Rust at Ibiza 6L

Hi guys, I have a rust problem on my Ibiza 6L (Bj 05/2006): Both hinges of the tailgate gammeln on the weld seams in front of them, on the left side even peels off on approx. 5cm width of the paint. (see picture) I would be interested to know if one of you had problems with rust on a seat and what experiences he/she had with the rusting guarantee of Seat. I find it simply an insolence that a grade ma l 3 years old car from the VW Group with less than 40,000km already massive rusts!!! PS: The paint on my Ibi is otherwise in perfectly maintained condition, which only makes me shake my head.