Can really tell from the picture.

What is the location? Does the garage get much water from cars? Is the garage floor sloped so that it drains, either to a floor drain or out the door?

What is the location of this area with respect to the garage (near the door)?

Wire brush it until it is real clean.

Then get a couple of sq ft of plastic sheathing and tape it to the bottom of the panel.

IT MUST BE TAPED TIGHTLY SO THAT NO AIR CAN BE BETWEEN IT AND THE PANEL.

If it is leaking then you will get moisture build up between the plastic and the metal panels.

If it is condensation you may or may not see water condensing on the surface of the plastic.

The garage wasn't getting water on it when I saw the dripping from this area. The garage does have a drain in the middle. Don't know if that could be leaking.

The rusted area covers two good sections of the garage area. The whitish area covers more.

I was hoping the whitish formation was a tell-tale sign of one or the other.

I'll try the