerful.

Wal.