Battery corrosion

I use agm's in all my vehicles and have not had any corrosion on the posts. Clean the post and connector as desert captain said. Be careful not get any of the baking soda into the battery through the caps. You can buy a small can of battery terminal protection spray at walmart or just about any auto supply. If you spray the connector and any exposed wire thoroughly it works very well. Or, you could coat it with dielectric grease. That would attract dust and dirt, but at least it would not corrode.

The answer to your question is baking soda. Mix a tablespoon into a cup of water and use a throw away paint brush to paint it on to the corroded terminals. Rinse with fresh water and wipe dry. It is also a good idea to pull the ring terminals off of the post and use a little sandpaper (wet or dry), to eliminate any remaining corrosion.

AGM's are amazing batteries but for the vast majority of RV'ers, as in those not full timing, they are simply not cost effective. Wet cells, I like Trojan's, will give you far more amps per buck and the maintenance is minimal. KISS. :C

Yes, AGM batteries. Overcharging is a common cause.