This is one of those things without a LOT more info it is pretty much worthless to even think about. If the metal is completely coated in about any automotive primer and paint it likely isn't going to rust. If it is coated with something sub-par like an aerosol paint that is very thin, then it will rust even though being fully coated. But more often than not the coating hasn't much to do with it, because the moisture gets UNDER the coating, at an edge, at a chip, at a worn spot, it gets under the coating and I don't care what you have on it, it will rust.
What exactly happen here, by the photo who knows.