- sorry, got to agree with MR11MOG here, there is no way that that can be 'invisibly' repaired.
'Chipsaway' and the like are (relatively) OK for e.g. bumper scuffs and minor panel damage but that it is on a horizontal panel,in full view and will catch the light whenever you look at it.
I would run some matching paint in the scratch (which I'm afraid will look awful!) to stop rust getting under the existing paint and clear coat and then get it fixed professionally when time and funds allow....
