I was doing this to my 2007 Ford chassis battery today and later wondered why not share this with the community.
To permanently eliminate battery terminal corrosion on conventional lead acid batteries, clean each terminal and surrounding area well. At the base where the lead metal meets the plastic battery case, apply a layer of silicone rubber caulk like this. Let cure for 24 hours, then you are good to go. You will never have to worry about corrosion on the terminals again until you replace the battery.
What happens over time, the seal between the dissimilar materials (lead and plastic) fails. Then acid wicks up the lead terminal to the outside and corrodes the connection.
Stores sell a quick fix, those red and green felt washers. They absorb the acid until saturated, but the silicone caulk eliminates the problem at the source. It is a permanent solution. Just be sure to leave adequate lead terminal exposed for your battery cables to attach. If you over-did it like I might have done here, you can always trim it with a razer blade.