Jeff, I use a mild chemical called Evapo-Rust. Don't know if it's available in B.C. though.
http://www.evaporust.com/evaporust.html
It will, with soaking, remove serious rust. But it's not a harsh chemical like Naval Jelly. It does remove all the patina though. I buy mine at Pep Boys auto parts store.
Steve
p.s.
Here are the distributors in B.C. if you're interested
http://www.nicks.ca/ER.dist.html