I also might add that when I started seeing corrosion like you have described I am probably gassing out of my batteries from being over charged. For me everything is now managed using smart mode charging techniques which doesn't boil out my batteries any more and my battery cable connections all look just fine.
I took extra care not the mutilate the ring terminals or break down their protective covering when being installed so that they will not show signs of corrosive actions against the bare metal scratches or breaks... Using the adhesive heat shrink end covers also keeps the weather from doing harm to your cable ends as well...
Leaving your cable ends like this whether you have use a crimper tool or hammered in place will not last very long being open to air and corrosive gases.. These need to be covered with adhesive heat shrink material.
Photos from GOOGLE Images
just my thoughts of course...
Roy Ken