Check your voltage under charging conditions. Too high and you can see actual acid residue out of the battery.. Basically they are boiling out some of the electrolyte in those situations. The normal out gassing when charging does not seem to be too bad in comparison under the hood usually.

Also I have forgotten where copper is in relation to steel. I used to place a few real copper pennies on top of my battery to sacrifice themselves over the terminals and their cable connections being attacked.

If the copper or whatever you can find to use as a sacrificial anode perhaps zinc. Is placed on the battery tray it might aid in protecting it.