I use Detoxit to clean connections.
http://www.deoxit.com/

For connections subject to corrosive environments, after reconnecting, I coat them with a thin covering of dielectric grease.

I suppose that for spade connectors you could try encapsulating them - say painting them with clear nail polish, or a blob of silicone caulk. If you block the ability of O2 to get to them, you will slow down the oxidation and buildup of crud.

Todd
'88 Westy