So i was getting out of my berlina black ap1 the other day and I noticed a streak running down the back of my trunk. Upon closer examination there is a small scratch / crack near the top of the trunk lid and it appears rusty liquid has been leaking from the spot all the way down the face of the trunk, probably due to rain. Its leaving a stain on the paint and it looks bad in certain light.

What would I do to go about fixing this problem? would a clay bar remove it? Also how would i fix the scratch/crack? will scratchx work on it?

I dont have a decent camera so its hard to get a good picture, ill do my best when i get home from work today.