[N1rve]

The red is battery terminal spray. You're supposed to spray it on the post (under the terminal) and not on the actual terminal.

Usually this happens on the POSITIVE side so I would pop that side off as well and check under there.

If you clean it and it comes back at an alarming rate, check the battery for leaks. On my Corolla (rarely driven), the positive side kept getting corroded at a really fast pace. Every 3 days I would need to clean it again. I bought the spray and sprayed it on (just like in your case).

What I found out was that the seal between the post (positive side) had failed, the post CAME OUT OF THE BATTERY. The corrosion was so bad I had to replace the ENTIRE positive side because it welded the terminal to the post.