Just to clear things up, North American molasses = British treacle. Sounds like a plan if you can't find oxalic acid. I had no luck finding any hardware store or building supply that knew wood bleach or oxalic acid, but finally located some on line at a taxidermy supply site. One word of caution: Be sure to degrease the parts thoroughly before trying rust removal solutions. Rust removers are not degreasers, so if the parts are oil soaked, you'll still have black spots of rust that remain. I found this using oxalic acid on a rusty steel crankset.