Doing a little wiring cleanup

Over a year ago I wired up a Merc. Mystique fan, a Ford PDB and a grounding bus bar near my 2nd battey.
My new mission is to extend and re-route all of the loomed wiring to under the battery, then along the firewall.
Last night I pulled the batteries and removed the rubber insulating mat and there it was, powdered oxidation on the battery shelf. Removed it and brought it to work today to grind out the corrosion and coat with POR 15 and paint.
At least with this out of the way I have easy access to the spark plugs and plug wire and all of my ancilliary wiring to to keep it out of the engine compartment.