This has happened twice now. Once back in December after a major rainstorm and recently after Tropical Storm Elsa. When my car sat, a huge rust spot appeared on my driveway after it rains. My car has never driven in snow, it has no rust on the frame. It's a 1986 Camaro IROC Z.

Does anyone know what could cause this and how to prevent it? Our HOA is very strict about stains of any kind on a driveway and moving is not an option. It only seems to happen during extremely heavy rains.

I've poked all around and can't find a major rust spot underneath. The only one I do see is a tiny one on the hood. Could that cause it?

 

Your HOA should already know that only FORDs rust away like that.

 

Perhaps it is red algae in the concrete and not rust?

 

It's rust.

 

Haha I wish. I have one of the very few older American cars in my town. Everyone think it's a menace or a POS. Sadly no real gearheads where I live.

 

it is from the battery tray-water getting into the battery and flooding out acid onto the area under the battery,rusting the metal. My 1990 G-van would do this,I relocated the battery in the van,but a shield could have been made.

 

Excellent suggestion.