How can rust be removed from a glass Cylinder?

I have an ultraViolet water sterilizer for my well water. I recently changed the sterilization bulb. I had the water tested but i had 3 cloraforms in it. I took the unit apart and noticed a glass cylinder was all over Rust.The rust is so bad that the sterilization light could’nt shine through to pureify the water so i replaced it at a cost of $90.00 about what i paid for the sterilization bulb. The Sterilization bulb slides right into this glass cylender.
I would like to know the best way of removeing this rust from my old glass cylender because i will keep it as a spare .
Thanx in advance