I have a plastic slinger (hdpe, I believe) that is attached to a dishwasher motor shaft that I'm trying to disassemble so that I can replace it's bearings. The sling will twist independently of the shaft, but it won't come off. I've been thinking of hitting it with a penetrating catalyst (PB Blaster) or possibly some acid (maybe naval jelly, possibly a soak in a strong citric acid solution), but, if memory serves me correctly, both will do a lot of damage to plastic. I'm pretty sure, if I'm careful, I can keep whatever I'm using off the aluminum, but I have no idea how to de-rust/loosen this. Any ideas?