I have some 9 pin noval Western Electric tubes with badly oxidized pins. At first I thought the heaters were burned out because of the oxidation! I tried soaking the pins in vinegar overnight but that had no effect. Tarn-X, Bleach, and a paste made from non abrasive cleanser all had no effect. Even scraping the pins with a knife blade doesn't accomplish much. The specs say the pins are "Sylvania alloy number 4", which is made from nickel, iron and chrome. My next thought is chrome polish or a small wire wheel in a dremel tool.