Just curious, my uncle said he thought that was from battery acid.

Sure enough, that's where the battery is. I'm thinking that when the car was new, there were filler caps, and there was also a plastic sleeve around the battery. I didn't use it when I replaced the battery, but that 2nd battery was a group 35 (smaller) sealed battery. I wonder if just gassing was enough to years later rust out the fender. Doesn't matter now, but maybe that simple piece of plastic does a huge job in protection...

 

Pic?

 

Unfortunately yes. 1997 SE with 205K mi. I've read about this problem before on the forum. Still runs great though!

 

I've seen that happen on other cars where the battery would be overfilled by a "quick lube" service attendant. The mix of acid and water would run down on the body and cause rust some years later.