Could this be battery acid leaking? It will scrub off with simple green. I did that 2 months ago and it came back.

 

Yep! I'll bet it is!
My 97 has a similar funky pattern from the spewed acid mist from the deceased batteries.
Mine is obvious it came from the batteries as the mist got entrained with the airflow that escapes from between the gap of the hood and fender while the truck was in motion.
Prev owner replaced both batts shortly before I bought it but the paint damage was already done.
From your pic I see a wet spot around one of the battery caps...
Maybe you just washed the truck and it hasn't dried yet, I hope.

I have seen many, many strong recommendations here on DTR and also on TDR to replace that leaky pair of wet cell style batteries with the new style sealed cylindrical cell batteries (Optima type batteries). Owners that did wonder why they waited so long!
I guarantee you, when one of my existing pair of wet cell batteries rolls belly-up, I plan on dropping a pair of Optima red tops in my truck.

Good luck and don't wait too long to get those leaky, stinkin' things out of that nice CTD...

Oh! by the way, if acid HAS been leaking inside the engine compartment, check down below the battery tray and see if there's any acid corrosion in the area of the little Airbag impact sensors that unfortunately are mounted directly where the acid drips.

Keith

 

Got the same exact thing, except mine is pitted. I now have Optimas. No acid...ever again.

 

Looks mine as well, I'm afraid it's battery acid. Could try ome polishing compund. I went to the optimas as well. Problem solved. Kevin

 

Cool, thanks guys. It will come of with simple green and a light green pad. I will put some weathertight electrical sealer on the terminal.