Ugly....

How can you tell the difference ? It looks like corrosion to me but I have zero knowledge. Thanks. Troy

Troy, if you see something like this, try to clean it up.  If it cleans up with a surface cleaner, it isn't corrosion.  If it's into the metal, it's corrosion.

In this case an old tooth brush and some kerosene made it bright and clean, then I re-treated with CorrosionX.  You want to avoid removing the zinc chromate, or if applicable, the paint.  However, sometimes it's necessary to make sure corrosion isn't forming under the paint.  Filiform corrosion is especially insidious.

Ok. Thanks. Like to see some pics of corrosion to see the difference. Troy

I hope I never have any to show you! :-)