I clean my valve pins in the summer, We have a product here called CLR. It's pretty strong stuff but it removes oxidization and scale. I mix it 50/50 with water in a small saucer and let the pins stand in it for 30 seconds then rinse well and dry. I then swab them with Deoxit and pop them back in till next summer.
http://www.jelmar.com/CLRbasic.htm

