In regards as to how to clean terminals with
corrosion on them, I have tried pretty much all of them from baking soda to coke, to ammonia, brake cleaner, petroleum products of several different flavors, etc.
My preferred method any more is just plain
water, but copious amounts applied when you do.
Just run a garden hose on the battery for a few minutes. No brushing or scrubbing needed unless the battery is dirty or oily, then using a rag under flowing
water will pretty much clean everything satisfactorily. Here is an example:
Tractor battery needing replacement
Same battery about 7 minutes later:
Keep in mind there was no scrubbing involved here, just water from a hose. It is such an easy thing to do if you have access to running water, and it prevent holes getting eaten into your clothes when you have to hike an old battery out.
When the new battery is in, or the terminal connections cleaned, just seal the terminals with something. You can use one of the many sprays (I do this whenever possible) or just anything that can seal out vapor- vaseline,
wheel bearing grease or clear spray
paint all seem to
work the same which is pretty good.